Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/137—Electrodes based on electro-active polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a slurry composition for a lithium ion secondary battery electrode, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery.
• Lithium ion secondary batteries are frequently used as secondary batteries used as power sources for these portable terminals.
• Mobile terminals are required to have more comfortable portability, and are rapidly becoming smaller, thinner, lighter, and higher performance. As a result, mobile terminals are used in various places.
• secondary batteries are also required to be smaller, thinner, lighter, and have higher performance as with mobile terminals.
• the electrode is usually obtained by mixing an electrode active material and, if necessary, a conductive material such as conductive carbon in a solvent to obtain a slurry composition, applying the slurry composition to a current collector, and drying. Manufactured.
• high temperature cycle characteristics high temperature cycle characteristics
• low temperature output characteristics low temperature characteristics
• Improvement is required.
• the electrode since the electrode is manufactured using the slurry composition as described above, it is considered that the properties of the slurry composition affect the performance of the lithium ion secondary battery. Therefore, development of a technology capable of improving the performance of the lithium ion secondary battery by controlling the properties of the slurry composition is required.
• the present invention was devised in view of the above problems, and a slurry composition for a lithium ion secondary battery capable of realizing a lithium ion secondary battery excellent in high temperature cycle characteristics and low temperature characteristics, and lithium ion using the same It aims at providing the electrode for secondary batteries, and a lithium ion secondary battery.
• a slurry composition for a lithium ion secondary battery containing water has a predetermined amount of a hydroxyl group-containing monomer unit, a fluorine-containing (meth) acrylate ester monomer unit, and an acid. It has been found that by including a water-soluble polymer containing a group-containing monomer unit, the high-temperature cycle characteristics and low-temperature characteristics of a lithium ion secondary battery can be improved, and the present invention has been completed. That is, the present invention is as follows.
• the water-soluble polymer comprises a lithium ion secondary containing 0.5% to 10% by weight of a hydroxyl group-containing monomer unit, a fluorine-containing (meth) acrylate monomer unit and an acid group-containing monomer unit.
• a slurry composition for battery electrodes [2] The slurry composition according to [1], wherein the water-soluble polymer has a 1% by weight aqueous solution viscosity of 10 mPa ⁇ s to 1000 mPa ⁇ s.
• the slurry composition according to [8], wherein the particulate binder is an acrylic soft polymer or a diene soft polymer.
• the slurry composition for lithium ion secondary batteries which can implement
• (meth) acrylic acid means acrylic acid and methacrylic acid.
• (meth) acrylate means an acrylate and a methacrylate.
• (meth) acrylonitrile means acrylonitrile and methacrylonitrile.
• a certain substance is water-soluble means that an insoluble content is less than 0.5% by weight when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C. Further, that a certain substance is water-insoluble means that an insoluble content is 90% by weight or more when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C.
• the slurry composition of this invention is a slurry composition for lithium ion secondary battery electrodes, Comprising: An electrode active material, a water-soluble polymer, and water are included. Moreover, it is preferable that the slurry composition of this invention contains a particulate-form binder.
• Electrode active material As the electrode active material for the positive electrode (hereinafter sometimes referred to as “positive electrode active material” as appropriate), a material capable of inserting and desorbing lithium ions is usually used. Such positive electrode active materials are roughly classified into those made of inorganic compounds and those made of organic compounds.
• Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, transition metal sulfides, lithium-containing composite metal oxides of lithium and transition metals, and the like.
• Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.
• transition metal oxide examples include MnO, MnO 2 , V 2 O 5 , V 6 O 13 , TiO 2 , Cu 2 V 2 O 3 , amorphous V 2 O—P 2 O 5 , MoO 3 , V 2 O 5 , V 6 O 13 and the like can be mentioned.
• MnO, V 2 O 5 , V 6 O 13 and TiO 2 are preferable from the viewpoint of cycle stability and capacity.
• transition metal sulfide examples include TiS 2 , TiS 3 , amorphous MoS 2 , FeS, and the like.
• lithium-containing composite metal oxide examples include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.
• lithium-containing composite metal oxide having a layered structure examples include lithium-containing cobalt oxide (LiCoO 2 ), lithium-containing nickel oxide (LiNiO 2 ), lithium composite oxide of Co—Ni—Mn, Ni—Mn— Examples thereof include lithium composite oxides of Al and lithium composite oxides of Ni—Co—Al.
• lithium-containing composite metal oxide having a spinel structure examples include lithium manganate (LiMn 2 O 4 ) or Li [Mn 3/2 M] in which a part of Mn of lithium manganate is substituted with another transition metal. 1/2 ] O 4 (where M is Cr, Fe, Co, Ni, Cu, etc.).
• lithium-containing composite metal oxide having an olivine type structure examples include Li X MPO 4 (wherein M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti).
• Examples of the positive electrode active material made of an organic compound include conductive polymer compounds such as polyacetylene and poly-p-phenylene.
• the positive electrode active material which consists of a composite material which combined the inorganic compound and the organic compound.
• a composite material covered with a carbon material may be produced by reducing and firing an iron-based oxide in the presence of a carbon source material, and the composite material may be used as a positive electrode active material.
• Iron-based oxides tend to have poor electrical conductivity, but can be used as a high-performance positive electrode active material by using a composite material as described above.
• positive electrode active material what carried out the element substitution of the said compound partially.
• mixture of said inorganic compound and organic compound as a positive electrode active material.
• positive electrode active material one type may be used alone, or two or more types may be used in combination at any ratio.
• the volume average particle diameter of the positive electrode active material particles is preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more, preferably 50 ⁇ m or less, more preferably 30 ⁇ m or less.
• the amount of the positive electrode active material is a ratio of the positive electrode active material in the electrode active material layer, and is preferably 90% by weight or more, more preferably 95% by weight or more, preferably 99.9% by weight or less, more preferably 99% by weight. % Or less.
• an electrode active material for a negative electrode is a substance that transfers electrons in the negative electrode.
• a material that can occlude and release lithium ions is usually used.
• An example of a suitable negative electrode active material is carbon. Examples of carbon include natural graphite, artificial graphite, and carbon black. Among these, natural graphite is preferably used.
• the negative electrode active material it is preferable to use a negative electrode active material containing at least one selected from the group consisting of tin, silicon, germanium and lead. This is because a negative electrode active material containing these elements has a small irreversible capacity. Among these, a negative electrode active material containing silicon is preferable. By using a negative electrode active material containing silicon, the electric capacity of the lithium ion secondary battery can be increased.
• the negative electrode active material one type may be used alone, or two or more types may be used in combination at any ratio. Therefore, two or more kinds of the negative electrode active materials may be used in combination. Among these, it is preferable to use a negative electrode active material containing a combination of carbon and one or both of metallic silicon and a silicon-based active material.
• a negative electrode active material containing a combination of carbon and one or both of metallic silicon and a silicon-based active material Li insertion and desorption from one or both of metallic silicon and a silicon-based active material occurs at a high potential, It is presumed that Li insertion and desorption from carbon occur at low potential. For this reason, since expansion and contraction are suppressed, the cycle characteristics of the lithium ion secondary battery can be improved.
• silicon-based active material examples include SiO, SiO 2 , SiO x (0.01 ⁇ x ⁇ 2), SiC, SiOC, and the like, and SiO x , SiC, and SiOC are preferable.
• SiO x is a compound formed from one or both of SiO and SiO 2 and metallic silicon. This SiO x can be produced, for example, by cooling and precipitating silicon monoxide gas generated by heating a mixture of SiO 2 and metal silicon.
• the compounding method include a method of compounding one or both of metallic silicon and silicon-based active material with carbon; conductive carbon and one or both of metallic silicon and silicon-based active material The method of compounding by granulating a mixture; etc. are mentioned.
• Examples of the method for coating one or both of metallic silicon and silicon-based active material with carbon include, for example, a method in which one or both of metallic silicon and silicon-based active material are subjected to heat treatment, and disproportionation; A method of performing chemical vapor deposition by subjecting one or both of the materials to a heat treatment; and the like.
• these methods include a method of subjecting SiO x to heat treatment in an atmosphere containing at least one or both of an organic gas and an organic vapor.
• This heat treatment is preferably 900 ° C. or more, more preferably 1000 ° C. or more, further preferably 1050 ° C. or more, particularly preferably 1100 ° C. or more, preferably 1400 ° C. or less, more preferably 1300 ° C. or less, particularly preferably 1200.
• SiO x can be disproportionated into a composite of silicon and silicon dioxide, and carbon can be chemically deposited on the surface.
• Another specific example is the following method. That is, one or both of metallic silicon and silicon-based active material is heat-treated in an inert gas atmosphere to disproportionate to obtain a silicon composite. This heat treatment is preferably performed at 900 ° C. or higher, more preferably 1000 ° C. or higher, particularly preferably 1100 ° C. or higher, and preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower.
• the silicon composite thus obtained is preferably pulverized to a particle size of 0.1 ⁇ m to 50 ⁇ m.
• the pulverized silicon composite is heated at 800 ° C. to 1400 ° C. under an inert gas stream.
• the heated silicon composite is subjected to a heat treatment in an atmosphere containing at least one or both of an organic gas and an organic vapor to chemically vapor-deposit carbon on the surface.
• This heat treatment is preferably performed at 800 ° C. or higher, more preferably 900 ° C. or higher, particularly preferably 1000 ° C. or higher, preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower, particularly preferably 1200 ° C. or lower.
• one or both of metal silicon and silicon-based active material is subjected to chemical vapor deposition with one or both of organic gas and organic vapor.
• This chemical vapor deposition treatment is preferably performed in a temperature range of 500 ° C. to 1200 ° C., more preferably 500 ° C. to 1000 ° C., and particularly preferably 500 ° C. to 900 ° C.
• This is heat-treated in an inert gas atmosphere to disproportionate.
• This heat treatment is preferably performed at 900 ° C. or higher, more preferably 1000 ° C. or higher, particularly preferably 1100 ° C. or higher, and preferably 1400 ° C. or lower, more preferably 1300 ° C. or lower.
• the amount of silicon atoms in the negative electrode active material is 0.1 parts by weight with respect to 100 parts by weight of the total carbon atoms. It is preferable that the amount be ⁇ 50 parts by weight. Thereby, a conductive path is formed satisfactorily and the conductivity of the negative electrode can be improved.
• a weight ratio of carbon to one or both of metallic silicon and a silicon-based active material (“carbon weight” / It is preferable that “weight of metal silicon and silicon-based active material”) be within a predetermined range. Specifically, the weight ratio is preferably 50/50 or more, more preferably 70/30 or more, preferably 97/3 or less, more preferably 90/10 or less. Thereby, the cycling characteristics of a lithium ion secondary battery can be improved.
• the negative electrode active material is preferably sized in the form of particles.
• a higher-density electrode can be formed when forming an electrode for a lithium ion secondary battery (hereinafter, also referred to as “electrode” as appropriate).
• the volume average particle diameter of the particles of the negative electrode active material is appropriately selected in consideration of other constituent requirements of the lithium ion secondary battery, and is preferably 0.1 ⁇ m or more, more preferably 1 ⁇ m or more, and particularly preferably 5 ⁇ m or more.
• the thickness is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less, and particularly preferably 20 ⁇ m or less.
• the specific surface area of the negative electrode active material is preferably 2 m 2 / g or more, more preferably 3 m 2 / g or more, particularly preferably 5 m 2 / g or more, preferably 20 m 2 / g or less, from the viewpoint of improving the output density. More preferably, it is 15 m 2 / g or less, particularly preferably 10 m 2 / g or less.
• the specific surface area of the negative electrode active material can be measured by, for example, the BET method.
• the amount of the negative electrode active material is a ratio of the negative electrode active material in the electrode active material layer, preferably 85% by weight or more, more preferably 88% by weight or more, preferably 99% by weight or less, more preferably 97% by weight or less. It is. By setting the amount of the negative electrode active material in the above range, it is possible to realize a negative electrode that exhibits flexibility and adhesion while exhibiting a high capacity.
• the water-soluble polymer usually has an action of uniformly dispersing the electrode active material in the slurry composition of the present invention. Further, the water-soluble polymer has an action of adjusting the viscosity of the slurry composition and can function as a thickener. Furthermore, the water-soluble polymer acts to bind the electrode active material and the current collector by interposing between the electrode active materials and between the electrode active material and the current collector in the electrode active material layer. Can play. In addition, the water-soluble polymer can form a stable layer that covers the electrode active material in the electrode active material layer, and can exert an action of suppressing decomposition of the electrolytic solution.
• the water-soluble polymer includes a hydroxyl group-containing monomer unit.
• a hydroxyl group-containing monomer unit is a structural unit having a structure formed by polymerizing a hydroxyl group-containing monomer.
• hydroxyl group-containing monomer examples include 2-hydroxyethyl acrylate, 2-hydroxy methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate.
• Hydroxyalkyl (meth) such as di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, and 2-hydroxyethyl methyl fumarate Acrylates; allyl alcohol, monoallyl ethers of polyhydric alcohols; vinyl alcohol, and the like.
• hydroxyalkyl (meth) acrylate is preferable, hydroxyalkyl acrylate is more preferable, and 2-hydroxyethyl acrylate is particularly preferable.
• a hydroxyl-containing monomer and a hydroxyl-containing monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the hydroxyl group-containing monomer does not include a monomer containing a carboxyl group.
• the proportion of the hydroxyl group-containing monomer unit in the water-soluble polymer is usually 0.5% by weight or more, preferably 1% by weight or more, more preferably 1.5% by weight or more, and usually 10% by weight or less, preferably It is 8% by weight or less, more preferably 5% by weight or less.
• the ratio of the hydroxyl group-containing monomer unit is at least the lower limit of the above range, the dispersibility of the particles such as the electrode active material and the particulate binder can be increased in the slurry composition of the present invention.
• the ratio of the hydroxyl group-containing monomer unit in the water-soluble polymer usually corresponds to the ratio (preparation ratio) of the hydroxyl group-containing monomer in all monomers of the water-soluble polymer.
• the water-soluble polymer contains a fluorine-containing (meth) acrylic acid ester monomer unit.
• the fluorine-containing (meth) acrylic acid ester monomer unit is a structural unit having a structure formed by polymerizing a fluorine-containing (meth) acrylic acid monomer.
• fluorine-containing (meth) acrylic acid ester monomer examples include monomers represented by the following formula (I).
• R 1 represents a hydrogen atom or a methyl group.
• R 2 represents a hydrocarbon group containing a fluorine atom.
• the carbon number of the hydrocarbon group is preferably 1 or more, and preferably 18 or less.
• the number of fluorine atoms contained in R 2 may be one or two or more.
• fluorine-containing (meth) acrylic acid ester monomers represented by formula (I) include (meth) acrylic acid alkyl fluoride, (meth) acrylic acid fluoride aryl, and (meth) acrylic acid fluoride.
• Aralkyl is mentioned. Of these, alkyl fluoride (meth) acrylate is preferable. Specific examples of such monomers include 2,2,2-trifluoroethyl (meth) acrylate, ⁇ - (perfluorooctyl) ethyl (meth) acrylate, 2,2, (meth) acrylic acid.
• a fluorine-containing (meth) acrylic acid ester monomer and a fluorine-containing (meth) acrylic acid ester monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Also good.
• the proportion of the fluorine-containing (meth) acrylic acid ester monomer unit in the water-soluble polymer is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and particularly preferably 0.5% by weight or more. Yes, preferably 50% by weight or less, more preferably 45% by weight or less, and particularly preferably 40% by weight or less.
• the ratio of the fluorine-containing (meth) acrylic acid ester monomer unit is not less than the lower limit of the above range, the output characteristics such as the low-temperature characteristics of the lithium ion secondary battery can be improved.
• the cycle characteristic of a lithium ion secondary battery can be improved and battery life can be lengthened.
• the ratio of the fluorine-containing (meth) acrylate monomer units in the water-soluble polymer is usually the ratio of the fluorine-containing (meth) acrylate monomer units in all monomers of the water-soluble polymer ( It matches the charging ratio).
• the water-soluble polymer includes an acid group-containing monomer unit.
• the acid group-containing monomer unit is a structural unit having a structure formed by polymerizing an acid group-containing monomer.
• An acid group refers to a group that exhibits acidity.
• acid groups include carboxylic acid groups such as carboxyl groups and carboxylic anhydride groups, sulfonic acid groups, and phosphoric acid groups. Of these, carboxylic acid groups and sulfonic acid groups are preferred.
• Examples of the acid group-containing monomer include an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated sulfonic acid monomer, and an ethylenically unsaturated phosphoric acid monomer.
• Examples of the ethylenically unsaturated carboxylic acid monomer include an ethylenically unsaturated monocarboxylic acid monomer and derivatives thereof, an ethylenically unsaturated dicarboxylic acid monomer and acid anhydrides thereof, and derivatives thereof.
• Examples of ethylenically unsaturated monocarboxylic acid monomers include acrylic acid, methacrylic acid, and crotonic acid.
• Examples of derivatives of ethylenically unsaturated monocarboxylic acid monomers include 2-ethylacrylic acid, isocrotonic acid, ⁇ -acetoxyacrylic acid, ⁇ -trans-aryloxyacrylic acid, ⁇ -chloro- ⁇ -E-methoxy Examples include acrylic acid and ⁇ -diaminoacrylic acid.
• Examples of ethylenically unsaturated dicarboxylic acid monomers include maleic acid, fumaric acid, and itaconic acid.
• Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acid monomers include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
• Examples of derivatives of ethylenically unsaturated dicarboxylic acid monomers include maleic acid substituted with hydrocarbon groups such as methylmaleic acid, dimethylmaleic acid, phenylmaleic acid; chloromaleic acid, dichloromaleic acid, fluoromaleic acid And maleic esters such as methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, fluoroalkyl maleate, and the like.
• ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid are preferable. This is because the solubility of the obtained water-soluble polymer in water can be further increased.
• ethylenically unsaturated sulfonic acid monomers include monomers sulfonated one of conjugated double bonds of diene compounds such as isoprene and butadiene, vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfone.
• diene compounds such as isoprene and butadiene
• vinyl sulfonic acid vinyl sulfonic acid
• styrene sulfonic acid styrene sulfonic acid
• allyl sulfonic acid sulfone.
• examples thereof include ethyl methacrylate, sulfopropyl methacrylate, sulfobutyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 3-allyloxy-2-hydroxypropanesulfonic acid (HAPS), and salts thereof.
• the salt include lithium
• Examples of the ethylenically unsaturated phosphoric acid monomer include monomers having an ethylenically unsaturated group and a —OP ( ⁇ O) (— OR a ) —OR b group (R a and R b is independently a hydrogen atom or any organic group.) or a salt thereof.
• Specific examples of the organic group as R a and R b include an aliphatic group such as an octyl group and an aromatic group such as a phenyl group.
• Specific examples of the ethylenically unsaturated phosphoric acid monomer include a compound containing a phosphoric acid group and an allyloxy group, and a phosphoric acid group-containing (meth) acrylic acid ester.
• Examples of the compound containing a phosphoric acid group and an allyloxy group include 3-allyloxy-2-hydroxypropane phosphoric acid.
• Examples of phosphate group-containing (meth) acrylic acid esters include dioctyl-2-methacryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, monomethyl-2-methacryloyloxyethyl phosphate, dimethyl-2-methacrylate.
• ethylenically unsaturated carboxylic acid monomers and ethylenically unsaturated sulfonic acid monomers preferred are acrylic acid, methacrylic acid, itaconic acid and 2- Examples include acrylamido-2-methylpropanesulfonic acid, acrylic acid and methacrylic acid are more preferable, and methacrylic acid is particularly preferable.
• the acid group-containing monomer and the acid group-containing monomer unit one type may be used alone, or two or more types may be used in combination at any ratio.
• the ratio of the acid group-containing monomer unit is preferably 20% by weight or more, more preferably 25% by weight or more, particularly preferably 30% by weight or more, and preferably 50% by weight or less.
• the amount is preferably 45% by weight or less, particularly preferably 40% by weight or less.
• the ratio of the acid group-containing monomer unit is at least the lower limit of the above range, the adhesion between the electrode active material layer and the current collector can be enhanced. Moreover, by being below the upper limit of the said range, the cycle characteristic of a lithium ion secondary battery can be improved and battery life can be lengthened.
• the ratio of the acid group-containing monomer unit in the water-soluble polymer usually corresponds to the ratio (preparation ratio) of the acid group-containing monomer in all the monomers of the water-soluble polymer.
• the water-soluble polymer preferably further contains a crosslinkable monomer unit.
• the crosslinkable monomer unit is a structural unit having a structure formed by polymerizing a crosslinkable monomer.
• the water-soluble polymer can be crosslinked, so that the strength and stability of the electrode active material layer can be increased.
• swelling of the electrode active material layer with respect to the electrolytic solution can be suppressed, and the low temperature characteristics of the lithium ion secondary battery can be improved.
• crosslinkable monomer a monomer capable of forming a crosslinked structure upon polymerization can be used.
• the crosslinkable monomer include monomers having two or more reactive groups per molecule. More specifically, a monofunctional monomer having a heat-crosslinkable crosslinkable group and one olefinic double bond per molecule, and a polyfunctional having two or more olefinic double bonds per molecule. Ionic monomers.
• thermally crosslinkable groups contained in the monofunctional monomer include epoxy groups, N-methylolamide groups, oxetanyl groups, oxazoline groups, and combinations thereof.
• an epoxy group is more preferable in terms of easy adjustment of crosslinking and crosslinking density.
• crosslinkable monomer having an epoxy group as a thermally crosslinkable group and having an olefinic double bond examples include vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl.
• Unsaturated glycidyl ethers such as ether; butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene Monoepoxides of dienes or polyenes such as; alkenyl epoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; and glycidyl acrylate, glycidyl methacrylate, Glycidyl crotonate, glycy Unsaturated carboxylic acids such as ru-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidy
• crosslinkable monomer having an N-methylolamide group as a thermally crosslinkable group and having an olefinic double bond have a methylol group such as N-methylol (meth) acrylamide (meta ) Acrylamides.
• crosslinkable monomer having an oxetanyl group as a thermally crosslinkable group and having an olefinic double bond examples include 3-((meth) acryloyloxymethyl) oxetane, 3-((meth) Acryloyloxymethyl) -2-trifluoromethyloxetane, 3-((meth) acryloyloxymethyl) -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, and 2-((meth) acryloyloxymethyl) ) -4-trifluoromethyloxetane.
• crosslinkable monomer having an oxazoline group as a heat crosslinkable group and having an olefinic double bond examples include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2- Oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and And 2-isopropenyl-5-ethyl-2-oxazoline.
• multifunctional monomers having two or more olefinic double bonds include allyl (meth) acrylate, ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Tetraethylene glycol di (meth) acrylate, trimethylolpropane-tri (meth) acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, trimethylolpropane-diallyl
• Examples include ethers, allyl or vinyl ethers of polyfunctional alcohols other than those described above, triallylamine, methylenebisacrylamide, and divinylbenzene.
• crosslinkable monomer ethylene dimethacrylate, allyl glycidyl ether, glycidyl methacrylate and divinylbenzene are preferable, and ethylene dimethacrylate and glycidyl methacrylate are more preferable.
• crosslinked monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the proportion of the crosslinkable monomer unit is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, particularly preferably 0.2% by weight or more, preferably 2%. % By weight or less, more preferably 1.5% by weight or less, particularly preferably 1% by weight or less.
• the ratio of the crosslinkable monomer unit is not less than the lower limit of the above range, the cycle characteristics of the lithium ion secondary battery can be improved and the battery life can be extended.
• the adhesiveness of an electrode active material layer and a collector can be improved because it is below the upper limit of the said range.
• the ratio of the crosslinkable monomer unit in the water-soluble polymer coincides with the ratio (charge ratio) of the crosslinkable monomer in all the monomers of the water-soluble polymer.
• the water-soluble polymer has any structural unit other than the above-mentioned hydroxyl group-containing monomer unit, fluorine-containing (meth) acrylate monomer unit, acid group-containing monomer unit and crosslinkable monomer unit. May be included.
• the water-soluble polymer may contain (meth) acrylic acid ester monomer units other than the fluorine-containing (meth) acrylic acid ester monomer units.
• the (meth) acrylic acid ester monomer unit is a structural unit having a structure formed by polymerizing a (meth) acrylic acid ester monomer. However, among the (meth) acrylate monomers, those containing fluorine are distinguished from (meth) acrylate monomers as fluorine-containing (meth) acrylate monomers.
• Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, Acrylic acid alkyl esters such as 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; and methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t -Butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl
• the proportion of the (meth) acrylic acid ester monomer unit is preferably 25% by weight or more, more preferably 30% by weight or more, particularly preferably 35% by weight or more, and preferably 75%. % By weight or less, more preferably 70% by weight or less, particularly preferably 65% by weight or less.
• the ratio of the (meth) acrylic acid ester monomer unit in the water-soluble polymer is usually the ratio of the (meth) acrylic acid ester monomer in all the monomers of the water-soluble polymer (preparation ratio). Match.
• the water-soluble polymer may contain a reactive surfactant unit.
• the reactive surfactant unit is a structural unit obtained by polymerizing a reactive surfactant monomer.
• the reactive surfactant unit forms part of the water-soluble polymer and can function as a surfactant.
• the reactive surfactant monomer is a monomer having a polymerizable group that can be copolymerized with other monomers and having a surfactant group (hydrophilic group and hydrophobic group).
• the reactive surfactant monomer has a polymerizable unsaturated group, and this group also acts as a hydrophobic group after polymerization.
• the polymerizable unsaturated group that the reactive surfactant monomer has include a vinyl group, an allyl group, a vinylidene group, a propenyl group, an isopropenyl group, and an isobutylidene group.
• One kind of the polymerizable unsaturated group may be used alone, or two or more kinds may be used in combination at any ratio.
• the reactive surfactant monomer usually has a hydrophilic group as a portion that exhibits hydrophilicity.
• Reactive surfactant monomers are classified into anionic, cationic and nonionic surfactants depending on the type of hydrophilic group.
• Examples of the anionic hydrophilic group include —SO 3 M, —COOM, and —PO (OM) 2 .
• M represents a hydrogen atom or a cation.
• Examples of cations include alkali metal ions such as lithium, sodium and potassium; alkaline earth metal ions such as calcium and magnesium; ammonium ions; ammonium ions of alkylamines such as monomethylamine, dimethylamine, monoethylamine and triethylamine; and And ammonium ions of alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine.
• Examples of the cationic hydrophilic group include —Cl, —Br, —I, and —SO 3 OR X.
• R X represents an alkyl group.
• Examples of R X is methyl group, an ethyl group, a propyl group, and isopropyl group.
• An example of a nonionic hydrophilic group is —OH.
• Suitable reactive surfactant monomers include compounds represented by the following formula (II).
• R represents a divalent linking group. Examples of R include —Si—O— group, methylene group and phenylene group.
• R 3 represents a hydrophilic group. An example of R 3 includes —SO 3 NH 4 .
• n represents an integer of 1 to 100.
• a suitable reactive surfactant monomer has a structural unit having a structure formed by polymerizing ethylene oxide and a structural unit having a structure formed by polymerizing butylene oxide, and Examples include compounds having an alkenyl group having a terminal double bond and —SO 3 NH 4 at the terminal (for example, trade names “Latemul PD-104” and “Latemul PD-105”, manufactured by Kao Corporation).
• a reactive surfactant monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the proportion of the reactive surfactant unit is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, particularly preferably 0.5% by weight or more, preferably 5%. % By weight or less, more preferably 4% by weight or less, particularly preferably 2% by weight or less.
• the dispersibility of the slurry composition can be improved by setting the ratio of the reactive surfactant unit to the lower limit value or more of the above range.
• durability of an electrode can be improved by setting it as below an upper limit.
• the ratio of the reactive surfactant unit in the water-soluble polymer usually coincides with the ratio (charge ratio) of the reactive surfactant monomer in all monomers of the water-soluble polymer.
• the water-soluble polymer may have include structural units having a structure formed by polymerizing the following monomers. That is, aromatic vinyl monomers such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, ⁇ -methylstyrene, divinylbenzene, etc.
• aromatic vinyl monomers such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, ⁇ -methylstyrene, divinylbenzene, etc.
• Unsaturated carboxylic acid amide monomers such as acrylamide; ⁇ , ⁇ -unsaturated nitrile compound monomers such as acrylonitrile and methacrylonitrile; olefin monomers such as ethylene and propylene; vinyl chloride, vinylidene chloride, etc.
• Halogen atom-containing monomers vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl Vinyl keto One or more of vinyl ketone monomers such as butyl vinyl ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; and heterocyclic compound-containing vinyl compound monomers such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole; Examples include a structural unit having a structure to be formed.
• the viscosity of a 1% by weight aqueous solution of the water-soluble polymer is preferably 10 mPa ⁇ s or more, more preferably 20 mPa ⁇ s or more, particularly preferably 50 mPa ⁇ s or more, preferably 1000 mPa ⁇ s or less, more preferably 800 mPa ⁇ s. s or less, particularly preferably 500 mPa ⁇ s or less.
• the viscosity By setting the viscosity to be equal to or higher than the lower limit of the above range, the strength of the water-soluble polymer can be increased and the durability of the electrode can be improved.
• the coating strength of the slurry composition of this invention can be made favorable by setting it as an upper limit or less, and the adhesive strength of a collector and an electrode active material layer can be improved.
• the viscosity can be adjusted by, for example, the molecular weight of the water-soluble polymer.
• the weight average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 700 or more, particularly preferably 1000 or more, preferably 500,000 or less, more preferably 450,000 or less, and particularly preferably 400,000 or less.
• the weight average molecular weight of the water-soluble polymer is polystyrene using gel permeation chromatography (GPC) as a developing solvent, a solution obtained by dissolving 0.85 g / ml sodium nitrate in a 10% by volume aqueous solution of dimethylformamide. It can be obtained as a conversion value.
• GPC gel permeation chromatography
• the water-soluble polymer can be produced, for example, by polymerizing a monomer composition containing the above-described monomer in an aqueous solvent. At this time, the ratio of each monomer in the monomer composition is usually a structural unit in the water-soluble polymer (for example, an acidic group-containing monomer unit, a fluorine-containing (meth) acrylic acid monomer unit, The ratio of the acid group-containing monomer unit and the crosslinkable monomer unit).
• a structural unit in the water-soluble polymer for example, an acidic group-containing monomer unit, a fluorine-containing (meth) acrylic acid monomer unit, The ratio of the acid group-containing monomer unit and the crosslinkable monomer unit.
• the aqueous solvent is not particularly limited as long as the water-soluble polymer can be dispersed.
• the boiling point at normal pressure is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, preferably 350 ° C. or lower, more preferably 300 ° C. or lower. Examples of the aqueous solvent will be given below. In the following examples, the number in parentheses after the solvent name is the boiling point (unit: ° C) at normal pressure, and the value after the decimal point is a value rounded off or rounded down.
• aqueous solvents examples include water (100); ketones such as diacetone alcohol (169) and ⁇ -butyrolactone (204); ethyl alcohol (78), isopropyl alcohol (82), and normal propyl alcohol (97).
• Alcohols propylene glycol monomethyl ether (120), methyl cellosolve (124), ethyl cellosolve (136), ethylene glycol tertiary butyl ether (152), butyl cellosolve (171), 3-methoxy-3-methyl-1-butanol (174), Ethylene glycol monopropyl ether (150), diethylene glycol monobutyl ether (230), triethylene glycol monobutyl ether (271), dipropylene glycol monomethyl ether (188), etc.
• Glycol ethers and 1,3-dioxolane (75), 1,4-dioxolane (101), ethers such as tetrahydrofuran (66) and the like.
• water is particularly preferable from the viewpoint that it is not flammable and a polymer dispersion can be easily obtained.
• water may be used as the main solvent, and an aqueous solvent other than the above-described water may be mixed and used within a range in which the dispersion state of the polymer can be ensured.
• the polymerization method is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used.
• the polymerization method any method such as ion polymerization, radical polymerization, and living radical polymerization can be used. It is easy to obtain a high molecular weight body, and since the polymer is obtained in a state of being dispersed in water as it is, no redispersion treatment is necessary, and it can be used for the production of the slurry composition of the present invention. From the viewpoint of efficiency, the emulsion polymerization method is particularly preferable.
• the emulsion polymerization method is usually performed by a conventional method. For example, it is carried out by the method described in “Experimental Chemistry Course” Vol. That is, water, an additive such as a dispersant, an emulsifier, a crosslinking agent, a polymerization initiator, and a monomer are added to a sealed container equipped with a stirrer and a heating device so as to have a predetermined composition, and the composition in the container
• a product is stirred to emulsify monomers and the like in water, and the temperature is increased while stirring to initiate polymerization.
• it is the method of putting into a sealed container and starting reaction similarly.
• polymerization initiators examples include organic compounds such as lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Peroxides; azo compounds such as ⁇ , ⁇ ′-azobisisobutyronitrile; ammonium persulfate; and potassium persulfate.
• a polymerization initiator may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• emulsifiers for example, emulsifiers, dispersants, polymerization initiators, and the like are generally used in these polymerization methods, and the amount used is generally the amount generally used.
• the polymerization temperature and polymerization time can be arbitrarily selected depending on the polymerization method and the type of polymerization initiator. Usually, the polymerization temperature is about 30 ° C. or more, and the polymerization time is about 0.5 to 30 hours. Further, additives such as amines may be used as a polymerization aid.
• a reaction solution containing a water-soluble polymer is usually obtained by polymerization.
• the obtained reaction solution is usually acidic, and the water-soluble polymer is often dispersed in an aqueous solvent.
• the water-soluble polymer dispersed in the aqueous solvent as described above can usually be made soluble in the aqueous solvent by adjusting the pH of the reaction solution to, for example, 7 to 13. You may take out a polymer from the reaction liquid obtained in this way.
• water is used as an aqueous solvent, and the slurry composition of the present invention is produced using a water-soluble polymer dissolved in water.
• Examples of the method for alkalinizing the pH to 7 to 13 include alkaline metal aqueous solutions such as lithium hydroxide aqueous solution, sodium hydroxide aqueous solution and potassium hydroxide aqueous solution; alkaline earth such as calcium hydroxide aqueous solution and magnesium hydroxide aqueous solution.
• Metal aqueous solution A method of mixing an alkaline aqueous solution such as an aqueous ammonia solution with the reaction solution.
• One kind of the alkaline aqueous solution may be used alone, or two or more kinds may be used in combination at any ratio.
• the amount of the water-soluble polymer is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, particularly preferably 0.5 parts by weight or more, preferably 100 parts by weight of the electrode active material. Is 10 parts by weight or less, more preferably 8 parts by weight or less, and particularly preferably 5 parts by weight or less. Adhesive strength can be ensured when the amount of the water-soluble polymer is not less than the lower limit of the above range. Moreover, a low temperature characteristic can be improved by being below an upper limit.
• the slurry composition of the present invention contains water.
• Water functions as a solvent or a dispersion medium, and can disperse the electrode active material or dissolve the water-soluble polymer.
• a solvent other than water may be used in combination with water.
• a liquid that can dissolve the particulate binder and the water-soluble polymer is combined with water, the dispersion of the electrode active material is stabilized by adsorbing the particulate binder and the water-soluble polymer on the surface of the electrode active material. Therefore, it is preferable.
• the type of liquid to be combined with water is preferably selected from the viewpoint of drying speed and environment.
• Preferred examples include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate, ⁇ -butyrolactone, Esters such as ⁇ -caprolactone; Nitriles such as acetonitrile and propionitrile; Ethers such as tetrahydrofuran and ethylene glycol diethyl ether: Alcohols such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; N-methyl Examples include pyrrolidone and amides such as N, N-dimethylformamide, among which N-methylpyrrolidone (NMP) is preferable. One of these
• the amount of the solvent is preferably adjusted so that the viscosity of the slurry composition of the present invention is suitable for coating.
• the solid content concentration of the slurry composition of the present invention is preferably 30% by weight or more, more preferably 35% by weight or more, preferably 70% by weight or less, more preferably 65% by weight or less. The amount is adjusted to be used.
• the solid content of the slurry composition indicates a substance that remains as a constituent component of the electrode active material layer after the slurry composition is dried.
• the slurry composition of the present invention preferably contains a particulate binder.
• a particulate binder By including the particulate binder, the binding property of the electrode active material layer can be improved, and the strength against mechanical force applied to the electrode during handling such as winding and transportation can be improved.
• the risk of a short circuit or the like due to foreign matter is reduced.
• the electrode active material can be stably held in the electrode active material layer, durability such as cycle characteristics and high-temperature storage characteristics can be improved.
• the particulate binder can be bound to the electrode active material not by a surface but by a point by being particulate.
• the output resistance of the lithium ion secondary battery can be improved by reducing the internal resistance.
• the particulate binder various polymers can be used, but a water-insoluble polymer is usually used.
• the polymer that forms the particulate binder include polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, poly An acrylonitrile derivative or the like may be used.
• a soft polymer for example, (I) Polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate / styrene copolymer, butyl acrylate / acrylonitrile copolymer, butyl acrylate / acrylonitrile / glycidyl methacrylate copolymer, etc.
• a soft polymer for example, (I) Polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate / styrene copolymer, butyl acrylate / acrylonitrile copolymer, butyl acrylate / acrylonitrile / glycidyl methacrylate copolymer, etc.
• An acrylic soft polymer which is a homopolymer of acrylic acid or a methacrylic acid derivative or a copolymer thereof with a monomer copolymerizable therewith;
• isobutylene-based soft polymers such as polyisobutylene, isobutylene-isoprene rubber, isobutylene-styrene copolymer;
• the diene soft polymer is a polymer containing an aliphatic conjugated diene monomer unit.
• the aliphatic conjugated diene monomer unit is a structural unit having a structure formed by polymerizing an aliphatic conjugated diene monomer.
• Examples of the aliphatic conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3 butadiene, 2-chloro-1,3-butadiene; And pentadiene having a conjugated double bond in a chain and a substituted product thereof; and hexadiene having a conjugated double bond in a side chain and a substituted product thereof. Of these, 1,3-butadiene is preferred.
• an aliphatic conjugated diene monomer and an aliphatic conjugated diene monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the proportion of the aliphatic conjugated diene monomer unit is preferably 20% by weight or more, more preferably 30% by weight or more, preferably 70% by weight or less, more preferably 60% by weight or less, Particularly preferred is 55% by weight or less.
• the ratio of the aliphatic conjugated diene monomer unit in the diene soft polymer is usually equal to the ratio (preparation ratio) of the aliphatic conjugated diene monomer in all the monomers of the diene soft polymer.
• the diene soft polymer preferably contains an aromatic vinyl monomer unit.
• the aromatic vinyl monomer unit is a structural unit having a structure formed by polymerizing an aromatic vinyl monomer.
• aromatic vinyl monomer examples include styrene, ⁇ -methylstyrene, vinyl toluene, and divinylbenzene. Of these, styrene is preferred.
• the diene soft polymer is preferably a polymer containing both an aliphatic conjugated diene monomer unit and an aromatic vinyl monomer unit. For example, a styrene-butadiene copolymer is preferable.
• an aromatic vinyl monomer and an aromatic vinyl monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the proportion of the aromatic vinyl monomer unit in the diene soft polymer is preferably 30% by weight or more, more preferably 35% by weight or more, preferably 79.5% by weight or less, more preferably 69% by weight or less. is there.
• the ratio of the aromatic vinyl monomer unit in the diene soft polymer usually matches the ratio (charge ratio) of the aromatic vinyl monomer in all the monomers of the diene soft polymer.
• the diene soft polymer preferably contains an ethylenically unsaturated carboxylic acid monomer unit.
• the ethylenically unsaturated carboxylic acid monomer unit means a structural unit having a structure formed by polymerizing an ethylenically unsaturated carboxylic acid monomer. Since the ethylenically unsaturated carboxylic acid monomer unit is a structural unit containing a carboxyl group (—COOH group) and having high strength, the binding property of the electrode active material layer to the current collector can be increased, or the electrode active material The strength of the layer can be improved.
• the diene soft polymer contains an ethylenically unsaturated carboxylic acid monomer unit, peeling of the electrode active material layer from the current collector can be stably prevented, and the mechanical strength of the electrode active material layer can be prevented. Can be improved.
• Examples of the ethylenically unsaturated carboxylic acid monomer include the same examples as those exemplified in the section of the water-soluble polymer. Moreover, an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated carboxylic acid monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the proportion of the ethylenically unsaturated carboxylic acid monomer unit in the diene soft polymer is preferably 0.5% by weight or more, more preferably 1% by weight or more, particularly preferably 2% by weight or more, preferably 10% by weight. % Or less, more preferably 8% by weight or less, and particularly preferably 7% by weight or less.
• the ratio of the ethylenically unsaturated carboxylic acid monomer unit in the diene soft polymer is usually the ratio of the ethylenically unsaturated carboxylic acid monomer in all the monomers of the diene soft polymer (preparation ratio). Match.
• the diene soft polymer may contain any structural unit other than those described above as long as the effects of the present invention are not significantly impaired.
• monomers corresponding to the above arbitrary structural units include vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, unsaturated monomers containing hydroxyalkyl groups, and unsaturated carboxylic acids. Examples include acid amide monomers. One of these may be used alone, or two or more of these may be used in combination at any ratio.
• vinyl cyanide monomer examples include acrylonitrile, methacrylonitrile, ⁇ -chloroacrylonitrile, and ⁇ -ethylacrylonitrile. Of these, acrylonitrile and methacrylonitrile are preferable.
• unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, and dimethyl itaco. Nates, monomethyl fumarate, monoethyl fumarate, and 2-ethylhexyl acrylate. Of these, methyl methacrylate is preferable.
• Examples of unsaturated monomers containing a hydroxyalkyl group include ⁇ -hydroxyethyl acrylate, ⁇ -hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2- Examples include hydroxypropyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, and 2-hydroxyethyl methyl fumarate. Of these, ⁇ -hydroxyethyl acrylate is preferred.
• Examples of the unsaturated carboxylic acid amide monomer include acrylamide, methacrylamide, and N, N-dimethylacrylamide. Of these, acrylamide and methacrylamide are preferable.
• the diene soft polymer has a structure formed by polymerizing monomers used in usual emulsion polymerization such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, etc. Units may be included.
• the acrylic soft polymer is a polymer containing a (meth) acrylic acid ester monomer unit.
• those containing fluorine are distinguished from (meth) acrylate monomers as fluorine-containing (meth) acrylate monomers. .
• Examples of (meth) acrylic acid ester monomers include the same examples as those exemplified in the section of the water-soluble polymer. Moreover, a (meth) acrylic acid ester monomer and a (meth) acrylic acid ester monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the proportion of the (meth) acrylic acid ester monomer unit in the acrylic soft polymer is preferably 50% by weight or more, more preferably 70% by weight or more, particularly preferably 90% by weight or more, and preferably 99% by weight or less. More preferably, it is 98 weight% or less, Most preferably, it is 97 weight% or less.
• the ratio of the (meth) acrylic acid ester monomer unit in the acrylic soft polymer is usually the ratio (preparation ratio) of the (meth) acrylic acid ester monomer in all monomers of the acrylic soft polymer. Match.
• the acrylic soft polymer is preferably a copolymer containing a combination of a (meth) acrylonitrile monomer unit and a (meth) acrylic acid ester monomer unit.
• the (meth) acrylonitrile monomer unit means a structural unit having a structure formed by polymerizing (meth) acrylonitrile. Since an acrylic soft polymer containing a combination of a (meth) acrylonitrile monomer unit and a (meth) acrylic acid ester monomer unit is stable to oxidation and reduction, it is easy to obtain a battery having a long life.
• the acrylic soft polymer may contain only a structural unit having a structure formed by polymerizing acrylonitrile as a (meth) acrylonitrile monomer unit, and has a structure formed by polymerizing methacrylonitrile. It may contain only structural units, and includes both a structural unit having a structure formed by polymerizing acrylonitrile and a structural unit having a structure formed by polymerizing methacrylonitrile in an arbitrary ratio. May be.
• the weight ratio (weight ratio represented by “(meth) acrylonitrile monomer unit / (meth) acrylate monomer unit”) is preferably within a predetermined range. Specifically, the weight ratio is preferably 1/99 or more, more preferably 2/98 or more, 30/70 or less, and more preferably 25/75 or less.
• the weight ratio of (meth) acrylonitrile monomer unit to (meth) acrylic acid ester monomer unit in acrylic soft polymer is usually (meth) acrylic acid ester in all monomers of acrylic soft polymer. This corresponds to the ratio of (meth) acrylonitrile monomer to monomer.
• the acrylic soft polymer preferably contains an ethylenically unsaturated carboxylic acid monomer unit. Since the ethylenically unsaturated carboxylic acid monomer unit is a structural unit containing a carboxyl group (—COOH group) and having high strength, the binding property of the electrode active material layer to the current collector can be increased, or the electrode active material The strength of the layer can be improved. Therefore, when the acrylic soft polymer contains an ethylenically unsaturated carboxylic acid monomer unit, peeling of the electrode active material layer from the current collector can be stably prevented, and the mechanical strength of the electrode active material layer can be prevented. Can be improved.
• Examples of the ethylenically unsaturated carboxylic acid monomer include the same examples as those exemplified in the section of the water-soluble polymer. Moreover, an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated carboxylic acid monomer unit may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the proportion of the ethylenically unsaturated carboxylic acid monomer unit in the acrylic soft polymer is preferably 0.5% by weight or more, more preferably 1% by weight or more, particularly preferably 2% by weight or more, preferably 10% by weight. % Or less, more preferably 8% by weight or less, and particularly preferably 7% by weight or less.
• the ratio of the ethylenically unsaturated carboxylic acid monomer unit in the acrylic soft polymer is usually the ratio (preparation ratio) of the ethylenically unsaturated carboxylic acid monomer in all the monomers of the acrylic soft polymer. Match.
• the acrylic soft polymer may contain a crosslinkable monomer unit.
• a crosslinkable monomer is a monomer that can form a crosslinked structure during or after polymerization by heating or irradiation with energy rays.
• the acrylic soft polymer contains a crosslinkable monomer unit, the particulate binders can be crosslinked, or the water-soluble polymer and the particulate binder can be crosslinked.
• crosslinkable monomer examples include the same examples as mentioned in the section of the water-soluble polymer.
• crosslinked monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the crosslinkable monomer unit may be introduced into the acrylic soft polymer by copolymerizing the crosslinkable monomer with the (meth) acrylic acid ester monomer unit.
• the crosslinkable monomer unit is introduced into the acrylic soft polymer by introducing a crosslinkable group into the acrylic soft polymer by a conventional modification means using a compound having a crosslinkable group (crosslinking agent). Also good.
• crosslinking agent for example, an organic peroxide, a crosslinking agent that exhibits an effect by heat or light, and the like are used. Moreover, a crosslinking agent may be used individually by 1 type, and may be used combining 2 or more types by arbitrary ratios. Among the cross-linking agents, an organic peroxide and a cross-linking agent capable of causing a cross-linking reaction by heat are preferable because they contain a heat cross-linkable cross-linking group.
• the ratio of the crosslinkable monomer unit in the acrylic soft polymer is preferably 0.01 with respect to 100 parts by weight of the total amount of the (meth) acrylonitrile monomer unit and the (meth) acrylic acid ester monomer unit.
• Part by weight or more more preferably 0.05 part by weight or more, preferably 5 parts by weight or less, more preferably 4 parts by weight or less, and particularly preferably 3 parts by weight or less.
• the acrylic soft polymer can also include any structural unit.
• monomers corresponding to these arbitrary structural units include styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, ⁇ -methyl.
• Aromatic vinyl monomers such as styrene and divinylbenzene; Olefin monomers such as ethylene and propylene; Diene monomers such as butadiene and isoprene; Monomers containing halogen atoms such as vinyl chloride and vinylidene chloride; Vinyl acetate Vinyl ester monomers such as vinyl propionate and vinyl butyrate; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone and isopropenyl Such as vinyl ketone Nyl ketone monomers; N-vinyl pyrrolidone, vinyl pyridine, vinyl ring-containing vinyl compound monomers such as vinyl imidazole; Unsaturated carboxylic acid amide monomers such as acrylamide and acrylamide-2-methylpropane sulfonic acid; Can be mentioned.
• any structural unit is small from the viewpoint of remarkably exhibiting the advantages of including the (meth) acrylonitrile monomer unit and the (meth) acrylic acid ester monomer unit in combination as described above. It is particularly preferable that it does not contain any structural unit.
• particulate binder may be used alone, or two or more types may be used in combination at any ratio.
• the weight average molecular weight of the polymer forming the particulate binder is preferably 10,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, more preferably 500,000 or less.
• the weight average molecular weight of the polymer forming the particulate binder is in the above range, the strength of the electrode and the dispersibility of the electrode active material are easily improved.
• the glass transition temperature of the particulate binder is preferably ⁇ 75 ° C. or higher, more preferably ⁇ 55 ° C. or higher, particularly preferably ⁇ 35 ° C. or higher, preferably 40 ° C. or lower, more preferably 30 ° C. or lower, still more preferably. 20 ° C. or lower, particularly preferably 15 ° C. or lower.
• the glass transition temperature of the particulate binder can be adjusted by combining various monomers.
• the volume average particle diameter D50 of the particulate binder is preferably 50 nm or more, more preferably 70 nm or more, preferably 500 nm or less, more preferably 400 nm or less.
• the volume average particle diameter D50 of the particulate binder is in the above range, the strength and flexibility of the obtained electrode can be improved.
• the amount of the particulate binder is preferably 0.5 parts by weight or more, more preferably 0.7 parts by weight or more, particularly preferably 1 part by weight or more, preferably 10 parts by weight with respect to 100 parts by weight of the electrode active material. Parts or less, more preferably 7 parts by weight or less, and particularly preferably 5 parts by weight or less.
• the method for producing the particulate binder is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method may be used.
• the emulsion polymerization method and the suspension polymerization method are preferable because they can be polymerized in water and used as they are as the material of the slurry composition of the present invention.
• the slurry composition of this invention can contain arbitrary components other than the electrode active material mentioned above, a water-soluble polymer, water, and a particulate binder.
• a water-soluble polymer examples include conductive materials, reinforcing materials, leveling agents, thickeners, nanoparticles, electrolyte additives, and the like.
• these components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the conductive material is a component that can improve electrical contact between the electrode active materials. By including a conductive material, the discharge rate characteristics of the lithium ion secondary battery can be improved. Examples of the conductive material include furnace black, acetylene black, ketjen black, carbon black, graphite, vapor grown carbon fiber, and conductive carbon such as carbon nanotube.
• a conductive material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the amount of the conductive material is preferably 1 to 20 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material.
• the reinforcing material for example, various inorganic and organic spherical, plate-like, rod-like or fibrous fillers can be used.
• a reinforcing material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
• the amount of the reinforcing material is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, preferably 20 parts by weight or less, more preferably 10 parts by weight with respect to 100 parts by weight of the electrode active material. It is as follows. By setting the amount of the reinforcing material in the above range, the lithium ion secondary battery can exhibit high capacity and high load characteristics.
• the leveling agent examples include surfactants such as alkyl surfactants, silicone surfactants, fluorine surfactants, and metal surfactants.
• a leveling agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. By using a leveling agent, it is possible to prevent the repelling that occurs during the application of the slurry composition of the present invention, and to improve the smoothness of the electrode.
• the amount of the leveling agent is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. When the leveling agent is within the above range, the productivity, smoothness, and battery characteristics during electrode production are excellent. Moreover, the dispersibility of an electrode active material can be improved in the slurry composition of this invention by containing surfactant, Furthermore, the smoothness of the electrode obtained by it can be improved.
• thickener examples include cellulose polymers such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose and salts thereof; (modified) poly (meth) acrylic acid and salts thereof; (modified) polyvinyl alcohol, acrylic acid or acrylic Polyvinyl alcohols such as copolymers of acid salts and vinyl alcohol, maleic anhydride or maleic acid or copolymers of fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, modified polyacrylic acid, oxidized starch, phosphorus Acid starch, casein, various modified starches, acrylonitrile-butadiene copolymer hydride, and the like.
• cellulose polymers and salts thereof (modified) poly (meth) acrylic acid and salts thereof are preferable, and cellulose polymers and salts thereof are more preferable.
• the salt include ammonium salt and alkali metal salt. One of these may be used alone, or two or more of these may be used in combination at any ratio.
• “(modified) poly” means “unmodified poly” or “modified poly”.
• the amount of the thickener is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. When the thickener is in the above range, the dispersibility of the electrode active material in the slurry composition of the present invention can be further enhanced, so that a smooth electrode can be obtained. For this reason, it is possible to realize further excellent load characteristics and cycle characteristics.
• the nanoparticles include particles such as fumed silica and fumed alumina.
• One kind of nanoparticles may be used alone, or two or more kinds of nanoparticles may be used in combination at any ratio. Since the thixotropy of the slurry composition of this invention can be adjusted when it contains a nanoparticle, the leveling property of the electrode obtained by it can be improved.
• the amount of the nanoparticles is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. When the nanoparticles are in the above range, the stability and productivity of the slurry composition of the present invention can be improved, and high battery characteristics can be realized.
• the electrolytic solution additive examples include vinylene carbonate.
• One electrolyte solution additive may be used alone, or two or more electrolyte solution additives may be used in combination at any ratio.
• the amount of the electrolytic solution additive is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. By setting the amount of the electrolytic solution additive in the above range, a lithium ion secondary battery excellent in cycle characteristics and high temperature characteristics can be realized.
• the slurry composition of the present invention since it has the above-described configuration, the slurry composition of the present invention usually has the following advantages.
• the slurry composition of the present invention is excellent in dispersibility. That is, in the slurry composition of the present invention, components such as an electrode active material, a particulate binder, and a conductive material are uniformly dispersed. Therefore, also in the electrode active material layer manufactured using the slurry composition of this invention, since the said component can be disperse
• the slurry composition of the present invention is excellent in dispersion stability. That is, the slurry composition of the present invention can maintain high dispersibility over a long period of time. Moreover, the slurry composition of the present invention is less likely to cause a change in viscosity over time. Therefore, since the slurry composition of the present invention hardly changes its properties due to storage, it can be stored for a long period of time.
• the layer is stable and is not easily destroyed by the passage of time and temperature. Furthermore, since the water-soluble polymer has a high affinity for water, it is highly water-soluble and hardly causes precipitation. Therefore, it is considered that the slurry composition of the present invention is excellent in dispersibility and dispersion stability.
• the slurry composition of the present invention can increase viscosity and thixotropy.
• the reason why the viscosity and thixotropy can be improved in this way is not necessarily clear, but according to the study of the present inventor, it is presumed as follows. That is, the water-soluble polymer of the present invention acts as a thickener in the slurry composition.
• the thixotropy of the slurry composition containing the water-soluble polymer can be improved by the action of the hydroxyl group-containing monomer unit. Therefore, it is considered that the viscosity and thixotropy of the slurry composition can be improved to an extent suitable for application.
• the slurry composition of the present invention can be produced, for example, by mixing an electrode active material, a water-soluble polymer and water, and if necessary, a particulate binder and optional components.
• the specific procedure at this time is arbitrary.
• the electrode active material, the water-soluble polymer, the particulate binder and the conductive material are simultaneously added to water.
• Method of mixing after dissolving water-soluble polymer in water, mixing particulate binder dispersed in water, and then mixing electrode active material and conductive material; electrode in particulate binder dispersed in water And a method of mixing an active material and a conductive material, and mixing a water-soluble polymer dissolved in water into the mixture.
• mixing means include, for example, mixing equipment such as a ball mill, a sand mill, a bead mill, a roll mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer.
• mixing equipment such as a ball mill, a sand mill, a bead mill, a roll mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer.
• Electrode for lithium ion secondary battery The electrode of the present invention (electrode for a lithium ion secondary battery) can be obtained by a production method including forming a film of the slurry composition of the present invention on a current collector and drying the film.
• the current collector is not particularly limited as long as it has electrical conductivity and is electrochemically durable, but a metal material is preferable because it has heat resistance.
• the material for the current collector include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum.
• the current collector used for the positive electrode is preferably aluminum
• the current collector used for the negative electrode is preferably copper.
• One kind of the above materials may be used alone, or two or more kinds thereof may be used in combination at any ratio.
• the shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 mm to 0.5 mm is preferable.
• the current collector is preferably used after roughening the surface in advance.
• the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.
• the mechanical polishing method for example, an abrasive cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like is used.
• an intermediate layer may be formed on the surface of the current collector.
• a film of the slurry composition of the present invention is formed on the current collector.
• membrane of a slurry composition is normally formed by apply
• a slurry composition may be apply
• the thickness of the slurry composition film can be appropriately set according to the thickness of the target electrode active material layer.
• the slurry composition of the present invention has excellent coating properties, a uniform film can be easily formed by the above coating. Moreover, since the slurry composition of this invention is excellent in a dispersibility and dispersion stability, the obtained film
• the liquid such as water is removed from the film by drying. Thereby, the electrode active material layer containing an electrode active material and a water-soluble polymer is formed in the surface of an electrical power collector, and an electrode is obtained.
• drying method examples include drying with warm air, hot air, low-humidity air, or the like; vacuum drying; drying with irradiation of energy rays such as infrared rays, far infrared rays, or electron beams. Among these, a drying method by irradiation with far infrared rays is preferable.
• the drying temperature and drying time are preferably a temperature and a time at which water can be removed from the slurry composition film. Specifically, the drying time is preferably 1 minute to 30 minutes, and the drying temperature is preferably 40 ° C. to 180 ° C.
• the porosity of the electrode active material layer can be lowered.
• the porosity is preferably 5% or more, more preferably 7% or more, preferably 30% or less, more preferably 20% or less.
• the electrode active material layer contains a polymer that can be cured by a curing reaction such as a crosslinking reaction
• the polymer may be cured after the electrode active material layer is formed.
• the thickness of the electrode active material layer formed as described above can be arbitrarily set according to the required battery performance.
• the thickness of the positive electrode active material layer is preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, preferably 300 ⁇ m or less, more preferably 250 ⁇ m or less.
• the thickness of the positive electrode active material layer is in the above range, high characteristics can be realized in both load characteristics and energy density.
• the thickness of the negative electrode active material layer is preferably 5 ⁇ m or more, more preferably 20 ⁇ m or more, particularly preferably 30 ⁇ m or more, preferably 1000 ⁇ m or less, more preferably 500 ⁇ m or less, still more preferably 300 ⁇ m or less, particularly preferably. Is 250 ⁇ m or less.
• load characteristics and cycle characteristics can be improved.
• the water content in the electrode active material layer is preferably 1000 ppm or less, and more preferably 500 ppm or less. By setting the moisture content of the electrode active material layer within the above range, an electrode having excellent durability can be realized.
• the amount of water can be measured by a known method such as the Karl Fischer method. Such a low water content can be achieved by appropriately adjusting the composition of the structural unit in the water-soluble polymer.
• the fluorine-containing (meth) acrylic acid ester monomer unit is preferably in the range of 0.5% by weight or more, more preferably 1% by weight or more, and preferably 20% by weight or less, more preferably 10% by weight or less. By doing so, the amount of water can be reduced.
• the adhesion strength between the current collector and the electrode active material layer is strong.
• the reason why such a strong adhesion strength is obtained is not necessarily clear, but according to the study of the present inventor, it is presumed as follows. That is, the hydroxyl group (—OH group) and acid group of the hydroxyl group-containing monomer unit have high polarity. Therefore, the water-soluble polymer can cause a strong interaction with the polar groups present on the surfaces of the electrode active material and the current collector, and thus can be firmly bound to the electrode active material and the current collector. In particular, it is considered that high binding properties can be expressed by the action of acid groups.
• the water-soluble polymer can act as a binder, and the water-soluble polymer increases the strength of the binding between the electrode active materials and the binding between the electrode active material and the current collector. It is presumed that the adhesion with the active material layer is improved. Moreover, since the slurry composition of this invention has high dispersibility, it is thought that the composition of a structural component is uniform also in the electrode active material layer regardless of the position. Therefore, in the electrode active material layer, a portion where the adhesion strength with the current collector is locally weak is unlikely to occur. Therefore, since the current collector and the electrode active material layer do not peel off starting from the portion, it is possible to improve the adhesion between the current collector and the electrode active material layer. Inferred.
• the electrode of the present invention has high flexibility and is not easily damaged even when it is bent.
• the reason for such a high flexibility is not necessarily clear, but according to the study of the present inventor, it is presumed as follows. That is, as described above, the electrode active material layer formed using the slurry composition of the present invention can improve the uniformity of the composition, so that a locally weak portion is generated in the electrode active material layer. Can be suppressed. For this reason, since the generation
• the lithium ion secondary battery of this invention is equipped with a positive electrode, a negative electrode, and electrolyte solution.
• the lithium ion secondary battery of the present invention may include a separator.
• one or both of the negative electrode and the positive electrode is an electrode of the present invention.
• the lithium ion secondary battery of the present invention is excellent in cycle characteristics and output characteristics, and in particular, the high temperature cycle characteristics and the low temperature characteristics can be remarkably improved.
• the reason why the lithium ion secondary battery of the present invention is excellent in cycle characteristics and output characteristics is not clear, but according to the study of the present inventors, it is presumed that the reason is as follows.
• the adhesion strength between the electrode active material layer and the current collector is high. Therefore, even if the electrode active material repeatedly expands and contracts due to charge and discharge, the electrode active material layer and the current collector are unlikely to peel off. Further, since the water-soluble polymer has high binding properties, the contact between the electrode active material layers and the contact between the electrode active material and the conductive material are hardly impaired. For this reason, since the electric conduction path is not easily cut by charging / discharging, the degree of increase in resistance accompanying charging / discharging is low. Moreover, in the electrode of this invention, a part of water-soluble polymer has adhered to the surface of the electrode active material.
• the coating can suppress decomposition of the electrolytic solution, it is possible to suppress an increase in resistance caused by a gas generated by the decomposition of the electrolytic solution. For these reasons, it is assumed that the lithium ion secondary battery of the present invention can exhibit excellent cycle characteristics.
• the fluorine-containing (meth) acrylic acid ester monomer unit has high ionic conductivity
• the water-soluble polymer also has high ionic conductivity. Therefore, even if the water-soluble polymer film covers the surface of the electrode active material, the degree of resistance increase due to the film can be reduced. Therefore, the resistance of the electrode can be suppressed.
• the swelling property of the water-soluble polymer with respect to electrolyte solution can be made small by including a fluorine-containing (meth) acrylic acid ester monomer unit. Therefore, swelling of the electrode can be suppressed in the lithium ion secondary battery. Therefore, swelling of the electrode active material layer can be suppressed, and the distance between the electrode active materials can be reduced.
• the internal resistance of the electrode can be suppressed.
• polymers containing fluorine-containing (meth) acrylic acid ester monomer units tend to become less compatible with the electrolyte solution, but in the water-soluble polymer according to the present invention, hydroxyl group-containing monomer units.
• the compatibility with the electrolytic solution is not deteriorated by the action of the acid group-containing monomer unit. Rather, since the water-soluble polymer has a hydroxyl group and an acid group, the affinity of the water-soluble polymer with respect to the polar solvent is increased, and the electrode active material layer has excellent wettability with respect to the electrolytic solution.
• the electrolytic solution can easily enter the electrode active material layer, the electric reaction field between the electrolytic solution and the electrode active material can be easily widened, and the internal resistance of the battery can be suppressed. .
• the lithium ion secondary battery of the present invention can exhibit excellent output characteristics.
• Electrolyte As the electrolytic solution, for example, a solution obtained by dissolving a lithium salt as a supporting electrolyte in a non-aqueous solvent may be used.
• the lithium salt include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi, and other lithium salts.
• LiPF 6 , LiClO 4 , and CF 3 SO 3 Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferably used.
• One of these may be used alone, or two or more of these may be used in combination at any ratio.
• the amount of the supporting electrolyte is preferably 1% by weight or more, more preferably 5% by weight or more, and preferably 30% by weight or less, more preferably 20% by weight or less with respect to the electrolytic solution. If the amount of the supporting electrolyte is too small or too large, the ionic conductivity is lowered, and the charging characteristics and discharging characteristics of the secondary battery may be lowered.
• the solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
• the solvent include alkyl carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (MEC); Esters such as butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferred because high ion conductivity is easily obtained and the use temperature range is wide.
• a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
• an additive may be included in the electrolytic solution as necessary.
• carbonate compounds such as vinylene carbonate (VC) are preferable.
• An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
• Examples of the electrolytic solution other than the above include a gel polymer electrolyte obtained by impregnating a polymer electrolyte such as polyethylene oxide and polyacrylonitrile with an electrolytic solution; an inorganic solid electrolyte such as lithium sulfide, LiI, and Li 3 N; Can do.
• separator As the separator, a porous substrate having a pore portion is usually used.
• separators include (a) a porous separator having pores, (b) a porous separator having a polymer coating layer formed on one or both sides, and (c) a porous resin coat containing inorganic ceramic powder. And a porous separator having a layer formed thereon.
• Examples of these include polypropylene, polyethylene, polyolefin or aramid porous separators; for solid polymer electrolytes such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride hexafluoropropylene copolymers Or a polymer film for a gel polymer electrolyte; a separator coated with a gelled polymer coat layer; a separator coated with a porous film layer composed of an inorganic filler and an inorganic filler dispersant; and the like.
• solid polymer electrolytes such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride hexafluoropropylene copolymers
• a polymer film for a gel polymer electrolyte a separator coated with a gelled polymer coat layer
• a separator coated with a porous film layer composed of an inorganic filler and an
• the manufacturing method of the lithium ion secondary battery of the present invention is not particularly limited.
• the above-described negative electrode and positive electrode may be overlapped via a separator, and this may be wound or folded in accordance with the shape of the battery and placed in the battery container, and the electrolyte may be injected into the battery container and sealed.
• an expanded metal; an overcurrent prevention element such as a fuse or a PTC element; a lead plate or the like may be inserted to prevent an increase in pressure inside the battery or overcharge / discharge.
• the shape of the battery may be any of, for example, a laminate cell type, a coin type, a button type, a sheet type, a cylindrical type, a square type, and a flat type.
• Adhesion strength The electrodes produced in the examples and comparative examples were cut into rectangles having a length of 100 mm and a width of 10 mm to obtain test pieces.
• Cellophane tape was affixed on the surface of the electrode active material layer of the test piece with the surface of the electrode active material layer facing down.
• a cellophane tape defined in JIS Z1522 was used.
• the cellophane tape was fixed on a horizontal test bench. Then, the stress when one end of the current collector was pulled vertically upward at a pulling speed of 50 mm / min and peeled was measured. This measurement was performed three times, the average value of the measured values was obtained, and the average value was taken as the peel strength.
• the higher the peel strength the higher the binding force of the electrode active material layer to the current collector, that is, the higher the adhesion strength.
• lithium ion secondary batteries of laminate type cells were produced and allowed to stand for 24 hours in an environment of 25 ° C. Thereafter, in a 25 ° C. environment, an operation of charging with a constant current method of 0.1 C over 5 hours was performed, and the voltage V0 at that time was measured. Thereafter, a discharge operation was performed at a discharge rate of 1 C in an environment of ⁇ 10 ° C., and the voltage V1 15 seconds after the start of discharge was measured.
• Example 1 (1-1. Production of water-soluble polymer) In a 5 MPa pressure vessel equipped with a stirrer, 4 parts 2-hydroxyethyl acrylate (hydroxyl group-containing monomer), 32.5 parts methacrylic acid (acid group-containing monomer), 0.8 ethylene dimethacrylate (crosslinkable monomer) Parts, 2,2,2-trifluoroethyl methacrylate (fluorine-containing (meth) acrylic acid ester monomer) 7.5 parts, ethyl acrylate (optional monomer) 55.2 parts, sodium dodecylbenzenesulfonate ( Surfactant (0.1 part), t-dodecyl mercaptan (molecular weight regulator) (0.1 part), ion-exchanged water (150 parts), and potassium persulfate (polymerization initiator) (0.5 part) were added and sufficiently stirred.
• 2-hydroxyethyl acrylate hydroxyl group-containing monomer
• methacrylic acid acid group-containing
• the mixture containing the particulate binder was adjusted to pH 8 by adding a 5% aqueous sodium hydroxide solution. Then, after removing the unreacted monomer from the mixture containing the particulate binder by heating under reduced pressure, the mixture was cooled to 30 ° C. or lower to obtain an aqueous dispersion containing the desired particulate binder.
• the slurry composition for positive electrode was applied on a 20 ⁇ m thick aluminum foil as a current collector with a comma coater so that the film thickness after drying was about 130 ⁇ m and dried. This drying was performed by conveying the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material.
• This positive electrode original fabric was rolled with a roll press to obtain a positive electrode having a positive electrode active material layer thickness of 80 ⁇ m. About this positive electrode, the adhesive strength and the softness
• the mixture containing the particulate binder was adjusted to pH 8 by adding a 5% aqueous sodium hydroxide solution. Then, after removing the unreacted monomer from the mixture containing the particulate binder by heating under reduced pressure, the mixture is cooled to 30 ° C. or lower, and an aqueous dispersion containing the desired particulate binder (a binder composition for negative electrode) Product).
• the negative electrode slurry composition obtained in the above step (1-5) was applied onto a 20 ⁇ m thick copper foil as a current collector with a comma coater so that the film thickness after drying was about 150 ⁇ m. And dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, the negative electrode original fabric was obtained by heat-processing at 120 degreeC for 2 minute (s). This negative electrode original fabric was rolled with a roll press to obtain a negative electrode having a negative electrode active material layer thickness of 80 ⁇ m.
• the positive electrode obtained in the above step (1-3) was cut into a 4 ⁇ 4 cm 2 square and placed so that the current collector-side surface was in contact with the aluminum packaging exterior.
• the square separator obtained in the above step (1-7) was disposed on the surface of the positive electrode active material layer of the positive electrode.
• the negative electrode obtained in the above step (1-6) was cut into a square of 4.2 ⁇ 4.2 cm 2 and arranged on the separator so that the surface on the negative electrode active material layer side faces the separator.
• Example 2 In the same manner as in Example 1, except that the amount of 2-hydroxyethyl acrylate was changed to 0.8 parts and the amount of ethyl acrylate was changed to 58.4 parts in the above step (1-1), lithium ion Secondary batteries were manufactured and evaluated.
• Example 3 In the same manner as in Example 1, except that the amount of 2-hydroxyethyl acrylate was changed to 9.5 parts and the amount of ethyl acrylate was changed to 49.7 parts in the above step (1-1), lithium ion Secondary batteries were manufactured and evaluated.
• Example 4 A lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1 except that 4 parts of 2-hydroxyethyl methacrylate was used instead of 2-hydroxyethyl acrylate in the above step (1-1).
• Example 5 Copolymerization was carried out in the same manner as in the above step (1-1) except that vinyl acetate was used in place of 2-hydroxyethyl acrylate, and the resulting polymer was hydrolyzed with sodium hydroxide to produce a polymer acetic acid.
• the vinyl unit was converted to a vinyl alcohol unit to obtain an aqueous solution containing a water-soluble polymer.
• the vinyl acetate unit refers to a structural unit having a structure formed by polymerizing vinyl acetate.
• a vinyl alcohol unit shows the structural unit which has a structure formed by superposing
• a lithium ion secondary battery was produced and evaluated in the same manner as in Example 1 except that the aqueous solution containing the water-soluble polymer thus obtained was used as a thickener in the above step (1-3).
• Example 6 A lithium ion secondary battery was prepared in the same manner as in Example 1 except that 7.5 parts of perfluorooctyl acrylate was used instead of 2,2,2-trifluoroethyl methacrylate in the above step (1-1). Manufactured and evaluated.
• Example 7 A lithium ion secondary battery was prepared in the same manner as in Example 1 except that 7.5 parts of perfluorobutyl acrylate was used instead of 2,2,2-trifluoroethyl methacrylate in the above step (1-1). Manufactured and evaluated.
• Example 8 Same as Example 1 except that the amount of 2,2,2-trifluoroethyl methacrylate was changed to 0.2 parts and the amount of ethyl acrylate was changed to 62.5 parts in the above step (1-1). Thus, a lithium ion secondary battery was manufactured and evaluated.
• Example 9 In the same manner as in Example 1, except that the amount of 2,2,2-trifluoroethyl methacrylate was changed to 48 parts and the amount of ethyl acrylate was changed to 14.7 parts in the above step (1-1). A lithium ion secondary battery was manufactured and evaluated.
• Example 10 A lithium ion secondary battery was produced in the same manner as in Example 1 except that the amount of methacrylic acid was changed to 22 parts and the amount of ethyl acrylate was changed to 65.7 parts in the above step (1-1). And evaluated.
• Example 11 A lithium ion secondary battery was produced in the same manner as in Example 1, except that the amount of methacrylic acid was changed to 48 parts and the amount of ethyl acrylate was changed to 39.7 parts in the above step (1-1). And evaluated.
• Example 12 In the above step (1-1), the same procedure as in Example 1 was performed except that 25 parts of 2-acrylamido-2-methylpropanesulfonic acid was used instead of methacrylic acid and the amount of ethyl acrylate was changed to 62.7 parts. A lithium ion secondary battery was manufactured and evaluated.
• Example 13 In the above step (1-1), 30.0 parts of methacrylic acid and 5.0 parts of 2-acrylamido-2-methylpropanesulfonic acid were used in combination as the acid group-containing monomer, and the amount of ethyl acrylate was 52.7. A lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1 except that the part was changed to a part.
• Example 14 In the step (1-1), the lithium ion secondary was changed in the same manner as in Example 1 except that the amount of ethylene dimethacrylate was changed to 0.1 part and the amount of ethyl acrylate was changed to 55.9 parts. A battery was manufactured and evaluated.
• Example 15 In the same manner as in Example 1, except that the amount of ethylene dimethacrylate was changed to 1.8 parts and the amount of ethyl acrylate was changed to 54.2 parts in the above step (1-1), lithium ion secondary A battery was manufactured and evaluated.
• Example 16 A lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1 except that 0.8 part of glycidyl methacrylate was used in place of ethylene dimethacrylate in the above step (1-1).
• Example 17 A lithium ion secondary battery was manufactured and evaluated in the same manner as in Example 1 except that 0.8 part of allyl glycidyl ether was used in place of ethylene dimethacrylate in the above step (1-1).
• Example 18 In the step (1-3), a lithium ion secondary battery was produced and evaluated in the same manner as in Example 1 except that no binder was used.
• Example 19 (19-1. Production of slurry composition for negative electrode)
• 100 parts of artificial graphite (average particle size: 24.5 ⁇ m) having a specific surface area of 5.5 m 2 / g as a negative electrode active material, and the water-soluble heavy of the above step (1-1) as a thickener 2 parts of the aqueous solution containing the coalesced was added in an amount corresponding to the solid content, and ion-exchanged water was further added to adjust the solid content concentration to 65%, followed by mixing at 25 ° C. for 60 minutes. Next, ion-exchanged water was added to adjust the solid content concentration to 60%, and the mixture was further mixed at 25 ° C.
• the negative electrode slurry composition obtained in the above step (19-1) was applied onto a 20 ⁇ m thick copper foil as a current collector with a comma coater so that the film thickness after drying was about 150 ⁇ m. And dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, the negative electrode original fabric was obtained by heat-processing at 120 degreeC for 2 minute (s). This negative electrode original fabric was rolled with a roll press to obtain a negative electrode having a negative electrode active material layer thickness of 80 ⁇ m. About this negative electrode, the adhesive strength and the softness
• a positive electrode was produced in the same manner as in the step (1-3) of Example 1 except that 1 part of a 2% aqueous solution of carboxymethyl cellulose (“MAC350HC” manufactured by Nippon Paper Chemical Co., Ltd.) was used as a thickener. .
• MAC350HC carboxymethyl cellulose
• Example 20 Implemented except that 90 parts of artificial graphite (volume average particle diameter: 24.5 ⁇ m) and 10 parts of SiO x (volume average particle diameter: 5 ⁇ m) were used as the negative electrode active material in combination with a specific surface area of 5.5 m 2 / g. In the same manner as in Example 19, a lithium ion secondary battery was produced and evaluated.
• Example 21 Implemented except that 70 parts of artificial graphite (volume average particle diameter: 24.5 ⁇ m) and 30 parts of SiO x (volume average particle diameter: 8 ⁇ m) were used in combination as the negative electrode active material with a specific surface area of 5.5 m 2 / g. In the same manner as in Example 19, a lithium ion secondary battery was produced and evaluated.
• the obtained powder was a powder having a volume average particle size of 3.5 ⁇ m and a BET specific surface area of 11 m 2 / g.
• Analysis by the Scherrer method from the half-value width of this diffraction line revealed that the obtained powder was a silicon composite powder having a crystallite size of 40 nm of silicon dispersed in silicon dioxide. confirmed.
• a lithium ion secondary battery was produced and evaluated in the same manner as in Example 19 except that the silicon composite powder thus obtained was used as the negative electrode active material.
• a lithium ion secondary battery was produced and evaluated in the same manner as in Example 19 except that the polycrystalline silicon powder thus obtained was used as the negative electrode active material.
• a lithium ion secondary was prepared in the same manner as in Example 1 except that 1 part of polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 1000000) was used as a thickener. A battery was manufactured and evaluated.
• Example 5 In the above step (19-1), the same procedure as in Example 19 was performed except that 1 part of a 2% aqueous solution of carboxymethylcellulose (“MAC350HC” manufactured by Nippon Paper Chemical Co., Ltd.) was used as a thickener, corresponding to the solid content. An ion secondary battery was manufactured and evaluated.
• MAC350HC carboxymethylcellulose
• Examples 1 to 18 and Comparative Examples 1 to 4 are obtained by applying the slurry composition to the positive electrode, and Examples 19 to 23 and Comparative Example 5 are those using the slurry composition as the negative electrode. It is applied. From the above table, it can be seen that the present invention can realize a lithium ion secondary battery having excellent high-temperature cycle characteristics and low-temperature characteristics. Moreover, by comparing an Example and a comparative example, it turns out that the slurry composition of this invention is excellent in dispersion stability. Furthermore, it turns out that the electrode manufactured using the slurry composition of this invention is excellent in adhesive strength and a softness

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