WO2023068237A1 - 無機固体電解質含有組成物、全固体二次電池用シート及び全固体二次電池、並びに、全固体二次電池用シート及び全固体二次電池の製造方法 - Google Patents
無機固体電解質含有組成物、全固体二次電池用シート及び全固体二次電池、並びに、全固体二次電池用シート及び全固体二次電池の製造方法 Download PDFInfo
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- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
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- C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
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- C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
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- C08L51/003—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
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- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
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Definitions
- the present invention relates to an inorganic solid electrolyte-containing composition, an all-solid secondary battery sheet and an all-solid secondary battery, and a method for producing an all-solid secondary battery sheet and an all-solid secondary battery.
- the negative electrode, electrolyte, and positive electrode are all solid, and can greatly improve safety and reliability, which are problems of secondary batteries using organic electrolytes. In addition, it is said that it will be possible to extend the service life. Furthermore, the all-solid secondary battery can have a structure in which the electrodes and the electrolyte are directly arranged in series. Therefore, it is possible to achieve a higher energy density than a secondary battery using an organic electrolyte, and it is expected to be applied to electric vehicles, large storage batteries, and the like.
- an inorganic solid electrolyte or the like is used as a material for forming constituent layers (a solid electrolyte layer, a negative electrode active material layer, a positive electrode active material layer, etc.).
- these inorganic solid electrolytes particularly oxide-based inorganic solid electrolytes and sulfide-based inorganic solid electrolytes, have been expected as electrolyte materials having high ionic conductivity approaching that of organic electrolytes.
- Such constituent layers using an inorganic solid electrolyte are usually formed using a material (constituent layer-forming material) containing an inorganic solid electrolyte and a binder, in consideration of the improvement of productivity.
- compositions containing polymer binders composed of graft polymers containing nitrogen-containing groups such as amide groups in side chains have been proposed.
- a nitrogen-containing polymer having a repeating unit having at least one of a substituent X having a pKa of 14 or less, a substituent having a polymer chain containing a hetero atom, and a specific substituent Z, and a periodic A solid electrolyte composition containing an inorganic solid electrolyte having ionic conductivity of a metal belonging to Group 1 or Group 2 of the Norm Table is described.
- Patent Documents 2 and 3 describe a composition containing a polymer binder composed of a graft polymer having a relatively high molecular weight (for example, a mass average molecular weight of 34,500 or more) having an amide group in a side chain.
- Patent Documents 4 and 5 describe compositions containing particulate polymer binders composed of graft polymers having amide groups in side chains.
- Constituent layers composed of solid particles such as inorganic solid electrolytes, active materials, and conductive aids tend to have increased interfacial resistance (lowered conductivity) due to restrictions on the state of interfacial contact between the solid particles.
- an all-solid secondary battery having such a constituent layer has a high battery resistance (decreased ionic conductivity), and furthermore, battery performance gradually deteriorates when repeatedly charged and discharged (decreased cycle characteristics). ).
- solid particles should be highly dispersed in a dispersion medium in constituent layer-forming materials used in the production of all-solid secondary batteries. Desired.
- the present invention is an inorganic solid electrolyte-containing composition that exhibits excellent dispersion characteristics (initial dispersibility and redispersion characteristics) even when the solid content concentration of solid particles is increased, and can realize a low-resistance all-solid secondary battery.
- An object of the present invention is to provide an inorganic solid electrolyte-containing composition.
- the present invention also provides a sheet for an all-solid secondary battery and an all-solid secondary battery, and a method for producing an all-solid secondary battery sheet and an all-solid secondary battery using this inorganic solid electrolyte-containing composition.
- the task is to provide
- the present inventors have made various studies on the polymer binder used in combination with the inorganic solid electrolyte and the dispersion medium. It is formed by a graft polymer having a specific molecular weight and having a constituent component (A) contained in a molecular chain, and is dissolved in the polymer binder in the dispersion medium rather than being dispersed in the form of particles. It was found that by imparting properties, excellent dispersibility (initial dispersibility) after preparation can be reproduced even if the solid content concentration of the solid particles is increased or even if the solid particles aggregate.
- the inorganic solid electrolyte-containing composition containing this specific polymer binder, inorganic solid electrolyte and dispersion medium as a constituent layer forming material, a sheet for an all-solid secondary battery having a constituent layer with low resistance, and further found that a low-resistance all-solid-state secondary battery can be realized.
- the present invention has been completed through further studies based on these findings.
- An inorganic solid electrolyte-containing composition containing an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, a polymer binder, and a dispersion medium,
- the polymer binder has a constituent component (A) containing at least one functional group selected from an amide group, an imide group and a sulfonamide group in the molecular chain serving as a side chain of the polymer, and has a weight average molecular weight of 1,000 to 30. 000 and dissolved in a dispersion medium.
- ⁇ 4> The inorganic solid electrolyte-containing composition according to any one of ⁇ 1> to ⁇ 3>, wherein the graft polymer has a component (X) containing a polymer chain having a number average molecular weight of 800 or more.
- ⁇ 5> The inorganic solid electrolyte-containing according to any one of ⁇ 1> to ⁇ 4>, wherein the graft polymer has a component (B) having at least one polar functional group from the following functional group group (a) Composition.
- An inorganic solid electrolyte-containing composition according to one.
- a sheet for an all-solid secondary battery having a layer formed using the inorganic solid electrolyte-containing composition according to any one of ⁇ 1> to ⁇ 8> above.
- An all-solid secondary battery comprising a positive electrode active material layer, a solid electrolyte layer and a negative electrode active material layer in this order, At least one layer of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is a layer formed using the inorganic solid electrolyte-containing composition according to any one of ⁇ 1> to ⁇ 8>. All-solid secondary battery.
- ⁇ 11> A method for producing a sheet for an all-solid secondary battery, comprising forming a film from the inorganic solid electrolyte-containing composition according to any one of ⁇ 1> to ⁇ 8> above.
- ⁇ 12> A method for manufacturing an all-solid secondary battery, comprising manufacturing an all-solid secondary battery through the manufacturing method according to ⁇ 11> above.
- the present invention can provide an inorganic solid electrolyte-containing composition that exhibits excellent dispersion characteristics even when the solid content concentration of solid particles is increased, and that can realize a low-resistance all-solid secondary battery. Moreover, the present invention can provide a sheet for an all-solid secondary battery and an all-solid secondary battery having a layer composed of this excellent inorganic solid electrolyte-containing composition. Furthermore, the present invention can provide a sheet for an all-solid secondary battery and a method for producing an all-solid secondary battery using this inorganic solid electrolyte-containing composition.
- FIG. 1 is a vertical cross-sectional view schematically showing an all-solid secondary battery according to a preferred embodiment of the present invention.
- FIG. 2 is a vertical cross-sectional view schematically showing a coin-type all-solid-state secondary battery produced in Examples.
- a numerical range represented by "to” means a range including the numerical values before and after “to” as lower and upper limits.
- the upper limit and lower limit forming the numerical range are described before and after "-" as a specific numerical range. It is not limited to a specific combination, and can be a numerical range in which the upper limit value and the lower limit value of each numerical range are appropriately combined.
- the expression of a compound (for example, when it is called with a compound at the end) is used to mean the compound itself, its salt, and its ion.
- (meth)acryl means one or both of acryl and methacryl.
- substituents, linking groups, etc. for which substitution or non-substitution is not specified are intended to mean that the group may have an appropriate substituent. Therefore, in the present invention, even when the YYY group is simply described, this YYY group includes not only the embodiment having no substituent but also the embodiment having a substituent. This also applies to compounds for which substitution or unsubstitution is not specified.
- Preferred substituents include, for example, the substituent Z described later.
- the respective substituents, etc. may be the same or different from each other. means that Further, even if not otherwise specified, when a plurality of substituents and the like are adjacent to each other, they may be connected to each other or condensed to form a ring.
- a polymer means a polymer, and is synonymous with a so-called high molecular compound.
- a polymer binder (also simply referred to as a binder) means a binder composed of a polymer, and includes a polymer itself and a binder formed by containing a polymer.
- the inorganic solid electrolyte-containing composition of the present invention comprises an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, a polymer binder containing a specific graft polymer described later, and a dispersion medium. and This polymer binder has the property of dissolving (soluble) in the dispersion medium contained in the inorganic solid electrolyte-containing composition.
- the polymer binder in the inorganic solid electrolyte-containing composition usually exists dissolved in the dispersion medium in the inorganic solid electrolyte-containing composition, depending on the content thereof.
- the polymer binder can stably exhibit the function of dispersing the solid particles in the dispersion medium, and maintain excellent (initial) dispersibility of the solid particles in the inorganic solid electrolyte-containing composition. Moreover, even if the solid particles aggregate or precipitate over time, the excellent initial dispersibility can be reproduced by performing the dispersion treatment (mixing treatment) again. In addition, direct contact between the solid particles can be ensured without intervening a polymer binder when the inorganic solid electrolyte-containing composition is formed into a film, and an increase in interfacial resistance can be suppressed.
- the fact that the polymer binder is dissolved in the dispersion medium in the inorganic solid electrolyte-containing composition is not limited to the embodiment in which all the polymer binders are dissolved in the dispersion medium.
- Part of the polymer binder may be insoluble in the inorganic solid electrolyte-containing composition as long as it is 80% or more.
- the method for measuring solubility is as follows. That is, a specified amount of the polymer binder to be measured is weighed in a glass bottle, 100 g of the same dispersion medium as the dispersion medium contained in the inorganic solid electrolyte-containing composition is added, and the mixture is placed on a mix rotor at a temperature of 25 ° C.
- the inorganic solid electrolyte-containing composition of the present invention is preferably slurry in which an inorganic solid electrolyte is dispersed in a dispersion medium.
- the polymer binder dissolves in the dispersion medium and interacts with, preferably adsorbs, the solid particles such as the inorganic solid electrolyte, thereby enhancing the dispersion characteristics of the solid particles.
- the adsorption of the polymer binder to the solid particles includes not only physical adsorption but also chemical adsorption (adsorption due to chemical bond formation, adsorption due to transfer of electrons, etc.).
- the inorganic solid electrolyte-containing composition of the present invention contains the above polymer binder in combination with the inorganic solid electrolyte and the dispersion medium, the dispersion characteristics exhibited by the polymer binder increase the solid content concentration of the solid particles. can be maintained even
- the solid content concentration at this time is not uniquely determined by changing the temperature of the composition, the type of solid particles, etc., but for example, it can be 50% by mass or more at 25 ° C., and further 55% by mass or more.
- the polymer binder contains solid particles (for example, inorganic solid electrolytes) such as inorganic solid electrolytes (and active materials and conductive aids that can coexist) in the constituent layers formed from the inorganic solid electrolyte-containing composition. , the inorganic solid electrolyte and the active material, and the active materials). Furthermore, it also functions as a binder that binds a base material such as a current collector and the solid particles. In addition, in the inorganic solid electrolyte-containing composition, the polymer binder may or may not have the function of binding the solid particles together.
- the inorganic solid electrolyte-containing composition of the present invention exhibits excellent dispersion characteristics even when the solid content concentration is increased, and when it is used as a constituent layer, the solid particles are dispersed by the polymer binder locally adsorbed on the surface of the other solid particles. can be adhered to. Therefore, by using this inorganic solid electrolyte-containing composition as a constituent layer forming material, a sheet for an all-solid secondary battery having a low-resistance constituent layer, and furthermore, an all-solid secondary battery sheet with high conductivity (low resistance) The following batteries can be realized.
- a polymer binder containing a graft polymer having a component (A) described later and having a mass average molecular weight of 1,000 to 30,000 is included in the component (A) in the inorganic solid electrolyte-containing composition.
- Functional groups such as amides facilitate adsorption to solid particles and may exist in an adsorbed state.
- the graft polymer is dissolved in the dispersion medium and exists in a state in which the molecular chains of the polymer are extended.
- the excluded volume effect between the binders due to the polymer graft chain increases, while the repulsive force between the binders due to the osmotic pressure effect increases.
- the binders are less likely to agglomerate and adhere to each other, thereby improving the dispersibility, and the solid particles adsorbed to the binder can also be highly dispersed by suppressing agglomeration and sedimentation. Therefore, even if the solid content concentration is increased, excellent (initial) dispersibility can be maintained, and even if the solid particles are once aggregated or precipitated, due to the above action of the polymer binder, excellent (initial) dispersibility immediately after preparation can be reproduced.
- the composition containing an inorganic solid electrolyte of the present invention can form a constituent layer in which the interfacial resistance between the solid particles is reduced and the inhibition of ion or electron conduction is suppressed while the solid particles are adhered or bound together.
- the interaction (relevance) between the inorganic solid electrolyte, the dispersion medium, and the polymer binder in the inorganic solid electrolyte-containing composition and in the constituent layers is improved, and the inorganic solid electrolyte-containing composition is improved. It is possible to realize excellent dispersion characteristics and resistance reduction when used as a constituent layer. Therefore, a low-resistance (high-conductivity) all-solid secondary battery can be realized.
- the graft polymer promotes close contact between solid particles due to functional groups such as amide contained in the constituent component (A) and is excellent in punctate deposition, direct contact between solid particles in the constituent layer is prevented. It is believed that the solid particles can be bound to each other, and even to the substrate, while being secured. Therefore, by using this inorganic solid electrolyte-containing composition as a constituent layer forming material, an all-solid secondary battery sheet having a constituent layer in which solid particles are firmly bound while having low resistance, and high conductivity ( It is possible to realize an all-solid secondary battery that has low resistance) and excellent cycle characteristics.
- the polymer binder contained in the constituent layer has a nitrogen atom in its molecular structure, it is easily deteriorated (oxidized) by oxygen (atoms or molecules), etc., and as the deterioration progresses, the binding property of the solid particles increases. And the interfacial contact state is gradually lowered, and the cycle characteristics tend to be further deteriorated. Therefore, in industrial production, for example, the roll-to-roll method with high productivity, it is difficult to completely remove oxygen in the production environment, storage environment, etc., and the polymer binder, and thus the inorganic solid electrolyte-containing composition and constituent layers is prone to oxidative deterioration.
- the binder containing the above-mentioned graft polymer is considered to exhibit oxidative degradation resistance to oxygen and the like because nitrogen atoms are contained in functional groups (bonds) such as amide groups.
- the polymer binder, the inorganic solid electrolyte-containing composition, and the constituent layers are resistant to oxidative deterioration, and even in industrial production methods, it is possible to realize constituent layers capable of suppressing further deterioration in cycle characteristics due to oxidative deterioration.
- the inorganic solid electrolyte-containing composition of the present invention is a sheet for an all-solid secondary battery (including an electrode sheet for an all-solid secondary battery) or a material for forming a solid electrolyte layer or an active material layer of an all-solid secondary battery ( It can be preferably used as a constituent layer forming material). In particular, it can be preferably used as a material for forming an electrode sheet or an active material layer for an all-solid secondary battery, and high conductivity and preferably high cycle characteristics can be achieved also in this embodiment.
- the inorganic solid electrolyte-containing composition of the present invention is preferably a non-aqueous composition.
- the non-aqueous composition includes not only a form containing no water but also a form having a water content (also referred to as water content) of preferably 500 ppm or less.
- the water content is more preferably 200 ppm or less, still more preferably 100 ppm or less, and particularly preferably 50 ppm or less.
- the water content indicates the amount of water contained in the inorganic solid electrolyte-containing composition (mass ratio to the inorganic solid electrolyte-containing composition). It is the value measured using titration.
- the composition containing an inorganic solid electrolyte of the present invention also includes an embodiment containing an active material, a conductive aid, etc. in addition to an inorganic solid electrolyte (a composition of this embodiment is referred to as an electrode composition).
- an electrode composition a composition of this embodiment is referred to as an electrode composition.
- the inorganic solid electrolyte-containing composition of the present invention contains an inorganic solid electrolyte.
- an inorganic solid electrolyte means an inorganic solid electrolyte
- a solid electrolyte means a solid electrolyte in which ions can move. Since the main ion-conducting materials do not contain organic substances, organic solid electrolytes (polymer electrolytes typified by polyethylene oxide (PEO), etc., organic electrolytes typified by lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), etc.) electrolyte salt).
- PEO polyethylene oxide
- LiTFSI lithium bis(trifluoromethanesulfonyl)imide
- the inorganic solid electrolyte is solid in a steady state, it is not usually dissociated or released into cations and anions. In this respect, it is clearly distinguished from electrolytes or inorganic electrolyte salts that are dissociated or released into cations and anions in polymers (LiPF 6 , LiBF 4 , lithium bis(fluorosulfonyl)imide (LiFSI), LiCl, etc.). be done.
- the inorganic solid electrolyte is not particularly limited as long as it has ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and generally does not have electronic conductivity.
- the inorganic solid electrolyte preferably has ion conductivity of lithium ions.
- a solid electrolyte material normally used in all-solid secondary batteries can be appropriately selected and used.
- the inorganic solid electrolyte includes (i) a sulfide-based inorganic solid electrolyte, (ii) an oxide-based inorganic solid electrolyte, (iii) a halide-based inorganic solid electrolyte, and (iv) a hydride-based inorganic solid electrolyte.
- a sulfide-based inorganic solid electrolyte is preferable from the viewpoint of being able to form a better interface between the active material and the inorganic solid electrolyte.
- Sulfide-based inorganic solid electrolyte contains sulfur atoms, has the ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and is electronically insulating. It is preferable to use a material having properties.
- the sulfide-based inorganic solid electrolyte preferably contains at least Li, S and P as elements and has lithium ion conductivity. good.
- Examples of sulfide-based inorganic solid electrolytes include lithium ion conductive inorganic solid electrolytes that satisfy the composition represented by the following formula (S1).
- L represents an element selected from Li, Na and K, preferably Li.
- M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al and Ge.
- A represents an element selected from I, Br, Cl and F;
- a1 to e1 indicate the composition ratio of each element, and a1:b1:c1:d1:e1 satisfies 1-12:0-5:1:2-12:0-10.
- a1 is preferably 1 to 9, more preferably 1.5 to 7.5.
- b1 is preferably 0-3, more preferably 0-1.
- d1 is preferably 2.5 to 10, more preferably 3.0 to 8.5.
- e1 is preferably 0 to 5, more preferably 0 to 3.
- composition ratio of each element can be controlled by adjusting the compounding amount of the raw material compound when producing the sulfide-based inorganic solid electrolyte as described below.
- the sulfide-based inorganic solid electrolyte may be amorphous (glass), crystallized (glass-ceramics), or only partially crystallized.
- glass glass
- glass-ceramics glass-ceramics
- Li--P--S type glass containing Li, P and S, or Li--P--S type glass ceramics containing Li, P and S can be used.
- Sulfide-based inorganic solid electrolytes include, for example, lithium sulfide (Li 2 S), phosphorus sulfide (e.g., diphosphorus pentasulfide (P 2 S 5 )), elemental phosphorus, elemental sulfur, sodium sulfide, hydrogen sulfide, lithium halide (e.g., LiI, LiBr, LiCl) and sulfides of the element represented by M above (eg, SiS 2 , SnS, GeS 2 ) can be produced by reacting at least two raw materials.
- Li 2 S lithium sulfide
- phosphorus sulfide e.g., diphosphorus pentasulfide (P 2 S 5 )
- elemental phosphorus e.g., elemental sulfur
- sodium sulfide sodium sulfide
- hydrogen sulfide e.g., lithium halide
- the ratio of Li 2 S and P 2 S 5 in the Li—P—S type glass and Li—P—S type glass ceramics is Li 2 S:P 2 S 5 molar ratio, preferably 60:40 to 90:10, more preferably 68:32 to 78:22.
- the lithium ion conductivity can be increased.
- the lithium ion conductivity can be preferably 1 ⁇ 10 ⁇ 4 S/cm or higher, more preferably 1 ⁇ 10 ⁇ 3 S/cm or higher. Although there is no particular upper limit, it is practical to be 1 ⁇ 10 ⁇ 1 S/cm or less.
- Li 2 SP 2 S 5 Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -LiCl, Li 2 SP 2 S 5 -H 2 S, Li 2 SP 2 S 5 -H 2 S-LiCl, Li 2 S—LiI—P 2 S 5 , Li 2 S—LiI—Li 2 OP 2 S 5 , Li 2 S—LiBr—P 2 S 5 , Li 2 S—Li 2 OP 2 S 5 , Li 2 S—Li 3 PO 4 —P 2 S 5 , Li 2 SP 2 S 5 —P 2 O 5 , Li 2 SP 2 S 5 —SiS 2 , Li 2 SP 2 S 5 —SiS 2- LiCl , Li2SP2S5 -SnS , Li2SP2S5 - Al2S3 , Li2S - GeS2 , Li2S - GeS2 - ZnS,
- Amorphization method include, for example, a mechanical milling method, a solution method, and a melt quenching method. This is because the process can be performed at room temperature, and the manufacturing process can be simplified.
- the oxide-based inorganic solid electrolyte contains oxygen atoms, has the ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and is electronically insulating. It is preferable to use a material having properties.
- the ion conductivity of the oxide-based inorganic solid electrolyte is preferably 1 ⁇ 10 ⁇ 6 S/cm or more, more preferably 5 ⁇ 10 ⁇ 6 S/cm or more, and 1 ⁇ 10 ⁇ 5 S/cm or more. /cm or more is particularly preferable. Although the upper limit is not particularly limited, it is practically 1 ⁇ 10 ⁇ 1 S/cm or less.
- a specific example of the compound is Li xa La ya TiO 3 [xa satisfies 0.3 ⁇ xa ⁇ 0.7, and ya satisfies 0.3 ⁇ ya ⁇ 0.7. ] ( LLT ) ; _ _ xb satisfies 5 ⁇ xb ⁇ 10, yb satisfies 1 ⁇ yb ⁇ 4, zb satisfies 1 ⁇ zb ⁇ 4, mb satisfies 0 ⁇ mb ⁇ 2, and nb satisfies 5 ⁇ nb ⁇ 20. satisfy .
- Li 7 La 3 Zr 2 O 12 having a garnet-type crystal structure.
- Phosphorus compounds containing Li, P and O are also desirable.
- lithium phosphate Li 3 PO 4
- LiPON in which part of the oxygen element of lithium phosphate is replaced with nitrogen element
- LiPOD 1 LiPON in which part of the oxygen element of lithium phosphate is replaced with nitrogen element
- LiPOD 1 LiPON in which part of the oxygen element of lithium phosphate is replaced with nitrogen element
- LiPOD 1 (D 1 is preferably Ti, V, Cr, Mn, Fe, Co, It is one or more elements selected from Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt and Au.) and the like.
- LiA 1 ON A 1 is one or more elements selected from Si, B, Ge, Al, C and Ga
- the halide-based inorganic solid electrolyte contains a halogen atom and has ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and electron Compounds having insulating properties are preferred.
- the halide-based inorganic solid electrolyte include, but are not limited to, compounds such as LiCl, LiBr, LiI, and Li 3 YBr 6 and Li 3 YCl 6 described in ADVANCED MATERIALS, 2018, 30, 1803075. Among them, Li 3 YBr 6 and Li 3 YCl 6 are preferred.
- the hydride-based inorganic solid electrolyte contains hydrogen atoms, has the ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and is electronically insulating. A compound having a property is preferred.
- the hydride-based inorganic solid electrolyte is not particularly limited, but examples include LiBH 4 , Li 4 (BH 4 ) 3 I, 3LiBH 4 --LiCl, and the like.
- the inorganic solid electrolyte is preferably particles.
- the particle size (volume average particle size) of the inorganic solid electrolyte is not particularly limited, but is preferably 0.01 ⁇ m or more, more preferably 0.1 ⁇ m or more.
- the upper limit is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less.
- the particle size of the inorganic solid electrolyte is measured by the following procedure. A 1% by mass dispersion of inorganic solid electrolyte particles is prepared by diluting it in a 20 mL sample bottle with water (heptane for water-labile substances). The diluted dispersion sample is irradiated with ultrasonic waves of 1 kHz for 10 minutes and immediately used for the test.
- the inorganic solid electrolyte may contain one type or two or more types.
- the content of the inorganic solid electrolyte in the inorganic solid electrolyte-containing composition is not particularly limited, but in terms of binding properties and dispersibility, it should be 50% by mass or more based on a solid content of 100% by mass. is preferred, 70% by mass or more is more preferred, and 90% by mass or more is particularly preferred. From the same viewpoint, the upper limit is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and particularly preferably 99% by mass or less.
- the content of the inorganic solid electrolyte in the inorganic solid electrolyte-containing composition is the total content of the active material and the inorganic solid electrolyte within the above range. is preferred.
- the solid content refers to a component that does not disappear by volatilization or evaporation when the inorganic solid electrolyte-containing composition is dried at 150° C. for 6 hours under a pressure of 1 mmHg under a nitrogen atmosphere. . Typically, it refers to components other than the dispersion medium described below.
- the polymer binder contained in the inorganic solid electrolyte-containing composition of the present invention has a component (A) described later, is formed by containing a graft polymer with a specific molecular weight, and is contained in the inorganic solid electrolyte-containing composition. It contains one or more polymer binders that dissolve in the dispersion medium.
- the dissolution in the dispersion medium exhibited by the polymer contained in the polymer binder and forming the polymer binder (also referred to as binder-forming polymer) is as described above.
- a graft polymer as a binder-forming polymer is a polymer having a component (A) and having a specific molecular weight. Concerning the binder-forming polymer, first, the components possessed by the graft polymer will be described.
- the graft polymer has a constituent component (A) containing at least one functional group of an amide group, an imide group and a sulfonamide group in the molecular chain serving as a side chain of the polymer.
- This component (A) has at least one of the above functional groups in the molecular chain that becomes the side chain of the polymer, and the polar functional group of the component (B) and the polymerization of the component (X), which will be described later. It is the building block that does not have a chain.
- This component (A) includes, for example, a component derived from a polycondensable compound having a polycondensable group and the above functional group.
- the polycondensable group is appropriately determined according to the main chain structure of the binder-forming polymer. A group (ethylenically unsaturated group) is selected.
- the functional group may be present in the molecular chain that becomes the side chain of the polymer, and for example, it is incorporated inside or at the end of the molecular chain that becomes the side chain of the polymer.
- the term “molecular chain forming a side chain of a polymer” refers to a molecular chain constituting a side chain of a graft polymer into which the component (A) is incorporated, other than the molecular chain constituting the main chain of the graft polymer. , which is usually a molecular chain bonded to a molecular chain (atomic group) that constitutes the main chain.
- the polycondensable compound leading to the component (A) is acrylamide, it refers to a molecular chain (—CONH 2 ) that bonds to an ethylenic double bond that is a polymerizable group.
- the main chain of a polymer means that all other molecular chains constituting the polymer are linear molecules that can be regarded as branched chains or pendant groups with respect to the main chain. say chain Depending on the weight average molecular weight of the branched chains or branched chains regarded as pendant groups, the longest chain among the molecular chains constituting the polymer is typically the main chain. However, the main chain does not include terminal groups possessed by polymer terminals.
- the side chains of a polymer refer to branched chains other than the main chain, including short chains and long chains (graft chains).
- the terminal group of the polymer is not particularly limited, and can take an appropriate group depending on the polymerization method or the like. Examples include hydrogen atoms, alkyl groups, aryl groups, hydroxy groups, and residues of polymerization initiators.
- the number of types of functional groups in the molecular chain that becomes the side chain of the polymer may be at least one, preferably two to four, more preferably one or two.
- the number of functional groups in the molecular chain that becomes the side chain of the polymer is not particularly limited, and depends on the number of functional groups possessed by the component (A) itself, the content of the component (A), the molecular weight of the graft polymer, and the like. , to be determined accordingly.
- RNA in each functional group represents a hydrogen atom or a substituent.
- Substituents that can be taken as RNA are not particularly limited, and include, for example, substituent Z described later. Among them, an alkyl group (including a cycloalkyl group), an aryl group, a heterocyclic group, and an alkoxy group are preferable, and an alkyl group or an aryl group is preferable.
- the number of carbon atoms in the alkyl group is preferably 1-20, more preferably 1-12, even more preferably 1-6.
- the number of carbon atoms in the aryl group is preferably 6-26, more preferably 6-20, even more preferably 6-12.
- NR NA in the sulfonamide group is preferably a substituent.
- an amide group is also included in an imide group, but an amide bond included in this group is not interpreted as an amide group.
- any of the two bonding portions * and ** may be bonded to the side of the molecular chain that serves as the main chain of the polymer. It is preferably attached to the side.
- the functional group possessed by the component (A) is preferably an amide group or a sulfonamide group, more preferably an amide group, in terms of dispersion characteristics and resistance.
- the combination is not particularly limited and can be determined as appropriate.
- a combination of an amide group and a sulfonamide group is preferred.
- One of the functional groups may be bonded directly to the main molecular chain or through a linking group described later, and the other bonding portion may be directly connected to the main molecular chain or described later. They may be combined via a linking group to form a cyclic structure together with the molecular chain.
- the imide group preferably constitutes a cyclic imide group, such as a tubular imide group derived from maleimide, together with the main molecular chain.
- the amide group or sulfonamide group preferably binds to the terminal group at the other binding portion to form an acyclic molecular chain (linear or branched).
- the terminal group that binds to the functional group is not particularly limited, and represents a hydrogen atom or a substituent.
- Substituents that can be used as terminal groups are not particularly limited, and include, for example, substituent Z described later.
- an alkyl group (including a cycloalkyl group), an aryl group, a heterocyclic group, and an alkoxy group are preferable, and an alkyl group or an aryl group is more preferable.
- the number of carbon atoms in the alkyl group is preferably 1-20, more preferably 2-12, even more preferably 3-8.
- the number of carbon atoms in the aryl group is the same as the number of carbon atoms in the aryl group that can be used as RNA . In the present invention, when either the above RNA or the terminal group has a hydrogen atom, this hydrogen atom is interpreted as the above RNA .
- the mode in which the functional group is bound to the main molecular chain is not particularly limited. may be combined.
- an amide group and an imide group are preferably directly bonded to the main molecular chain.
- the linking group is not particularly limited, but for example, an alkylene group (having preferably 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, and still more preferably 1 to 3 carbon atoms), an alkenylene group (having preferably 2 to 6 carbon atoms , more preferably 2 to 3), an arylene group (the number of carbon atoms is preferably 6 to 24, more preferably 6 to 10), an oxygen atom, a sulfur atom, an imino group (-NR N -: R N is a hydrogen atom, a carbon represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms.), carbonyl group, phosphoric acid linking group (-OP(OH)(O)-O-),
- the linking group is preferably an alkylene group, an arylene group, a carbonyl group, an oxygen atom, a sulfur atom or an imino group, or a group related to a combination thereof, and an alkylene group, an arylene group, a carbonyl group, an oxygen atom, a sulfur atom or an imino group. , or combinations thereof are more preferred.
- a group containing a -CO-O- group can be mentioned, and a -CO-O-alkylene group is preferred.
- One of preferred embodiments of this linking group is one other than the above functional groups.
- the number of atoms constituting the linking group is preferably 1-36, more preferably 1-24, even more preferably 1-12.
- the number of connecting atoms in the connecting group is preferably 12 or less, more preferably 10 or less, and particularly preferably 8 or less.
- the lower limit is 1 or more.
- the number of connecting atoms means the minimum number of atoms connecting predetermined structural parts. For example, in the case of a --CO--O--CH 2 --CH 2 -- group, the number of atoms constituting the linking group is 9, and the number of linking atoms is 4.
- the component (A) is preferably a component represented by the following formula (A1).
- X 1 represents a hydrogen atom or a substituent.
- Substituents that can be taken as X 1 are not particularly limited, and include groups selected from substituents Z described later, among which alkyl groups are preferred.
- X 1 is preferably a hydrogen atom or a methyl group.
- L 1 represents a single bond or a divalent linking group, preferably a single bond.
- the linking group that can be used as L 1 is not particularly limited, and any of the above linking groups that link the functional group and the molecular chain serving as the main chain can be applied without particular restriction. However, the linking group that can be used as L1 does not form a urethane group or a urea group together with the amide group in formula (A1).
- Y 1 and Y 2 each represent a hydrogen atom or a substituent.
- Substituents that can be taken as Y 1 and Y 2 are not particularly limited, one substituent is synonymous with the above RNA , the other substituent is synonymous with the Both are more preferably alkyl groups.
- the substituents that can be used as Y 1 and Y 2 do not form an imide group together with the amide group in formula (A1).
- Y 1 and Y 2 may be the same or different, and one of Y 1 and Y 2 is preferably a hydrogen atom or an alkyl group and the other is an alkyl group.
- the alkyl group that can be used as Y 1 and Y 2 preferably has the same meaning as the alkyl group that can be used as the above RNA , such as methyl, ethyl, normal propyl, Isopropyl, normal butyl, tertiary butyl, linear or branched octyl group, linear or branched dodecyl group, and the like.
- the combination of alkyl groups that can be used as Y 1 and Y 2 is not particularly limited, and the alkyl groups listed above can be combined as appropriate.
- the constituent represented by formula (A1) may have a substituent.
- the carbon atom to which X 1 is not bonded in the molecular chain that is the main chain of the graft polymer is represented as an unsubstituted carbon atom (methylene group: —CH 2 —), but a substituted You may have a group.
- the constituent and the substituent that the unsubstituted carbon atom may have are not particularly limited, but include, for example, the above substituents that can be taken as X 1 .
- the terminal groups Y 1 and Y 2 that bind to the functional group may have a substituent, but preferably have no substituent, and are unsubstituted alkyl groups (especially unsubstituted A straight-chain or branched-chain alkyl group) is more preferable.
- component (A) examples include components possessed by the polymers synthesized in Examples, components derived from acrylamide compounds, components derived from maleimide compounds, and the like. It is not limited to these.
- the binder-forming polymer preferably has a component that incorporates a graft structure in its chemical structure, such as component (X) having a polymer chain.
- component (X) having a polymer chain.
- this component is a component (X).
- This component (X) is preferably a component that does not have the functional group in the component (A) above and the polar functional group described later in the partial structure other than the polymer chain.
- the binder-forming polymer becomes a polymer having a graft structure, which enhances the excluded volume effect between the polymer binders and improves the dispersion characteristics.
- This component (X) is, for example, a component derived from a polycondensable compound having a polycondensable group and a polymer chain.
- the polycondensable group is appropriately determined according to the main chain structure of the binder-forming polymer, and is synonymous with the polycondensable group possessed by the constituent component (A).
- a polymer chain is a molecular chain in which two or more repeating units of one type or two or more types are bonded, and becomes a graft chain of a graft polymer.
- Such a polymer chain is not particularly limited, and a chain composed of an ordinary polymer, for example, a sequential polymerization polymer or a chain polymerization polymer, which will be described later, can be applied without particular limitation.
- a polymer chain having a repeating unit represented by the following formula (L P ) for example, a polymer chain made of polyester, a polymer chain made of polysiloxane, a polymer chain made of (meth)acrylic polymer is preferable, and polyester A polymer chain consisting of or a polymer chain consisting of polysiloxane is more preferable.
- X represents a divalent substituent
- L represents a single bond or a linking group
- n represents the (average) degree of polymerization.
- the substituent that can be taken as X is not particularly limited, and includes a group obtained by removing one hydrogen atom from a group appropriately selected from the substituent Z described later. Preferably, it is described later in terms of dispersion characteristics.
- Each group that can be taken as R 1 X4 is exemplified.
- X may have a substituent, and in particular when the polymer chain having a repeating unit represented by formula (L P ) is a chain composed of a chain polymer, -L X4 - in formula (X2) to be described later.
- L is selected according to the type of the polymer chain.
- L is a single bond in the case of a chain polymer chain, and a linking group in the case of a chain polymer polymer chain.
- the linking group that can be used as L is not particularly limited as long as it is a group that can bond with another repeating unit, and is appropriately selected according to the type of polymer chain.
- This linking group is usually a linking group having a heteroatom, for example, an ester bond (-CO-O-), an ether bond (-O-), a carbonate bond (-O-CO-), an amide bond (- CO-N(R N )-), urethane bond (-N(R N )-CO-), urea bond (-N(R N )-CO-N(R N )-), imide bond (-CO- N(R N )—CO—).
- R 3 N represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. Note that any bonding portion of the linking group may be bonded to the X described above.
- n indicates the (average) degree of polymerization, and may be 2 or more, and is appropriately determined in consideration of the number-average molecular weight of polymer chains described later.
- the degree of polymerization n is preferably 3-500, more preferably 4-300, even more preferably 4-100.
- 50, 40 or 15 can be set as the upper limit in each numerical range.
- Two or more repeating units in the polymer chain may be the same or different. When two or more repeating units are different, the binding mode is not particularly limited, and may be random, alternating, or block.
- Examples of the polymer chain having a repeating unit represented by the above formula (L P ) include a chain polymer chain, a polymer chain comprising a sequential polymer polymer, and more specifically, a (meth)acrylic
- a polymer chain consisting of a polymer, a polymer chain consisting of polystyrene, a polymer chain consisting of a polyether, a polymer chain consisting of a polyester, a polymer chain consisting of a polycarbonate, and a polymer chain consisting of a polysiloxane are preferable, and a polymer chain consisting of a polyester or a polysiloxane A polymer chain consisting of is more preferred.
- the group that binds to the end of the polymer chain is not particularly limited, and can be an appropriate group depending on the polymerization method or the like. Examples thereof include a hydrogen atom, an alkyl group, an aryl group, and a hydroxy group, preferably an alkyl group (having preferably 1 to 20 carbon atoms, more preferably 4 to 20 carbon atoms, more preferably 4 to 12). Although this group may further have a substituent, it is preferably unsubstituted.
- polymer chains made of polyether include polyalkyleneoxy chains, polyaryleneoxy chains, etc.
- the alkylene group and the arylene group are appropriately selected from the substituents Z described later, and a hydrogen atom is added from an alkyl group or an aryl group.
- one removed group is included, preferably an alkylene group and an arylene group that can be taken as R 1 X4 described later.
- a polymer chain having a structure represented by -(SiR 2 -O)n- is preferred.
- R represents a hydrogen atom or a substituent, preferably a substituent.
- the substituent is not particularly limited, and includes those selected from the substituent Z described later, preferably an alkyl group or an aryl group, more preferably an alkyl group having 1 to 6 carbon atoms.
- the (average) repetition number n is as described above.
- Examples of the component (X) having a polymer chain composed of polysiloxane include components derived from terminal (meth)acrylic-modified silicone compounds (eg product number X-22-174ASX manufactured by Shin-Etsu Silicone Co., Ltd.). .
- Polymer chains made of polyester include known chains made of polyester.
- a polyester polymer chain obtained by reacting a polyol such as alkylene glycol with a polybasic acid such as an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid, or a polyester obtained by ring-opening polymerization of a cyclic ester compound such as a caprolactone monomer.
- Polymeric chains are included.
- the chain polymer chain include a (meth)acrylic polymer chain and a polystyrene polymer chain.
- the polymer chain composed of the (meth)acrylic polymer preferably has a constituent component derived from the (meth)acrylic compound (M1) described later and a constituent component derived from the vinyl compound (M2) described later.
- M1 the constituent component derived from the (meth)acrylic compound
- M2 the vinyl compound
- a polymer chain having a constituent component derived from one or more (meth)acrylic acid ester compounds is more preferable, and a polymer chain having a constituent component derived from a (meth)acrylic acid alkyl ester compound is even more preferable.
- the (meth)acrylic acid alkyl ester compound preferably contains an ester compound of a long-chain alkyl group having 4 or more carbon atoms (preferably 6 or more carbon atoms), and further includes an ester compound of a short-chain alkyl group having 3 or less carbon atoms. can also contain
- the content of each component in the polymer chain is not particularly limited and is set as appropriate.
- the content of the component derived from the (meth)acrylic compound (M1) in the polymer chain is, for example, preferably 30 to 100% by mass, and may be 50 to 80% by mass.
- the content of the component derived from the (meth)acrylic acid alkyl ester compound is preferably 50 to 100% by mass, and may be 60 to 80% by mass.
- a component derived from a (meth)acrylic acid long-chain alkyl ester compound and a component derived from a (meth)acrylic acid short-chain alkyl ester compound are included, it is derived from the (meth)acrylic acid long-chain alkyl ester compound.
- the content of the component to be used is preferably 20 to 100% by mass, more preferably 50 to 100% by mass, and the content of the component derived from the (meth)acrylic acid short-chain alkyl ester compound is , preferably 5 to 80% by mass, more preferably 5 to 40% by mass.
- the polymer chain is preferably bonded to the polycondensable group directly or via a linking group.
- a linking group is not particularly limited. is preferably 6, more preferably 2 to 3), an arylene group (having preferably 6 to 24 carbon atoms, more preferably 6 to 10 carbon atoms), an oxygen atom, a sulfur atom, an imino group (-NR N -: R N is hydrogen atom, alkyl group having 1 to 6 carbon atoms or aryl group having 6 to 10 carbon atoms.), carbonyl group, phosphoric acid linking group (-O-P(OH)(O)-O-), phosphonic acid linking A group (--P(OH)(O)--O--), a group related to a combination thereof, and the like can be mentioned.
- the linking group is preferably not one of the functional groups defined in the component (A) above.
- a group formed by combining an alkylene group, an arylene group, a carbonyl group, an oxygen atom, a sulfur atom and an imino group is preferable. is more preferred.
- the linking group includes a chain transfer agent (eg, 3-mercaptopropionic acid) used for synthesizing the polymer chain, a linking group containing a structural portion derived from a polymerization initiator, etc., and furthermore, the structural portion and the chain transfer agent.
- a linking group to which a structural moiety derived from the (meth)acrylic compound (M1) reacting with is also preferably exemplified.
- linking group examples include the linking group in the component (X) contained in the polymer synthesized in Examples.
- the number of atoms constituting the linking group is preferably 1-36, more preferably 1-24, even more preferably 1-12.
- the number of connecting atoms in the connecting group is preferably 12 or less, more preferably 10 or less, and particularly preferably 8 or less.
- the lower limit is 1 or more.
- the number of atoms constituting the linking group is 10, and the number of linking atoms is 5.
- Component (X) is preferably a component represented by the following formula (X1) or (X2).
- R X1 to R X3 each represent a hydrogen atom or a substituent.
- Substituents that can be used as R X1 to R X3 are not particularly limited, and include groups selected from substituents Z described later. Among them, an alkyl group or a halogen atom is preferable.
- Each of R 1 X1 and R 1 X3 is preferably a hydrogen atom, and R 1 X2 is preferably a hydrogen atom or methyl.
- L X1 represents a linking group.
- the linking group that can be used as L X1 the above linking group that links the polycondensable group and the polymer chain can be applied without particular limitation.
- L X1 is more preferably a group containing a --CO--O-- group, an oxygen atom, and particularly preferably a --CO--O-- group.
- the number of atoms constituting the connecting group and the number of connecting atoms are as described above, but the number of atoms constituting L X1 is particularly preferably 1 to 6, and the number of connecting atoms is 1 to 3. is more preferred.
- R X4 represents a hydrocarbon group or an alkylsilylene group.
- the hydrocarbon group that can be taken as R X4 is not particularly limited, and includes an alkylene group, an alkenyl group, an arylene group and the like, with an alkylene group being preferred.
- Examples of the alkylene group and the like that can be used as R 1 X4 include groups obtained by removing one hydrogen atom from each corresponding group of the substituent Z described later. However, the number of carbon atoms in the alkylene group is more preferably 1-8.
- the alkylene group preferably has 1 to 6 carbon atoms.
- the alkylsilylene group that can be used as R X4 is not particularly limited, and preferably includes the -SiR 2 - group in the polymer chain having the structure represented by -(SiR 2 -O)n- described above.
- L X2 represents a linking group and has the same meaning as the linking group that can be taken as L.
- R X5 represents a substituent and has the same definition as the group that binds to the end of the polymer chain having the repeating unit represented by the above formula (L P ).
- the substituent that can be taken as R 1 X5 may further have a substituent, but is preferably unsubstituted.
- n X represents the average degree of polymerization, is a number of 2 or more, and has the same meaning as the average degree of polymerization n of the polymer chain having the repeating unit represented by the above formula (L P ).
- Each substituent and linking group in the above formula (X1) preferably does not contain a nitrogen atom.
- the constituent represented by the above formula (X1) may have one type of repeating unit -(R X4 -L X2 )- in one component, or may have two or more types.
- the binder-forming polymer has a plurality of constituents represented by formula (X1), the constituents represented by formula (X1) may be the same or different.
- the polymer chain -(R X4 -L X2 ) n X - bonded to L X1 preferably includes, for example, the above-described chain composed of a sequentially polymerized polymer, and poly Polymer chains made of ether, polymer chains made of polysiloxane, polymer chains made of polyester, polymer chains made of polycarbonate, and the like are particularly preferable.
- R X1 to R X3 each represent a hydrogen atom or a substituent, and have the same meanings as R X1 to R X3 in formula (X1).
- L X3 represents a linking group.
- the linking group that can be used as L X3 the above linking group that links the polycondensable group and the polymer chain can be applied without particular limitation.
- a linking group containing a structural moiety derived from a chain transfer agent or the like used for synthesizing the polymer chain is more preferable, and this structural moiety and a structural moiety derived from a (meth)acrylic compound (M1) that reacts with the chain transfer agent is particularly preferred.
- M1 (meth)acrylic compound
- Examples thereof include -COO-alkylene group -OCO-alkylene group -S- group (the alkylene group is synonymous with the alkylene group that can be taken as R X4 ).
- 3-mercaptopropionic acid and glycidyl Linking groups included in reaction products with meth)acrylates may be mentioned.
- R X6 to R X8 each represent a hydrogen atom or a substituent, and have the same meaning as R X1 to R X3 in formula (X1).
- L X4 represents a single bond or a linking group.
- the linking group that can be used as L X4 the above linking group that links the polycondensable group and the polymer chain can be applied without particular limitation.
- the linking group that can be used as L X4 is more preferably a group containing a —CO—O— group or a group containing a —CO—NR N — group (R N is as described above), and a —CO—O— group. or -CO-NR N - groups are particularly preferred.
- R X9 represents a hydrogen atom or a substituent, preferably a substituent.
- Substituents that can be taken as R 1 X9 are not particularly limited, and groups selected from substituents Z described later can be mentioned. Among them, an alkyl group or an aryl group is preferable, and a long-chain alkyl group having 4 or more carbon atoms is more preferable.
- the substituent that can be taken as R 1 X9 may further have a substituent (for example, a halogen atom), but is preferably unsubstituted.
- m X represents the average degree of polymerization, is a number of 2 or more, and has the same meaning as the average degree of polymerization n of the polymer chain having the repeating unit represented by the above formula (L P ).
- Each substituent and linking group in the above formula (X2) preferably does not contain a nitrogen atom.
- the constituent represented by formula (X2) may have one type of repeating unit or two or more types of repeating units in one component.
- the constituents represented by formula (X2) may be the same or different.
- the polymer chain that binds to L X3 preferably includes, for example, the above-described chain polymer chain polymer chain, a (meth)acrylic polymer polymer chain, and a polystyrene polymer chain.
- a polymer chain such as the following is particularly preferred.
- Component (X) preferably has an SP value of, for example, 12.0 to 22.5 MPa 1/2 in that it can further enhance the excluded volume effect between polymer binders to achieve excellent dispersion characteristics. It is preferably 12.5 to 22.5 MPa 1/2 , more preferably 16.0 to 21.5 MPa 1/2 .
- the SP value of the component (X) is a value calculated by the method described later.
- the difference (absolute value) in the SP value between the component (X) and the dispersion medium described later is not particularly limited, but from the viewpoint of improving the solubility of the polymer binder in the dispersion medium and the dispersion characteristics, it is from 0.0 to 6.0 MPa 1/2 is preferred, 0.0 to 3.0 MPa 1/2 is more preferred, 0.0 to 2.0 MPa 1/2 is even more preferred, and 0.0 to 1.0 MPa 1/2 is particularly preferred.
- the component (X) may be a repeating unit having a degree of polymerization of 2 or more, and is a component derived from a macromonomer having a polymer chain with a number average molecular weight of 800 or more in the measurement method described later.
- the number average molecular weight of the polymer chain of the macromonomer is appropriately determined in consideration of the molecular weight of the graft polymer, the content of the constituent component (X) and the like, and is preferably 900 to 25,000 in terms of dispersion characteristics. , more preferably 2,000 to 20,000, and may be 2,000 to 15,000. The upper limit of the number average molecular weight of the polymer chains can also be 5,000.
- the component (X) is not particularly limited, but may be a component derived from a (meth)acrylic compound (M1) described later or a component derived from a vinyl compound (M2) described later, or these compounds (M1) or ( It is preferably a component derived from a compound in which a polymer chain is introduced (substituted) into M2).
- the polar functional group functions as a linking group and is selected from the following functional group group (a). not be a polar functional group.
- the component (X) is derived from a compound having the polycondensable group and the polymer chain, the above-mentioned linking group that links the polycondensable group and the polymer chain has a polar functional group.
- this polar functional group does not sufficiently exhibit the function of adsorption or adhesion to solid particles, the aspect in which the component (X) does not have a polar functional group (does not correspond to the component (B) components).
- the component (X) may contain a nitrogen atom, for example, it may contain a nitrogen atom as a component forming a polymer chain.
- component (X) examples include those possessed by the graft polymers synthesized in Examples and those shown below, but the present invention is not limited thereto.
- R Y and R Z each represent a linking group or a substituent.
- degree of polymerization of the repeating unit is specifically shown in the following specific examples, it can be changed as appropriate in the present invention.
- the binder-forming polymer preferably has at least one (one) polar functional group from the following functional group group (a), and more preferably has a component (B) having a polar functional group, for example.
- component (B) when a component has the following polar functional group and the functional group defined in component (A) above, this component is referred to as component (B).
- This component (B) is preferably a component that does not have the functional group defined in component (A) and the polymer chain defined in component (X).
- Component (B) may have at least one (one) polar functional group, and usually preferably has 1 to 3 polar functional groups.
- the number of polar functional groups possessed by the graft polymer is not particularly limited, and is appropriately determined according to the number of polar functional groups possessed by the component (B) itself, the content of the component (B), the molecular weight of the graft polymer, and the like. be.
- This component (B) may have a polar functional group, and is derived from, for example, a polycondensable compound having at least one (one) polar functional group from the following functional group group (a): constituents.
- the polycondensable compound is preferably a compound having, for example, a polycondensable group, a polar functional group or a substituent having a polar functional group, and a linking group that appropriately connects the polycondensable group and the substituent.
- the polycondensable group is synonymous with the polycondensable group in the component (A).
- the substituent is not particularly limited, but includes, for example, a group selected from the substituents Z described later, preferably an alkyl group.
- the linking group any of the above linking groups that link the polycondensable group and the polymer chain can be applied without particular limitation. However, a --CO--O-- group is particularly preferred.
- the sulfonic acid group, phosphoric acid group (phosphoryl group), phosphonic acid group, and the like included in the functional group (a) are not particularly limited, but are synonymous with the corresponding groups of the substituent Z described later.
- the dicarboxylic anhydride group is not particularly limited, but includes a group obtained by removing one or more hydrogen atoms from a dicarboxylic anhydride, and a component itself obtained by copolymerizing a polymerizable dicarboxylic anhydride. do.
- the group obtained by removing one or more hydrogen atoms from a dicarboxylic anhydride is preferably a group obtained by removing one or more hydrogen atoms from a cyclic dicarboxylic anhydride.
- Examples include non-cyclic dicarboxylic anhydrides such as acetic anhydride, propionic anhydride and benzoic anhydride, and cyclic dicarboxylic anhydrides such as maleic anhydride, phthalic anhydride, fumaric anhydride, succinic anhydride and itaconic anhydride. be done.
- the polymerizable dicarboxylic acid anhydride is not particularly limited, but includes a dicarboxylic acid anhydride having an unsaturated bond in the molecule, preferably a polymerizable cyclic dicarboxylic acid anhydride. Specific examples include maleic anhydride and itaconic anhydride.
- An ether group (--O--), a thioether group (--S--), and a thioester group (--CO--S--, --CS--O--, --CS--S--) mean the bond shown in parentheses.
- the terminal group bonded to this group is not particularly limited, and may be a group selected from substituents Z described later, for example, an alkyl group.
- Ether groups are included in carboxy groups, hydroxy groups, oxetane groups, epoxy groups, dicarboxylic acid anhydride groups and the like, but -O- included in these groups is not an ether group. The same applies to thioether groups.
- the fluoroalkyl group is a group in which at least one hydrogen atom of an alkyl group or a cycloalkyl group is substituted with a fluorine atom, and the number of carbon atoms thereof is preferably 1 to 20, more preferably 2 to 15, and further preferably 3 to 10. preferable.
- the number of fluorine atoms on the carbon atoms may be one in which some of the hydrogen atoms are replaced, or one in which all of the hydrogen atoms are replaced (perfluoroalkyl group).
- a group capable of forming a salt such as a sulfonic acid group (sulfo group), a phosphoric acid group, a phosphonic acid group, a carboxyl group, etc. may form a salt.
- Salts include various metal salts, ammonium or amine salts, and the like.
- the polar functional group possessed by the component (B) is preferably a carboxy group, a hydroxy group, or an epoxy group in terms of adsorption (adhesion) to solid particles and dispersion characteristics.
- the component (B) has two or more polar functional groups, the combination thereof is not particularly limited and can be determined as appropriate. For example, a combination of a carboxy group, a sulfonic acid group, or a phosphonic acid group and any one of a hydroxy group, an oxetane group, an epoxy group, and an ether group is preferred, and a combination of a carboxy group and a hydroxy group is more preferred.
- the polycondensable compound leading to the component (B) is not particularly limited as long as it has the above polar functional group, and examples thereof include compounds obtained by introducing the above polar functional group into the raw material compound constituting the binder-forming polymer.
- examples thereof include compounds obtained by introducing the above polar functional group into the raw material compound constituting the binder-forming polymer.
- a (meth)acrylic compound (M1) or a vinyl compound (M2), which will be described later, or a compound obtained by introducing the above polar functional group into these compounds (M1) or (M2) can be mentioned.
- component (A) and component (X), and component (B) are different components. This makes it possible to improve dispersion characteristics and suppress an increase in resistance.
- the binder-forming polymer may have other constituents in addition to the constituents described above.
- Other constituents may be those that do not fall under each of the above constituents, and include, for example, constituents derived from the (meth)acrylic compound (M1) or vinyl compound (M2) described later.
- a component derived from a (meth)acrylic acid alkyl ester compound is preferable, and a component derived from an acrylic acid ester compound having a long-chain alkyl group is more preferable in terms of solubility in a dispersion medium.
- the number of carbon atoms in the long-chain alkyl group can be, for example, 3-20, preferably 4-16, more preferably 6-14.
- the binder-forming polymer may have one or more of the above components.
- each component, especially other components, preferably does not have crosslinkable groups such as ethylenically unsaturated groups such as carbon-carbon double bonds.
- the content of each constituent component in the binder-forming polymer is not particularly limited, and is determined by appropriately considering the physical properties of the entire polymer, and is set, for example, within the following ranges.
- the content of each component in the binder-forming polymer is set within the following range, for example, so that the total content of all components is 100% by mass.
- the content of the constituent component (A) is not particularly limited, but can be appropriately determined with respect to the total content of all the constituent components, taking into consideration, for example, improvement of dispersion characteristics, suppression of increase in resistance, and the like.
- the content of the component (A) is, for example, preferably 2 to 60% by mass, more preferably 5 to 40% by mass, even more preferably 7.5 to 30% by mass, 10 to 25 mass % is particularly preferred.
- the content of the component (A) is preferably 10 mol % or more, more preferably 20 mol % or more, based on the total number of moles of all the components.
- the upper limit can be 90 mol % or less, preferably 60 mol % or less.
- the content of the constituent component (X) is not particularly limited, but can be appropriately determined in consideration of, for example, dispersion characteristics with respect to the total content of all constituent components.
- the content of the component (X) is, for example, preferably 20 to 90% by mass, more preferably 30 to 80% by mass, even more preferably 40 to 70% by mass, and 40 to It is more preferably 60% by mass.
- the content of the component (X) is preferably 0.1 to 60 mol%, more preferably 1 to 20 mol%, more preferably 3 to 10 mol%, based on the total number of moles of all the components. More preferably, it is mol %.
- the content of the constituent component (B) is not particularly limited, but is appropriately determined in consideration of, for example, the dispersion characteristics and the adhesion (binding property) of the solid particles with respect to the total content of all constituent components. be able to.
- the content of the component (B) is, for example, preferably 0 to 20% by mass, more preferably 0.1 to 10% by mass, even more preferably 1 to 8% by mass.
- the content of the constituent component (B) is preferably 0.1 to 30 mol%, more preferably 1 to 20 mol%, more preferably 3 to 10 mol%, based on the total number of moles of all constituent components. More preferably, it is mol %.
- the content of each constituent component is appropriately determined in consideration of the content of the constituent component (B).
- the content of the component (B) containing a carboxy group as a polar functional group is preferably 0 to 18% by mass, more preferably 0.1 to 14% by mass, and 0.2 to 8% by mass. % by mass is more preferred, and 0.5 to 3% by mass is even more preferred.
- the content of the component (B) containing a hydroxy group or an epoxy group as a polar functional group is preferably 0 to 18% by mass, more preferably 0.1 to 8% by mass, and more preferably 0.3 to It is more preferably 6% by mass.
- the content of other constituent components is not particularly limited, but is preferably 0 to 60% by mass, more preferably 10 to 50% by mass, more preferably 20 to 50% by mass, based on the total content of all constituent components It is more preferably 40% by mass.
- the content of other constituent components is preferably 0 to 80 mol%, more preferably 1 to 60 mol%, and 5 to 50 mol% of the total number of moles of all constituent components. It is even more preferable to have
- the graft polymer contains a plurality of each component, the content of each component is the total content of the plurality of components.
- Binder-forming polymer is not particularly limited as long as it is a graft polymer having the constituent component (A) described above, a weight average molecular weight described later, and a graft polymer soluble in a dispersion medium, and various known polymers can be used. can be used.
- the molecular structure of the binder-forming polymer is a graft structure among (multi)branched structures (graft structure, star structure, dendritic structure, etc.). Adsorption with solid particles is improved by adopting a graft structure.
- the primary structure of the main chain and graft chain in the graft polymer is not particularly limited, and may have any bonding pattern such as random structure, block structure, alternating structure, graft structure, and the like.
- the (multi)branched structure refers to a polymer chain having a branched structure.
- one or more other polymer chains (side chains) are bonded to the main chain A structure that has
- a polymer with a graft structure refers to a polymer in which a large number of polymer chains are bonded (as side chains) to one main chain in a branched form, and includes, for example, a constituent component (X) having a polymer chain. Refers to a polymer structure.
- the binder-forming polymer can be synthesized by selecting raw material compounds (monomers) and polymerizing the raw material compounds by a known method.
- the polymerization initiator used for synthesizing the binder-forming polymer is not particularly limited, and may be peroxide initiators, azo polymerization initiators, redox initiators, photoradical initiators, and the like. In particular, it is preferable to use an azo initiator because of ease of handling during polymerization.
- the amount of the initiator used during polymerization the amount of the initiator used can be appropriately selected with respect to the target polymer molecular weight. It is preferably 0.001 to 30% by mass, even more preferably 0.01 to 20% by mass. When a large amount of the initiator is used, the decomposition product of the initiator may be contained in the polymer, but the decomposition product of the initiator may be contained in the polymer.
- the binder-forming polymer will be described below, but the description can also be applied to polymer chains constituting each polymer chain (main chain and side chain) in the binder-forming polymer having a graft structure.
- the binder-forming polymer for example, at least one bond selected from a urethane bond, a urea bond, an amide bond, an imide bond, an ester bond and a silyloxy bond, or a polymer having a polymer chain of a carbon-carbon double bond in the main chain. is preferably mentioned.
- the polymer chain of carbon-carbon double bonds refers to a polymer chain formed by polymerizing carbon-carbon double bonds (ethylenically unsaturated groups).
- the above bond is not particularly limited as long as it is contained in the main chain of the polymer, and may be contained in a constituent component (repeating unit) and/or contained as a bond connecting different constituent components. .
- the number of the bonds contained in the main chain is not limited to 1, and may be 2 or more, preferably 1 to 6, more preferably 1 to 4.
- the binding mode of the main chain is not particularly limited, and may have two or more types of bonds at random. It can be a chain.
- polymers having urethane bonds, urea bonds, amide bonds, imide bonds or ester bonds in the main chain among the above bonds include sequential polymerization (polycondensation, polymerization) of polyurethane, polyurea, polyamide, polyimide, polyester, polysiloxane, etc. addition or addition condensation) polymers, or copolymers thereof.
- the copolymer may be a block copolymer having each of the above polymers as a segment, or a random copolymer in which two or more constituent components of each of the above polymers are randomly bonded.
- Polymers having a polymer chain of carbon-carbon double bonds in the main chain include chain-polymerized polymers such as fluorine-based polymers (fluorine-containing polymers), hydrocarbon-based polymers, vinyl polymers, and (meth)acrylic polymers.
- the polymerization mode of these chain-polymerized polymers is not particularly limited, and they may be block copolymers, alternating copolymers or random copolymers, but random copolymers are preferred.
- the binder-forming polymer any of the above polymers can be appropriately selected, but a vinyl polymer or (meth)acrylic polymer is preferred.
- Examples of the (meth)acrylic polymer suitable as the binder-forming polymer include copolymers of the constituent components described above and containing 50% by mass or more of the constituent component derived from the (meth)acrylic compound. be done.
- the components (X), (A) and (B) are components derived from a (meth)acrylic compound, the content of each component in the content of the components derived from the (meth)acrylic compound is calculated.
- the content of the component derived from the (meth)acrylic compound is more preferably 60% by mass or more, particularly preferably 70% by mass or more.
- the upper limit content can be 100% by mass, but can also be 97% by mass or less.
- the (meth)acrylic polymer a copolymer with a vinyl compound (M2) other than the (meth)acrylic compound (M1) is also preferable.
- the content of the component derived from the vinyl compound (M2) is 50% by mass or less, preferably 3 to 40% by mass, more preferably 3 to 30% by mass.
- Examples of vinyl polymers suitable as binder-forming polymers include polymers composed of copolymers of the above constituent components and containing 50% by mass or more of constituent components derived from vinyl compounds.
- the constituents (X), (A) and (B) are constituents derived from a vinyl compound
- the content of each constituent is included in the content of the constituents derived from the vinyl compound.
- the content of the constituent component derived from the vinyl compound is more preferably 60% by mass or more, and even more preferably 65% by mass or more. Although the upper limit content can be 100% by mass, it is preferably 95% by mass or less, more preferably 90% by mass or less.
- a copolymer with a (meth)acrylic compound (M1) is also preferred. In this case, the content of the component derived from the (meth)acrylic compound (M1) may be less than 50% by mass, for example, preferably 0 to 40% by mass, and 0 to 30% by mass. is more preferred.
- (meth)acrylic compound (M1) among (meth)acrylic acid ester compounds, (meth)acrylamide compounds, (meth)acrylonitrile compounds, etc., the above constituent components (X), (A) and (B) Compounds other than lead compounds are included. Among them, (meth)acrylic acid ester compounds are preferred. Examples of (meth)acrylic acid ester compounds include (meth)acrylic acid alkyl ester compounds, (meth)acrylic acid aryl ester compounds, etc., and (meth)acrylic acid alkyl ester compounds are preferred. The number of carbon atoms in the alkyl group constituting the (meth)acrylic acid alkyl ester compound is not particularly limited.
- the number of carbon atoms in the aryl group constituting the aryl ester is not particularly limited, but may be, for example, 6 to 24, preferably 6 to 10, more preferably 6.
- the nitrogen atom of the amide group may be substituted with an alkyl group or an aryl group.
- the vinyl compound (M2) is not particularly limited, but among vinyl compounds copolymerizable with the (meth)acrylic compound (M1), other than the vinyl compounds that lead to the above constituent components (X), (A) and (B). are preferred, for example, styrene compounds, vinylnaphthalene compounds, vinylcarbazole compounds, vinylimidazole compounds, aromatic vinyl compounds such as vinylpyridine compounds, allyl compounds, vinyl ether compounds, vinyl ester compounds (for example, vinyl acetate compounds ), dialkyl itaconate compounds, and the like.
- the vinyl compound include "vinyl-based monomers" described in JP-A-2015-88486.
- the (meth)acrylic compound (M1) and the vinyl compound (M2) may have a substituent, it is one of preferred embodiments that they are unsubstituted.
- the substituent is not particularly limited, and includes groups selected from the substituents Z described later, but groups other than the polar functional groups included in the functional group group (a) described above are preferred.
- the (meth)acrylic compound (M1) and vinyl compound (M2) are preferably compounds represented by the following formula (b-1). This compound is preferably different from the compound that leads to component (A), (X) or (B) described above.
- R 1 is a hydrogen atom, a hydroxy group, a cyano group, a halogen atom, an alkyl group (preferably 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 6 carbon atoms), an alkenyl group (2 carbon atoms to 24 are preferred, 2 to 12 are more preferred, and 2 to 6 are particularly preferred), an alkynyl group (having preferably 2 to 24 carbon atoms, more preferably 2 to 12, and particularly preferably 2 to 6), or an aryl group ( preferably 6 to 22 carbon atoms, more preferably 6 to 14 carbon atoms).
- a hydrogen atom or an alkyl group is preferable, and a hydrogen atom or a methyl group is more preferable.
- R2 represents a hydrogen atom or a substituent.
- Substituents that can be taken as R 2 are not particularly limited. particularly preferred), aryl groups (preferably 6 to 22 carbon atoms, more preferably 6 to 14 carbon atoms), aralkyl groups (preferably 7 to 23 carbon atoms, more preferably 7 to 15 carbon atoms), and cyano groups.
- the carbon number of the alkyl group is synonymous with the carbon number of the alkyl group constituting the (meth)acrylic acid alkyl ester compound, and the preferred range is also the same.
- L 1 is a linking group, which is not particularly limited, but any of the above linking groups that link the polycondensable group and the polymer chain can be applied without particular limitation.
- L 1 is particularly preferably a -CO-O- group.
- n is 0 or 1, preferably 1; However, when —(L 1 ) n —R 2 represents one type of substituent (for example, an alkyl group), n is 0 and R 2 is a substituent (alkyl group).
- R 2 is a substituent (alkyl group).
- the binder-forming polymer may have one type of the (meth)acrylic compound (M1) or the vinyl compound (M2), or may have two or more types.
- the binder-forming polymer may have a substituent.
- the substituent is not particularly limited, but preferably includes a group selected from the following substituents Z.
- Substituent Z - alkyl groups preferably alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.
- alkenyl groups preferably alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, oleyl, etc.
- alkynyl groups preferably alkynyl groups having 2 to 20 carbon atoms, such as ethynyl, butadiynyl, phenylethynyl, etc.
- cycloalkyl groups Preferably a cycloalkyl group having 3 to 20 carbon atoms, for example, cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.
- alkyl group usually means including a cycloalkyl group, but here it is separately described ), an aryl group (preferably an aryl group having 6 to 26 carbon atoms, such as phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), an aralkyl group (preferably having 7 to 23 aralkyl groups such as benzyl, phenethyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, more preferably 5 or 6 having at least one oxygen, sulfur or nitrogen atom It is a membered heterocyclic group, including aromatic heterocyclic groups and aliphatic heterocyclic groups, such as tetrahydropyran ring group, tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, and 2-imidazolyl.
- an aryl group preferably an aryl group having 6 to 26 carbon
- alkoxy groups preferably alkoxy groups having 1 to 20 carbon atoms, such as methoxy, ethoxy, isopropyloxy, benzyloxy, etc.
- aryloxy groups Preferably, an aryloxy group having 6 to 26 carbon atoms, such as phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.
- a heterocyclic oxy group bonded to the above heterocyclic group
- alkoxycarbonyl group preferably an alkoxycarbonyl group having 2 to 20 carbon atoms, such as ethoxycarbonyl, 2-ethylhexyloxycarbonyl, dodecyloxycarbonyl, etc.
- aryloxycarbonyl group preferably aryl having 6 to 26 carbon atoms Oxycarbonyl group, e.g
- alkylsulfonyl groups preferably alkylsulfonyl groups having 1 to 20 carbon atoms, such as methylsulfonyl and ethylsulfonyl
- arylsulfonyl groups preferably arylsulfonyl groups having 6 to 22 carbon atoms, such as benzenesulfonyl
- alkylsilyl groups preferably carbon 1-20 alkylsilyl groups, such as monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl, etc.
- arylsilyl groups preferably C6-42 arylsilyl groups, such as triphenylsilyl, etc
- R P is a hydrogen atom or a substituent (preferably a group selected from substituent Z). Further, each of the groups exemplified for the substituent Z may be further substituted with the substituent Z described above.
- the alkyl group, alkylene group, alkenyl group, alkenylene group, alkynyl group and/or alkynylene group, etc. may be cyclic or chain, and may be linear or branched.
- the polymer binder or binder-forming polymer used in the present invention preferably has the following physical properties or characteristics.
- the weight average molecular weight of the binder-forming polymer is 1,000 to 30,000.
- the weight average molecular weight of the graft polymer is preferably 2,000 or more, more preferably 4,000 or more, and even more preferably 6,000 or more.
- the upper limit is preferably 25,000 or less, more preferably 20,000 or less, and even more preferably 15,000 or less.
- the molecular weights of polymers, polymer chains and macromonomers refer to mass average molecular weights or number average molecular weights converted to standard polystyrene by gel permeation chromatography (GPC).
- GPC gel permeation chromatography
- a method for the measurement as a basis, a method set to the following condition 1 or condition 2 (priority) can be mentioned.
- an appropriate eluent may be selected and used.
- the glass transition temperature Tg of the binder-forming polymer is not particularly limited, and can be 120° C. or lower.
- the temperature is preferably 50° C. or lower, more preferably ⁇ 30° C. or lower, and even more preferably ⁇ 40° C. or lower in terms of further improving the dispersion characteristics and further improving the cycle characteristics.
- the lower limit is not particularly limited, and can be -160° C., for example.
- the glass transition temperature Tg of the binder-forming polymer can be appropriately adjusted depending on the polymer composition (types or contents of constituent components), molecular structure, and the like.
- the glass transition temperature Tg of the binder-forming polymer is the glass transition temperature measured by the following method.
- the glass transition point is measured using a dried sample of the binder-forming polymer with a differential scanning calorimeter (DSC7000, manufactured by SII Technology) under the following conditions. The same sample is measured twice, and the result of the second measurement is adopted.
- ⁇ Atmosphere in the measurement chamber Nitrogen (50 mL/min)
- ⁇ Temperature increase rate 5°C/min
- ⁇ Measurement start temperature -100°C
- ⁇ Measurement end temperature 200°C
- Sample pan Aluminum pan
- Tg is calculated by rounding off the decimal point of the intermediate temperature between the falling start point and the falling end point on the DSC chart.
- the glass transition temperature Tg can be adjusted by the type or composition (type and content of constituent components) of the binder-forming polymer.
- the binder-forming polymer preferably has an SP value of 15.0 to 25.0 MPa 1/2 , more preferably 15.5 to 25.0 MPa 1/2 , in terms of dispersion characteristics. It is more preferably 0 to 23.0 MPa 1/2 , still more preferably 17.0 to 21.0 MPa 1/2 , and particularly preferably 18.0 to 20.5 MPa 1/2 .
- a method for calculating the SP value will be described. First, the SP value (MPa 1/2 ) of each component constituting the binder-forming polymer is obtained by the Hoy method (HL Hoy JOURNAL OF PAINT TECHNOLOGY Vol. 42, No. 541, 1970, unless otherwise specified).
- the binder-forming polymer is a chain polymerization polymer
- the constituent component is the same unit as the constituent component derived from the raw material compound.
- the binder-forming polymer is a stepwise polymerized polymer
- the units are different from the constituent components derived from the raw material compound.
- the constituent components are determined as follows for convenience.
- the structural component derived from the polyisocyanate compound is a unit obtained by bonding two --NH--CO-- groups to --O-- groups in a structural unit derived from the polyisocyanate compound.
- the structural component derived from the polyol compound is a unit obtained by removing two —O— groups from the structural unit derived from the polyol compound.
- the mass fraction of a component is the mass fraction of the component (raw material compound leading to this component) in the binder-forming polymer.
- the SP value of the polymer can be adjusted by the type or composition (type and content of constituent components) of the binder-forming polymer.
- the SP value of the binder-forming polymer satisfies the SP value difference (absolute value) in the range described below with respect to the SP value of the dispersion medium, it is easy to exhibit solubility in the dispersion medium, and more advanced properties can be achieved. preferred in that respect.
- the water concentration of the binder is preferably 100 ppm (by mass) or less. Moreover, this binder may be obtained by drying the polymer by crystallizing it, or by using the binder dispersion as it is.
- the binder-forming polymer is preferably amorphous. In the present invention, a polymer being "amorphous" typically means that no endothermic peak due to crystalline melting is observed when measured at the glass transition temperature.
- the binder-forming polymer may be a non-crosslinked polymer or a crosslinked polymer. Further, when the polymer is crosslinked by heating or voltage application, the molecular weight may be larger than the above molecular weight. Preferably, the binder-forming polymer has a weight-average molecular weight within the above range at the start of use of the all-solid secondary battery.
- binder-forming polymers include the polymers synthesized in Examples, but the present invention is not limited to these.
- the binder-forming polymer contained in the polymer binder may be of one type or two or more types.
- the polymer binder may contain other polymers and the like as long as the action of the binder-forming polymer described above is not impaired.
- polymers that are commonly used as binders for all-solid secondary batteries can be used without particular limitations.
- One or two or more polymer binders may be contained in the inorganic solid electrolyte-containing composition.
- the content of the polymer binder in the inorganic solid electrolyte-containing composition is not particularly limited, but is preferably 0.1 to 5.0% by mass in terms of dispersion characteristics, ionic conductivity, and binding properties. It is preferably 0.2 to 4.0% by mass, and even more preferably 0.3 to 2.0% by mass. Further, the content of the polymer binder in 100% by mass of the solid content of the inorganic solid electrolyte-containing composition is, for the same reason, preferably 0.1 to 6.0% by mass, and 0.3 to 5.0% by mass. It is more preferably 0% by mass, and even more preferably 0.4 to 2.5% by mass.
- the mass ratio of the total mass (total mass) of the inorganic solid electrolyte and the active material to the mass of the polymer binder is preferably in the range of 1,000 to 1. This ratio is more preferably 500-2, even more preferably 100-10.
- the dispersion medium contained in the inorganic solid electrolyte-containing composition may be any organic compound that exhibits a liquid state in the environment of use. Examples thereof include various organic solvents. Specific examples include alcohol compounds, ether compounds, amide compounds, Examples include amine compounds, ketone compounds, aromatic compounds, aliphatic compounds, nitrile compounds, ester compounds and the like.
- the dispersion medium may be either a non-polar dispersion medium (hydrophobic dispersion medium) or a polar dispersion medium (hydrophilic dispersion medium), but a non-polar dispersion medium is preferable in that excellent dispersibility can be exhibited.
- a non-polar dispersion medium generally has a low affinity for water.
- examples thereof include ester compounds, ketone compounds, ether compounds, aromatic compounds, and aliphatic compounds.
- alcohol compounds include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 2-butanol, ethylene glycol, propylene glycol, glycerin, 1,6-hexanediol, cyclohexanediol, sorbitol, xylitol, 2 -methyl-2,4-pentanediol, 1,3-butanediol, 1,4-butanediol.
- ether compounds include alkylene glycol (diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, etc.), alkylene glycol monoalkyl ether (ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, diethylene glycol monobutyl ether, etc.), alkylene glycol dialkyl ethers (ethylene glycol dimethyl ether, etc.), dialkyl ethers (dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, etc.), cyclic ethers (tetrahydrofuran, dioxane (including 1,2-, 1,3- and 1,4-isomers), etc.).
- alkylene glycol diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, etc.
- amide compounds include N,N-dimethylformamide, N-methyl-2-pyrrolidone, 2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, ⁇ -caprolactam, formamide, N-methylformamide, and acetamide. , N-methylacetamide, N,N-dimethylacetamide, N-methylpropanamide, hexamethylphosphoric triamide and the like.
- amine compounds include triethylamine, diisopropylethylamine, and tributylamine.
- Ketone compounds include, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), cyclopentanone, cyclohexanone, cycloheptanone, dipropyl ketone, dibutyl ketone, diisopropyl ketone, diisobutyl ketone (DIBK), isobutyl propyl ketone, sec- Butyl propyl ketone, pentyl propyl ketone, butyl propyl ketone and the like.
- aromatic compounds include benzene, toluene, xylene, perfluorotoluene, and the like.
- aliphatic compounds include hexane, heptane, octane, nonane, decane, dodecane, cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, cyclooctane, decalin, paraffin, gasoline, naphtha, kerosene, and light oil.
- Nitrile compounds include, for example, acetonitrile, propionitrile, isobutyronitrile, and the like.
- Ester compounds include, for example, ethyl acetate, propyl acetate, butyl acetate, ethyl butyrate, propyl butyrate, isopropyl butyrate, butyl butyrate, isobutyl butyrate, butyl pentanoate, pentyl pentanoate, ethyl isobutyrate, propyl isobutyrate, and isopropyl isobutyrate.
- ether compounds, ketone compounds, aromatic compounds, aliphatic compounds, and ester compounds are preferred, and ester compounds, ketone compounds, aromatic compounds, and ether compounds are more preferred.
- the number of carbon atoms in the compound constituting the dispersion medium is not particularly limited, preferably 2 to 30, more preferably 4 to 20, even more preferably 6 to 15, and particularly preferably 7 to 12.
- the dispersion medium preferably has an SP value (unit: MPa 1/2 ) of 14 to 24, more preferably 15 to 22, and 16 to 20, in terms of dispersion characteristics of solid particles. is more preferred.
- the difference (absolute value) in the SP value between the dispersion medium and the binder-forming polymer is not particularly limited, but the molecular chain of the binder-forming polymer spreads in the dispersion medium to improve the dispersibility of the solid particles. It is preferably 3 MPa 1/2 or less, more preferably 0 to 2 MPa 1/2 , and even more preferably 0 to 1 MPa 1/2 in terms of further improving the properties.
- the SP value of the dispersion medium is a value obtained by converting the SP value calculated by the above Hoy method into the unit MPa 1/2 .
- the SP value of the dispersion medium means the SP value of the dispersion medium as a whole, and is the product of the SP value and the mass fraction of each dispersion medium. Sum up. Specifically, the SP value is calculated in the same manner as the method for calculating the SP value of the polymer described above, except that the SP value of each dispersion medium is used instead of the SP value of the constituent components. SP values (units omitted) of main dispersion media are shown below.
- MIBK MIBK (18.4), diisopropyl ether (16.8), dibutyl ether (17.9), diisopropyl ketone (17.9), DIBK (17.9), butyl butyrate (17.1), butyl acetate (18 .9), toluene (18.5), ethylcyclohexane (17.1), cyclooctane (18.8), isobutyl ethyl ether (15.3), N-methylpyrrolidone (NMP, 25.4), perfluoro Toluene (13.4)
- the dispersion medium preferably has a boiling point of 50°C or higher, more preferably 70°C or higher, at normal pressure (1 atm).
- the upper limit is preferably 250°C or lower, more preferably 220°C or lower.
- the content of the dispersion medium in the inorganic solid electrolyte-containing composition is not particularly limited and can be appropriately set. For example, it is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and particularly preferably 40 to 60% by mass in the inorganic solid electrolyte-containing composition.
- the content of the dispersion medium can be set to 50% by mass or less, 45% by mass or less, or even 40% by mass or less.
- the lower limit is not particularly limited, it can be, for example, 20% by mass.
- the inorganic solid electrolyte-containing composition of the present invention preferably contains an active material capable of inserting and releasing metal ions belonging to Group 1 or Group 2 of the periodic table.
- the active material include a positive electrode active material and a negative electrode active material, which will be described below.
- an inorganic solid electrolyte-containing composition containing an active material positive electrode active material or negative electrode active material
- an electrode composition positive electrode composition or negative electrode composition
- the positive electrode active material is an active material capable of inserting and releasing metal ions belonging to Group 1 or Group 2 of the periodic table, and preferably capable of reversibly inserting and releasing lithium ions.
- the material is not particularly limited as long as it has the above properties, and may be a transition metal oxide, an organic substance, an element such as sulfur that can be combined with Li, or the like. Among them, it is preferable to use a transition metal oxide as the positive electrode active material. objects are more preferred.
- the transition metal oxide may contain an element M b (an element of group 1 (Ia) of the periodic table of metals other than lithium, an element of group 2 (IIa) of the periodic table, Al, Ga, In, Ge, Sn, Pb, elements such as Sb, Bi, Si, P and B) may be mixed.
- the mixing amount is preferably 0 to 30 mol % with respect to the amount (100 mol %) of the transition metal element Ma . More preferred is one synthesized by mixing so that the Li/M a molar ratio is 0.3 to 2.2.
- transition metal oxide examples include (MA) a transition metal oxide having a layered rock salt structure, (MB) a transition metal oxide having a spinel structure, (MC) a lithium-containing transition metal phosphate compound, (MD ) lithium-containing transition metal halide phosphate compounds and (ME) lithium-containing transition metal silicate compounds.
- transition metal oxides having a layered rocksalt structure include LiCoO 2 (lithium cobaltate [LCO]), LiNi 2 O 2 (lithium nickelate), LiNi 0.85 Co 0.10 Al 0.85 . 05O2 ( lithium nickel cobalt aluminum oxide [NCA]), LiNi1 /3Co1/ 3Mn1 / 3O2 (lithium nickel manganese cobaltate [NMC]) and LiNi0.5Mn0.5O2 ( lithium manganese nickelate).
- LiCoO 2 lithium cobaltate [LCO]
- LiNi 2 O 2 lithium nickelate
- 05O2 lithium nickel cobalt aluminum oxide [NCA]
- LiNi1 /3Co1/ 3Mn1 / 3O2 lithium nickel manganese cobaltate [NMC]
- LiNi0.5Mn0.5O2 lithium manganese nickelate
- transition metal oxides having a spinel structure include LiMn 2 O 4 (LMO), LiCoMnO 4 , Li 2 FeMn 3 O 8 , Li 2 CuMn 3 O 8 , Li 2 CrMn 3 O 8 and Li 2NiMn3O8 .
- Examples of (MC) lithium-containing transition metal phosphate compounds include olivine-type iron phosphates such as LiFePO 4 and Li 3 Fe 2 (PO 4 ) 3 , iron pyrophosphates such as LiFeP 2 O 7 , and LiCoPO 4 . and monoclinic Nasicon-type vanadium phosphates such as Li 3 V 2 (PO 4 ) 3 (lithium vanadium phosphate).
- lithium-containing transition metal halogenated phosphate compounds include iron fluorophosphates such as Li 2 FePO 4 F, manganese fluorophosphates such as Li 2 MnPO 4 F, and Li 2 CoPO 4 F. and other cobalt fluoride phosphates.
- Lithium-containing transition metal silicate compounds include, for example, Li 2 FeSiO 4 , Li 2 MnSiO 4 , Li 2 CoSiO 4 and the like. In the present invention, transition metal oxides having a (MA) layered rocksalt structure are preferred, and LCO or NMC is more preferred.
- the shape of the positive electrode active material is not particularly limited, it is preferably particulate.
- the particle size (volume average particle size) of the positive electrode active material is not particularly limited. For example, it can be 0.1 to 50 ⁇ m.
- the particle size of the positive electrode active material particles can be measured in the same manner as the particle size of the inorganic solid electrolyte.
- a normal pulverizer or classifier is used to reduce the positive electrode active material to a predetermined particle size. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a whirling jet mill, a sieve, or the like is preferably used.
- wet pulverization can also be performed in which a dispersion medium such as water or methanol is allowed to coexist.
- a dispersion medium such as water or methanol is allowed to coexist.
- Classification is preferably carried out in order to obtain a desired particle size. Classification is not particularly limited, and can be performed using a sieve, an air classifier, or the like. Both dry and wet classification can be used.
- the positive electrode active material obtained by the calcination method may be washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent before use.
- the positive electrode active material may be used singly or in combination of two or more.
- the content of the positive electrode active material in the inorganic solid electrolyte-containing composition is not particularly limited, and is preferably 10 to 97% by mass, more preferably 30 to 95% by mass, and 40 to 93% by mass based on a solid content of 100% by mass. is more preferred, and 50 to 90% by mass is particularly preferred.
- the negative electrode active material is an active material capable of inserting and releasing metal ions belonging to Group 1 or Group 2 of the periodic table, and preferably capable of reversibly inserting and releasing lithium ions.
- the material is not particularly limited as long as it has the above properties, and carbonaceous materials, metal oxides, metal composite oxides, elemental lithium, lithium alloys, negative electrode active materials that can be alloyed with lithium (alloyable). substances and the like. Among them, carbonaceous materials, metal composite oxides, and lithium simple substance are preferably used from the viewpoint of reliability. An active material that can be alloyed with lithium is preferable from the viewpoint that the capacity of an all-solid secondary battery can be increased.
- a carbonaceous material used as a negative electrode active material is a material substantially composed of carbon.
- petroleum pitch carbon black such as acetylene black (AB), graphite (natural graphite, artificial graphite such as vapor-grown graphite, etc.), and various synthetics such as PAN (polyacrylonitrile)-based resin or furfuryl alcohol resin
- PAN polyacrylonitrile
- various carbon fibers such as PAN-based carbon fiber, cellulose-based carbon fiber, pitch-based carbon fiber, vapor growth carbon fiber, dehydrated PVA (polyvinyl alcohol)-based carbon fiber, lignin carbon fiber, vitreous carbon fiber and activated carbon fiber.
- carbonaceous materials can be classified into non-graphitizable carbonaceous materials (also referred to as hard carbon) and graphitic carbonaceous materials according to the degree of graphitization.
- the carbonaceous material preferably has the interplanar spacing or density and crystallite size described in JP-A-62-22066, JP-A-2-6856 and JP-A-3-45473.
- the carbonaceous material does not have to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-90844, graphite having a coating layer described in JP-A-6-4516, etc. can be used.
- hard carbon or graphite is preferably used, and graphite is more preferably used.
- the oxide of a metal or metalloid element that is applied as a negative electrode active material is not particularly limited as long as it is an oxide that can occlude and release lithium.
- examples include oxides, composite oxides of metal elements and metalloid elements (collectively referred to as metal composite oxides), and oxides of metalloid elements (metalloid oxides).
- metal composite oxides composite oxides of metal elements and metalloid elements
- metalloid elements metalloid elements
- amorphous oxides are preferred, and chalcogenides, which are reaction products of metal elements and Group 16 elements of the periodic table, are also preferred.
- the metalloid element refers to an element that exhibits intermediate properties between metal elements and non-metalloid elements, and usually includes the six elements boron, silicon, germanium, arsenic, antimony and tellurium, and further selenium.
- amorphous means one having a broad scattering band with an apex in the region of 20° to 40° in 2 ⁇ value in an X-ray diffraction method using CuK ⁇ rays, and a crystalline diffraction line. may have.
- the strongest intensity among the crystalline diffraction lines seen at 2 ⁇ values of 40° to 70° is 100 times or less than the diffraction line intensity at the top of the broad scattering band seen at 2 ⁇ values of 20° to 40°. is preferable, more preferably 5 times or less, and it is particularly preferable not to have a crystalline diffraction line.
- amorphous oxides of metalloid elements or chalcogenides are more preferable, and elements of groups 13 (IIIB) to 15 (VB) of the periodic table (for example, , Al, Ga, Si, Sn, Ge, Pb, Sb and Bi) are particularly preferable.
- elements of groups 13 (IIIB) to 15 (VB) of the periodic table for example, , Al, Ga, Si, Sn, Ge, Pb, Sb and Bi
- preferred amorphous oxides and chalcogenides include Ga 2 O 3 , GeO, PbO, PbO 2 , Pb 2 O 3 , Pb 2 O 4 , Pb 3 O 4 , Sb 2 O 3 and Sb 2 .
- Examples of negative electrode active materials that can be used together with amorphous oxides mainly composed of Sn, Si, and Ge include carbonaceous materials capable of absorbing and/or releasing lithium ions or lithium metal, elemental lithium, lithium alloys, and lithium. and a negative electrode active material that can be alloyed with.
- the oxides of metals or semimetals, especially metal (composite) oxides and chalcogenides preferably contain at least one of titanium and lithium as a constituent component.
- lithium-containing metal composite oxides include composite oxides of lithium oxide and the above metal (composite) oxides or chalcogenides, more specifically Li 2 SnO 2 . mentioned.
- the negative electrode active material such as a metal oxide, contain a titanium element (titanium oxide).
- Li 4 Ti 5 O 12 lithium titanate [LTO]
- LTO lithium titanate
- the lithium alloy as the negative electrode active material is not particularly limited as long as it is an alloy normally used as a negative electrode active material for secondary batteries. % added lithium aluminum alloy.
- the negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is commonly used as a negative electrode active material for secondary batteries. Such an active material expands and contracts greatly upon charging and discharging of an all-solid secondary battery, and accelerates deterioration of cycle characteristics. A decrease in characteristics can be suppressed.
- active materials include (negative electrode) active materials (alloys, etc.) containing silicon element or tin element, metals such as Al and In, and negative electrode active materials containing silicon element that enable higher battery capacity.
- (Silicon element-containing active material) is preferable, and a silicon element-containing active material having a silicon element content of 50 mol % or more of all constituent elements is more preferable.
- negative electrodes containing these negative electrode active materials are carbon negative electrodes (graphite, acetylene black, etc. ), more Li ions can be occluded. That is, the amount of Li ions stored per unit mass increases. Therefore, the battery capacity (energy density) can be increased. As a result, there is an advantage that the battery driving time can be lengthened.
- Silicon element-containing active materials include, for example, silicon materials such as Si and SiOx (0 ⁇ x ⁇ 1), and silicon-containing alloys containing titanium, vanadium, chromium, manganese, nickel, copper, lanthanum, etc.
- SiOx itself can be used as a negative electrode active material (semimetal oxide), and since Si is generated by the operation of the all-solid secondary battery, the negative electrode active material that can be alloyed with lithium (the can be used as a precursor substance).
- negative electrode active materials containing tin examples include Sn, SnO, SnO 2 , SnS, SnS 2 , active materials containing silicon and tin, and the like.
- composite oxides with lithium oxide, such as Li 2 SnO 2 can also be mentioned.
- the above-described negative electrode active material can be used without any particular limitation.
- the above silicon materials or silicon-containing alloys are more preferred, and silicon (Si) or silicon-containing alloys are even more preferred.
- the chemical formula of the compound obtained by the above firing method can be calculated by inductively coupled plasma (ICP) emission spectrometry as a measurement method and from the difference in mass of the powder before and after firing as a simple method.
- ICP inductively coupled plasma
- the shape of the negative electrode active material is not particularly limited, it is preferably particulate.
- the particle size of the negative electrode active material is not particularly limited, it is preferably 0.1 to 60 ⁇ m.
- the particle size of the negative electrode active material particles can be measured in the same manner as the particle size of the inorganic solid electrolyte. In order to obtain a predetermined particle size, an ordinary pulverizer or classifier is used as in the case of the positive electrode active material.
- the negative electrode active materials may be used singly or in combination of two or more.
- the content of the negative electrode active material in the inorganic solid electrolyte-containing composition is not particularly limited. It is more preferably 80% by mass, and even more preferably 40 to 75% by mass.
- the negative electrode active material layer when the negative electrode active material layer is formed by charging the secondary battery, instead of the negative electrode active material, a metal belonging to Group 1 or Group 2 of the periodic table generated in the all-solid secondary battery Ions can be used.
- a negative electrode active material layer can be formed by combining this ion with an electron and depositing it as a metal.
- the surfaces of the positive electrode active material and the negative electrode active material may be surface-coated with another metal oxide.
- surface coating agents include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si or Li.
- Specific examples include spinel titanate, tantalum-based oxides , niobium -based oxides, and lithium niobate -based compounds.
- Specific examples include Li4Ti5O12 , Li2Ti2O5 , and LiTaO3 .
- the surface of the electrode containing the positive electrode active material or the negative electrode active material may be surface-treated with sulfur or phosphorus.
- the surface of the particles of the positive electrode active material or the negative electrode active material may be surface-treated with actinic rays or an active gas (such as plasma) before and after the surface coating.
- the inorganic solid electrolyte-containing composition of the present invention preferably contains a conductive aid.
- the silicon atom-containing active material as the negative electrode active material is preferably used together with the conductive aid.
- the conductive aid there is no particular limitation on the conductive aid, and any commonly known conductive aid can be used.
- electronic conductive materials such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black and furnace black, amorphous carbon such as needle coke, vapor grown carbon fiber or carbon nanotube.
- carbonaceous materials such as graphene or fullerene, metal powders such as copper and nickel, metal fibers, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives.
- conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives.
- conductive aids those that can function as an active material in the active material layer during charging and discharging of the battery are classified as active materials rather than conductive aids. Whether or not it functions as an active material when the battery is charged and discharged is not univocally determined by the combination with the active material.
- the conductive aid may contain one type, or may contain two or more types.
- the shape of the conductive aid is not particularly limited, but is preferably particulate.
- the content of the conductive aid in the inorganic solid electrolyte-containing composition is preferably 0 to 10% by mass based on 100% by mass of solid content.
- the inorganic solid electrolyte-containing composition of the present invention also preferably contains a lithium salt (supporting electrolyte).
- a lithium salt that is usually used in this type of product is preferable, and there is no particular limitation.
- the content of the lithium salt is preferably 0.1 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of the solid electrolyte.
- the upper limit is preferably 50 parts by mass or less, more preferably 20 parts by mass or less.
- the inorganic solid electrolyte-containing composition of the present invention may contain no dispersant other than the polymer binder because the polymer binder also functions as a dispersant, but may contain a dispersant.
- the dispersing agent those commonly used in all-solid secondary batteries can be appropriately selected and used. Generally compounds intended for particle adsorption and steric and/or electrostatic repulsion are preferably used.
- an ionic liquid inorganic solid electrolyte-containing composition of the present invention, as other components other than the above components, an ionic liquid, a thickener, a cross-linking agent (such as those that undergo a cross-linking reaction by radical polymerization, condensation polymerization, or ring-opening polymerization). , a polymerization initiator (such as one that generates an acid or radical by heat or light), an antifoaming agent, a leveling agent, a dehydrating agent, an antioxidant, and the like.
- the ionic liquid is contained in order to further improve the ionic conductivity, and known liquids can be used without particular limitation.
- polymers other than the binder-forming polymer described above, and commonly used binders and the like may be contained.
- the inorganic solid electrolyte-containing composition of the present invention contains an inorganic solid electrolyte, the above-mentioned polymer binder, a dispersion medium, preferably a conductive aid, and optionally a lithium salt and any other component, for example, various commonly used By mixing with a mixer, it can be prepared as a mixture, preferably as a slurry. In the case of an electrode composition, an active material is further mixed.
- the mixing method is not particularly limited, and can be performed using known mixers such as ball mills, bead mills, planetary mixers, blade mixers, roll mills, kneaders, disk mills, rotation-revolution mixers, and narrow-gap dispersers. can. Each component may be mixed all at once, or may be mixed sequentially.
- the mixing environment is not particularly limited, but examples include dry air, inert gas, and the like.
- the mixing conditions are not particularly limited and can be set as appropriate.
- the mixing temperature can be 15 to 40°C.
- the rotation speed of the rotation/revolution mixer can be set to 200 to 3,000 rpm.
- the inorganic solid electrolyte-containing composition of the present invention has excellent redispersibility of solid particles and is resistant to oxidative deterioration.
- the conditions for redispersing the inorganic solid electrolyte-containing composition of the present invention after preparation are not particularly limited, and the mixing conditions described above can be appropriately employed.
- the sheet for an all-solid secondary battery of the present invention is a sheet-shaped molded article that can form a constituent layer of an all-solid secondary battery, and includes various aspects according to its use.
- a sheet preferably used for a solid electrolyte layer also referred to as a solid electrolyte sheet for an all-solid secondary battery
- an electrode or a sheet preferably used for a laminate of an electrode and a solid electrolyte layer (electrode for an all-solid secondary battery sheet).
- these various sheets are collectively referred to as a sheet for an all-solid secondary battery.
- each layer constituting the sheet for an all-solid secondary battery may have a single layer structure or a multilayer structure.
- the solid electrolyte layer or the active material layer on the substrate is formed from the inorganic solid electrolyte-containing composition of the present invention. Therefore, this all-solid secondary battery sheet can be used as a solid electrolyte layer of an all-solid secondary battery by appropriately peeling off the base material, or used as it is as an electrode (a laminate of a current collector and an active material layer). , low resistance (high conductivity) of an all-solid secondary battery, desirably excellent cycle characteristics can be realized.
- the solid electrolyte sheet for an all-solid secondary battery of the present invention may be a sheet having a solid electrolyte layer. It may be a sheet (a sheet from which the base material has been removed) formed from The solid electrolyte sheet for an all-solid secondary battery may have other layers in addition to the solid electrolyte layer. Other layers include, for example, a protective layer (release sheet), a current collector, a coat layer, and the like.
- a protective layer release sheet
- the solid electrolyte sheet for an all-solid secondary battery of the present invention for example, a sheet having, on a substrate, a layer composed of the composition containing the inorganic solid electrolyte of the present invention, a normal solid electrolyte layer, and a protective layer in this order. is mentioned.
- the solid electrolyte layer of the solid electrolyte sheet for an all-solid secondary battery is preferably formed from the inorganic solid electrolyte-containing composition of the present invention.
- the content of each component in the solid electrolyte layer is not particularly limited, but is preferably synonymous with the content of each component in the solid content of the inorganic solid electrolyte-containing composition of the present invention.
- the layer thickness of each layer constituting the solid electrolyte sheet for an all-solid secondary battery is the same as the layer thickness of each layer described in the all-solid secondary battery described later.
- the base material is not particularly limited as long as it can support the solid electrolyte layer, and examples thereof include sheet bodies (plate-shaped bodies) such as materials described later in the current collector, organic materials, inorganic materials, and the like.
- sheet bodies plate-shaped bodies
- organic materials include various polymers, and specific examples include polyethylene terephthalate, polypropylene, polyethylene, cellulose, and the like.
- inorganic materials include glass and ceramics.
- the electrode sheet for an all-solid secondary battery of the present invention may be an electrode sheet having an active material layer, and the active material layer is formed on a substrate (current collector). It may be a sheet that does not have a substrate and is formed from an active material layer (a sheet from which the substrate has been removed). This electrode sheet is usually a sheet having a current collector and an active material layer. A mode having a layer and an active material layer in this order is also included.
- the solid electrolyte layer and active material layer of the electrode sheet are preferably formed from the inorganic solid electrolyte-containing composition of the present invention.
- each component in the solid electrolyte layer or active material layer is not particularly limited, but is preferably the content of each component in the solid content of the inorganic solid electrolyte-containing composition (electrode composition) of the present invention. Synonymous.
- the layer thickness of each layer constituting the electrode sheet of the present invention is the same as the layer thickness of each layer described in the all-solid secondary battery described later.
- the electroded sheet may have other layers as described above.
- the sheet for an all-solid secondary battery of the present invention includes a low-resistance constituent layer to which solid particles containing an inorganic solid electrolyte are bound, and a constituent layer in which the polymer binder is resistant to oxidative deterioration.
- this constituent layer By using this constituent layer as a constituent layer of an all-solid secondary battery, it is possible to achieve low resistance (high conductivity) and preferably excellent cycle characteristics of the all-solid secondary battery.
- the sheet for an all-solid secondary battery of the present invention is industrially produced, for example, by roll-to-roll with high productivity, using the inorganic solid electrolyte-containing composition of the present invention, which has excellent dispersion characteristics even when the solid content concentration is increased. It can also be produced by the method.
- the method for producing the all-solid secondary battery sheet of the present invention is not particularly limited, and the sheet can be produced by forming each of the above layers using the inorganic solid electrolyte-containing composition of the present invention.
- a layer (coated and dried layer) composed of an inorganic solid electrolyte-containing composition (coated and dried) by forming a film (coating and drying) on a substrate or a current collector (may be via another layer).
- a layer coated and dried layer
- an all-solid secondary battery sheet having a base material or current collector and a coated dry layer can be produced.
- the adhesion between the current collector and the active material layer can be strengthened.
- the coated dry layer is a layer formed by applying the inorganic solid electrolyte-containing composition of the present invention and drying the dispersion medium (that is, using the inorganic solid electrolyte-containing composition of the present invention, Layer) composed of a composition obtained by removing the dispersion medium from the inorganic solid electrolyte-containing composition of the present invention.
- the dispersion medium may remain as long as it does not impair the effects of the present invention.
- the applied dry layer obtained as described above can also be pressurized. Pressurization conditions and the like will be described later in the method for manufacturing an all-solid secondary battery.
- a base material, a protective layer (especially a peeling sheet), etc. can also be peeled off.
- the all-solid secondary battery of the present invention includes a positive electrode active material layer, a negative electrode active material layer facing the positive electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. have.
- the all-solid secondary battery of the present invention is not particularly limited as long as it has a solid electrolyte layer between the positive electrode active material layer and the negative electrode active material layer. configuration can be adopted.
- the positive electrode active material layer is preferably formed on the positive electrode current collector and constitutes the positive electrode.
- the negative electrode active material layer is preferably formed on the negative electrode current collector to constitute the negative electrode.
- At least one layer of the negative electrode active material layer, the positive electrode active material layer and the solid electrolyte layer is formed of the inorganic solid electrolyte-containing composition of the present invention, and at least one of the negative electrode active material layer and the positive electrode active material layer is formed of the inorganic solid electrolyte-containing composition of the present invention. It is preferably formed of an inorganic solid electrolyte-containing composition.
- the all-solid secondary battery of the present invention in which at least one of the constituent layers is formed from the inorganic solid electrolyte-containing composition of the present invention, can be manufactured by an industrially advantageous roll-to-roll method, and It exhibits resistance (high conductivity) and desirably exhibits excellent cycling properties.
- the all-solid secondary battery of the present invention exhibits low resistance and high ionic conductivity, it is also possible to draw a large current.
- forming the constituent layers of the all-solid secondary battery with the inorganic solid electrolyte-containing composition of the present invention means that the all-solid secondary battery sheet of the present invention (however, the inorganic solid electrolyte-containing composition of the present invention If the sheet has a layer other than the formed layer, the sheet from which this layer is removed) is included.
- each constituent layer (including a current collector and the like) that constitutes the all-solid secondary battery may have a single-layer structure or a multi-layer structure.
- the active material layer or the solid electrolyte layer formed of the composition containing an inorganic solid electrolyte of the present invention preferably has a component type and a content thereof that are the same as those in the solid content of the composition containing an inorganic solid electrolyte of the present invention. are the same.
- the thicknesses of the negative electrode active material layer, the solid electrolyte layer, and the positive electrode active material layer are not particularly limited. The thickness of each layer is preferably 10 to 1,000 ⁇ m, more preferably 20 ⁇ m or more and less than 500 ⁇ m, considering the dimensions of a general all-solid secondary battery.
- the thickness of at least one of the positive electrode active material layer and the negative electrode active material layer is more preferably 50 ⁇ m or more and less than 500 ⁇ m.
- Each of the positive electrode active material layer and the negative electrode active material layer may have a current collector on the side opposite to the solid electrolyte layer.
- the positive electrode current collector and the negative electrode current collector are preferably electronic conductors. In the present invention, either one of the positive electrode current collector and the negative electrode current collector, or both of them may simply be referred to as the current collector.
- Examples of materials for forming the positive electrode current collector include aluminum, aluminum alloys, stainless steel, nickel and titanium, as well as materials obtained by treating the surface of aluminum or stainless steel with carbon, nickel, titanium or silver (thin films are formed). ) are preferred, and among them, aluminum and aluminum alloys are more preferred.
- Materials for forming the negative electrode current collector include aluminum, copper, copper alloys, stainless steel, nickel and titanium, and the surface of aluminum, copper, copper alloys or stainless steel is treated with carbon, nickel, titanium or silver. is preferred, and aluminum, copper, copper alloys and stainless steel are more preferred.
- a film sheet is usually used, but a net, a punched one, a lath, a porous body, a foam, a molded body of fibers, and the like can also be used.
- the thickness of the current collector is not particularly limited, it is preferably 1 to 500 ⁇ m. It is also preferable that the surface of the current collector is roughened by surface treatment.
- a functional layer or member is appropriately interposed or disposed between or outside each layer of the negative electrode current collector, the negative electrode active material layer, the solid electrolyte layer, the positive electrode active material layer, and the positive electrode current collector.
- the all-solid secondary battery of the present invention may be used as an all-solid secondary battery with the above structure.
- the housing may be made of metal or resin (plastic). When using a metallic one, for example, an aluminum alloy or a stainless steel one can be used. It is preferable that the metal casing be divided into a positive electrode side casing and a negative electrode side casing and electrically connected to the positive electrode current collector and the negative electrode current collector, respectively. It is preferable that the housing on the positive electrode side and the housing on the negative electrode side are joined and integrated via a gasket for short-circuit prevention.
- FIG. 1 is a cross-sectional view schematically showing an all-solid secondary battery (lithium ion secondary battery) according to a preferred embodiment of the present invention.
- the all-solid secondary battery 10 of the present embodiment has a negative electrode current collector 1, a negative electrode active material layer 2, a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode current collector 5 in this order when viewed from the negative electrode side. .
- Each layer is in contact with each other and has an adjacent structure. By adopting such a structure, during charging, electrons (e ⁇ ) are supplied to the negative electrode side, and lithium ions (Li + ) are accumulated there.
- a light bulb is used as a model for the operating portion 6, and is lit by discharge.
- an all-solid secondary battery having the layer configuration shown in FIG. A battery produced by inserting the secondary battery laminate 12 into a 2032-type coin case 11 is sometimes called a (coin-type) all-solid-state secondary battery 13 .
- the all-solid secondary battery 10 In the all-solid secondary battery 10, all of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are formed from the inorganic solid electrolyte-containing composition of the present invention. This all-solid secondary battery 10 exhibits excellent battery performance.
- the inorganic solid electrolyte and polymer binder contained in the positive electrode active material layer 4, the solid electrolyte layer 3, and the negative electrode active material layer 2 may be of the same type or different types. In the present invention, either one of the positive electrode active material layer and the negative electrode active material layer, or both of them may simply be referred to as an active material layer or an electrode active material layer. Moreover, either or both of the positive electrode active material and the negative electrode active material may be simply referred to as an active material or an electrode active material.
- the solid electrolyte layer comprises an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, a polymer binder, and any of the above components within a range that does not impair the effects of the present invention. and usually does not contain a positive electrode active material and/or a negative electrode active material.
- the positive electrode active material layer includes an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, a positive electrode active material, a polymer binder, and the above-described materials as long as the effects of the present invention are not impaired.
- the negative electrode active material layer includes an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, a negative electrode active material, a polymer binder, and the above-described It contains optional ingredients and the like.
- the negative electrode active material layer can be a lithium metal layer.
- the lithium metal layer include a layer formed by depositing or molding lithium metal powder, a lithium foil, a lithium deposition film, and the like.
- the thickness of the lithium metal layer can be, for example, 1 to 500 ⁇ m regardless of the thickness of the negative electrode active material layer.
- the composition layer is formed from the inorganic solid electrolyte-containing composition of the present invention, even if it is manufactured by an industrially advantageous roll-to-roll method, it is possible to achieve a low resistance all-solid secondary battery, preferably a further cycle. An all-solid secondary battery with excellent characteristics can be realized.
- the positive electrode current collector 5 and the negative electrode current collector 1 are respectively as described above.
- An all-solid secondary battery can be manufactured by a conventional method. Specifically, an all-solid secondary battery can be produced by forming each of the above layers using the inorganic solid electrolyte-containing composition of the present invention. Details will be described below.
- the all-solid secondary battery of the present invention is obtained by applying the inorganic solid electrolyte-containing composition of the present invention onto a suitable substrate (for example, a metal foil that serves as a current collector) to form a coating film (film formation). ) can be produced by performing a method (method for producing a sheet for an all-solid secondary battery of the present invention) including (via) the step.
- a suitable substrate for example, a metal foil that serves as a current collector
- an inorganic solid electrolyte-containing composition for forming a solid electrolyte layer is applied onto the positive electrode active material layer to form a solid electrolyte layer. Furthermore, an inorganic solid electrolyte-containing composition containing a negative electrode active material is applied as a negative electrode material (negative electrode composition) on the solid electrolyte layer to form a negative electrode active material layer.
- an all-solid secondary battery having a structure in which a solid electrolyte layer is sandwiched between a positive electrode active material layer and a negative electrode active material layer by stacking a negative electrode current collector (metal foil) on a negative electrode active material layer. can be done.
- a desired all-solid secondary battery can also be obtained by enclosing this in a housing.
- the negative electrode active material layer, the solid electrolyte layer and the positive electrode active material layer are formed on the negative electrode current collector as a base material, and the positive electrode current collector is stacked to form a solid two-layer structure. Subsequent batteries can also be manufactured.
- Another method is the following method. That is, a positive electrode sheet for an all-solid secondary battery is produced as described above. In addition, an inorganic solid electrolyte-containing composition containing a negative electrode active material is applied as a negative electrode material (negative electrode composition) on a metal foil that is a negative electrode current collector to form a negative electrode active material layer. A negative electrode sheet for the next battery is produced. Next, a solid electrolyte layer is formed on the active material layer of one of these sheets as described above. Furthermore, the other of the all-solid secondary battery positive electrode sheet and the all-solid secondary battery negative electrode sheet is laminated on the solid electrolyte layer so that the solid electrolyte layer and the active material layer are in contact with each other. Thus, an all-solid secondary battery can be manufactured.
- Another method is the following method. That is, as described above, a positive electrode sheet for an all-solid secondary battery and a negative electrode sheet for an all-solid secondary battery are produced. Separately from this, an inorganic solid electrolyte-containing composition is applied onto a substrate to prepare a solid electrolyte sheet for an all-solid secondary battery comprising a solid electrolyte layer. Further, the all-solid secondary battery positive electrode sheet and the all-solid secondary battery negative electrode sheet are laminated so as to sandwich the solid electrolyte layer peeled from the substrate. Thus, an all-solid secondary battery can be manufactured.
- a positive electrode sheet for an all-solid secondary battery, a negative electrode sheet for an all-solid secondary battery, and a solid electrolyte sheet for an all-solid secondary battery are produced as described above.
- the all-solid secondary battery positive electrode sheet or the all-solid secondary battery negative electrode sheet and the all-solid secondary battery solid electrolyte sheet were brought into contact with the positive electrode active material layer or the negative electrode active material layer and the solid electrolyte layer. Apply pressure to the state. In this way, the solid electrolyte layer is transferred to the all-solid secondary battery positive electrode sheet or all-solid secondary battery negative electrode sheet.
- the solid electrolyte layer obtained by peeling the base material of the solid electrolyte sheet for all-solid secondary batteries and the negative electrode sheet for all-solid secondary batteries or the positive electrode sheet for all-solid secondary batteries (the solid electrolyte layer and the negative electrode active material layer or (with the positive electrode active material layer in contact) and pressurized.
- an all-solid secondary battery can be manufactured.
- the pressurization method, pressurization conditions, and the like in this method are not particularly limited, and the method, pressurization conditions, and the like described in the pressurization step described later can be applied.
- the solid electrolyte layer or the like can be formed, for example, on a substrate or an active material layer by pressure-molding a composition containing an inorganic solid electrolyte or the like under pressure conditions described later, or by sheet-molding a solid electrolyte or an active material. You can also use your body.
- the inorganic solid electrolyte-containing composition of the present invention may be used for any one of the positive electrode composition, the inorganic solid electrolyte-containing composition, and the negative electrode composition.
- the inorganic solid electrolyte-containing composition of the present invention for at least one of the composition and the negative electrode composition, and the inorganic solid electrolyte-containing composition of the present invention can be used for either composition.
- examples of the material include commonly used compositions.
- the negative electrode active material layer without forming a negative electrode active material layer during the production of the all-solid secondary battery, it is accumulated in the negative electrode current collector during initialization or charging during use, which belongs to the first group or second group of the periodic table.
- the negative electrode active material layer can also be formed by combining metal ions with electrons and depositing the metal on the negative electrode current collector or the like.
- the method of applying the inorganic solid electrolyte-containing composition is not particularly limited and can be selected as appropriate. Examples thereof include coating (preferably wet coating), spray coating, spin coating, dip coating, slit coating, stripe coating, and bar coating. At this time, the inorganic solid electrolyte-containing composition may be dried after each application, or may be dried after being applied in multiple layers.
- the drying temperature is not particularly limited.
- the lower limit is preferably 30°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher.
- the upper limit is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.
- the dispersion medium By heating in such a temperature range, the dispersion medium can be removed and a solid state (coated dry layer) can be obtained.
- the temperature does not become too high and each member of the all-solid secondary battery is not damaged.
- the all-solid secondary battery can exhibit excellent overall performance, and can obtain good binding properties and good ionic conductivity.
- the inorganic solid electrolyte-containing composition After applying the inorganic solid electrolyte-containing composition, after laminating the constituent layers, or after producing the all-solid secondary battery, it is preferable to pressurize each layer or the all-solid secondary battery.
- a hydraulic cylinder press machine etc. are mentioned as a pressurization method.
- the applied pressure is not particularly limited, and is generally preferably in the range of 5 to 1500 MPa.
- the applied inorganic solid electrolyte-containing composition may be heated at the same time as being pressurized.
- the heating temperature is not particularly limited, and generally ranges from 30 to 300.degree. It is also possible to press at a temperature higher than the glass transition temperature of the inorganic solid electrolyte.
- pressing can also be performed at a temperature higher than the glass transition temperature of the polymer contained in the polymer binder. However, generally the temperature does not exceed the melting point of the polymer. Pressurization may be performed after drying the coating solvent or dispersion medium in advance, or may be performed while the solvent or dispersion medium remains. Each composition may be applied at the same time, or the application and drying presses may be performed simultaneously and/or sequentially. After coating on separate substrates, they may be laminated by transfer.
- the atmosphere in the film forming method is not particularly limited, and can be air, dry air (dew point ⁇ 20° C. or less), inert gas (for example, argon gas, in helium gas, in nitrogen gas, etc.).
- inert gas for example, argon gas, in helium gas, in nitrogen gas, etc.
- high pressure may be applied for a short period of time (for example, within several hours), or moderate pressure may be applied for a long period of time (one day or more).
- a restraining tool such as screw tightening pressure
- the all-solid secondary battery can be used in order to keep applying moderate pressure.
- the press pressure may be uniform or different with respect to the pressed portion such as the seat surface.
- the press pressure can be changed according to the area or film thickness of the portion to be pressed. Also, the same part can be changed step by step with different pressures.
- the pressing surface may be smooth or roughened.
- the inorganic solid electrolyte-containing composition of the present invention can maintain excellent dispersion characteristics even when the solid content concentration is increased. Therefore, the inorganic solid electrolyte-containing composition can be applied by setting the solid content to a high concentration.
- the formation (film formation) of each layer described above, particularly the application and drying of the inorganic solid electrolyte-containing composition of the present invention can be carried out in a so-called batch system using a sheet-shaped base material. It can also be carried out by a roll-to-roll method, which is highly productive among industrial production methods.
- the all-solid secondary battery manufactured as described above is preferably initialized after manufacturing or before use. Initialization is not particularly limited, and can be performed, for example, by performing initial charge/discharge while press pressure is increased, and then releasing the pressure to the general working pressure of all-solid secondary batteries.
- the all-solid secondary battery of the present invention can be applied to various uses. There are no particular restrictions on the mode of application, but for example, when installed in electronic equipment, notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, cordless phone slaves, pagers, handy terminals, mobile faxes, mobile phones, etc. Copiers, portable printers, headphone stereos, video movies, liquid crystal televisions, handy cleaners, portable CDs, minidiscs, electric shavers, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power sources, etc.
- Other consumer products include automobiles (electric vehicles, etc.), electric vehicles, motors, lighting equipment, toys, game devices, road conditioners, clocks, strobes, cameras, and medical devices (pacemakers, hearing aids, shoulder massagers, etc.). . Furthermore, it can be used for various military applications and space applications. It can also be combined with a solar cell.
- a monomer solution was prepared by dissolving uniformly. 500 g of toluene (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added to a 2 L three-necked flask, and the mixture was stirred at 80° C., and the above monomer solution was added dropwise over 2 hours. After completion of dropping, the mixture was stirred at 80°C for 2 hours, then heated to 90°C and stirred for 2 hours.
- toluene manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.
- butyl butyrate was added thereto, and methanol was distilled off under reduced pressure to obtain a butyl butyrate solution of macromonomer M-1.
- the solid content concentration was 49% by mass.
- the SP value of macromonomer M-1 was 16.5 MPa 1/2 . Then, using the macromonomer M-1, a polymer S-1 was synthesized as follows.
- Synthesis Examples S-2 to S-16 Synthesis of Polymers S-2 to S-16 and Preparation of Binder Solutions S-2 to S-16]
- Synthesis Example S-1 Synthesis Example S except that a compound that leads each component so that the polymers S-2 to S-16 have the compositions shown in Table 1 (types and contents of the components)
- Polymers S-2 to S-16 ((meth)acrylic graft polymer) were synthesized in the same manner as in Example-1 to obtain binder solutions S-2 to S-16 composed of the respective polymers.
- Polymers S-5A and S-5 ((meth)acrylic graft polymer) were used in Synthesis Example S-1 with a polymerization initiator amount of 1.5 g to 2.0 g (polymer S-5A) or 0.8 g ( Synthesized by adjusting the mass average molecular weight in the same manner as in Synthesis Example S-1, except that the polymer was changed to Polymer S-5).
- solutions S-5A and S-5 of binders composed of polymer S-5A or S-5 were obtained, respectively.
- Synthesis Examples S-17 to S-20 Synthesis of Polymers S-17 to S-20 and Preparation of Binder Solutions S-17 to S-20
- Synthesis Example S-1 X-22-174ASX (product number, manufactured by Shin-Etsu Silicone Co., Ltd., SP value: 12.8 MPa 1/2 ) was used as the macromonomer M-2 in place of the solution of the macromonomer M-1,
- Synthesis Example S-1 except that a compound that leads to each constituent component is used so that the polymers S-17 to S-20 have the composition (type and content of the constituent component) shown in Table 1.
- Polymers S-17 to S-20 ((meth)acrylic graft polymer) were synthesized to obtain binder solutions S-17 to S-20 composed of the respective polymers.
- Synthesis Examples T-1 to T-4 Synthesis of Polymers T-1 to T-4 and Preparation of Binder Solutions T-1 to T-4
- Synthesis Example S-1 Synthesis Example S except that a compound that leads to each constituent component is used so that the polymers T-1 to T-4 have the compositions shown in Table 1 (types and contents of constituent components) -In the same way as in -1, polymer T-1 ((meth)acrylic graft polymer), polymers T-2 to T-4 (linear (meth)acrylic polymers) are synthesized, and binders made of each polymer Solutions T-1 to T-4 were obtained respectively.
- Synthesis Examples T-5 and T-6 Synthesis of Polymers T-5 and T-6, and Preparation of Binder Dispersions T-5 and T-6
- Synthesis Example S-1 Synthesis Example S except that a compound that leads each component so that the polymers T-5 and T-6 have the compositions shown in Table 1 (types and contents of the components)
- Binder dispersions T-5 and T- in which polymers T-5 (linear (meth)acrylic polymer) and T-6 ((meth)acrylic graft polymer) are dispersed in butyl butyrate in the same manner as in -1 6 (solid content concentration 40% by mass) was obtained.
- the average particle sizes of the binders in dispersions T-5 and T-6 were 400 nm and 450 nm, respectively.
- Synthesis Example T-7 Synthesis of Polymer T-7 and Preparation of Binder Solution T-7
- polymer T-7 ((meth)acrylic graft polymer) was synthesized in the same manner as in Synthesis Example S-1, except that the amount of polymerization initiator was changed, and a binder made of this polymer. to obtain a solution T-7.
- Synthesis Example T-8 Synthesis of Polymer T-8 and Preparation of Binder Solution T-8
- Synthesis Example S-1 Same as Synthesis Example S-1, except that in Synthesis Example S-1, a compound that leads to each constituent component is used so that the polymer T-8 has the composition (type and content of constituent components) shown in Table 1. Then, a polymer T-8 ((meth)acrylic graft polymer) was synthesized to obtain a binder solution T-8 comprising this polymer.
- Table 1 shows the composition, mass average molecular weight and SP value of each synthesized polymer, and the degree of polymerization, number average molecular weight and SP value of the constituent component (X).
- the mass average molecular weight, number average molecular weight and SP value were measured by the methods described above.
- the state of the binder in each composition described later was measured by the method described above for the solubility in the dispersion medium. Judge and show.
- Table 1 when the polymer has two types of components corresponding to each component, it is written together using "/".
- Ph represents a phenyl group
- Me represents a methyl group
- R Y and R Z represent linking groups or substituents that do not contain the above functional groups.
- Li 2 S lithium sulfide
- P 2 S 5 diphosphorus pentasulfide
- Example 1 Each composition shown in Tables 2-1 to 2-4 (collectively referred to as Table 2) was prepared as follows. ⁇ Preparation of Inorganic Solid Electrolyte-Containing Composition> 60 g of zirconia beads with a diameter of 5 mm were put into a zirconia 45 mL container (manufactured by Fritsch), 7.88 g of LPS synthesized in Synthesis Example A above, and 0.8 g of the binder solution or dispersion shown in Table 2-1 or Table 2-4. 12 g (mass of solid content) and 12 g (total amount) of butyl butyrate as a dispersion medium were added. After that, this container was set in a planetary ball mill P-7 (trade name). The mixture was mixed for 10 minutes at a temperature of 25° C. and a rotation speed of 150 rpm to prepare inorganic solid electrolyte-containing compositions (slurries) K-1 to K-24 and Kc11 to Kc18, respectively.
- ⁇ Preparation of negative electrode composition 60 g of zirconia beads with a diameter of 5 mm were added to a zirconia 45 mL container (manufactured by Fritsch), 3.62 g of LPS synthesized in Synthesis Example A, and the binder solution or dispersion liquid shown in Table 2-3 or Table 2-4 was 0. .06 g (mass solids) and 12 g (total) of butyl butyrate were charged.
- This container was set in a planetary ball mill P-7 (trade name) and mixed at a temperature of 25° C. and a rotation speed of 300 rpm for 60 minutes.
- composition content is the content (% by mass) relative to the total mass of the composition
- solid content is the content (% by mass) relative to 100% by mass of the solid content of the composition. Omit units.
- ⁇ Evaluation 1 Storage stability test (redispersibility)> For each composition prepared as described above, LPS, a polymer binder, a dispersion medium, an active material and a conductive aid are added to each composition in the same proportions as the proportions of the composition content and solid content shown in Table 2.
- a composition (slurry) for evaluation of dispersibility was prepared by mixing under the same preparation conditions as in . For each of the prepared compositions, the generation (presence or absence) of aggregates of solid particles was confirmed using a grindometer (manufactured by Asahi Soken Co., Ltd.). The size of the aggregate at this time was defined as X ( ⁇ m) and used as an index of the initial dispersibility.
- each prepared composition was allowed to stand at 25°C for 24 hours, and then mixed again at a temperature of 25°C using a planetary ball mill P-7 (trade name).
- the number of revolutions and time for remixing were the same as those for preparing the inorganic solid electrolyte composition, the positive electrode composition, and the negative electrode composition.
- the remixed composition was checked for the occurrence (presence or absence) of solid particle agglomerates using the grindometer described above.
- the size of the aggregate at this time was defined as Y ( ⁇ m) and used as an index of redispersibility after storage.
- the size of the agglomerate was defined as the point at which conspicuous spots appeared in the material applied to the grindometer (see JIS K-5600-2-5 6.6).
- the storage stability of the solid electrolyte composition (redispersibility of solid particles) is determined by the ease with which aggregates are generated (aggregation or sedimentation). ) was evaluated. In this test, the smaller the size X of the aggregates, the better the initial dispersibility, and the smaller the size Y, the better the storage stability. In this test, the evaluation standard "D" or more for the size Y of the aggregate is a pass level, and if the size Y is 8 ⁇ m or less (the evaluation standard is "C" or more), the size X of the aggregate is also evaluated. included. Table 2 shows the results.
- LPS LPS synthesized in Synthesis Example A
- NMC LiNi1 /3Co1 / 3Mn1 / 3O2 Si: Silicon (APS 1 to 5 ⁇ m, manufactured by Alfa Aesar)
- AB Acetylene black
- VGCF Carbon nanofiber
- All-solid secondary battery No. 1 having the layer structure shown in FIG. 401 was made.
- All-solid secondary battery positive electrode sheet No. having the solid electrolyte layer obtained above. 201 (the aluminum foil of the solid electrolyte-containing sheet has been peeled off) was cut into a disk shape with a diameter of 14.5 mm, and as shown in FIG. I put it in the type coin case 11.
- a disc-shaped lithium foil with a diameter of 15 mm was placed on the solid electrolyte layer.
- the 2032 type coin case 11 is crimped to form the No. 2032 coin case shown in FIG. 401 all-solid secondary battery 13 was manufactured.
- the all-solid secondary battery manufactured in this manner has the layer structure shown in FIG. 1 (wherein the lithium foil corresponds to the negative electrode active material layer 2 and the negative electrode current collector 1).
- All-solid secondary battery No. 401 positive electrode sheet No. for an all-solid secondary battery having a solid electrolyte layer.
- All-solid secondary battery No. 1 except that the positive electrode sheet for an all-solid secondary battery having a solid electrolyte layer was used.
- 401, all-solid secondary battery No. 402-424 and c101-c108 were prepared respectively.
- All-solid secondary battery No. 1 having the layer structure shown in FIG. 501 was made.
- Negative electrode sheet No. for all-solid secondary battery provided with the solid electrolyte obtained above. 301 (the aluminum foil of the solid electrolyte-containing sheet has already been peeled off) was cut into a disk shape with a diameter of 14.5 mm, and as shown in FIG. I put it in the type coin case 11.
- a positive electrode sheet (positive electrode active material layer) punched out with a diameter of 14.0 mm from a positive electrode sheet for an all-solid secondary battery prepared as described below was placed on the solid electrolyte layer.
- a stainless steel foil (positive electrode current collector) is further stacked on it, and the all-solid secondary battery laminate 12 (stainless steel foil-aluminum foil-positive electrode active material layer-solid electrolyte layer-negative electrode active material layer-copper foil A laminate) was formed. After that, by crimping the 2032 type coin case 11, the all-solid secondary battery No. 2 shown in FIG. 501 was manufactured.
- All-solid-state secondary battery No. 1 was fabricated as follows.
- a positive electrode sheet for a solid secondary battery used for manufacturing No. 501 was prepared.
- - Preparation of positive electrode composition - 180 zirconia beads with a diameter of 5 mm were placed in a zirconia 45 mL container (manufactured by Fritsch), 2.7 g of LPS synthesized in Synthesis Example A above, KYNAR FLEX 2500-20 (trade name, PVdF-HFP: polyfluoride 0.3 g of a vinylidene hexafluoropropylene copolymer (manufactured by Arkema Co., Ltd.) in terms of solid content and 22 g of butyl butyrate were added.
- This container was set in a planetary ball mill P-7 (trade name) manufactured by Fritsch, and stirred at 25° C. and 300 rpm for 60 minutes. After that, 7.0 g of LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NMC) was added as a positive electrode active material, and similarly, the container was set in a planetary ball mill P-7 and heated at 25° C. Mixing was continued at 100 rpm for 5 minutes to prepare a positive electrode composition.
- - Production of positive electrode sheet for solid secondary battery The positive electrode composition obtained above was applied onto a 20 ⁇ m thick aluminum foil (positive electrode current collector) using a baker applicator (trade name: SA-201, manufactured by Tester Sangyo Co., Ltd.) and heated at 100° C.
- the positive electrode composition was dried (the dispersion medium was removed). Then, using a heat press, the dried positive electrode composition was pressurized at 25° C. (10 MPa, 1 minute) to prepare a positive electrode sheet for an all-solid secondary battery having a positive electrode active material layer with a thickness of 80 ⁇ m. .
- All-solid secondary battery No. 501 a negative electrode sheet for an all-solid secondary battery having a solid electrolyte layer, No. No. 301 shown in the "electrode active material layer (sheet No.)" column of Tables 4-2 and 4-3.
- All-solid secondary battery No. 1 except for using a negative electrode sheet for an all-solid secondary battery having a solid electrolyte layer represented by 501, all-solid secondary battery No. 502-524 and c201-c208 were prepared respectively.
- ⁇ Evaluation 3 Measurement of ionic conductivity> The ionic conductivity of each manufactured all-solid secondary battery was measured. Specifically, for each all-solid secondary battery, AC impedance was measured in a constant temperature bath at 25° C. using a 1255B FREQUENCY RESPONSE ANALYZER (trade name, manufactured by SOLARTRON) at a voltage amplitude of 5 mV and a frequency of 1 MHz to 1 Hz. From this, the resistance in the layer thickness direction of the sample for ion conductivity measurement was obtained, and the ion conductivity was obtained by calculation using the following formula (C1). The results are shown in Tables 4-1 to 4-3 (collectively referred to as Table 4).
- ionic conductivity ⁇ (mS/cm) 1000 x sample layer thickness (cm)/[resistance ( ⁇ ) x sample area (cm 2 )]
- the thickness of the sample layer is the value obtained by subtracting the thickness of the current collector (total thickness of the solid electrolyte layer and the electrode active material layer), which is measured before putting the laminate 12 into the 2032 type coin case 11. is.
- the sample area is the area of a disk-shaped sheet with a diameter of 14.5 mm. It was determined which of the following evaluation criteria the obtained ionic conductivity ⁇ was included in. The ionic conductivity ⁇ in this test passes the evaluation standard “D” or higher.
- the inorganic solid electrolyte-containing composition No. 1 of the comparative example containing a polymer binder formed of a graft polymer having an excessively large molecular weight even though it contained the constituent component (A).
- Kc18 is inferior in dispersibility and has insufficient ionic conductivity for an all-solid secondary battery.
- the electrode compositions shown in PKc21 to PKc28 and NKc21 to NKc28 also show the same tendency as the inorganic solid electrolyte-containing compositions Kc11 to Kc18.
- the inorganic solid electrolyte-containing composition No. 1 of the present invention containing the constituent component (A) and containing a polymer binder soluble in a dispersion medium formed of a graft polymer having a specific weight average molecular weight.
- K-1 to K-24 are excellent in dispersion characteristics.
- PK-1 to PK-24 and NK-1 to NK-24 also have excellent dispersing properties.
- the composition of the present invention can be used even if the solid content concentration is increased to, for example, 50% by mass or more.
- Stability Test Redispersibility
- ⁇ Evaluation 3 Measurement of Ionic Conductivity> were found to yield results similar to those of each composition having a solid content concentration of 40% by mass.
- the graft polymer contains the component (A), it is thought that the adsorption to the solid particles is promoted and the adhesion (binding force) of the solid particles can be strengthened, improving the cycle characteristics of the all-solid secondary battery. I know it works.
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Abstract
Description
例えば、アミド基等の窒素含有基を側鎖に含むグラフトポリマーで構成されたポリマーバインダーを含有する組成物が種々提案されている。例えば、特許文献1には、pKaが14以下である置換基X、ヘテロ原子を含むポリマー鎖を有する置換基及び特定の置換基Zの少なくともいずれかをもつ繰り返し単位を有する含窒素ポリマーと、周期律表第一族又は第二族に属する金属のイオンの伝導性を有する無機固体電解質とを含有する固体電解質組成物が記載されている。また、特許文献2及び3には、側鎖にアミド基を有する比較的高分子量(例えば、質量平均分子量34,500以上)のグラフトポリマーで構成されたポリマーバインダーを含有する組成物が記載されている。更に、特許文献4及び5には、側鎖にアミド基を有するグラフトポリマーで構成された粒子状のポリマーバインダーを含有する組成物が記載されている。
また、全固体二次電池の製造に用いる構成層形成材料には、電池性能(例えば、抵抗、サイクル特性)の向上等の観点から、固体粒子が分散媒中に高度に分散していることが求められる。しかも、近年、全固体二次電池の実用化に向けた開発が急速に進行しており、これに対応した対策も求められている。例えば、生産性の向上、製造コスト低減の観点から、固体粒子等の固形分濃度を高めた無機固体電解質含有組成物(スラリーの濃厚化)の実用が望まれている。しかし、固体粒子等の固形分濃度を高めると、優れた分散性を示す無機固体電解質含有組成物であっても経時により固体粒子がある程度の凝集若しくは沈殿することは避けられない。そのため、実用化に向けた構成層形成材料には、固形分濃度を高めても、経時により凝集若しくは沈殿した固体粒子を、調製直後(初期)の優れた分散状態に、再度分散させることができる特性(再分散特性)が求められる。
<1>周期律表第1族若しくは第2族に属する金属のイオンの伝導性を有する無機固体電解質と、ポリマーバインダーと、分散媒とを含有する無機固体電解質含有組成物であって、
ポリマーバインダーが、アミド基、イミド基、スルホンアミド基の少なくとも1種の官能基をポリマーの側鎖となる分子鎖中に含む構成成分(A)を有する、質量平均分子量が1,000~30,000であるグラフトポリマーを含み、かつ分散媒に溶解する、無機固体電解質含有組成物。
<2>構成成分(A)が分子鎖中にアミド基を含む、請求項1に記載の無機固体電解質含有組成物。
<5>グラフトポリマーが下記官能基群(a)のうち少なくとも1つの極性官能基を有する構成成分(B)を有する、<1>~<4>のいずれか1つに記載の無機固体電解質含有組成物。
<官能基群(a)>
スルホン酸基、リン酸基、ホスホン酸基、ヒドロキシ基、カルボキシ基、オキセタン基、エポキシ基、ジカルボン酸無水物基、チオール基、エーテル基、チオエーテル基、チオエステル基、フルオロアルキル基、及びこれらの塩
<6>構成成分(A)が、数平均分子量800以上の重合鎖及び下記官能基群(a)に含まれる官能基を有さない構成成分である、<1>~<5>のいずれか1つに記載の無機固体電解質含有組成物。
<官能基群(a)>
スルホン酸基、リン酸基、ホスホン酸基、ヒドロキシ基、カルボキシ基、オキセタン基、エポキシ基、ジカルボン酸無水物基、チオール基、エーテル基、チオエーテル基、チオエステル基、フルオロアルキル基、及びこれらの塩
<7>活物質を含有する、<1>~<6>のいずれか1つに記載の無機固体電解質含有組成物。
<8>導電助剤を含有する、<1>~<7>のいずれか1つに記載の無機固体電解質含有組成物。
<9>上記<1>~<8>のいずれか1つに記載の無機固体電解質含有組成物を用いて形成した層を有する全固体二次電池用シート。
<10>正極活物質層と固体電解質層と負極活物質層とをこの順で具備する全固体二次電池であって、
正極活物質層、固体電解質層及び負極活物質層の少なくとも1つの層が、<1>~<8>のいずれか1つに記載の無機固体電解質含有組成物を用いて形成した層である、全固体二次電池。
<11>上記<1>~<8>のいずれか1つに記載の無機固体電解質含有組成物を製膜する、全固体二次電池用シートの製造方法。
<12>上記<11>に記載の製造方法を経て全固体二次電池を製造する、全固体二次電池の製造方法。
本発明の上記及び他の特徴及び利点は、適宜添付の図面を参照して、下記の記載からより明らかになるであろう。
本発明において化合物の表示(例えば、化合物と末尾に付して呼ぶとき)については、この化合物そのもののほか、その塩、そのイオンを含む意味に用いる。また、本発明の効果を損なわない範囲で、置換基を導入するなど一部を変化させた誘導体を含む意味である。
本発明において、(メタ)アクリルとは、アクリル及びメタアクリルの一方又は両方を意味する。(メタ)アクリレートについても同様である。
本発明において、置換又は無置換を明記していない置換基、連結基等(以下、置換基等という。)については、その基に適宜の置換基を有していてもよい意味である。よって、本発明において、単に、YYY基と記載されている場合であっても、このYYY基は、置換基を有しない態様に加えて、更に置換基を有する態様も包含する。これは置換又は無置換を明記していない化合物についても同義である。好ましい置換基としては、例えば後述する置換基Zが挙げられる。
本発明において、特定の符号で示された置換基等が複数あるとき、又は複数の置換基等を同時若しくは択一的に規定するときには、それぞれの置換基等は互いに同一でも異なっていてもよいことを意味する。また、特に断らない場合であっても、複数の置換基等が隣接するときにはそれらが互いに連結したり縮環したりして環を形成していてもよい意味である。
本発明において、ポリマーは、重合体を意味するが、いわゆる高分子化合物と同義である。また、ポリマーバインダー(単にバインダーともいう。)は、ポリマーで構成されたバインダーを意味し、ポリマーそのもの、及びポリマーを含んで形成されたバインダーを包含する。
本発明の無機固体電解質含有組成物は、周期律表第1族若しくは第2族に属する金属のイオンの伝導性を有する無機固体電解質と、後述する特定のグラフトポリマーを含むポリマーバインダーと、分散媒とを含有する。
このポリマーバインダーは、無機固体電解質含有組成物に含有される分散媒に対して溶解する特性(可溶性)を有している。無機固体電解質含有組成物中でのポリマーバインダーは、その含有量にもよるが、通常、無機固体電解質含有組成物中において分散媒に溶解した状態で存在する。これにより、ポリマーバインダーが固体粒子を分散媒中に分散させる機能を安定的に発揮して、無機固体電解質含有組成物中における固体粒子の優れた(初期)分散性を維持できる。しかも、固体粒子が経時等により固体粒子が凝集若しくは沈殿しても、再度分散処理(混合処理)することにより、優れた初期分散性を再現できる。また、無機固体電解質含有組成物の製膜に際して、固体粒子同士の、ポリマーバインダーを介在しない直接的な接触を確保でき、界面抵抗の上昇を抑制できる。
溶解度の測定方法は下記の通りである。すなわち、測定対象とするポリマーバインダーをガラス瓶内に規定量秤量し、そこへ無機固体電解質含有組成物が含有する分散媒と同種の分散媒100gを添加し、25℃の温度下、ミックスローター上において80rpmの回転速度で24時間攪拌する。こうして得られた24時間攪拌後の混合液の透過率を以下条件により測定する。この試験(透過率測定)をバインダー溶解量(上記規定量)を変更して行い、透過率が99.8%となる上限濃度X(質量%)をポリマーバインダーの上記分散媒に対する溶解度とする。
<透過率測定条件>
動的光散乱(DLS)測定
装置:大塚電子製DLS測定装置 DLS-8000
レーザ波長、出力:488nm/100mW
サンプルセル:NMR管
また、ポリマーバインダーは、無機固体電解質含有組成物で形成した構成層中において、無機固体電解質(更には、共存しうる、活物質、導電助剤)等の固体粒子同士(例えば、無機固体電解質同士、無機固体電解質と活物質、活物質同士)を結着させる結着剤として、機能する。更に、集電体等の基材と固体粒子とを結着させる結着剤としても機能する。なお、無機固体電解質含有組成物中において、ポリマーバインダーは固体粒子同士を結着させる機能を有していてもいなくてもよい。
本発明においては、上述のように、無機固体電解質含有組成物中及び構成層中における、無機固体電解質、分散媒及びポリマーバインダーの相互作用(関連性)が改善され、無機固体電解質含有組成物の優れた分散特性と、構成層としたときの抵抗低減とを実現できる。それゆえに、低抵抗(高伝導度)の全固体二次電池を実現できる。
更に、構成層に含有されるポリマーバインダーは、分子構造中に窒素原子を有していると、酸素(原子若しくは分子)等により劣化(酸化)しやすく、劣化の進行により固体粒子の結着性及び界面接触状態を徐々に低下させて、サイクル特性の更なる低下を引き起こす傾向を示す。そのため、工業的製造、例えば生産性が高いロール・トゥ・ロール法においては、製造環境、保存環境等の酸素を完全に除去することは難しく、ポリマーバインダー、ひいては無機固体電解質含有組成物及び構成層は、酸化劣化しやすくなる。しかし、上記グラフトポリマーを含むバインダーは、窒素原子がアミド基等の官能基(結合)中に含まれているため、酸素等に対する酸化劣化耐性を示すと考えられる。その結果、このポリマーバインダー、無機固体電解質含有組成物、更に構成層は、酸化劣化しにくく、工業的製造法においても、酸化劣化によるサイクル特性の更なる低下を抑制可能な構成層を実現できる。
以下、本発明の無機固体電解質含有組成物が含有する成分及び含有しうる成分について説明する。
本発明の無機固体電解質含有組成物は、無機固体電解質を含有する。
本発明において、無機固体電解質とは、無機の固体電解質のことであり、固体電解質とは、その内部においてイオンを移動させることができる固体状の電解質のことである。主たるイオン伝導性材料として有機物を含むものではないことから、有機固体電解質(ポリエチレンオキシド(PEO)などに代表される高分子電解質、リチウムビス(トリフルオロメタンスルホニル)イミド(LiTFSI)などに代表される有機電解質塩)とは明確に区別される。また、無機固体電解質は定常状態では固体であるため、通常カチオン及びアニオンに解離又は遊離していない。この点で、電解液、又は、ポリマー中でカチオン及びアニオンに解離若しくは遊離している無機電解質塩(LiPF6、LiBF4、リチウムビス(フルオロスルホニル)イミド(LiFSI)、LiClなど)とも明確に区別される。無機固体電解質は周期律表第1族若しくは第2族に属する金属のイオンの伝導性を有するものであれば、特に限定されず、電子伝導性を有さないものが一般的である。本発明の全固体二次電池がリチウムイオン電池の場合、無機固体電解質は、リチウムイオンのイオン伝導性を有することが好ましい。
上記無機固体電解質は、全固体二次電池に通常使用される固体電解質材料を適宜選定して用いることができる。例えば、無機固体電解質としては、(i)硫化物系無機固体電解質、(ii)酸化物系無機固体電解質、(iii)ハロゲン化物系無機固体電解質、及び、(iv)水素化物系無機固体電解質が挙げられ、活物質と無機固体電解質との間により良好な界面を形成することができる観点から、硫化物系無機固体電解質が好ましい。
硫化物系無機固体電解質は、硫黄原子を含有し、かつ、周期律表第1族若しくは第2族に属する金属のイオン伝導性を有し、かつ、電子絶縁性を有するものが好ましい。硫化物系無機固体電解質は、元素として少なくともLi、S及びPを含有し、リチウムイオン伝導性を有しているものが好ましいが、適宜に、Li、S及びP以外の他の元素を含んでもよい。
La1Mb1Pc1Sd1Ae1 (S1)
式中、LはLi、Na及びKから選択される元素を示し、Liが好ましい。Mは、B、Zn、Sn、Si、Cu、Ga、Sb、Al及びGeから選択される元素を示す。Aは、I、Br、Cl及びFから選択される元素を示す。a1~e1は各元素の組成比を示し、a1:b1:c1:d1:e1は1~12:0~5:1:2~12:0~10を満たす。a1は1~9が好ましく、1.5~7.5がより好ましい。b1は0~3が好ましく、0~1がより好ましい。d1は2.5~10が好ましく、3.0~8.5がより好ましい。e1は0~5が好ましく、0~3がより好ましい。
硫化物系無機固体電解質は、例えば硫化リチウム(Li2S)、硫化リン(例えば五硫化二燐(P2S5))、単体燐、単体硫黄、硫化ナトリウム、硫化水素、ハロゲン化リチウム(例えばLiI、LiBr、LiCl)及び上記Mで表される元素の硫化物(例えばSiS2、SnS、GeS2)の中の少なくとも2つ以上の原料の反応により製造することができる。
酸化物系無機固体電解質は、酸素原子を含有し、かつ、周期律表第1族若しくは第2族に属する金属のイオン伝導性を有し、かつ、電子絶縁性を有するものが好ましい。
酸化物系無機固体電解質は、イオン伝導度として、1×10-6S/cm以上であることが好ましく、5×10-6S/cm以上であることがより好ましく、1×10-5S/cm以上であることが特に好ましい。上限は特に制限されないが、1×10-1S/cm以下であることが実際的である。
またLi、P及びOを含むリン化合物も望ましい。例えばリン酸リチウム(Li3PO4); リン酸リチウムの酸素元素の一部を窒素元素で置換したLiPON; LiPOD1(D1は、好ましくは、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zr、Nb、Mo、Ru、Ag、Ta、W、Pt及びAuから選ばれる1種以上の元素である。)等が挙げられる。
更に、LiA1ON(A1は、Si、B、Ge、Al、C及びGaから選ばれる1種以上の元素である。)等も好ましく用いることができる。
ハロゲン化物系無機固体電解質は、ハロゲン原子を含有し、かつ、周期律表第1族若しくは第2族に属する金属のイオンの伝導性を有し、かつ、電子絶縁性を有する化合物が好ましい。
ハロゲン化物系無機固体電解質としては、特に制限されないが、例えば、LiCl、LiBr、LiI、ADVANCED MATERIALS,2018,30,1803075に記載のLi3YBr6、Li3YCl6等の化合物が挙げられる。中でも、Li3YBr6、Li3YCl6が好ましい。
水素化物系無機固体電解質は、水素原子を含有し、かつ、周期律表第1族若しくは第2族に属する金属のイオン伝導性を有し、かつ、電子絶縁性を有する化合物が好ましい。
水素化物系無機固体電解質としては、特に制限されないが、例えば、LiBH4、Li4(BH4)3I、3LiBH4-LiCl等が挙げられる。
無機固体電解質の粒子径の測定は、以下の手順で行う。無機固体電解質粒子を、水(水に不安定な物質の場合はヘプタン)を用いて20mLサンプル瓶中で1質量%の分散液を希釈調製する。希釈後の分散液試料は、1kHzの超音波を10分間照射し、その直後に試験に使用する。この分散液試料を用い、レーザ回折/散乱式粒度分布測定装置LA-920(商品名、HORIBA社製)を用いて、温度25℃で測定用石英セルを使用してデータ取り込みを50回行い、体積平均粒子径を得る。その他の詳細な条件等は必要により日本産業規格(JIS) Z 8828:2013「粒子径解析-動的光散乱法」の記載を参照する。1水準につき5つの試料を作製しその平均値を採用する。
無機固体電解質の、無機固体電解質含有組成物中の含有量は、特に制限されないが、結着性の点、更には分散性の点で、固形分100質量%において、50質量%以上であることが好ましく、70質量%以上であることがより好ましく、90質量%以上であることが特に好ましい。上限としては、同様の観点から、99.9質量%以下であることが好ましく、99.5質量%以下であることがより好ましく、99質量%以下であることが特に好ましい。
ただし、無機固体電解質含有組成物が後述する活物質を含有する場合、無機固体電解質含有組成物中の無機固体電解質の含有量は、活物質と無機固体電解質との合計含有量が上記範囲であることが好ましい。
本発明において、固形分(固形成分)とは、無機固体電解質含有組成物を、1mmHgの気圧下、窒素雰囲気下150℃で6時間乾燥処理したときに、揮発若しくは蒸発して消失しない成分をいう。典型的には、後述の分散媒以外の成分を指す。
本発明の無機固体電解質含有組成物が含有するポリマーバインダーは、後述する構成成分(A)を有し、特定の分子量のグラフトポリマーを含んで形成され、無機固体電解質含有組成物に含有されている分散媒に溶解するポリマーバインダーを1種又は2種以上含んでいる。このポリマーバインダーを無機固体電解質及び分散媒と併用することにより、固形分濃度を高めても無機固体電解質含有組成物に優れた分散特性を発現させ、かつ構成層としたときに固体粒子の結着力を維持しながら界面抵抗の上昇を低減することができる。
バインダー形成ポリマーとしてのグラフトポリマーは、構成成分(A)を有し、特定の分子量を有するポリマーである。
バインダー形成ポリマーについて、まず、グラフトポリマーが有する構成成分について、説明する。
グラフトポリマーは、アミド基、イミド基、スルホンアミド基の少なくとも1種の官能基をポリマーの側鎖となる分子鎖中に含む構成成分(A)を有している。この構成成分(A)は、上記官能基をポリマーの側鎖となる分子鎖中に少なくとも1種有し、後述する、構成成分(B)が有する極性官能基及び構成成分(X)が有する重合鎖を有さない構成成分である。グラフトポリマーが構成成分(A)を有することにより、固体粒子、特に活物質への吸着が促進され、また優れた点状析出性を発現して、分散特性の改善及び抵抗上昇の抑制を可能とする。
この構成成分(A)は、例えば、重縮合性基と上記官能基とを有する重縮合性化合物に由来する構成成分が挙げられる。重縮合性基としては、バインダー形成ポリマーの主鎖構造に応じて適宜に決定され、例えば、後述する逐次重合ポリマーである場合、縮合性官能基が選択され、連鎖重合ポリマーである場合、重合性基(エチレン性不飽和基)が選択される。
本発明において、ポリマーの側鎖となる分子鎖とは、構成成分(A)が組み込まれたグラフトポリマーについて、その側鎖を構成する分子鎖をいい、グラフトポリマーの主鎖を構成する分子鎖以外の分子鎖、通常、主鎖を構成する分子鎖(原子群)に結合している分子鎖となる。例えば、構成成分(A)を導く重縮合性化合物がアクリルアミドである場合、重合性基であるエチレン性二重結合に結合する分子鎖(-CONH2)をいう。
本発明において、ポリマー(重合鎖を含む。)の主鎖とは、ポリマーを構成する、それ以外のすべての分子鎖が、主鎖に対して枝分れ鎖若しくはペンダント基とみなしうる線状分子鎖をいう。枝分れ鎖若しくはペンダント基とみなす分岐鎖の質量平均分子量にもよるが、典型的には、ポリマーを構成する分子鎖のうち最長鎖が主鎖となる。ただし、ポリマー末端が有する末端基は主鎖に含まない。これに対して、ポリマーの側鎖とは、主鎖以外の分岐鎖をいい、短鎖及び長鎖(グラフト鎖)を含む。ポリマーの末端基は、特に制限されず、重合方法等により適宜の基をとりうる。例えば、水素原子、アルキル基、アリール基、ヒドロキシ基、更には重合開始剤等の残基が挙げられる。
各官能基におけるRNAは、水素原子又は置換基を示す。RNAとして採りうる置換基としては、特に制限されず、例えば後述する置換基Zが挙げられる。中でも、アルキル基(シクロアルキル基を含む。)、アリール基、ヘテロ環基、更にはアルコキシ基が好ましく、アルキル基又はアリール基が好ましい。アルキル基の炭素数としては、1~20であることが好ましく、1~12であることがより好ましく、1~6であることが更に好ましい。アリール基の炭素数としては、6~26であることが好ましく、6~20であることがより好ましく、6~12であることが更に好ましい。スルホンアミド基中のNRNAは置換基が好ましい。
本発明において、アミド基は、イミド基中にも含まれるが、この基に含まれるアミド結合をアミド基と解釈しない。
上記官能基は、2つの結合部*及び**のうちいずれの結合部がポリマーの主鎖となる分子鎖側に結合していてもよいが、結合部*がポリマーの主鎖となる分子鎖側に結合していることが好ましい。
構成成分(A)が複数種の官能基を有する場合、その組み合わせは、特に制限されず、適宜に決定することができる。例えば、アミド基とスルホンアミド基との組み合わせが好ましい。複数種の官能基の組み合わせにおいて、官能基の間には後述する連結基を有することが好ましい。
官能基に結合する末端基は、特に制限されず、水素原子又は置換基を示す。末端基として採りうる置換基としては、特に制限されず、例えば後述する置換基Zが挙げられる。中でも、アルキル基(シクロアルキル基を含む。)、アリール基、ヘテロ環基、更にはアルコキシ基が好ましく、アルキル基又はアリール基がより好ましい。アルキル基の炭素数としては、1~20であることが好ましく、2~12であることがより好ましく、3~8であることが更に好ましい。アリール基の炭素数としては、RNAとして採りうるアリール基の炭素数と同じである。
本発明において、上記RNAと末端基とのいずれか一方が水素原子を採る場合、この水素原子を上記RNAとして解釈する。
連結基としては、特に限定されないが、例えば、アルキレン基(炭素数は1~12が好ましく、1~6がより好ましく、1~3が更に好ましい)、アルケニレン基(炭素数は2~6が好ましく、2~3がより好ましい)、アリーレン基(炭素数は6~24が好ましく、6~10がより好ましい)、酸素原子、硫黄原子、イミノ基(-NRN-:RNは水素原子、炭素数1~6のアルキル基若しくは炭素数6~10のアリール基を示す。)、カルボニル基、リン酸連結基(-O-P(OH)(O)-O-)、ホスホン酸連結基(-P(OH)(O)-O-)、又はこれらの組み合わせに係る基等が挙げられる。連結基としては、アルキレン基、アリーレン基、カルボニル基、酸素原子、硫黄原子若しくはイミノ基、又はこれらの組み合わせに係る基が好ましく、アルキレン基、アリーレン基、カルボニル基、酸素原子、硫黄原子若しくはイミノ基、又はこれらの組み合わせに係る基がより好ましい。例えば、-CO-O-基を含む基が挙げられ、-CO-O-アルキレン基が好ましい。この連結基は、上記官能基以外のものが好ましい態様の1つである。
上記連結基を構成する原子の数は、1~36であることが好ましく、1~24であることがより好ましく、1~12であることが更に好ましい。連結基の連結原子数は12以下であることが好ましく、10以下であることがより好ましく、8以下であることが特に好ましい。下限としては、1以上である。上記連結原子数とは所定の構造部間を結ぶ最少の原子数をいう。例えば、-CO-O-CH2-CH2-基の場合、連結基を構成する原子の数は9となるが、連結原子数は4となる。
Y1及びY2がともにアルキル基の場合、Y1及びY2として採りうるアルキル基としては、上記RNAとして採りうるアルキル基と同義である態様が好ましく、例えば、メチル、エチル、ノルマルプロピル、イソプロピル、ノルマルブチル、ターシャリーブチル、直鎖若しくは分岐鎖のオクチル基、直鎖若しくは分岐鎖のドデシル基等が挙げられる。Y1及びY2として採りうるアルキル基同士の組み合わせは、特に制限されず、上記で挙げたアルキル基同士を適宜に組み合わせることができる。
本発明においては、官能基に結合する末端基、Y1及びY2は、置換基を有していてもよいが、有していないことが好ましく、無置換のアルキル基(特に、無置換の直鎖若しくは分岐鎖のアルキル基)であることがより好ましい。
バインダー形成ポリマーは、その化学構造中にグラフト構造を組み込む構成成分を有していることが好ましく、例えば重合鎖を有する構成成分(X)が挙げられる。本発明において、ある構成成分が重合鎖と上記構成成分(A)で規定する官能基及び後述する構成成分(B)で規定する極性官能基の一方又は両方を有する場合、この構成成分は構成成分(X)とする。この構成成分(X)は、重合鎖以外の部分構造中に上記構成成分(A)における官能基及び後述する極性官能基を有さない構成成分であることが好ましい。バインダー形成ポリマーが構成成分(X)を有することにより、バインダー形成ポリマーがグラフト構造を有するポリマーとなって、ポリマーバインダー同士の排除体積効果を高めることができ、分散特性を改善できる。
この構成成分(X)は、例えば、重縮合性基と重合鎖とを有する重縮合性化合物に由来する構成成分が挙げられる。重縮合性基としては、バインダー形成ポリマーの主鎖構造に応じて適宜に決定され、上記構成成分(A)が有する重縮合性基と同義である。
重合鎖は、1種又は2種以上の繰り返し単位が2つ以上結合した分子鎖であり、グラフトポリマーのグラフト鎖となる。このような重合鎖としては、特に制限されず、通常のポリマー、例えば後述する逐次重合ポリマー又は連鎖重合ポリマーからなる鎖を特に限定されることなく適用できる。本発明においては、下記式(LP)で表される繰り返し単位を有する重合鎖(例えば、ポリエステルからなる重合鎖、ポリシロキサンからなる重合鎖、(メタ)アクリルポリマーからなる重合鎖が好ましく、ポリエステルからなる重合鎖又はポリシロキサンからなる重合鎖がより好ましい。
Xとして採りうる置換基は、特に制限されず、後述する置換基Zから適宜に選択された基から水素原子を更に1つ除去した基が挙げられ、好ましくは、分散特性の点で、後述するRX4として採りうる各基が挙げられる。Xは置換基を有していてもよく、特に式(LP)で表される繰り返し単位を有する重合鎖が連鎖重合ポリマーからなる鎖である場合、後述する式(X2)における-LX4-RX9で表される基を有していることが好ましい。
Lは、重合鎖の種類に応じて選択され、例えば、連鎖重合ポリマーからなる鎖である場合、単結合をとり、逐次重合ポリマーからなる鎖である場合、連結基をとる。Lとして採りうる連結基は、別の繰り返し単位と結合しうる基であれば特に制限されず、重合鎖の種類に応じて適宜に選択される。この連結基は、通常、ヘテロ原子を有する連結基であり、例えば、エステル結合(-CO-O-)、エーテル結合(-O-)、カーボネート結合(-O-CO-)、アミド結合(-CO-N(RN)-)、ウレタン結合(-N(RN)-CO-)、ウレア結合(-N(RN)-CO-N(RN)-)、イミド結合(-CO-N(RN)-CO-)が挙げられる。上記各結合において、RNは水素原子、炭素数1~6のアルキル基若しくは炭素数6~10のアリール基を示す。なお、上記連結基はいずれの結合部分が上記Xと結合してもよい。連結基としては、エステル結合、エーテル結合、カーボネート結合等がより好ましい。
nは、(平均)重合度を示し、2以上であればよく、後述する重合鎖の数平均分子量を考慮して適宜に決定される。例えば、重合度nとしては、3~500が好ましく、4~300がより好ましく、4~100が更に好ましい。なお、各数値範囲における上限として、50、40又は15とすることもできる。
重合鎖において、2以上有する繰り返し単位は、同一でも異なっていてもよい。2以上の繰り返し単位が異なる場合、結合様式は特に制限されず、ランダムでも交互でもブロックでもよい。
(メタ)アクリルポリマーからなる重合鎖としては、後述する(メタ)アクリル化合物(M1)に由来する構成成分、後述するビニル化合物(M2)に由来する構成成分を有することが好ましい。中でも、1種若しくは2種以上の(メタ)アクリル酸エステル化合物に由来する構成成分を有する重合鎖がより好ましく、(メタ)アクリル酸アルキルエステル化合物に由来する構成成分を有する重合鎖が更に好ましい。(メタ)アクリル酸アルキルエステル化合物は、炭素数4以上(好ましくは炭素数6以上)の長鎖アルキル基のエステル化合物を含むことが好ましく、更に炭素数3以下の短鎖アルキル基のエステル化合物を含むこともできる。重合鎖中における各構成成分の含有量は、特に制限されず、適宜に設定される。例えば、重合鎖中における(メタ)アクリル化合物(M1)に由来する構成成分の含有量は、例えば、30~100質量%であることが好ましく、50~80質量%とすることもできる。(メタ)アクリル酸アルキルエステル化合物に由来する構成成分の含有量は、50~100質量%であることが好ましく、60~80質量%とすることもできる。また、(メタ)アクリル酸長鎖アルキルエステル化合物に由来する構成成分と(メタ)アクリル酸短鎖アルキルルエステル化合物に由来する構成成分とを含む場合、(メタ)アクリル酸長鎖アルキルエステル化合物に由来する構成成分の含有量は、20~100質量%であることが好ましく、50~100質量%であることがより好ましく、(メタ)アクリル酸短鎖アルキルルエステル化合物に由来する構成成分の含有量は、5~80質量%であることが好ましく、5~40質量%であることがより好ましい。
このような連結基としては、特に限定されないが、例えば、アルキレン基(炭素数は1~12が好ましく、1~6がより好ましく、1~3が更に好ましい)、アルケニレン基(炭素数は2~6が好ましく、2~3がより好ましい)、アリーレン基(炭素数は6~24が好ましく、6~10がより好ましい)、酸素原子、硫黄原子、イミノ基(-NRN-:RNは水素原子、炭素数1~6のアルキル基若しくは炭素数6~10のアリール基を示す。)、カルボニル基、リン酸連結基(-O-P(OH)(O)-O-)、ホスホン酸連結基(-P(OH)(O)-O-)、又はこれらの組み合わせに係る基等が挙げられる。ただし、連結基は、上記構成成分(A)で規定する各官能基ではないものが好ましい。
連結基としては、アルキレン基、アリーレン基、カルボニル基、酸素原子、硫黄原子及びイミノ基を組み合わせてなる基が好ましく、アルキレン基、アリーレン基、カルボニル基、酸素原子、硫黄原子及びイミノ基を組み合わせてなる基がより好ましい。連結基としては、上記重合鎖の合成に用いる連鎖移動剤(例えば3-メルカプトプロピオン酸)、重合開始剤等に由来する構造部を含む連結基、更には、この構造部と、上記連鎖移動剤と反応する(メタ)アクリル化合物(M1)に由来する構造部とが結合した連結基も好ましく挙げられる。連結基の具体例としては、実施例で合成したポリマーが含む構成成分(X)中の連結基が挙げられる。
上記連結基を構成する原子の数は、1~36であることが好ましく、1~24であることがより好ましく、1~12であることが更に好ましい。連結基の連結原子数は12以下であることが好ましく、10以下であることがより好ましく、8以下であることが特に好ましい。下限としては、1以上である。例えば、-O-C(=O)-CH2-CH2-S-の場合、連結基を構成する原子の数は10となるが、連結原子数は5となる。
RX4として採りうる炭化水素基は、特に制限されず、アルキレン基、アルケニル基、アリーレン基等が挙げられ、アルキレン基が好ましい。RX4として採りうるアルキレン基等は後述する置換基Zの対応する各基から水素原子を更に1つ除去した基が挙げられる。ただし、アルキレン基の炭素数は、1~8であることがより好ましい。-(RX4-LX2)-がアルキレンオキシ基である場合、アルキレン基の炭素数は1~6であることが更に好ましい。
RX4として採りうるアルキルシリレン基は、特に制限されず、上述の、-(SiR2-O)n-で表される構造を有する重合鎖における-SiR2-基が好ましく挙げられる。
RX5は、置換基を示し、上記式(LP)で表される繰り返し単位を有する重合鎖の末端に結合する基と同義である。RX5として採りうる置換基は、更に置換基を有していてもよいが、無置換であることが好ましい。
nXは、平均重合度を示し、2以上の数であり、上記式(LP)で表される繰り返し単位を有する重合鎖の平均重合度nと同義である。
上記式(X1)で表される構成成分は、1つの成分中に、繰り返し単位-(RX4-LX2)-を1種有していてもよく、2種以上有していてもよい。
バインダー形成ポリマーが式(X1)で表される構成成分を複数有する場合、式(X1)で表される構成成分は同一でも異なっていてもよい。
LX4は単結合又は連結基を示す。LX4として採りうる連結基としては、上記重縮合性基と上記重合鎖とを連結する上述の連結基を特に制限されることなく適用できる。ただし、LX4として採りうる連結基は、-CO-O-基を含む基又は-CO-NRN-基(RNは上記の通り。)を含む基が更に好ましく、-CO-O-基又は-CO-NRN-基が特に好ましい。また、連結基を構成する原子の数及び連結原子数は上述の通りであるが、LX4を構成する原子の数は1~6であることが特に好ましく、連結原子数は1~3であることが更に好ましい。
RX9は水素原子又は置換基を示し、置換基であることが好ましい。RX9として採りうる置換基としては、特に制限されず、後述する置換基Zから選択される基を挙げることができる。中でも、アルキル基又はアリール基が好ましく、炭素数4以上の長鎖アルキル基がより好ましい。RX9として採りうる置換基は、更に置換基(例えばハロゲン原子)を有していてもよいが、無置換であることが好ましい。
上記式(X2)で表される構成成分は、1つの成分中に、繰り返し単位を1種有していてもよく、2種以上有していてもよい。
バインダー形成ポリマーが式(X2)で表される構成成分を複数有する場合、式(X2)で表される構成成分は同一でも異なっていてもよい。
構成成分(X)としては、繰り返し単位の重合度が2以上であればよく、後述する測定方法における数平均分子量が800以上の重合鎖を有するマクロモノマーに由来する構成成分である。マクロモノマーの重合鎖の数平均分子量は、グラフトポリマーの分子量、構成成分(X)等の含有量等を考慮して適宜に決定され、例えば、分散特性の点で、900~25,000が好ましく、2,000~20,000がより好ましく、2,000~15,000とすることもできる。重合鎖の数平均分子量の上限は、5,000とすることもできる。
また、構成成分(X)は窒素原子を含んでいてもよく、例えば、重合鎖を形成する構成成分として窒素原子を含んでいてもよい。
バインダー形成ポリマーは、下記官能基群(a)のうち少なくとも1つ(1種)の極性官能基を有することが好ましく、例えば極性官能基を有する構成成分(B)を有することがより好ましい。本発明において、構成成分が下記極性官能基と上記構成成分(A)で規定する官能基を有している場合、この構成成分は構成成分(B)とする。この構成成分(B)は、上記構成成分(A)で規定する官能基、及び構成成分(X)で規定する重合鎖を有さない構成成分であることが好ましい。バインダー形成ポリマーが構成成分(B)を有することにより、構成成分(X)の官能基によるグラフトポリマーと固体粒子との吸着性若しくは密着性を強化できる。
構成成分(B)は、極性官能基を少なくとも1つ(1種)有していればよく、通常、1~3種の極性官能基を有していることが好ましい。グラフトポリマーが有する極性官能基の数は、特に制限されず、構成成分(B)自体が有する極性官能基数、構成成分(B)の含有量、グラフトポリマーの分子量等に応じて、適宜に決定される。
この構成成分(B)は、極性官能基を有していればよく、例えば、下記官能基群(a)のうち少なくとも1つ(1種)の極性官能基を有する重縮合性化合物に由来する構成成分が挙げられる。重縮合性化合物は、例えば、重縮合性基と、極性官能基又は極性官能基を有する置換基と、適宜に重縮合性基及び置換基を連結する連結基とを有する化合物であることが好ましい。重縮合性基としては、上記構成成分(A)における重縮合性基と同義である。置換基としては、特に制限されないが、例えば、後述する置換基Zから選択される基が挙げられ、アルキル基が好ましい。連結基としては、上記重縮合性基と上記重合鎖とを連結する上述の連結基を特に制限されることなく適用できる。ただし、-CO-O-基が特に好ましい。
スルホン酸基(スルホ基)、リン酸基、ホスホン酸基、カルボキシ基、ヒドロキシ基、オキセタン基、エポキシ基、ジカルボン酸無水物基、チオール基(スルファニル基)、エーテル基、チオエーテル基、チオエステル基、フルオロアルキル基、及びこれらの塩
ジカルボン酸無水物基としては、特に制限されないが、ジカルボン酸無水物から1つ以上の水素原子を除去してなる基、更には重合性ジカルボン酸無水物が共重合してなる構成成分自体を包含する。ジカルボン酸無水物から1つ以上の水素原子を除去してなる基としては、環状ジカルボン酸無水物から1つ以上の水素原子を除去してなる基が好ましい。例えば、無水酢酸、無水プロピオン酸、無水安息香酸等の非環状ジカルボン酸無水物、無水マレイン酸、無水フタル酸、無水フマル酸、無水コハク酸、無水イタコン酸等の環状ジカルボン酸無水物等が挙げられる。重合性ジカルボン酸無水物としては、特に制限されないが、分子内に不飽和結合を有するジカルボン酸無水物が挙げられ、好ましくは重合性環状ジカルボン酸無水物である。具体的には、無水マレイン酸、無水イタコン酸等が挙げられる。
フルオロアルキル基は、アルキル基若しくはシクロアルキル基の少なくとも1つの水素原子をフッ素原子で置換した基であり、その炭素数は、1~20が好ましく、2~15がより好ましく、3~10が更に好ましい。炭素原子上のフッ素原子数は水素原子の一部を置き換えたものでもよく、すべて置き換えたもの(パーフルオロアルキル基)でもよい。
スルホン酸基(スルホ基)、リン酸基、ホスホン酸基、カルボキシ基等の塩をとりうる基は塩を形成していてもよい。塩としては、各種の金属塩、アンモニウム若しくはアミンの塩等が挙げられる。
構成成分(B)が有する極性官能基は、固体粒子との吸着性(密着性)、更には分散特性の点で、カルボキシ基、ヒドロキシ基又はエポキシ基が好ましい。
構成成分(B)が2種以上の極性官能基を有する場合、その組み合わせは、特に制限されず、適宜に決定することができる。例えば、カルボキシ基、スルホン酸基、ホスホン酸基のいずれかと、ヒドロキシ基、オキセタン基、エポキシ基、エーテル基のいずれかとの組み合わせが好ましく、カルボキシ基とヒドロキシ基との組み合わせがより好ましい。
バインダー形成ポリマーは、上記の各構成成分に加えて、その他の構成成分を有していてもよい。その他の構成成分としては、上記の各構成成分に該当しないものであればよく、例えば後述する(メタ)アクリル化合物(M1)又はビニル化合物(M2)に由来する構成成分が挙げられる。中でも、(メタ)アクリル酸アルキルエステル化合物に由来する構成成分が好ましく、分散媒への溶解性等の点で、長鎖アルキル基のアクリル酸エステル化合物に由来する構成成分がより好ましい。長鎖アルキル基の炭素数としては、例えば、3~20とすることができ、4~16であることが好ましく、6~14であることがより好ましい。
本発明において、各構成成分、特にその他の構成成分は、架橋性基、例えば、エチレン性不飽和基、例えば炭素-炭素二重結合を有さないことが好ましい。
バインダー形成ポリマーにおける各構成成分の含有量は、例えば、全構成成分の合計含有量が100質量%となるように下記の範囲に設定される。
構成成分(A)の含有量は、特に制限されないが、全構成成分の合計含有量に対して、例えば、分散特性の改善、抵抗の上昇抑制等を考慮して適宜決定することができる。構成成分(A)の含有量としては、例えば、2~60質量%であることが好ましく、5~40質量%であることがより好ましく、7.5~30質量%であることが更に好ましく、10~25質量%であることが特に好ましい。構成成分(A)の含有量は、全構成成分の合計モル数に対しては、10モル%以上であることが好ましく、20モル%以上であることがより好ましい。上限としては、90モル%以下とすることができ、60モル%以下であることが好ましい。
各構成成分の含有量は、グラフトポリマーが各構成成分を複数含む場合、複数の構成成分の合計含有量とする。
バインダー形成ポリマーは、上述の構成成分(A)を有し、後述する質量平均分子量を有するポグラフトポリマーであって分散媒に溶解するグラフトポリマーであれば、特に制限されず、公知の各種ポリマーを用いることができる。
バインダー形成ポリマーの分子構造は、(多)分岐構造(グラフト構造、スター構造、樹状構造等)の中でもグラフト構造である。グラフト構造を採ることにより、固体粒子との吸着性が向上する。グラフトポリマーにおける主鎖及びグラフト鎖の一次構造(構成成分の結合様式)は、特に制限されず、ランダム構造、ブロック構造、交互構造、グラフト構造等のいずれの結合様式をもとりうる。
本発明において、(多)分岐構造とは、ポリマーの重合鎖が分岐構造を有しているものをいい、例えば主鎖に対して別の重合鎖(側鎖)が1本又は複数本結合している構造をいう。これに対して、グラフト構造のポリマーは、1つの主鎖に多数の重合鎖が(側鎖として)枝状に結合しているポリマーをいい、例えば、重合鎖を有する構成成分(X)を含むポリマー構造をいう。
バインダー形成ポリマーを合成する際の重合開始剤としては、特に制限なく用いることができ、過酸化物系開始剤、アゾ重合開始剤、レドックス開始剤、光ラジカル開始剤等を用いることができる。特に、重合時の扱いやすさから、アゾ開始剤と使用することが好ましい。また、重合時の開始剤の使用量としては、狙いのポリマー分子量に対して開始剤の使用量を適切に選択することができ、モノマーの全体量に対して、0.0001~50質量%が好ましく、0.001~30質量%がより好ましく、0.01~20質量%が更に好ましい。開始剤を多量に使用する場合には、開始剤の分解物がポリマー中に含まれることがあるが、ポリマー中に開始剤の分解物を含んでいても構わない。
バインダー形成ポリマーとしては、例えば、ウレタン結合、ウレア結合、アミド結合、イミド結合、エステル結合及びシリルオキシ結合から選ばれる少なくとも1種の結合、又は炭素-炭素二重結合の重合鎖を主鎖に有するポリマーが好ましく挙げられる。本発明において、炭素-炭素二重結合の重合鎖とは、炭素-炭素二重結合(エチレン性不飽和基)が重合して形成される重合鎖といい、具体的には、炭素-炭素不飽和結合を有するモノマーを重合(単独重合又は共重合)してなる重合鎖をいう。
上記結合のうちウレタン結合、ウレア結合、アミド結合、イミド結合又はエステル結合を主鎖に有するポリマーとしては、例えば、ポリウレタン、ポリウレア、ポリアミド、ポリイミド、ポリエステル、ポリシロキサン等の逐次重合(重縮合、重付加若しくは付加縮合)ポリマー、又は、これらの共重合体が挙げられる。共重合体は、上記各ポリマーをセグメントとするブロック共重合体、上記各ポリマーのうち2つ以上のポリマーを構成する各構成成分がランダムに結合したランダム共重合体でもよい。
バインダー形成ポリマーとしては、上記各ポリマーを適宜に選択することができるが、ビニルポリマー又は(メタ)アクリルポリマーが好ましい。
(メタ)アクリル化合物(M1)及びビニル化合物(M2)は、置換基を有していてもよいが、無置換であることが好ましい態様の1つである。置換基としては、特に制限されず、後述する置換基Zから選択される基が挙げられるが、上述の官能基群(a)に含まれる極性官能基以外の基が好ましい。
上記式(b-1)において、重合性基を形成する炭素原子であってR1が結合していない炭素原子は無置換炭素原子(H2C=)として表しているが、置換基を有していてもよい。置換基としては、特に制限されないが、例えば、R1としてとりうる上記基が挙げられる。
バインダー形成ポリマーは、上記(メタ)アクリル化合物(M1)又はビニル化合物(M2)を1種有していても、2種以上有していてもよい。
アルキル基(好ましくは炭素数1~20のアルキル基、例えばメチル、エチル、イソプロピル、t-ブチル、ペンチル、ヘプチル、1-エチルペンチル、ベンジル、2-エトキシエチル、1-カルボキシメチル等)、アルケニル基(好ましくは炭素数2~20のアルケニル基、例えば、ビニル、アリル、オレイル等)、アルキニル基(好ましくは炭素数2~20のアルキニル基、例えば、エチニル、ブタジイニル、フェニルエチニル等)、シクロアルキル基(好ましくは炭素数3~20のシクロアルキル基、例えば、シクロプロピル、シクロペンチル、シクロヘキシル、4-メチルシクロヘキシル等、本発明においてアルキル基というときには通常シクロアルキル基を含む意味であるが、ここでは別記する。)、アリール基(好ましくは炭素数6~26のアリール基、例えば、フェニル、1-ナフチル、4-メトキシフェニル、2-クロロフェニル、3-メチルフェニル等)、アラルキル基(好ましくは炭素数7~23のアラルキル基、例えば、ベンジル、フェネチル等)、ヘテロ環基(好ましくは炭素数2~20のヘテロ環基で、より好ましくは、少なくとも1つの酸素原子、硫黄原子、窒素原子を有する5又は6員環のヘテロ環基である。ヘテロ環基には芳香族ヘテロ環基及び脂肪族ヘテロ環基を含む。例えば、テトラヒドロピラン環基、テトラヒドロフラン環基、2-ピリジル、4-ピリジル、2-イミダゾリル、2-ベンゾイミダゾリル、2-チアゾリル、2-オキサゾリル、ピロリドン基等)、アルコキシ基(好ましくは炭素数1~20のアルコキシ基、例えば、メトキシ、エトキシ、イソプロピルオキシ、ベンジルオキシ等)、アリールオキシ基(好ましくは炭素数6~26のアリールオキシ基、例えば、フェノキシ、1-ナフチルオキシ、3-メチルフェノキシ、4-メトキシフェノキシ等)、ヘテロ環オキシ基(上記ヘテロ環基に-O-基が結合した基)、アルコキシカルボニル基(好ましくは炭素数2~20のアルコキシカルボニル基、例えば、エトキシカルボニル、2-エチルヘキシルオキシカルボニル、ドデシルオキシカルボニル等)、アリールオキシカルボニル基(好ましくは炭素数6~26のアリールオキシカルボニル基、例えば、フェノキシカルボニル、1-ナフチルオキシカルボニル、3-メチルフェノキシカルボニル、4-メトキシフェノキシカルボニル等)、ヘテロ環オキシカルボニル基(上記ヘテロ環基に-O-CO-基が結合した基)、アミノ基(好ましくは炭素数0~20のアミノ基、アルキルアミノ基、アリールアミノ基を含み、例えば、アミノ(-NH2)、N,N-ジメチルアミノ、N,N-ジエチルアミノ、N-エチルアミノ、アニリノ等)、スルファモイル基(好ましくは炭素数0~20のスルファモイル基、例えば、N,N-ジメチルスルファモイル、N-フェニルスルファモイル等)、アシル基(アルキルカルボニル基、アルケニルカルボニル基、アルキニルカルボニル基、アリールカルボニル基、ヘテロ環カルボニル基を含み、好ましくは炭素数1~20のアシル基、例えば、アセチル、プロピオニル、ブチリル、オクタノイル、ヘキサデカノイル、アクリロイル、メタクリロイル、クロトノイル、ベンゾイル、ナフトイル、ニコチノイル等)、アシルオキシ基(アルキルカルボニルオキシ基、アルケニルカルボニルオキシ基、アルキニルカルボニルオキシ基、ヘテロ環カルボニルオキシ基を含み、好ましくは炭素数1~20のアシルオキシ基、例えば、アセチルオキシ、プロピオニルオキシ、ブチリルオキシ、オクタノイルオキシ、ヘキサデカノイルオキシ、アクリロイルオキシ、メタクリロイルオキシ、クロトノイルオキシ、ニコチノイルオキシ等)、アリーロイルオキシ基(好ましくは炭素数7~23のアリーロイルオキシ基、例えば、ベンゾイルオキシ、ナフトイルオキシ等)、カルバモイル基(好ましくは炭素数1~20のカルバモイル基、例えば、N,N-ジメチルカルバモイル、N-フェニルカルバモイル等)、アシルアミノ基(好ましくは炭素数1~20のアシルアミノ基、例えば、アセチルアミノ、ベンゾイルアミノ等)、アルキルチオ基(好ましくは炭素数1~20のアルキルチオ基、例えば、メチルチオ、エチルチオ、イソプロピルチオ、ベンジルチオ等)、アリールチオ基(好ましくは炭素数6~26のアリールチオ基、例えば、フェニルチオ、1-ナフチルチオ、3-メチルフェニルチオ、4-メトキシフェニルチオ等)、ヘテロ環チオ基(上記ヘテロ環基に-S-基が結合した基)、アルキルスルホニル基(好ましくは炭素数1~20のアルキルスルホニル基、例えば、メチルスルホニル、エチルスルホニル等)、アリールスルホニル基(好ましくは炭素数6~22のアリールスルホニル基、例えば、ベンゼンスルホニル等)、アルキルシリル基(好ましくは炭素数1~20のアルキルシリル基、例えば、モノメチルシリル、ジメチルシリル、トリメチルシリル、トリエチルシリル等)、アリールシリル基(好ましくは炭素数6~42のアリールシリル基、例えば、トリフェニルシリル等)、アルコキシシリル基(好ましくは炭素数1~20のアルコキシシリル基、例えば、モノメトキシシリル、ジメトキシシリル、トリメトキシシリル、トリエトキシシリル等)、アリールオキシシリル基(好ましくは炭素数6~42のアリールオキシシリル基、例えば、トリフェニルオキシシリル等)、ホスホリル基(好ましくは炭素数0~20のリン酸基、例えば、-OP(=O)(RP)2)、ホスホニル基(好ましくは炭素数0~20のホスホニル基、例えば、-P(=O)(RP)2)、ホスフィニル基(好ましくは炭素数0~20のホスフィニル基、例えば、-P(RP)2)、ホスホン酸基(好ましくは炭素数0~20のホスホン酸基、例えば、-PO(ORP)2)、スルホ基(スルホン酸基)、カルボキシ基、ヒドロキシ基、スルファニル基、シアノ基、ハロゲン原子(例えばフッ素原子、塩素原子、臭素原子、ヨウ素原子等)が挙げられる。RPは、水素原子又は置換基(好ましくは置換基Zから選択される基)である。
また、これらの置換基Zで挙げた各基は、上記置換基Zが更に置換していてもよい。
上記アルキル基、アルキレン基、アルケニル基、アルケニレン基、アルキニル基及び/又はアルキニレン基等は、環状でも鎖状でもよく、また直鎖でも分岐していてもよい。
本発明に用いるポリマーバインダー又はバインダー形成ポリマーは、下記の物性若しくは特性等を有することが好ましい。
本発明において、ポリマー、ポリマー鎖及びマクロモノマーの分子量については、特に断らない限り、ゲルパーミエーションクロマトグラフィー(GPC)によって標準ポリスチレン換算の質量平均分子量又は数平均分子量をいう。その測定法としては、基本として下記条件1又は条件2(優先)に設定した方法が挙げられる。ただし、ポリマー又はマクロモノマーの種類によっては適宜適切な溶離液を選定して用いればよい。
(条件1)
カラム:TOSOH TSKgel Super AWM-H(商品名、東ソー社製)を2本つなげる
キャリア:10mMLiBr/N-メチルピロリドン
測定温度:40℃
キャリア流量:1.0ml/min
試料濃度:0.1質量%
検出器:RI(屈折率)検出器
(条件2)
カラム:TOSOH TSKgel Super HZM-H、TOSOH TSKgel Super HZ4000、TOSOH TSKgel Super HZ2000(いずれも商品名、東ソー社製)をつないだカラムを用いる。
キャリア:テトラヒドロフラン
測定温度:40℃
キャリア流量:1.0ml/min
試料濃度:0.1質量%
検出器:RI(屈折率)検出器
バインダー形成ポリマーのガラス転移温度Tgは下記方法により測定されるガラス転移温度とする。すなわち、ガラス転移点は、バインダー形成ポリマーの乾燥試料を用いて、示差走査熱量計(SIIテクノロジー社製、DSC7000)を用いて下記の条件で測定する。測定は同一の試料で二回実施し、二回目の測定結果を採用する。
・測定室内の雰囲気:窒素(50mL/min)
・昇温速度:5℃/min
・測定開始温度:-100℃
・測定終了温度:200℃
・試料パン:アルミニウム製パン
・測定試料の質量:5mg
・Tgの算定:DSCチャートの下降開始点と下降終了点の中間温度の小数点以下を四捨五入することでTgを算定する。
ガラス転移温度Tgは、バインダー形成ポリマーの種類又は組成(構成成分の種類及び含有量)等によって、調整できる。
SP値の算出方法について説明する。
まず、バインダー形成ポリマーを構成する各構成成分のSP値(MPa1/2)を、特に断らない限り、Hoy法によって求める(H.L.Hoy JOURNAL OF PAINT TECHNOLOGY Vol.42,No.541,1970,76-118、及びPOLYMER HANDBOOK 4th、59章、VII 686ページ Table5、Table6及びTable6中の下記式参照)。
構成成分は、バインダー形成ポリマーが連鎖重合系ポリマーである場合、原料化合物に由来する構成成分と同じ単位とする。一方、バインダー形成ポリマーが逐次重合ポリマーである場合、原料化合物に由来する構成成分と異なる単位とする。例えば、ポリウレタンを例に挙げると、便宜的に構成成分を次のように決定する。ポリイソシアネート化合物に由来する構成成分として、ポリイソシアネート化合物に由来する構成単位に対して2つの-NH-CO-基に-O-基を結合させた単位とする。一方、ポリオール化合物に由来する構成成分としては、ポリオール化合物に由来する構成単位に対して、2つの-O-基を除去した単位とする。
SPp 2=(SP1 2×W1)+(SP2 2×W2)+・・・
上記計算式中、SP1、SP2・・・は構成成分のSP値を示し、W1、W2・・・は構成成分の質量分率を示す。本発明において、構成成分の質量分率は、当該構成成分(この構成成分を導く原料化合物)のバインダー形成ポリマー中の質量分率とする。
バインダー形成ポリマーは、非晶質であることが好ましい。本発明において、ポリマーが「非晶質」であるとは、典型的には、ガラス転移温度で測定したときに結晶融解に起因する吸熱ピークが見られないことをいう。
ポリマーバインダーの、無機固体電解質含有組成物中の含有量は、特に制限されないが、分散特性及びイオン伝導度、更には結着性の点で、0.1~5.0質量%であることが好ましく、0.2~4.0質量%であることがより好ましく、0.3~2.0質量%であることが更に好ましい。また、ポリマーバインダーの、無機固体電解質含有組成物の固形分100質量%中の含有量は、同様の理由から、0.1~6.0質量%であることが好ましく、0.3~5.0質量%であることがより好ましく、0.4~2.5質量%であることが更に好ましい。
本発明において、固形分100質量%において、ポリマーバインダーの質量に対する、無機固体電解質と活物質の合計質量(総量)の質量比[(無機固体電解質の質量+活物質の質量)/(ポリマーバインダーの合計質量)]は、1,000~1の範囲が好ましい。この比率は更に500~2がより好ましく、100~10が更に好ましい。
無機固体電解質含有組成物が含有する分散媒としては、使用環境において液状を示す有機化合物であればよく、例えば、各種有機溶媒が挙げられ、具体的には、アルコール化合物、エーテル化合物、アミド化合物、アミン化合物、ケトン化合物、芳香族化合物、脂肪族化合物、ニトリル化合物、エステル化合物等が挙げられる。
分散媒としては、非極性分散媒(疎水性の分散媒)でも極性分散媒(親水性の分散媒)でもよいが、優れた分散性を発現できる点で、非極性分散媒が好ましい。非極性分散媒とは、一般に水に対する親和性が低い性質をいうが、本発明においては、例えば、エステル化合物、ケトン化合物、エーテル化合物、芳香族化合物、脂肪族化合物等が挙げられる。
ケトン化合物としては、例えば、アセトン、メチルエチルケトン、メチルイソブチルケトン(MIBK)、シクロペンタノン、シクロヘキサノン、シクロヘプタノン、ジプロピルケトン、ジブチルケトン、ジイソプロピルケトン、ジイソブチルケトン(DIBK)、イソブチルプロピルケトン、sec-ブチルプロピルケトン、ペンチルプロピルケトン、ブチルプロピルケトンなどが挙げられる。
芳香族化合物としては、例えば、ベンゼン、トルエン、キシレン、パーフルオロトルエン等が挙げられる。
脂肪族化合物としては、例えば、ヘキサン、ヘプタン、オクタン、ノナン、デカン、ドデカン、シクロヘキサン、メチルシクロヘキサン、エチルシクロヘキサン、シクロヘプタン、シクロオクタン、デカリン、パラフィン、ガソリン、ナフサ、灯油、軽油等が挙げられる。
ニトリル化合物としては、例えば、アセトニトリル、プロピオニトリル、イソブチロニトリルなどが挙げられる。
エステル化合物としては、例えば、酢酸エチル、酢酸プロピル、酢酸ブチル、酪酸エチル、酪酸プロピル、酪酸イソプロピル、酪酸ブチル、酪酸イソブチル、ペンタン酸ブチル、ペンタン酸ペンチル、イソ酪酸エチル、イソ酪酸プロピル、イソ酪酸イソプロピル、イソ酪酸イソブチル、ピバル酸プロピル、ピバル酸イソプロピル、ピバル酸ブチル、ピバル酸イソブチルなどが挙げられる。
分散媒のSP値は、上述のHoy法により算出したSP値を単位MPa1/2に換算した値とする。無機固体電解質含有組成物が2種以上の分散媒を含有する場合、分散媒のSP値は、分散媒全体としてのSP値を意味し、各分散媒のSP値と質量分率との積の総和とする。具体的には、構成成分のSP値に代えて各分散媒のSP値を用いること以外は上述のポリマーのSP値の算出方法と同様にして算出する。
主な分散媒のSP値(単位を省略する)を以下に示す。
MIBK(18.4)、ジイソプロピルエーテル(16.8)、ジブチルエーテル(17.9)、ジイソプロピルケトン(17.9)、DIBK(17.9)、酪酸ブチル(17.1)、酢酸ブチル(18.9)、トルエン(18.5)、エチルシクロヘキサン(17.1)、シクロオクタン(18.8)、イソブチルエチルエーテル(15.3)、N-メチルピロリドン(NMP、25.4)、パーフルオロトルエン(13.4)
本発明において、無機固体電解質含有組成物中の、分散媒の含有量は、特に制限されず適宜に設定することができる。例えば、無機固体電解質含有組成物中、20~80質量%が好ましく、30~70質量%がより好ましく、40~60質量%が特に好ましい。高固形分濃度に設定する場合、分散媒の含有量は、50質量%以下に設定することもでき、45質量%以下、更には40質量%以下に設定することもできる。下限は特に限定されないが、例えば20質量%とすることができる。
本発明の無機固体電解質含有組成物には、周期律表第1族若しくは第2族に属する金属のイオンの挿入放出が可能な活物質を含有することが好ましい。活物質としては、以下に説明するが、正極活物質及び負極活物質が挙げられる。
本発明において、活物質(正極活物質又は負極活物質)を含有する無機固体電解質含有組成物を電極組成物(正極組成物又は負極組成物)ということがある。
正極活物質は、周期律表第1族若しくは第2族に属する金属のイオンの挿入放出が可能な活物質であり、可逆的にリチウムイオンを挿入及び放出できるものが好ましい。その材料は、上記特性を有するものであれば、特に制限はなく、遷移金属酸化物、又は、有機物、硫黄などのLiと複合化できる元素などでもよい。
中でも、正極活物質としては、遷移金属酸化物を用いることが好ましく、遷移金属元素Ma(Co、Ni、Fe、Mn、Cu及びVから選択される1種以上の元素)を有する遷移金属酸化物がより好ましい。また、この遷移金属酸化物に元素Mb(リチウム以外の金属周期律表の第1(Ia)族の元素、第2(IIa)族の元素、Al、Ga、In、Ge、Sn、Pb、Sb、Bi、Si、P及びBなどの元素)を混合してもよい。混合量としては、遷移金属元素Maの量(100モル%)に対して0~30モル%が好ましい。Li/Maのモル比が0.3~2.2になるように混合して合成されたものが、より好ましい。
遷移金属酸化物の具体例としては、(MA)層状岩塩型構造を有する遷移金属酸化物、(MB)スピネル型構造を有する遷移金属酸化物、(MC)リチウム含有遷移金属リン酸化合物、(MD)リチウム含有遷移金属ハロゲン化リン酸化合物及び(ME)リチウム含有遷移金属ケイ酸化合物等が挙げられる。
(MB)スピネル型構造を有する遷移金属酸化物の具体例として、LiMn2O4(LMO)、LiCoMnO4、Li2FeMn3O8、Li2CuMn3O8、Li2CrMn3O8及びLi2NiMn3O8が挙げられる。
(MC)リチウム含有遷移金属リン酸化合物としては、例えば、LiFePO4及びLi3Fe2(PO4)3等のオリビン型リン酸鉄塩、LiFeP2O7等のピロリン酸鉄類、LiCoPO4等のリン酸コバルト類並びにLi3V2(PO4)3(リン酸バナジウムリチウム)等の単斜晶ナシコン型リン酸バナジウム塩が挙げられる。
(MD)リチウム含有遷移金属ハロゲン化リン酸化合物としては、例えば、Li2FePO4F等のフッ化リン酸鉄塩、Li2MnPO4F等のフッ化リン酸マンガン塩及びLi2CoPO4F等のフッ化リン酸コバルト類が挙げられる。
(ME)リチウム含有遷移金属ケイ酸化合物としては、例えば、Li2FeSiO4、Li2MnSiO4、Li2CoSiO4等が挙げられる。
本発明では、(MA)層状岩塩型構造を有する遷移金属酸化物が好ましく、LCO又はNMCがより好ましい。
焼成法によって得られた正極活物質は、水、酸性水溶液、アルカリ性水溶液、有機溶剤にて洗浄した後使用してもよい。
負極活物質は、周期律表第1族若しくは第2族に属する金属のイオンの挿入放出が可能な活物質であり、可逆的にリチウムイオンを挿入及び放出できるものが好ましい。その材料は、上記特性を有するものであれば、特に制限はなく、炭素質材料、金属酸化物、金属複合酸化物、リチウム単体、リチウム合金、リチウムと合金形成可能(合金化可能)な負極活物質等が挙げられる。中でも、炭素質材料、金属複合酸化物又はリチウム単体が信頼性の点から好ましく用いられる。全固体二次電池の大容量化が可能となる点では、リチウムと合金化可能な活物質が好ましい。
これらの炭素質材料は、黒鉛化の程度により難黒鉛化炭素質材料(ハードカーボンともいう。)と黒鉛系炭素質材料に分けることもできる。また炭素質材料は、特開昭62-22066号公報、特開平2-6856号公報、同3-45473号公報に記載される面間隔又は密度、結晶子の大きさを有することが好ましい。炭素質材料は、単一の材料である必要はなく、特開平5-90844号公報記載の天然黒鉛と人造黒鉛の混合物、特開平6-4516号公報記載の被覆層を有する黒鉛等を用いることもできる。
炭素質材料としては、ハードカーボン又は黒鉛が好ましく用いられ、黒鉛がより好ましく用いられる。
Sn、Si、Geを中心とする非晶質酸化物に併せて用いることができる負極活物質としては、リチウムイオン又はリチウム金属を吸蔵及び/又は放出できる炭素質材料、リチウム単体、リチウム合金、リチウムと合金化可能な負極活物質が好適に挙げられる。
負極活物質、例えば金属酸化物は、チタン元素を含有すること(チタン酸化物)も好ましい。具体的には、Li4Ti5O12(チタン酸リチウム[LTO])がリチウムイオンの吸蔵放出時の体積変動が小さいことから急速充放電特性に優れ、電極の劣化が抑制されリチウムイオン二次電池の寿命向上が可能となる点で好ましい。
一般的に、これらの負極活物質を含有する負極(例えば、ケイ素元素含有活物質を含有するSi負極、スズ元素を有する活物質を含有するSn負極等)は、炭素負極(黒鉛及びアセチレンブラックなど)に比べて、より多くのLiイオンを吸蔵できる。すなわち、単位質量あたりのLiイオンの吸蔵量が増加する。そのため、電池容量(エネルギー密度)を大きくすることができる。その結果、バッテリー駆動時間を長くすることができるという利点がある。
ケイ素元素含有活物質としては、例えば、Si、SiOx(0<x≦1)等のケイ素材料、更には、チタン、バナジウム、クロム、マンガン、ニッケル、銅、ランタン等を含むケイ素含有合金(例えば、LaSi2、VSi2、La-Si、Gd-Si、Ni-Si)、又は組織化した活物質(例えば、LaSi2/Si)、他にも、SnSiO3、SnSiS3等のケイ素元素及びスズ元素を含有する活物質等が挙げられる。なお、SiOxは、それ自体を負極活物質(半金属酸化物)として用いることができ、また、全固体二次電池の稼働によりSiを生成するため、リチウムと合金化可能な負極活物質(その前駆体物質)として用いることができる。
スズ元素を有する負極活物質としては、例えば、Sn、SnO、SnO2、SnS、SnS2、更には上記ケイ素元素及びスズ元素を含有する活物質等が挙げられる。また、酸化リチウムとの複合酸化物、例えば、Li2SnO2を挙げることもできる。
負極活物質の、無機固体電解質含有組成物中における含有量は特に制限されず、固形分100質量%において、10~90質量%であることが好ましく、20~85質量%がより好ましく、30~80質量%であることがより好ましく、40~75質量%であることが更に好ましい。
正極活物質及び負極活物質の表面は別の金属酸化物で表面被覆されていてもよい。表面被覆剤としてはTi、Nb、Ta、W、Zr、Al、Si又はLiを含有する金属酸化物等が挙げられる。具体的には、チタン酸スピネル、タンタル系酸化物、ニオブ系酸化物、ニオブ酸リチウム系化合物等が挙げられ、具体的には、Li4Ti5O12、Li2Ti2O5、LiTaO3、LiNbO3、LiAlO2、Li2ZrO3、Li2WO4、Li2TiO3、Li2B4O7、Li3PO4、Li2MoO4、Li3BO3、LiBO2、Li2CO3、Li2SiO3、SiO2、TiO2、ZrO2、Al2O3、B2O3等が挙げられる。
また、正極活物質又は負極活物質を含む電極表面は硫黄又はリンで表面処理されていてもよい。
更に、正極活物質又は負極活物質の粒子表面は、上記表面被覆の前後において活性光線又は活性気体(プラズマ等)により表面処理を施されていてもよい。
本発明の無機固体電解質含有組成物は、導電助剤を含有していることが好ましく、例えば、負極活物質としてのケイ素原子含有活物質は導電助剤と併用されることが好ましい。
導電助剤としては、特に制限はなく、一般的な導電助剤として知られているものを用いることができる。例えば、電子伝導性材料である、天然黒鉛、人造黒鉛などの黒鉛類、アセチレンブラック、ケッチェンブラック、ファーネスブラックなどのカーボンブラック類、ニードルコークスなどの無定形炭素、気相成長炭素繊維若しくはカーボンナノチューブなどの炭素繊維類、グラフェン若しくはフラーレンなどの炭素質材料であってもよいし、銅、ニッケルなどの金属粉、金属繊維でもよく、ポリアニリン、ポリピロール、ポリチオフェン、ポリアセチレン、ポリフェニレン誘導体などの導電性高分子を用いてもよい。
本発明において、活物質と導電助剤とを併用する場合、上記の導電助剤のうち、電池を充放電した際に周期律表第一族若しくは第二族に属する金属のイオン(好ましくはLiイオン)の挿入と放出が起きず、活物質として機能しないものを導電助剤とする。したがって、導電助剤の中でも、電池を充放電した際に活物質層中において活物質として機能しうるものは、導電助剤ではなく活物質に分類する。電池を充放電した際に活物質として機能するか否かは、一義的ではなく、活物質との組み合わせにより決定される。
導電助剤の形状は、特に制限されないが、粒子状が好ましい。
本発明の無機固体電解質含有組成物が導電助剤を含む場合、無機固体電解質含有組成物中の導電助剤の含有量は、固形分100質量%において、0~10質量%が好ましい。
本発明の無機固体電解質含有組成物は、リチウム塩(支持電解質)を含有することも好ましい。
リチウム塩としては、通常この種の製品に用いられるリチウム塩が好ましく、特に制限はなく、例えば、特開2015-088486号公報の段落0082~0085記載のリチウム塩が好ましい。
本発明の無機固体電解質含有組成物がリチウム塩を含む場合、リチウム塩の含有量は、固体電解質100質量部に対して、0.1質量部以上が好ましく、5質量部以上がより好ましい。上限としては、50質量部以下が好ましく、20質量部以下がより好ましい。
本発明の無機固体電解質含有組成物は、上述のポリマーバインダーが分散剤としても機能するため、このポリマーバインダー以外の分散剤を含有していなくてもよいが、分散剤を含有してもよい。分散剤としては、全固体二次電池に通常使用されるものを適宜選定して用いることができる。一般的には粒子吸着と立体反発及び/又は静電反発を意図した化合物が好適に使用される。
本発明の無機固体電解質含有組成物は、上記各成分以外の他の成分として、適宜に、イオン液体、増粘剤、架橋剤(ラジカル重合、縮合重合又は開環重合により架橋反応するもの等)、重合開始剤(酸又はラジカルを熱又は光によって発生させるものなど)、消泡剤、レベリング剤、脱水剤、酸化防止剤等を含有することができる。イオン液体は、イオン伝導度をより向上させるため含有されるものであり、公知のものを特に制限されることなく用いることができる。また、上述のバインダー形成ポリマー以外のポリマー、通常用いられる結着剤等を含有していてもよい。
本発明の無機固体電解質含有組成物は、無機固体電解質、上述のポリマーバインダー、分散媒、好ましくは、導電助剤、更には適宜に、リチウム塩、任意の他の成分を、例えば通常用いる各種の混合機で混合することにより、混合物として、好ましくはスラリーとして、調製することができる。電極組成物の場合は更に活物質を混合する。
混合方法は、特に制限されず、ボールミル、ビーズミル、プラネタリミキサ―、ブレードミキサ―、ロールミル、ニーダー、ディスクミル、自公転式ミキサー、狭ギャップ式分散機等の公知の混合機を用いて行うことができる。各成分は、一括して混合してもよく、順次混合してもよい。混合する環境は特に制限されないが、乾燥空気下又は不活性ガス下等が挙げられる。また、混合条件も、特に制限されず、適宜に設定され、例えば、混合温度は15~40℃とすることができる。また、自公転ミキサー等の回転数を200~3,000rpmとすることができる。
本発明の無機固体電解質含有組成物は、固体粒子の再分散性に優れ、更には酸化劣化しにくいから、調製後に保存することもでき、使用するたびに調製しなくてもよい。なお、本発明の無機固体電解質含有組成物を調製後に再分散させる条件としては、特に制限されず、上記混合条件を適宜採用できる。
本発明の全固体二次電池用シートは、全固体二次電池の構成層を形成しうるシート状成形体であって、その用途に応じて種々の態様を含む。例えば、固体電解質層に好ましく用いられるシート(全固体二次電池用固体電解質シートともいう。)、電極、又は電極と固体電解質層との積層体に好ましく用いられるシート(全固体二次電池用電極シート)等が挙げられる。本発明において、これら各種のシートをまとめて全固体二次電池用シートという。
本発明において、全固体二次電池用シートを構成する各層は、単層構造であっても複層構造であってもよい。
なお、固体電解質層又は活物質層が本発明の無機固体電解質含有組成物で形成されない場合、通常の構成層形成材料で形成される。
本発明の全固体二次電池用シートは、固形分濃度を高めても分散特性に優れる本発明の無機固体電解質含有組成物を用いて、工業的製造、例えば生産性が高いロール・トゥ・ロール法で作製することもできる。
本発明の全固体二次電池用シートの製造方法は、特に制限されず、本発明の無機固体電解質含有組成物を用いて、上記の各層を形成することにより、製造できる。例えば、好ましくは基材若しくは集電体上(他の層を介していてもよい。)に、製膜(塗布乾燥)して無機固体電解質含有組成物からなる層(塗布乾燥層)を形成する方法が挙げられる。これにより、基材若しくは集電体と、塗布乾燥層とを有する全固体二次電池用シートを作製することができる。特に、本発明の無機固体電解質含有組成物を集電体上で製膜して全固体二次電池用シートを作製すると、集電体と活物質層との密着を強化できる。ここで、塗布乾燥層とは、本発明の無機固体電解質含有組成物を塗布し、分散媒を乾燥させることにより形成される層(すなわち、本発明の無機固体電解質含有組成物を用いてなり、本発明の無機固体電解質含有組成物から分散媒を除去した組成からなる層)をいう。活物質層及び塗布乾燥層は、本発明の効果を損なわない範囲であれば分散媒が残存していてもよく、残存量としては、例えば、各層中、3質量%以下とすることができる。
本発明の全固体二次電池用シートの製造方法において、塗布、乾燥等の各工程については、下記全固体二次電池の製造方法において説明する。
また、本発明の全固体二次電池用シートの製造方法においては、基材、保護層(特に剥離シート)等を剥離することもできる。
本発明の全固体二次電池は、正極活物質層と、この正極活物質層に対向する負極活物質層と、正極活物質層及び負極活物質層の間に配置された固体電解質層とを有する。本発明の全固体二次電池は、正極活物質層及び負極活物質層の間に固体電解質層を有するものであれば、それ以外の構成は特に限定されず、例えば全固体二次電池に関する公知の構成を採用できる。正極活物質層は、好ましくは正極集電体上に形成され、正極を構成する。負極活物質層は、好ましくは負極集電体上に形成され、負極を構成する。
本発明においては、全ての層が本発明の無機固体電解質含有組成物で形成されることも好ましい態様の1つである。本発明において、全固体二次電池の構成層を本発明の無機固体電解質含有組成物で形成するとは、本発明の全固体二次電池用シート(ただし、本発明の無機固体電解質含有組成物で形成した層以外の層を有する場合はこの層を除去したシート)で構成層を形成する態様を包含する。
なお、活物質層又は固体電解質層が本発明の無機固体電解質含有組成物で形成されない場合、公知の材料を用いることができる。
本発明において、全固体二次電池を構成する各構成層(集電体等を含む。)は単層構造であっても複層構造であってもよい。
本発明の無機固体電解質含有組成物で形成された活物質層又は固体電解質層は、好ましくは、含有する成分種及びその含有量について、本発明の無機固体電解質含有組成物の固形分におけるものと同じである。
負極活物質層、固体電解質層及び正極活物質層の厚さは、それぞれ、特に制限されない。各層の厚さは、一般的な全固体二次電池の寸法を考慮すると、それぞれ、10~1,000μmが好ましく、20μm以上500μm未満がより好ましい。本発明の全固体二次電池においては、正極活物質層及び負極活物質層の少なくとも1層の厚さが、50μm以上500μm未満であることが更に好ましい。
正極活物質層及び負極活物質層は、それぞれ、固体電解質層とは反対側に集電体を備えていてもよい。
正極集電体及び負極集電体は、電子伝導体が好ましい。
本発明において、正極集電体及び負極集電体のいずれか、又は、両方を合わせて、単に、集電体と称することがある。
正極集電体を形成する材料としては、アルミニウム、アルミニウム合金、ステンレス鋼、ニッケル及びチタンなどの他に、アルミニウム又はステンレス鋼の表面にカーボン、ニッケル、チタンあるいは銀を処理させたもの(薄膜を形成したもの)が好ましく、その中でも、アルミニウム及びアルミニウム合金がより好ましい。
負極集電体を形成する材料としては、アルミニウム、銅、銅合金、ステンレス鋼、ニッケル及びチタンなどの他に、アルミニウム、銅、銅合金又はステンレス鋼の表面にカーボン、ニッケル、チタンあるいは銀を処理させたものが好ましく、アルミニウム、銅、銅合金及びステンレス鋼がより好ましい。
集電体の厚さは、特に制限されないが、1~500μmが好ましい。また、集電体表面は、表面処理により凹凸を付けることも好ましい。
本発明において、負極集電体、負極活物質層、固体電解質層、正極活物質層及び正極集電体の各層の間又はその外側には、機能性の層若しくは部材等を適宜介在若しくは配設してもよい。
本発明の全固体二次電池は、用途によっては、上記構造のまま全固体二次電池として使用してもよいが、乾電池の形態とするためには更に適当な筐体に封入して用いることが好ましい。筐体は、金属性のものであっても、樹脂(プラスチック)製のものであってもよい。金属性のものを用いる場合には、例えば、アルミニウム合金又は、ステンレス鋼製のものを挙げることができる。金属性の筐体は、正極側の筐体と負極側の筐体に分けて、それぞれ正極集電体及び負極集電体と電気的に接続させることが好ましい。正極側の筐体と負極側の筐体とは、短絡防止用のガスケットを介して接合され、一体化されることが好ましい。
全固体二次電池10においては、正極活物質層、固体電解質層及び負極活物質層のいずれも本発明の無機固体電解質含有組成物で形成されている。この全固体二次電池10は優れた電池性能を示す。正極活物質層4、固体電解質層3及び負極活物質層2が含有する無機固体電解質及びポリマーバインダーは、それぞれ、互いに同種であっても異種であってもよい。
本発明において、正極活物質層及び負極活物質層のいずれか、又は、両方を合わせて、単に、活物質層又は電極活物質層と称することがある。また、正極活物質及び負極活物質のいずれか、又は両方を合わせて、単に、活物質又は電極活物質と称することがある。
正極活物質層は、周期律表第一族若しくは第二族に属する金属のイオンの伝導性を有する無機固体電解質と、正極活物質と、ポリマーバインダーと、本発明の効果を損なわない範囲で上述の任意の成分等とを含有する。
負極活物質層は、周期律表第一族若しくは第二族に属する金属のイオンの伝導性を有する無機固体電解質、負極活物質と、ポリマーバインダーと、本発明の効果を損なわない範囲で上述の任意の成分等とを含有する。
全固体二次電池10においては、負極活物質層をリチウム金属層とすることができる。リチウム金属層としては、リチウム金属の粉末を堆積又は成形してなる層、リチウム箔及びリチウム蒸着膜等が挙げられる。リチウム金属層の厚さは、上記負極活物質層の上記厚さにかかわらず、例えば、1~500μmとすることができる。
正極集電体5及び負極集電体1は、それぞれ、上記した通りである。
全固体二次電池は、常法によって、製造できる。具体的には、全固体二次電池は、本発明の無機固体電解質含有組成物等を用いて、上記の各層を形成することにより、製造できる。以下、詳述する。
例えば、正極集電体である金属箔上に、正極用材料(正極組成物)として、正極活物質を含有する無機固体電解質含有組成物を塗布して正極活物質層を形成し、全固体二次電池用正極シートを作製する。次いで、この正極活物質層の上に、固体電解質層を形成するための無機固体電解質含有組成物を塗布して、固体電解質層を形成する。更に、固体電解質層の上に、負極用材料(負極組成物)として、負極活物質を含有する無機固体電解質含有組成物を塗布して、負極活物質層を形成する。負極活物質層の上に、負極集電体(金属箔)を重ねることにより、正極活物質層と負極活物質層の間に固体電解質層が挟まれた構造の全固体二次電池を得ることができる。これを筐体に封入して所望の全固体二次電池とすることもできる。
また、各層の形成方法を逆にして、基材としての負極集電体上に、負極活物質層、固体電解質層及び正極活物質層を形成し、正極集電体を重ねて、全固体二次電池を製造することもできる。
また別の方法として、次の方法が挙げられる。すなわち、上記のようにして、全固体二次電池用正極シート及び全固体二次電池用負極シートを作製する。また、これとは別に、無機固体電解質含有組成物を基材上に塗布して、固体電解質層からなる全固体二次電池用固体電解質シートを作製する。更に、全固体二次電池用正極シート及び全固体二次電池用負極シートで、基材から剥がした固体電解質層を挟むように積層する。このようにして、全固体二次電池を製造することができる。
上記の製造方法においては、正極組成物、無機固体電解質含有組成物及び負極組成物のいずれか1つに本発明の無機固体電解質含有組成物を用いればよく、無機固体電解質含有組成物、又は正極組成物及び負極組成物の少なくとも一方に、本発明の無機固体電解質含有組成物を用いることが好ましく、いずれの組成物に本発明の無機固体電解質含有組成物を用いることもできる。
本発明の無機固体電解質含有組成物以外の組成物で固体電解質層又は活物質層を形成する場合、その材料としては、通常用いられる組成物等が挙げられる。また、全固体二次電池の製造時に負極活物質層を形成せずに、後述する初期化若しくは使用時の充電で負極集電体に蓄積した、周期律表第一族若しくは第二族に属する金属のイオンを電子と結合させて、金属として負極集電体等の上に析出させることにより、負極活物質層を形成することもできる。
無機固体電解質含有組成物の塗布方法は、特に制限されず、適宜に選択できる。例えば、塗布(好ましくは湿式塗布)、スプレー塗布、スピンコート塗布、ディップコート塗布、スリット塗布、ストライプ塗布、バーコート塗布が挙げられる。
このとき、無機固体電解質含有組成物は、それぞれ塗布した後に乾燥処理を施してもよいし、重層塗布した後に乾燥処理をしてもよい。乾燥温度は特に制限されない。下限は、30℃以上が好ましく、60℃以上がより好ましく、80℃以上が更に好ましい。上限は、300℃以下が好ましく、250℃以下がより好ましく、200℃以下が更に好ましい。このような温度範囲で加熱することで、分散媒を除去し、固体状態(塗布乾燥層)にすることができる。また、温度を高くしすぎず、全固体二次電池の各部材を損傷せずに済むため好ましい。これにより、全固体二次電池において、優れた総合性能を示し、かつ良好な結着性と、良好なイオン伝導度を得ることができる。
また、塗布した無機固体電解質含有組成物は、加圧と同時に加熱してもよい。加熱温度としては特に制限されず、一般的には30~300℃の範囲である。無機固体電解質のガラス転移温度よりも高い温度でプレスすることもできる。なお、ポリマーバインダーに含まれるポリマーのガラス転移温度よりも高い温度でプレスすることもできる。ただし、一般的にはこのポリマーの融点を越えない温度である。
加圧は塗布溶媒又は分散媒を予め乾燥させた状態で行ってもよいし、溶媒又は分散媒が残存している状態で行ってもよい。
なお、各組成物は同時に塗布してもよいし、塗布乾燥プレスを同時及び/又は逐次行ってもよい。別々の基材に塗布した後に、転写により積層してもよい。
プレス時間は短時間(例えば数時間以内)で高い圧力をかけてもよいし、長時間(1日以上)かけて中程度の圧力をかけてもよい。全固体二次電池用シート以外、例えば全固体二次電池の場合には、中程度の圧力をかけ続けるために、全固体二次電池の拘束具(ネジ締め圧等)を用いることもできる。
プレス圧はシート面等の被圧部に対して均一であっても異なる圧であってもよい。
プレス圧は被圧部の面積又は膜厚に応じて変化させることができる。また同一部位を段階的に異なる圧力で変えることもできる。
プレス面は平滑であっても粗面化されていてもよい。
上記のようにして製造した全固体二次電池は、製造後又は使用前に初期化を行うことが好ましい。初期化は特に制限されず、例えば、プレス圧を高めた状態で初充放電を行い、その後、全固体二次電池の一般使用圧力になるまで圧力を解放することにより、行うことができる。
本発明の全固体二次電池は種々の用途に適用することができる。適用態様には特に制限はないが、例えば、電子機器に搭載する場合、ノートパソコン、ペン入力パソコン、モバイルパソコン、電子ブックプレーヤー、携帯電話、コードレスフォン子機、ページャー、ハンディーターミナル、携帯ファックス、携帯コピー、携帯プリンター、ヘッドフォンステレオ、ビデオムービー、液晶テレビ、ハンディークリーナー、ポータブルCD、ミニディスク、電気シェーバー、トランシーバー、電子手帳、電卓、メモリーカード、携帯テープレコーダー、ラジオ、バックアップ電源などが挙げられる。その他民生用として、自動車(電気自動車等)、電動車両、モーター、照明器具、玩具、ゲーム機器、ロードコンディショナー、時計、ストロボ、カメラ、医療機器(ペースメーカー、補聴器、肩もみ機など)などが挙げられる。更に、各種軍需用、宇宙用として用いることができる。また、太陽電池と組み合わせることもできる。
表1-1及び表1-2(併せて表1という。)に示す、バインダー形成ポリマーを以下のようにして合成した。
[合成例S-1:ポリマーS-1の合成、及びバインダー溶液S-1の調製]
まず、構成成分(X)としてマクロモノマーM-1を以下のようにして合成した。
1Lメスシリンダーに、アクリル酸ドデシル(東京化成工業社製)460g、3-メルカプトプロピオン酸16.5g及び重合開始剤V-601(富士フイルム和光純薬社製)7.8gを加え、撹拌して均一に溶解してモノマー溶液を調製した。2L3口フラスコに、トルエン(富士フイルム和光純薬社製)500gを加え、80℃で攪拌したところへ、上記モノマー溶液を2時間かけて滴下した。滴下終了後、80℃で2時間撹拌した後、90℃に昇温して2時間撹拌した。次いで、2,2,6,6-テトラメチルピペリジン-1-オキシル(富士フイルム和光純薬社製)275mg、メタクリル酸グリシジル(東京化成工業社製)27.5g、及びテトラブチルアンモニウムブロミド(富士フイルム和光純薬社製)5.5gを加え、120℃で3時間撹拌した。溶液を室温で静置した後、1800gのメタノールに流し込み、上澄みを除いた。そこへ酪酸ブチルを加え、メタノールを減圧留去することでマクロモノマーM-1の酪酸ブチル溶液を得た。固形分濃度は49質量%であった。マクロモノマーM-1のSP値は16.5MPa1/2であった。
次いで、マクロモノマーM-1を用いてポリマーS-1を以下のようにして合成した。
100mLメスシリンダーに、アクリル酸ドデシル(東京化成工業社製)3g、マクロモノマーM-1の溶液10.2g(固形分量5g)、N,N-ジメチルアクリルアミド(東京化成工業社製)2g及び重合開始剤V-601(商品名、富士フイルム和光純薬社製)1.5gを加え、酪酸ブチル10gに溶解してモノマー溶液を調製した。
300mL3つ口フラスコに酪酸ブチル40gを加え80℃で撹拌したところへ、上記モノマー溶液を2時間かけて滴下した。滴下終了後、90℃に昇温し、2時間撹拌した。得られた重合液をメタノール100gに流し込み、10分撹拌した後に10分間静置した。上澄みを除いた後に得られる沈殿物を酪酸ブチル15gに溶解し、30hPa、60℃で1時間加熱することでメタノールを留去した。
こうして、ポリマーS-1((メタ)アクリルグラフトポリマー)を合成し、このポリマーからなるバインダーの溶液S-1(濃度32質量%)を得た。
合成例S-1において、ポリマーS-2~S-16が表1に示す組成(構成成分の種類及び含有量)となるように各構成成分を導く化合物を用いたこと以外は、合成例S-1と同様にして、ポリマーS-2~S-16((メタ)アクリルグラフトポリマー)を合成して、各ポリマーからなるバインダーの溶液S-2~S-16をそれぞれ得た。
なお、ポリマーS-5A及びS-5((メタ)アクリルグラフトポリマー)は、合成例S-1において、重合開始剤量を1.5gから2.0g(ポリマーS-5A)又は0.8g(ポリマーS-5)に変更したこと以外は、合成例S-1と同様にして、質量平均分子量を調整して、合成した。こうして、ポリマーS-5A又はS-5からなるバインダーの溶液S-5A及びS-5をそれぞれ得た。
合成例S-1において、マクロモノマーM-1の溶液に代えてマクロモノマーM-2としてX-22-174ASX(商品番号、信越シリコーン社製、SP値:12.8MPa1/2)を用い、かつポリマーS-17~S-20が表1に示す組成(構成成分の種類及び含有量)となるように各構成成分を導く化合物を用いたこと以外は、合成例S-1と同様にして、ポリマーS-17~S-20((メタ)アクリルグラフトポリマー)を合成して、各ポリマーからなるバインダーの溶液S-17~S-20をそれぞれ得た。
まず、構成成分(X)としてマクロモノマーM-3を以下のようにして合成した。
500mL三口フラスコに、ε-カプロラクトン156g、2-エチル-1-ヘキサノール44gを導入し、窒素を吹き込みながら、攪拌溶解した。モノブチル錫オキシド0.1gを加え、100℃に加熱した。8時間後、ガスクロマトグラフィーにて原料が消失したのを確認後、5℃まで冷却した。そこへ、酪酸ブチル233g、2,6-ジ-t-ブチル-4-メチルフェノール0.1g及びトリエチルアミン38gを添加した後、メタクリル酸クロリド32gを添加した。1時間後、1H-NMRにて原料が消失したのを確認後、1M(mol/L)の塩酸30g及び酢酸エチル300gを加え、水で抽出、洗浄した。得られた有機層を硫酸ナトリウムで乾燥し、30hPa、70℃で濃縮することでマクロモノマーM-3を得た。マクロモノマーM-3のSP値は17.1MPa1/2であった。
次いで、合成例S-1において、マクロモノマーM-1の溶液に代えてマクロモノマーM-3を用い、かつポリマーS-21~S-24が表1に示す組成(構成成分の種類及び含有量)となるように各構成成分を導く化合物を用いたこと以外は、合成例S-1と同様にして、ポリマーS-21~S-24((メタ)アクリルグラフトポリマー)を合成して、各ポリマーからなるバインダーの溶液S-21~S-24をそれぞれ得た。
合成例S-1において、ポリマーT-1~T-4が表1に示す組成(構成成分の種類及び含有量)となるように各構成成分を導く化合物を用いたこと以外は、合成例S-1と同様にして、ポリマーT-1((メタ)アクリルグラフトポリマー)、ポリマーT-2~T-4(直鎖状の(メタ)アクリルポリマー)を合成して、各ポリマーからなるバインダーの溶液T-1~T-4をそれぞれ得た。
合成例S-1において、ポリマーT-5及びT-6が表1に示す組成(構成成分の種類及び含有量)となるように各構成成分を導く化合物を用いたこと以外は、合成例S-1と同様にして、ポリマーT-5(直鎖状の(メタ)アクリルポリマー)及びT-6((メタ)アクリルグラフトポリマー)を酪酸ブチルに分散させたバインダー分散液T-5及びT-6(固形分濃度40質量%)をそれぞれ得た。この分散液T-5及びT-6中のバインダーの平均粒子径は、順に、400nm、450nmであった。
合成例S-1において、重合開始剤量を変更したこと以外は、合成例S-1と同様にして、ポリマーT-7((メタ)アクリルグラフトポリマー)を合成して、このポリマーからなるバインダーの溶液T-7を得た。
合成例S-1において、ポリマーT-8が表1に示す組成(構成成分の種類及び含有量)となるように各構成成分を導く化合物を用いたこと以外は、合成例S-1と同様にして、ポリマーT-8((メタ)アクリルグラフトポリマー)を合成して、このポリマーからなるバインダーの溶液T-8を得た。
なお、表1において、ポリマーが各構成成分に相当する構成成分を2種有する場合、「/」を用いて併記する。
表中、構成成分欄中の「-」は該当する構成成分を有していないことを示す。
- 構成成分(X) -
M-1~M-3:上記各合成例で合成したマクロモノマーに由来する構成成分であり、その化学構造を以下に示す。
なお、上記各合成例で合成又は準備したマクロモノマーが有する重合鎖の数平均分子量は、表1に示すように、いずれも800以上であった。
- 構成成分(A) -
各構成成分の化学構造を以下に示す。
- 構成成分(B) -
各構成成分の化学構造を以下に示す。
-その他の構成成分 -
化学構造を以下に示す。
[合成例A]
硫化物系無機固体電解質は、T.Ohtomo,A.Hayashi,M.Tatsumisago,Y.Tsuchida,S.Hama,K.Kawamoto,Journal of Power Sources,233,(2013),pp231-235、及び、A.Hayashi,S.Hama,H.Morimoto,M.Tatsumisago,T.Minami,Chem.Lett.,(2001),pp872-873の非特許文献を参考にして合成した。
具体的には、アルゴン雰囲気下(露点-70℃)のグローブボックス内で、硫化リチウム(Li2S、Aldrich社製、純度>99.98%)2.42g及び五硫化二リン(P2S5、Aldrich社製、純度>99%)3.90gをそれぞれ秤量し、メノウ製乳鉢に投入し、メノウ製乳棒を用いて、5分間混合した。Li2S及びP2S5の混合比は、モル比でLi2S:P2S5=75:25とした。
次いで、ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを66g投入し、上記の硫化リチウムと五硫化二リンの混合物全量を投入し、アルゴン雰囲気下で容器を完全に密閉した。遊星ボールミルP-7(商品名、フリッチュ社製)に容器をセットし、温度25℃で、回転数510rpmで20時間メカニカルミリングを行うことで、黄色粉体の硫化物系無機固体電解質(Li-P-S系ガラス、以下、LPSと表記することがある。)6.20gを得た。Li-P-S系ガラスの粒子径は15μmであった。
表2-1~表2-4(まとめて表2という。)に示す各組成物を以下のようにして調製した。
<無機固体電解質含有組成物の調製>
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを60g投入し、上記合成例Aで合成したLPS7.88g、表2-1又は表2-4に示すバインダー溶液又は分散液0.12g(固形分質量)、及び分散媒として酪酸ブチル12g(総量)を投入した。その後に、この容器を遊星ボールミルP-7(商品名)にセットした。温度25℃、回転数150rpmで10分間混合して、無機固体電解質含有組成物(スラリー)K-1~K-24及びKc11~Kc18をそれぞれ調製した。
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを60g投入し、合成例Aで合成したLPSを4.6g、及び、分散媒として酪酸ブチル12g(総量)を投入した。遊星ボールミルP-7(商品名)にこの容器をセットし、25℃で、回転数200rpmで30分間攪拌した。その後、この容器に、正極活物質としてNMC(アルドリッチ社製)を3.2g、導電助剤としてアセチレンブラック(AB)を0.14g、表2-2又は表2-4に示すバインダー溶液又は分散液を0.06g(固形分質量)投入し、遊星ボールミルP-7(商品名)に容器をセットし、温度25℃、回転数200rpmで30分間混合を続け、正極組成物(スラリー)PK-1~PK-24及びPKc21~PKc28をそれぞれ調製した。
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを60g投入し、合成例Aで合成したLPSを3.62g、表2-3又は表2-4に示すバインダー溶液又は分散液0.06g(固形分質量)、及び酪酸ブチルを12g(総量)投入した。遊星ボールミルP-7(商品名)にこの容器をセットし、温度25℃、回転数300rpmで60分間混合した。その後、負極活物質としてケイ素(Si)4.0g及び導電助剤としてVGCF(昭和電工社製)0.32gを投入し、同様に、遊星ボールミルP-7(商品名)に容器をセットして、温度25℃、回転数100rpmで10分間混合して、負極組成物(スラリー)NK-1~NK-24及びNKc21~NKc28をそれぞれ調製した。
上述のようにして調製した各組成物について、表2に示す組成物含有量及び固形分含有量の割合と同じ割合で、LPS、ポリマーバインダー、分散媒、活物質及び導電助剤を各組成物の調製条件と同様にして混合して、分散性評価用組成物(スラリー)を調製した。調製した各組成物について、グラインドメーター(あさひ総研社製)を用いて固体粒子の凝集物の発生(有無)を確認した。このときの凝集物のサイズをX(μm)として、初期分散性の指標とした。
一方、調製した各組成物を25℃で24時間放置した後、遊星ボールミルP-7(商品名)を用いて温度25℃で再度混合した。再混合時の回転数及び時間は無機固体電解質組成物、正極組成物、負極組成物それぞれの調製条件と同条件にした。再混合した組成物について、上記グラインドメーターを用いて固体粒子の凝集物の発生(有無)を確認した。このときの凝集物のサイズをY(μm)として、保存後の再分散性の指標とした。
なお、凝集物のサイズは、グラインドメーターへの塗布物が顕著な斑点が現れる点とした(JIS K-5600-2-5 6.6を参照)。
凝集物のサイズX及びYが下記評価基準のいずれに含まれるかにより、固体電解質組成物の保存安定性(固体粒子の再分散性)として凝集物の発生のしやすさ(凝集性又は沈降性)を評価した。本試験において、上記凝集物のサイズXが小さいほど初期分散性に優れ、サイズYが小さいほど保存安定性に優れることを示す。本試験では、凝集物のサイズYについて評価基準「D」以上が合格レベルであり、サイズYが8μm以下(評価基準が「C」以上)である場合は、凝集物のサイズXをも評価に含めた。結果を表2に示す。
- 評価基準 -
A: Y≦ 5μm かつ X≦ 5μm
B: 5μm<Y≦ 8μm かつ 5μm<X≦ 8μm
C: 5μm<Y≦ 8μm かつ 8μm<X≦12μm
D: 8μm<Y≦10μm
E:10μm<Y≦20μm
F:20μm<Y
上述のようにして調製した各組成物について、表2に示す組成物含有量及び固形分含有量の割合と同じ割合で、LPS、ポリマーバインダー、分散媒、活物質及び導電助剤を各組成物の調製条件と同様にして混合して、分散性評価用組成物(スラリー)を調製した。調製した各組成物を、グラインドメーター(あさひ総研社製)を用いて固体粒子の凝集物が発生しているかを確認した。本試験において、グラインドメーターで線状痕及び粒状痕が発生する粒子サイズを観察し、5μm以下である場合を凝集物がないと定義した。また、各組成物を25℃でベーカー式アプリケーター(商品名:SA-201)を用いて均一に(液切れせずに一定の塗布厚で)塗布できるかを評価した。
この評価(凝集物の有無及び塗布可能性)を、組成物中の固形分濃度を徐々に高めていき、凝集物が発生し、又は均一に塗布できなくなるまで繰り返して行い、凝集物の発生がなく均一に塗布できた最大固形分濃度が下記評価基準のいずれに含まれるかにより、高固形分濃度としたときの分散性を評価した。結果を表2に示す。
本試験において、最大固形分濃度が高いほど、組成物の固形分濃度を高めても固体粒子の優れた分散性を維持できることを示し、評価基準「D」以上が合格レベルである。
- 評価基準 -
A:70質量%以上
B:70質量%未満、65質量%以上
C:65質量%未満、60質量%以上
D:60質量%未満、55質量%以上
E:55質量%未満、50質量%以上
F:50質量%未満
LPS:合成例Aで合成したLPS
NMC:LiNi1/3Co1/3Mn1/3O2
Si:ケイ素(APS1~5μm、Alfa Aesar社製)
AB:アセチレンブラック
VGCF:カーボンナノファイバー
上記で得られた表3-1又は表3-4の「固体電解質組成物No.」欄に示す各無機固体電解質含有組成物を厚み20μmのアルミニウム箔上に、ベーカー式アプリケーター(商品名:SA-201、テスター産業社製)を用いて塗布し、80℃で2時間加熱して、無機固体電解質含有組成物を乾燥(分散媒を除去)させた。その後、ヒートプレス機を用いて、120℃の温度及び40MPaの圧力で10秒間、乾燥させた無機固体電解質含有組成物を加熱及び加圧して、全固体二次電池用固体電解質シート(表3-1及び表3-4において固体電解質シートと表記する。)101~124及びc11~c18をそれぞれ作製した。固体電解質層の膜厚は40μmであった。
上記で得られた表3-2又は表3-4の「電極組成物No.」欄に示す各正極組成物を厚み20μmのアルミニウム箔上にベーカー式アプリケーター(商品名:SA-201)を用いて塗布し、80℃で1時間加熱し、更に110℃で1時間加熱して、正極組成物を乾燥(分散媒を除去)した。その後、ヒートプレス機を用いて、乾燥させた正極組成物を25℃で加圧(10MPa、1分)して、膜厚70μmの正極活物質層を有する全固体二次電池用正極シート(表3-2及び表3-4において正極シートと表記する。)201~224及びc21~c28をそれぞれ作製した。
上記で得られた表3-3又は表3-4の「電極組成物No.」欄に示す各負極組成物を厚み20μmの銅箔上に、ベーカー式アプリケーター(商品名:SA-201)を用いて塗布し、80℃で1時間加熱し、更に110℃で1時間加熱して、負極組成物を乾燥(分散媒を除去)させた。その後、ヒートプレス機を用いて、乾燥させた負極組成物を25℃で加圧(10MPa、1分)して、膜厚60μmの負極活物質層を有する全固体二次電池用負極シート(表3-3及び表3-4において負極シートと表記する。)301~324及びc31~c38をそれぞれ作製した。
まず、全固体二次電池の製造に用いる、固体電解質層を備えた全固体二次電池用正極シート、及び固体電解質層を備えた全固体二次電池用負極シートをそれぞれ作製した。
表4-1及び表4-3の「電極活物質層(シートNo.)」欄に示す各全固体二次電池用正極シートの正極活物質層上に、上記で作製した、表4-1及び表4-3の「固体電解質層(シートNo.)」欄に示す固体電解質シートを固体電解質層が正極活物質層に接するように重ね、プレス機を用いて25℃で50MPa加圧して転写(積層)した後に、25℃、600MPaで加圧することで、膜厚25μmの固体電解質層を備えた全固体二次電池用正極シート(正極活物質層の膜厚50μm)No.201~224及びc21~c28をそれぞれ作製した。
表4-2及び表4-3の「電極活物質層(シートNo.)」欄に示す各全固体二次電池用負極シートの負極活物質層上に、上記で作製した、表4-2及び表4-3の「固体電解質層(シートNo.)」欄に示す固体電解質シートを固体電解質層が負極活物質層に接するように重ね、プレス機を用いて25℃で50MPa加圧して転写(積層)した後に、25℃、600MPaで加圧することで、膜厚25μmの固体電解質層を備えた全固体二次電池用負極シート(負極活物質層の膜厚40μm)301~324及びc31~c38をそれぞれ作製した。
上記で得られた固体電解質層を備えた全固体二次電池用正極シートNo.201(固体電解質含有シートのアルミニウム箔は剥離済み)を直径14.5mmの円板状に切り出し、図2に示すように、スペーサーとワッシャー(図2において図示せず)を組み込んだステンレス製の2032型コインケース11に入れた。次いで、固体電解質層上に直径15mmの円盤状に切り出したリチウム箔を重ねた。その上に更にステンレス箔を重ねた後、2032型コインケース11をかしめることで、図2に示すNo.401の全固体二次電池13を製造した。
このようにして製造した全固体二次電池は、図1に示す層構成を有する(ただし、リチウム箔が負極活物質層2及び負極集電体1に相当する)。
上記で得られた固体電解質を備えた全固体二次電池用負極シートNo.301(固体電解質含有シートのアルミニウム箔は剥離済み)を直径14.5mmの円板状に切り出し、図2に示すように、スペーサーとワッシャー(図2において図示せず)を組み込んだステンレス製の2032型コインケース11に入れた。次いで、下記で作製した全固体二次電池用正極シートから直径14.0mmで打ち抜いた正極シート(正極活物質層)を固体電解質層上に重ねた。その上に更にステンレス鋼箔(正極集電体)を重ねて全固体二次電池用積層体12(ステンレス鋼箔-アルミニウム箔-正極活物質層-固体電解質層-負極活物質層-銅箔からなる積層体)を形成した。その後、2032型コインケース11をかしめることで、図2に示す全固体二次電池No.501を製造した。
- 正極組成物の調製 -
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを180個投入し、上記合成例Aで合成したLPSを2.7g、KYNAR FLEX 2500-20(商品名、PVdF-HFP:ポリフッ化ビニリデンヘキサフルオロプロピレン共重合体、アルケマ社製)を固形分質量として0.3g、及び酪酸ブチルを22g投入した。フリッチュ社製遊星ボールミルP-7(商品名)にこの容器をセットし、25℃で、回転数300rpmで60分間攪拌した。その後、正極活物質としてLiNi1/3Co1/3Mn1/3O2(NMC)7.0gを投入し、同様にして、遊星ボールミルP-7に容器をセットし、25℃、回転数100rpmで5分間混合を続け、正極組成物を調製した。
- 固体二次電池用正極シートの作製 -
上記で得られた正極組成物を厚み20μmのアルミニウム箔(正極集電体)上に、ベーカー式アプリケーター(商品名:SA-201、テスター産業社製)により塗布し、100℃で2時間加熱し、正極組成物を乾燥(分散媒を除去)した。その後、ヒートプレス機を用いて、乾燥させた正極組成物を25℃で加圧(10MPa、1分)し、膜厚80μmの正極活物質層を有する全固体二次電池用正極シートを作製した。
製造した各全固体二次電池のイオン伝導度を測定した。具体的には、各全固体二次電池について、25℃の恒温槽中、1255B FREQUENCY RESPONSE ANALYZER(商品名、SOLARTRON社製)を用いて、電圧振幅5mV、周波数1MHz~1Hzまで交流インピーダンス測定した。これにより、イオン伝導度測定用試料の層厚方向の抵抗を求め、下記式(C1)により計算して、イオン伝導度を求めた。結果を表4-1~表4-3(まとめて表4という。)に示す。
式(C1):イオン伝導度σ(mS/cm)=
1000×試料層厚(cm)/[抵抗(Ω)×試料面積(cm2)]
式(C1)において、試料層厚は、積層体12を2032型コインケース11に入れる前に測定し、集電体の厚みを差し引いた値(固体電解質層及び電極活物質層の合計層厚)である。試料面積は、直径14.5mmの円板状シートの面積である。
得られたイオン伝導度σが下記評価基準のいずれに含まれるかを判定した。
本試験におけるイオン伝導度σは、評価基準「D」以上が合格である。
- 評価基準 -
A:0.30≦σ
B:0.25≦σ<0.30
C:0.20≦σ<0.25
D:0.15≦σ<0.20
E:0.10≦σ<0.15
F: σ<0.10
構成成分(A)を含有しないグラフト構造又は直鎖構造のポリマーで形成されたポリマーバインダーを含有する比較例の無機固体電解質含有組成物No.Kc11、Kc12、Kc14、及び構成成分(A)を含有していても直鎖構造のポリマー又は粒子状のグラフトポリマーで形成されたポリマーバインダーを含有する比較例の無機固体電解質含有組成物No.Kc13、Kc15及びKc16は、いずれも、分散特性(保存安定性及びスラリー濃厚化)に劣り、更に全固体二次電池のイオン伝導度も十分ではない。また、構成成分(A)を含有していても分子量が大き過ぎるグラフトポリマーで形成されたポリマーバインダーを含有する比較例の無機固体電解質含有組成物No.Kc17、更に構成成分(A)を含有しないグラフトポリマーで形成されたポリマーバインダーを含有する比較例の無機固体電解質含有組成物No.Kc18は、分散特性に劣り、更に全固体二次電池のイオン伝導度も十分ではない。更に、PKc21~PKc28及びNKc21~NKc28に示す電極組成物も、無機固体電解質含有組成物Kc11~Kc18と同様の傾向を示すことが分かる。
また、上記本発明の組成物は、上記<評価2:スラリー濃厚化試験(固形分濃度試験)>の結果から、固形分濃度を例えば50質量%以上に高めても、上記<評価1:保存安定性試験(再分散性)>及び<評価3:イオン伝導度測定>について、固形分濃度が40質量%である上記各組成物と同様の結果が得られることが分かる。更に、グラフトポリマーは構成成分(A)を含むことから、固体粒子に対する吸着が促進されて固体粒子の密着力(結着力)を強化できると考えられ、全固体二次電池のサイクル特性を改善しうることが分かる。
2 負極活物質層
3 固体電解質層
4 正極活物質層
5 正極集電体
6 作動部位
10 全固体二次電池
11 2032型コインケース
12 全固体二次電池用積層体
13 コイン型全固体二次電池
Claims (12)
- 周期律表第1族若しくは第2族に属する金属のイオンの伝導性を有する無機固体電解質と、ポリマーバインダーと、分散媒とを含有する無機固体電解質含有組成物であって、
前記ポリマーバインダーが、アミド基、イミド基、スルホンアミド基の少なくとも1種の官能基をポリマーの側鎖となる分子鎖中に含む構成成分(A)を有する、質量平均分子量が1,000~30,000であるグラフトポリマーを含み、かつ前記分散媒に溶解する、無機固体電解質含有組成物。 - 前記構成成分(A)が前記分子鎖中にアミド基を含む、請求項1に記載の無機固体電解質含有組成物。
- 前記グラフトポリマーが数平均分子量800以上の重合鎖を含む構成成分(X)を有する、請求項1~3のいずれか1項に記載の無機固体電解質含有組成物。
- 前記グラフトポリマーが下記官能基群(a)のうち少なくとも1つの極性官能基を有する構成成分(B)を有する、請求項1~4のいずれか1項に記載の無機固体電解質含有組成物。
<官能基群(a)>
スルホン酸基、リン酸基、ホスホン酸基、ヒドロキシ基、カルボキシ基、オキセタン基、エポキシ基、ジカルボン酸無水物基、チオール基、エーテル基、チオエーテル基、チオエステル基、フルオロアルキル基、及びこれらの塩 - 前記構成成分(A)が、数平均分子量800以上の重合鎖及び下記官能基群(a)に含まれる官能基を有さない構成成分である、請求項1~5のいずれか1項に記載の無機固体電解質含有組成物。
<官能基群(a)>
スルホン酸基、リン酸基、ホスホン酸基、ヒドロキシ基、カルボキシ基、オキセタン基、エポキシ基、ジカルボン酸無水物基、チオール基、エーテル基、チオエーテル基、チオエステル基、フルオロアルキル基、及びこれらの塩 - 活物質を含有する、請求項1~6のいずれか1項に記載の無機固体電解質含有組成物。
- 導電助剤を含有する、請求項1~7のいずれか1項に記載の無機固体電解質含有組成物。
- 請求項1~8のいずれか1項に記載の無機固体電解質含有組成物を用いて形成した層を有する全固体二次電池用シート。
- 正極活物質層と固体電解質層と負極活物質層とをこの順で具備する全固体二次電池であって、
前記正極活物質層、前記固体電解質層及び前記負極活物質層の少なくとも1つの層が請求項1~8のいずれか1項に記載の無機固体電解質含有組成物を用いて形成した層である、全固体二次電池。 - 請求項1~8のいずれか1項に記載の無機固体電解質含有組成物を製膜する、全固体二次電池用シートの製造方法。
- 請求項11に記載の製造方法を経て全固体二次電池を製造する、全固体二次電池の製造方法。
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| JP2015159067A (ja) * | 2014-02-25 | 2015-09-03 | 富士フイルム株式会社 | 複合固体電解質組成物、これを用いた電池用電極シートおよび全固体二次電池、ならびに電池用電極シートおよび全固体二次電池の製造方法 |
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Also Published As
| Publication number | Publication date |
|---|---|
| US20240283012A1 (en) | 2024-08-22 |
| EP4421826A1 (en) | 2024-08-28 |
| JPWO2023068237A1 (ja) | 2023-04-27 |
| EP4421826A4 (en) | 2025-09-03 |
| KR20240049842A (ko) | 2024-04-17 |
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