JP2008108459A - Method for producing electrode material for non-aqueous electrolyte secondary battery, electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery - Google Patents

Abstract

A method for producing an electrode material for a nonaqueous electrolyte secondary battery capable of providing a nonaqueous electrolyte secondary battery having excellent productivity, low cost and high discharge capacity, and an electrode for a nonaqueous electrolyte secondary battery, and The nonaqueous electrolyte secondary battery used is provided.
In a method for producing an electrode material for a non-aqueous electrolyte secondary battery by vapor-growing an active material on a substrate, a release layer is formed on a part of the active material layer forming surface of the substrate, A step of forming an active material layer by vapor-phase growth of an active material on a release layer forming surface and a non-forming surface on a substrate, and then removing the release layer and the active material layer on the release layer from the substrate The manufacturing method of the electrode material for nonaqueous electrolyte secondary batteries characterized by comprising.
[Selection figure] None

Description

  The present invention provides an electrode material for a nonaqueous electrolyte secondary battery that can provide a nonaqueous electrolyte secondary battery that is excellent in productivity, inexpensive, and has a high discharge capacity, and an electrode for a nonaqueous electrolyte secondary battery, It relates to a non-aqueous electrolyte secondary battery using

  Along with the downsizing of electronic devices, there is a need for inexpensive and high-capacity secondary batteries. In particular, non-aqueous solvent lithium secondary batteries with higher energy density have attracted attention as compared with nickel-cadmium and nickel-hydrogen batteries. In recent years, high targets have been set for the price and capacity required for lithium secondary batteries, and further cost reduction and capacity increase are required.

For example, graphite powder has been studied as a negative electrode material of a lithium secondary battery. Graphite powder has been used because of its excellent cycle characteristics, small electrode expansion, and low cost. However, the negative electrode material made of graphite has a limit of theoretical capacity of 372 mAh / g, and further increase in capacity cannot be expected.
In addition, in order to use graphite powder as an electrode, it is necessary to fix it on a current collector with a binder, and in order to further improve current collection, carbon black or vapor-grown carbon fiber is supported in the electrode as a conductive aid. In some cases, it was added as a material. Therefore, the weight ratio of the graphite powder as an active material in the electrode is reduced, and there is a problem that the battery capacity is reduced.

  Therefore, in recent years, there has been a study on a method of directly forming an active material on a current collector by vapor-phase growth of an alloy-based negative electrode such as Si, Sn, or Al that forms an alloy with lithium having a large theoretical capacity instead of a graphite negative electrode. Has been made. However, these alloy-based negative electrodes manufactured by vapor phase growth have a problem that the manufacturing cost is higher than that of graphite.

On the other hand, an electrode for a nonaqueous electrolyte secondary battery requires an undeposited portion of an electrode material for adhering a current collecting tab or the like to a part of the electrode surface in assembling the battery. However, for example, in the case of forming an active material layer on a current collector continuously in a roll-to-roll manner in an alloy thin film manufactured by vapor phase growth, in order to form the non-film-forming portion for current collection There is a problem that it is necessary to form the film intermittently and productivity is lowered. Further, the boundary between the film-formed part and the non-film-formed part is not clear, and it is not preferable as the non-film-formed part for bonding a current collecting tab or the like.
Further, in the case of a method of removing a film-forming part in a subsequent process without forming an unfilmed part during vapor phase growth, it is difficult to peel this from the base because the adhesion between the base and the alloy thin film is high. It is virtually impossible to form a non-film-forming portion for current collection.

  Therefore, in further increasing the capacity of the lithium secondary battery, for example, in the case of a negative electrode material, not only the capacity is increased by using an alloy-based active material manufactured by vapor phase growth, but also inexpensive and excellent productivity. The law is strongly sought.

  Under these circumstances, Patent Document 1 discloses that in the method of forming the active material layer on both sides of the current collector, the active material layer is continuously formed at the same time on both sides, so that the current collector component diffuses into the active material layer. It describes that an electrode material for a lithium secondary battery that can be controlled to be substantially the same and has excellent cycle characteristics is manufactured.

  Patent Document 2 discloses a method of forming an active material layer on both sides of a current collector by continuously forming an active material layer composed of a plurality of layers on each side so that the active material on the current collector is formed. It describes that an electrode material for a lithium secondary battery that controls diffusion, has a high charge / discharge capacity, and has excellent cycle characteristics is manufactured.

Patent Documents 1 and 2 describe that an alloy-based active material is manufactured by vapor phase growth and that a high discharge capacity can be expected and a tab is attached to a portion where no active material layer is formed. However, there is no detailed description of the portion where the active material layer is not formed, and no mention is made of the formation method.
JP 2002-289180 A JP 2003-7288 A

  The present invention was devised in view of the above-mentioned problems, and is a method of vapor-depositing an active material on a substrate, but intermittently forms a film to form an unfilmed portion for current collection, etc. For manufacturing a non-aqueous electrolyte secondary battery electrode material capable of providing a non-aqueous electrolyte secondary battery that is inexpensive and excellent in productivity, and an electrode for a non-aqueous electrolyte secondary battery, and using the same An object is to provide a nonaqueous electrolyte secondary battery.

  As a result of intensive studies on a method for producing an electrode material by vapor-phase growth of an active material on a substrate, the present inventors have found a method that can be obtained at low cost and good productivity, and completed the present invention.

  That is, the gist of the present invention is to form a release layer on a part of the active material layer forming surface of the substrate in a method of producing an electrode material for a non-aqueous electrolyte secondary battery by vapor-growing an active material on the substrate. Then, the active material is vapor-phase grown on the release layer forming surface and the non-formed surface on the substrate to form an active material layer, and then the release layer and the active material layer on the release layer are formed on the substrate. And a method for producing an electrode material for a non-aqueous electrolyte secondary battery (Claim 1).

  In another aspect of the present invention, the release layer contains a polymer binder, The method for producing an electrode material for a nonaqueous electrolyte secondary battery according to claim 1 (claim 2), Exist.

  According to another aspect of the present invention, there is provided the method for producing an electrode material for a nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the release layer contains a filler. Exist.

  In another aspect of the present invention, the release layer is formed on the substrate, the surface of the substrate is roughened, and then the active material is vapor-phase grown. The manufacturing method of the electrode material for nonaqueous electrolyte secondary batteries as described in (4).

  Further, another gist of the present invention includes a non-aqueous solution comprising an electrode material produced by the method for producing a non-aqueous electrolyte secondary battery electrode material according to any one of claims 1 to 4. It exists in the electrode for electrolyte secondary batteries (Claim 5).

  Further, according to another aspect of the present invention, in the nonaqueous electrolyte secondary battery including a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, the electrode (positive electrode and / or negative electrode) is described in claim 5. The nonaqueous electrolyte secondary battery is characterized in that it is an electrode for a nonaqueous electrolyte secondary battery (claim 6).

  According to the present invention, although it is a method for vapor-phase growth of an active material on a substrate, there is no need to intermittently form a film to form an unfilmed part for current collection, and A high-performance non-aqueous electrolyte secondary battery having a clear boundary with an undeposited portion, being inexpensive and excellent in productivity is provided.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below, but the present invention is not limited to the following descriptions, and the present invention is arbitrarily modified and implemented without departing from the gist of the present invention. be able to.

[1] Electrode Material for Nonaqueous Electrolyte Secondary Battery (1) Active Material First, an active material suitable for the electrode material for nonaqueous electrolyte secondary battery according to the present invention will be described.
Although an active material is not specifically limited, It is comprised with the element which can occlude / release lithium ion and the additional element contained depending on the case.

[Elements that can occlude and release lithium ions]
The element capable of occluding / releasing lithium ions is defined as an element capable of occluding / releasing lithium ions in the form of elemental simple substance or compound, and Si, Sn, Al, Zn, Ag, Ge, Pb, C, etc. are elements (such as oxides) in which Co, Ni, Mn, etc. are elements capable of occluding and releasing lithium ions. When these elements are used for the negative electrode material, they are not particularly limited, but are preferably Si and Sn elements, and more preferably Si elements. Moreover, when using these elements for a positive electrode material, Preferably they are Co, Ni, Mn, and Fe element, More preferably, they are Co and Mn element.

[Additive elements]
The active material may contain an additive element other than an element capable of inserting and extracting lithium ions. The additive element is not particularly limited, but is selected from Group 2, Group 4, Group 5, Group 8, Group 8, Group 9, Group 13, Group 14, Group 15, Group 16 and Group 16 of the periodic table It is a seed or two or more elements, more preferably B, C, N, Ti, Zr, W, and O elements, and still more preferably C, N, and O elements.

[composition]
The composition of the active material is not particularly limited, but the content of elements capable of occluding and releasing lithium ions is usually 10 atomic% or more, preferably 25 atomic% or more, more preferably 40 atomic% or more. 95 atomic percent or less, preferably 85 atomic percent or less, and more preferably 80 atomic percent or less.

  The composition of the active material is, for example, as shown in the examples below, using an X-ray photoelectron spectrometer (for example, “ESCA” manufactured by ULVAC-PHI), so that the surface of the electrode material made of the active material becomes flat. It can be obtained by placing the sample on the sample stage, using the Kα ray of aluminum as an X-ray source, performing depth profile measurement while performing Ar sputtering, and calculating the atomic concentration of each element in the active material.

[Composition when the element capable of inserting and extracting lithium ions is Si and the additive elements are C and O]
In the case of an active material represented by the general formula SiCxOy, where x is an element capable of inserting and extracting lithium ions, and the additive element is C or further O, x is not particularly limited. 0.05 or more, preferably 0.08 or more, more preferably 0.15 or more, particularly preferably 0.25 or more, usually 0.90 or less, preferably 0.75 or less, more preferably 0.60 or less, Especially preferably, it is 0.45 or less.

  Further, y is not particularly limited, but is usually 0.0 or more, preferably 0.05 or more, usually 0.90 or less, preferably 0.70 or less, more preferably 0.50 or less, and particularly preferably 0.00. 40 or less.

[Form]
The form of the active material is a thin film. In the present invention, the electrode material of the thin film active material can be obtained by vapor-phase growth of the active material on a substrate serving as a current collector.

<Thin film active material>
(Construction)
Examples of the structure of the thin film active material formed on the current collector include a columnar structure and a layered structure.

(Film thickness)
The film thickness of the thin film active material corresponds to the thickness of the active material layer of the electrode using the thin film active material, and is not particularly limited, but is usually 1 μm or more, preferably 3 μm or more, and usually 100 μm or less, preferably 60 μm or less. More preferably, it is 30 μm or less. If the film thickness of the thin film active material is within this range, it is preferable because the thin film active material can be prevented from peeling from the current collector substrate due to expansion / contraction associated with charge / discharge, and good cycle characteristics can be obtained.

(2) Substrate Hereinafter, a substrate on which an active material layer made of the active material as described above is formed by vapor phase growth, that is, a current collector for a negative electrode and a positive electrode will be described.

[Substrate for negative electrode]
<Material>
Examples of the material for the negative electrode substrate, that is, the current collector, include copper, nickel, stainless steel, etc. Among them, copper that is easy to process into a thin film and inexpensive is preferable. The copper foil includes a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method, both of which can be used as a current collector. When the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.

  A current collector made of copper foil produced by a rolling method has copper crystals arranged in the rolling direction, so that it is difficult to break even if the negative electrode using this is rounded sharply or rounded to an acute angle, and is a small cylindrical battery Can be suitably used. For example, an electrolytic copper foil is prepared by immersing a metal drum in an electrolytic solution in which copper ions are dissolved, and flowing current while rotating the copper drum, thereby depositing copper on the surface of the drum and peeling it off. It is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

<Thickness>
A current collector made of copper foil or the like is preferable in that the thinner the negative electrode, the thinner the negative electrode can be produced, and the negative electrode active material having a larger surface area can be packed in a battery container having the same storage volume. If the thickness is excessively thin, the strength is insufficient, and the copper foil may be cut by winding or the like during battery manufacture. For this reason, the current collector made of copper foil or the like is preferably about 5 to 70 μm thick. In the case of forming the active material on both sides of the copper foil, the copper foil is preferably thinner, but in this case, from the viewpoint of avoiding the occurrence of cracks in the copper foil due to the expansion / contraction of the active material accompanying charging / discharging, A more preferable thickness of the copper foil is 10 to 35 μm.

  When a metal foil other than copper foil is used as the current collector, one having a suitable thickness can be used depending on the metal foil, but the thickness is generally in the range of about 5 to 70 μm. Is within.

<Physical properties>
The following physical properties are desired for the current collector.
(1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material layer forming surface of the current collector defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.05 μm or more, preferably 0.1 μm or more, particularly preferably. Is 0.15 μm or more, usually 1.5 μm or less, preferably 1.3 μm or less, particularly preferably 1.0 μm or less.

  By setting the average surface roughness (Ra) of the current collector within the range between the lower limit and the upper limit described above, good charge / discharge cycle characteristics can be expected. By setting it to the above lower limit or more, the area of the interface with the active material is increased, and the adhesion with the active material is improved. The upper limit of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally difficult to obtain as foils having a practical thickness as a battery. 1.5 μm or less is preferable.

(2) Tensile strength The tensile strength of the current collector is not particularly limited, but is usually 100 N / mm ² or more, preferably 250 N / mm ² or more, more preferably 400 N / mm ² or more, and particularly preferably 500 N / mm ² or more. It is. The tensile strength is preferably as high as possible, but is usually 1000 N / mm ² or less from the viewpoint of industrial availability.

  The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as described in JISZ2241 (metal material tensile test method). If the current collector has a high tensile strength, cracking of the current collector due to expansion / contraction of the active material accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(3) 0.2% proof stress of 0.2% proof stress current collector is not particularly limited, normally 30 N / mm ² or more, preferably 150 N / mm ² or more, particularly preferably 300N / mm ² or more. The 0.2% proof stress is preferably as high as possible, but usually 900 N / mm ² or less is desirable from the viewpoint of industrial availability.

  The 0.2% proof stress is the magnitude of the load necessary to give a plastic (permanent) strain of 0.2%. It means that The 0.2% proof stress in the present invention is measured by the same apparatus and method as the elongation rate. If the current collector has a high 0.2% proof stress, plastic deformation of the current collector due to expansion / contraction of the active material accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. The 0.2% yield strength in the present invention is measured by the same apparatus and method as the tensile strength.

[Substrate for positive electrode]
As the substrate for the positive electrode, that is, the current collector, for example, a valve metal or an alloy thereof that forms a passive film on the surface by anodic oxidation in an electrolytic solution is preferably used. Examples of the valve metal include metals belonging to Groups 4, 5, and 13 of the periodic table and alloys thereof. Specifically, Al, Ti, Zr, Hf, Nb, Ta and alloys containing these metals can be exemplified, and Al, Ti, Ta and alloys containing these metals can be preferably used. . In particular, Al and its alloys are desirable because of their light weight and high energy density.
The thickness of the positive electrode current collector is not particularly limited, but is usually about 5 to 70 μm.

(3) Manufacturing method of electrode material for nonaqueous electrolyte secondary battery Next, the manufacturing method of the electrode material for nonaqueous electrolyte secondary battery of this invention is demonstrated.
In the method for producing an electrode material for a non-aqueous electrolyte secondary battery according to the present invention, a release layer is formed on a part of the active material layer forming surface on a substrate (hereinafter sometimes referred to as “current collector” as appropriate). After that, the active material raw material described above is vapor-grown on the substrate on the surface on which the release layer is formed and on the surface on which the release layer is formed, and the active material obtained by vapor-phase growth on the release layer and the release layer from the substrate. Removing the material layer.

[Peeling layer forming step]
<Peeling layer>
Hereinafter, the release layer formed on the substrate before vapor phase growth of the active material will be described in detail.
In the present invention, the release layer refers to a layer that can be easily released from the substrate after vapor phase growth of the active material.

(Material)
The material of the release layer is not particularly limited as long as it forms a layer that can be peeled off from the substrate after vapor phase growth, and examples thereof include a masking tape and a polymer binder. The release layer can contain a filler. Among them, those containing a polymer binder are preferable because they are easy to peel off from the substrate, and those containing a filler are preferable because they have heat resistance.

  Here, as the masking tape, for example, a polyester film, a polyimide film, a polypropylene film, a fluororesin film, or the like with a rubber-based or silicone-based adhesive can be used.

  Examples of the polymer binder include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, and cellulose, and rubber-like materials such as styrene / butadiene rubber, isoprene rubber, butadiene rubber, and ethylene / propylene rubber. Polymer, styrene / butadiene / styrene block copolymer, hydrogenated product thereof, styrene / ethylene / butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer, styrene / acrylic copolymer and hydrogenated product thereof Soft elastomeric polymers such as thermoplastic elastomeric polymers such as syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, or propylene / α-olefin (2 to 12 carbon atoms) copolymer, Polyvinylidene fluoride, polytetraph Oroechiren, or it can be used fluorine-based polymers such as polytetrafluoroethylene-ethylene copolymer. These may be used alone or in combination of two or more.

Further, as the filler, for example, carbon powder such as graphite and carbon black, ceramic powder such as alumina and zirconia, and metal powder such as iron and copper can be used. These may be used alone or in combination of two or more.
The particle size of the filler is not particularly limited, but is usually about 0.01 μm to 50 μm in average particle size.

  The filler can be used in combination with the polymer binder and the like, for example, in the form of a powdered toner in which the filler and the polymer binder are mixed and combined. At this time, the amount of the polymer binder used with respect to the filler is not particularly limited, but is about 0.1 to 20% by weight. If the ratio of the polymer binder to the filler is within this range, it is preferable because heat resistance can be expected.

(thickness)
The thickness of the release layer formed on the substrate is not particularly limited, but it is uneconomical if it is too thick, and if it is too thin, the strength is insufficient and the active material layer may be peeled off together with the release layer. It can be difficult. For this reason, it is preferable that the thickness of a peeling layer is about 0.5-300 micrometers.

  When a masking tape is used as the release layer, a suitable thickness can be used according to each tape, but the thickness is generally in the range of about 30 to 300 μm.

(Heat-resistant)
Although the heat-resistant temperature of a peeling layer is not specifically limited, Usually, 80 degreeC or more, Preferably it is 100 degreeC or more, More preferably, it is 140 degreeC or more. When the heat resistant temperature is within this range, it is preferable that peeling of the release layer due to radiant heat or the like hardly occurs when the active material is vapor-phase grown on the substrate. In the case of a polymer binder, the upper limit of the heat resistant temperature is usually about 300 ° C.

<Formation method of release layer>
Examples of a method for forming a release layer on a part of a substrate include, for example, a method of attaching a masking tape on a substrate, and a coating solution prepared by dispersing a polymer binder in an aqueous solvent and / or an organic solvent. A method of applying and drying a coating solution prepared by mixing and dispersing a filler, a polymer binder, and a solvent prepared so as to have the above-mentioned composition after drying. Etc.

<Peeling layer formation site>
The site for forming the release layer on the substrate is not particularly limited as long as it is a part on the substrate, but it is usually provided at a site where a current collecting tab or the like is adhered.

[Roughening the surface of the substrate]
After forming a release layer on the substrate, the active material can be vapor-phase grown after a step of roughening the surface of the substrate. A method for roughening the substrate surface will be described below.

  Examples of the method for roughening the substrate surface include wet / dry etching, electrolytic plating, and a method for mechanically roughening. For example, when the substrate is a copper foil, the wet etching is performed by spraying an etching solution such as ferric chloride aqueous solution or hydrogen peroxide / sulfuric acid aqueous solution on the surface of the copper foil, or immersing the copper foil in the etching solution. be able to. Moreover, plasma etching etc. can be used for dry etching, for example. Electroplating can be performed by electrolytic treatment using copper sulfate or the like as an electrolytic solution. Moreover, the method of roughening mechanically can be performed by roughening the surface using, for example, abrasive grains.

  The degree of the roughening treatment is not particularly limited as long as the release layer formed on the substrate, particularly the release layer at the site where the tab or the like is adhered is not removed.

[Active material vapor phase growth process]
<Active material ingredients>
Among active material raw materials (hereinafter sometimes referred to as “raw materials” as appropriate), as a raw material of an element capable of occluding and releasing lithium ions, a single element, a compound, a composition, a mixture, or the like of the element may be used. I can do it. Examples of elements that can occlude and release lithium ions include Si, Sn, Al, Zn, Ag, Ge, Pb, and C in the above-described elemental unit, and Co, Ni, and Mn in the form of compounds (for example, oxides). Examples of such single bodies include crystalline Si, amorphous Si, metal Sn, Al, Zn, Ag, Co, and Ni, and examples of compounds include silicon compounds (SiC, Si ₃ N ₄ , Sublimable compounds such as SiS, SiS ₂ and SiO), Co compounds, Mn compounds and the like can be used.

  The sublimable compound containing an element capable of occluding and releasing lithium ions is, for example, as described above, but when a sublimable compound is used, it is easy to suppress the reaction with the container in the vapor deposition method described below, and It is preferable because the composition of the active material can be easily controlled. In particular, SiC is preferable because oxygen mixed from the atmosphere reacts with carbon in SiC, so that the amount of oxygen contained in the active material can be reduced and the amount of carbon can be adjusted.

  When a sublimable compound is used for at least a part of the active material, the ratio of the sublimable compound in the active material is usually 20% by weight or more, preferably 30% by weight or more, and more preferably 40% by weight. In addition, it is usually 100% by weight or less, preferably 90% by weight or less, and more preferably 70% by weight or less. When the ratio of the sublimable compound is within this range, the effect using the above-described sublimable compound is easily obtained, which is preferable.

The types of additive elements are as described above. Among the raw materials, for example, as a raw material for C element, carbon such as natural graphite, artificial graphite, and amorphous carbon, and reactive species with carbon such as carbide are used. As a raw material of N element, nitride or the like can be cited. In addition, when the raw material is a gas, as a C element raw material, a gas containing C (CH ₄ , C ₂ H ₆ , C ₃ H _8, etc.), a gas obtained by vaporizing C by graphite arc discharge, resistance heating, or the like. As a source of N element, a gas containing NH (NH ₃ , N _2, etc.) can be used.

  In addition, in the case of vapor phase growth such as vapor deposition described later, it is most effective to raise the heating temperature of the active material raw material in order to increase the growth rate, but oxygen mixed from the atmosphere reacts with the active material at the same time. It becomes easy to form a large amount of oxide. In the case where the additive element contains a C element, the reaction between oxygen and carbon in the atmosphere progresses as the temperature increases, so that the amount of oxygen contained in the active material can be reduced.

Further, for example, when Si is an element capable of inserting and extracting lithium ions, Si _x C _{y and the} like having a higher evaporation rate than Si alone are formed and evaporated by the reaction of Si and carbon. It is preferable because the speed is increased.
In addition, a single compound combining an element capable of inserting and extracting active lithium ions and an additive element may be used, or a plurality of compounds may be used.
In addition, the form of the raw material of the element which can occlude / release lithium ions, the sublimable compound containing the element which can occlude / release lithium ions, and the additive element is, for example, powder, granule, pellet, lump, plate Used as a shape.

<Method of vapor phase growth of active material>
The active material can be formed by A: sputtering, B: vacuum deposition, C: CVD, D: ion plating, which will be described in detail below. E: The active material may be formed by a combination of two or more of these A to D vapor phase growth methods.

A. Sputtering In sputtering, active material material emitted from a target made of the above-mentioned raw material is collided and deposited on a substrate on which a release layer is formed by using plasma under reduced pressure to form a thin film of the active material. According to sputtering, there are advantages that the interface state between the formed active material layer and the substrate is good and the adhesion of the active material layer to the substrate is high.

  As a method for applying the sputtering voltage to the target, either a DC voltage or an AC voltage can be used. At that time, it is possible to control the collision energy of ions from the plasma by applying a substantially negative bias voltage to the current collector.

  The ultimate vacuum in the chamber before starting the active material formation is usually 0.1 Pa or less in order to prevent impurities from being mixed.

  As the sputtering gas, an inert gas such as Ne, Ar, Kr, or Xe is used. Among these, argon gas is preferably used in terms of sputtering efficiency. When the element N is contained in the active material, it is preferable for production to coexist as a trace amount of nitrogen gas in the inert gas. Usually, the sputtering gas pressure is about 0.05 to 70 Pa.

  The current collector for forming the active material layer by sputtering can also be controlled in temperature by water cooling or a heater. The temperature range of the current collector is usually room temperature to 900 ° C, but preferably 150 ° C or less.

  The growth rate in forming the active material layer by sputtering is usually 0.01 to 0.5 μm / min.

  Note that before forming the active material layer, the surface of the substrate can be etched by pre-treatment such as reverse sputtering or other plasma treatment. Such pretreatment is effective for removing contaminants and oxide films on the substrate surface and improving the adhesion of the active material.

B. Vacuum deposition In the vacuum deposition, the raw material as an active material is melted and evaporated and deposited on a substrate on which a release layer is formed at least partially. Vacuum deposition has an advantage that a film can be formed at a higher growth rate than sputtering. Vacuum deposition can be advantageously used in terms of manufacturing cost from the viewpoint of shortening the time for forming an active material layer having a predetermined thickness as compared with sputtering. Specific examples of the method include an induction heating method, a resistance heating method, and an electron beam heating vapor deposition method. In the induction heating method, a vapor deposition crucible such as graphite is formed by inductive current, in the resistance heating method by an energized heating current such as a vapor deposition boat, and in electron beam heating vapor deposition, the vapor deposition material is heated and melted and evaporated by an electron beam.

  The heating temperature of the active material material during vacuum deposition is usually 200 ° C. higher than the melting point of the element capable of inserting and extracting lithium ions, preferably 250 ° C. higher than the melting point of the element capable of inserting and extracting lithium ions, More preferably, the temperature is 300 ° C. or more higher than the melting point of the element capable of inserting and extracting lithium ions. If the heating temperature of the active material raw material is within this range, the vapor phase growth rate is large and preferable.

In particular, when the element capable of inserting and extracting lithium ions is Si and the active material contains C as an additive element, the heating temperature of the active material raw material when the active material is vapor-phase grown is usually 1650 ° C. or higher, preferably It is 1750 degreeC or more, More preferably, it is 1800 degreeC or more. If the heating temperature of the active material raw material is within this range, carbon reacts with oxygen during vapor phase growth to form carbon monoxide and the like, which is preferable because the amount of oxygen in the atmosphere can be reduced and battery characteristics are excellent.
Although there is no restriction | limiting in particular about the upper limit of the heating temperature of the said active material raw material, Usually, it is about 2500 degreeC. In addition, the measurement of the heating temperature at the time of heating an active material raw material can be performed using temperature measuring instruments, such as a thermocouple and a radiation thermometer.

As an atmosphere for vacuum deposition, a vacuum is generally used. When the element that can occlude and release lithium ions is Si and the additive element is C or O, the pressure is reduced while introducing a small amount of oxygen gas together with the inert gas, and the heating temperature is adjusted. At the same time, it is possible to grow while controlling the composition of the SiC _x O _y active material.

  In addition, as oxygen concentration in vapor deposition gas, it can obtain by analyzing the mass spectrum of vapor deposition gas, for example using a quadrupole mass filter. Moreover, when using argon gas with which oxygen gas coexists as vapor deposition gas, it calculates | requires by measuring the argon gas with an oxygen analyzer.

  The ultimate vacuum in the chamber before starting the vapor phase growth is usually 0.1 Pa or less in order to prevent impurities from being mixed.

  In the vacuum deposition heating method, as a material for a container for holding and / or heating the active material, a carbon material such as artificial graphite or carbon, a refractory metal such as quartz, ceramics, or W can be used. In addition, a carbon material is preferable because C can be mixed in the active material grown during vacuum deposition and the amount of oxygen in the active material can be reduced. The concentration of C in the formed active material layer is usually 5 atomic% or more, preferably 7.5 atomic% or more, more preferably 15 atomic% or more, particularly preferably 20 atomic%, and usually 48. Atomic% or less, preferably 43 atomic% or less, more preferably 38 atomic% or less, and particularly preferably 33 atomic% or less.

  As an atmosphere for vacuum deposition, a vacuum is generally used. In the case where the active material contains the element N, it is also possible to form a reduced amount of nitrogen gas together with the inert gas, reduce the pressure, and form simultaneously under vacuum using an assist such as ionization.

  The current collector for forming the active material by vacuum deposition can also be controlled in temperature by a heater or the like. The temperature range of the current collector is usually room temperature to 900 ° C, but preferably 150 ° C or less.

  The growth rate in forming an active material by vacuum deposition is usually about 0.1 to 500 μm / min.

  As in the case of sputtering, the substrate surface may be etched by irradiating ions with an ion gun or the like before depositing the active material on the substrate. By such etching treatment, the adhesion between the substrate and the active material can be further enhanced. By forming ions to collide with the substrate during the formation of the active material layer, the adhesion of the active material to the substrate can be further improved.

C. CVD (Chemical Vapor Deposition)
In CVD, the above-mentioned raw material which becomes an active material is deposited on a substrate on which a release layer is formed by a gas phase chemical reaction. In general, CVD has a feature that various materials with high purity can be synthesized in order to control a compound gas in a reaction chamber by gas inflow. Specific methods include thermal CVD, plasma CVD, photo CVD, cat -CVD etc. can be mentioned. In thermal CVD, a raw material gas of a halogen compound having a high vapor pressure is introduced into a reaction vessel heated to about 1000 ° C. together with a carrier gas and a reaction gas to cause a thermochemical reaction to form an active material layer. Plasma CVD uses plasma instead of thermal energy. Photo CVD uses light energy instead of thermal energy. Cat-CVD is a catalytic chemical vapor deposition method, in which an active material layer is formed by applying a catalytic decomposition reaction between a source gas and a heating catalyst.

Si sources used in CVD are SiH ₄ , SiCl _{4 and the} like, and additive element sources are NH ₃ , N ₂ , CH ₄ , C ₂ H ₆ , C ₃ H _{8 and the} like. These may be used alone or in combination of two or more.

D. Ion plating In ion plating, the raw material as an active material is melted and evaporated, and the evaporated particles are ionized and excited under plasma, thereby forming an active material layer firmly on the substrate on which the release layer is formed. Specifically, examples of the method for melting and evaporating the raw material include an induction heating method, a resistance heating method, an electron beam heating vapor deposition method, and the like. Examples thereof include cathodic thermionic irradiation method, high frequency excitation method, HCD method, cluster ion beam method, and multi-arc method. Moreover, the method of evaporating the raw material and the method of ionization and excitation can be selected as appropriate and performed in combination.

E: Combination of A to D For example, the first thin film layer is formed by sputtering using the advantage of the high growth rate of the vacuum deposition method and the strong adhesion to the current collector by sputtering, and then vacuum is applied. By forming the second thin film layer at a high speed by a vapor deposition method, an interface region having good adhesion to the current collector can be formed, and an active material layer can be formed at a high growth rate. By such a hybrid combination method of growth methods, an electrode having a high charge / discharge capacity and excellent charge / discharge cycle characteristics can be efficiently produced.

  The active material layer formed by a combination of sputtering and vacuum deposition is preferably formed continuously while maintaining a reduced pressure atmosphere. This is because contamination of impurities can be prevented by continuously forming the first thin film layer and the second thin film layer without being exposed to the atmosphere. For example, it is preferable to use a thin film forming apparatus that sequentially performs sputtering and vacuum deposition while moving the current collector in the same vacuum environment.

  In the case where the active material layer is formed on both surfaces of the current collector, the formation of the active material layer on one surface of the current collector and the formation of the active material layer on the other surface of the current collector are performed under a reduced pressure atmosphere. It is preferable to carry out continuously while keeping.

  In addition, after the active material layer is formed, post-treatment such as heat treatment can be performed to control the crystallinity of the active material or to improve the adhesion to the current collector.

<Film thickness>
The thickness of the active material layer formed by vapor phase growth is preferably within the range of the preferred thickness of the thin film active material described above when it is used as a thin film active material.

[Active material removal process]
<Removal method of release layer>
As a method of removing the active material layer formed on the release layer from the release layer and the vapor-grown active material layer from the substrate, for example, when the release layer is a masking tape, a masking tape is used. By peeling off, the active material layer can be peeled and removed together with the peeling layer. In the case where the release layer is a polymer binder or a filler with a polymer binder such as a resin-adhered ceramic powder, the polymer binder or resin can be peeled off using a method similar to the masking tape or using a solvent. The active material layer on the release layer is removed together with the release layer by swelling or dissolving it, for example, the electrode is passed in an S shape while being curved between rollers having a radius of curvature of about 1 cm in diameter. Thus, there may be mentioned a method of removing the active material layer by using the rigidity of the active material layer to peel off at the release layer.

[2] Electrode for nonaqueous electrolyte secondary battery The electrode for nonaqueous electrolyte secondary battery of the present invention includes an electrode material produced by the above production method.

  Such an electrode of the present invention is extremely useful as a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and an electrode in a nonaqueous electrolyte secondary battery such as a lithium secondary battery equipped with an electrolyte, that is, a negative electrode and / or a positive electrode. Useful. For example, a non-aqueous electrolyte secondary comprising a combination of a metal chalcogenide-based positive electrode for a lithium secondary battery that is usually used and an organic electrolyte mainly composed of a carbonate-based solvent, using the electrode of the present invention as a negative electrode. The battery is inexpensive, excellent in productivity, large in capacity, and excellent in cycle characteristics.

[3] Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, and at least one of a positive electrode and a negative electrode. The electrode of the present invention is used as the electrode.
There is no particular limitation on the selection of members other than the electrodes, which are necessary for the battery configuration such as the electrolyte constituting the nonaqueous electrolyte secondary battery of the present invention.
Although the material etc. which comprise the nonaqueous electrolyte secondary battery of this invention are illustrated below, the material which can be used is not limited to these specific examples.

[Positive electrode]
When the negative electrode of the present invention is used as an electrode, the positive electrode is formed on the current collector substrate by forming a positive electrode active material and an active material layer containing an organic substance (binder) having a binding and thickening effect, Usually, a process in which a slurry in which a positive electrode active material and a binder are dispersed in water or an organic solvent is thinly applied and dried on a current collector substrate, followed by pressing to a predetermined thickness and density. It is formed by.

<Positive electrode active material>
The positive electrode active material is not particularly limited as long as it has a function capable of inserting and extracting lithium. For example, lithium transition metal composite oxide materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide A transition metal oxide material such as manganese dioxide; a carbonaceous material such as graphite fluoride can be used. Specifically, LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and their non-stoichiometric compounds, MnO ₂ , TiS ₂ , FeS ₂ , Nb ₃ S ₄ , Mo ₃ S ₄ , CoS ₂ , V ₂ O ₆ , P ₂ O ₆ , CrO ₃ , V ₃ O ₃ , TeO ₂ , GeO ₂ or the like can be used. These may be used alone or in combination of two or more.

<Conductive agent>
A positive electrode conductive agent can be used for the positive electrode active material layer. The positive electrode conductive agent may be any electron conductive material that does not cause a chemical change at the charge / discharge potential of the positive electrode active material to be used. For example, natural graphite (such as flake graphite), graphite such as artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, metal fiber, etc. Conductive fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and organic conductive materials such as polyphenylene derivatives It can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite and acetylene black are particularly preferable. These may be used alone or in combination of two or more.
Although the addition amount of a electrically conductive agent is not specifically limited, 1-50 weight% is preferable with respect to a positive electrode active material, and 1-30 weight% is especially preferable. In the case of carbon or graphite, 2 to 15% by weight is particularly preferable with respect to the positive electrode active material.

<Binder>
There is no restriction | limiting in particular as a binder used for formation of a positive electrode active material layer, Any of a thermoplastic resin and a thermosetting resin may be sufficient. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin) , Polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrif Oroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer or (Na ⁺ ) ion crosslinked product, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinked product of the material, ethylene-methyl acrylate copolymer, or (Na ⁺ ) ion crosslinked product of the material, ethylene-methacrylic acid Examples thereof include an acid methyl copolymer or a (Na ⁺ ) ion-crosslinked product of the above materials, and these materials can be used alone or as a mixture. Among these materials, more preferable materials are polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

<Other additives>
In addition to the conductive agent described above, the positive electrode active material layer may further contain a filler, a dispersant, an ionic conductor, a pressure enhancer, and other various additives. Any filler can be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 weight% is preferable as content in an active material layer.

<solvent>
In preparing the positive electrode active material slurry, an aqueous solvent or an organic solvent is used as a dispersion medium. As the aqueous solvent, water is usually used, and additives such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone may be added to water up to about 30% by weight or less. it can.
As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. .

  A positive electrode active material, a binder as a binder, an organic substance having a thickening effect, a positive electrode conductive agent blended as necessary, and other fillers are mixed in these solvents to prepare a positive electrode active material slurry, This is applied and dried on the positive electrode current collector substrate so as to have a predetermined thickness, and then pressed to a predetermined thickness and density to form a positive electrode active material layer.

  The upper limit of the concentration of the positive electrode active material in the positive electrode active material slurry is usually 70% by weight or less, preferably 55% by weight or less, and the lower limit is usually 30% by weight or more, preferably 40% by weight or more. If the concentration of the positive electrode active material exceeds this upper limit, the positive electrode active material in the positive electrode active material slurry tends to aggregate, and if it falls below the lower limit, the positive electrode active material tends to settle during storage of the positive electrode active material slurry.

  Further, the upper limit of the concentration of the binder in the positive electrode active material slurry is usually 30% by weight or less, preferably 10% by weight or less, and the lower limit is usually 0.1% by weight or more, preferably 0.5% or more. . When the concentration of the binder exceeds the upper limit, the internal resistance of the positive electrode obtained is increased, and when the concentration is lower than the lower limit, the binding property of the positive electrode active material layer is deteriorated.

<Current collector>
As the positive electrode current collector, the aforementioned positive electrode substrate can be used.

[Negative electrode]
When the positive electrode of the present invention is used as an electrode, the negative electrode is formed on the current collector substrate by forming an active material layer containing a negative electrode active material and an organic substance (binder) having a binding and thickening effect, Usually, a process in which a slurry in which a negative electrode active material and a binder are dispersed in water or an organic solvent is thinly applied and dried on a current collector substrate, followed by pressing to a predetermined thickness and density. It is formed by.

<Negative electrode active material>
The negative electrode active material is not particularly limited as long as it has a function capable of occluding and releasing lithium. For example, natural graphite (scaly graphite, spheroidized graphite, etc.), artificial graphite (mesocarbon microbeads, etc.) Graphite, amorphous carbon obtained by firing pitch, resin, etc., multi-phase structure material composed of graphite and amorphous carbon, metals such as silicon, aluminum, tin, silicon monoxide, lithium titanate, etc. These oxides are mentioned. Among these negative electrode active materials, natural graphite, artificial graphite, and multiphase structural materials in which graphite and amorphous carbon are combined are generally used industrially and are preferable because they are inexpensive and easy to handle. These may be used alone or in combination of two or more.

<Binder>
As the binder, a polymer that is stable against a liquid solvent described later is preferable. For example, resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, cellulose, rubbery polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber or ethylene / propylene rubber, styrene / butadiene / styrene block Polymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers and thermoplastic elastomeric polymers such as hydrogenated products, syndiotactic 1,2-polybutadiene , Ethylene / vinyl acetate copolymer, or soft resinous polymer such as propylene / α-olefin (carbon number 2 to 12) copolymer, polyvinylidene fluoride, polytetrafluoroethylene, or polytetrafluoroethylene / ethylene The fluoropolymer of the polymer or the like, and the like alkali metal ion (especially lithium ion) polymer composition having ion conductivity. These may be used alone or in combination of two or more.

  Examples of the polymer composition having ion conductivity include polyether polymer compounds such as polyethylene oxide and polypropylene oxide, crosslinked polymers of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, and polyvinylpyrrolidone. , A polymer in which a lithium salt or an alkali metal salt mainly composed of lithium is combined with a polymer compound such as polyvinylidene carbonate or polyacrylonitrile, or a high dielectric such as propylene carbonate, ethylene carbonate or γ-butyrolactone. A polymer in which an organic compound having a rate or an ion-dipole interaction force is blended can be used.

  Specifically, resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, polyimide, or cellulose and derivatives thereof (for example, carboxymethylcellulose), styrene / butadiene rubber, isoprene rubber, butadiene rubber, or ethylene are usually used.・ Fluorine polymers such as rubbery polymers such as propylene rubber, polyvinylidene fluoride, polytetrafluoroethylene, or polytetrafluoroethylene / ethylene copolymers, polyether polymer compounds such as polyethylene oxide and polypropylene oxide, Examples thereof include crosslinked polymers of polyether compounds, preferably polyethylene, polypropylene, polyimide, styrene / butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, or polyethylene. Ethylene oxide and the like, more preferably, polyethylene, styrene-butadiene, polyvinylidene fluoride, or polytetrafluoroethylene. These are currently used industrially and are suitable because they are easy to handle.

<Conductive agent>
The negative electrode active material may include a conductive agent. The conductive agent may be any electronic conductive material that does not cause a chemical change at the charge / discharge potential of the negative electrode active material to be used. For example, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, carbon fibers, vapor grown carbon fibers (VGCF), conductive fibers such as metal fibers, fluorine Carbon powders, metal powders such as copper, etc. can be contained alone or as a mixture thereof. Of these conductive agents, acetylene black and VGCF are particularly preferable. These may be used alone or in combination of two or more.
Although the addition amount of a electrically conductive agent is not specifically limited, 1-30 weight% is preferable with respect to a negative electrode active material, and 1-15 weight% is especially preferable.

<solvent>
For the preparation of the negative electrode active material slurry, an aqueous solvent or an organic solvent is used as a dispersion medium. As the aqueous solvent, water is usually used, and additives such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone may be added to water up to about 30% by weight or less. it can.
As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. .

A negative electrode active material, a binder as a binder, an organic substance having a thickening effect, a negative electrode conductive agent blended as necessary, and other fillers are mixed in these solvents to prepare a negative electrode active material slurry, This is applied and dried on the negative electrode current collector substrate so as to have a predetermined thickness, and then pressed to a predetermined thickness and density to form a negative electrode active material layer.
The upper limit of the concentration of the negative electrode active material in this negative electrode active material slurry is usually 70% by weight or less, preferably 55% by weight or less, and the lower limit is usually 30% by weight or more, preferably 40% by weight or more. When the concentration of the negative electrode active material exceeds the upper limit, the negative electrode active material in the negative electrode active material slurry tends to aggregate, and when the concentration is lower than the lower limit, the negative electrode active material tends to settle during storage of the negative electrode active material slurry.

  Further, the upper limit of the concentration of the binder in the negative electrode active material slurry is usually 30% by weight or less, preferably 10% by weight or less, and the lower limit is usually 0.1% by weight or more, preferably 0.5% or more. . When the concentration of the binder exceeds this upper limit, the internal resistance of the negative electrode obtained increases, and when the concentration is lower than the lower limit, the binding property of the negative electrode active material layer becomes poor.

<Current collector>
As the negative electrode current collector, the above-described negative electrode substrate can be used.

[Electrolytes]
Any electrolyte such as an electrolytic solution or a solid electrolyte can be used as the electrolyte. Here, the electrolyte refers to all ionic conductors, and both the electrolytic solution and the solid electrolyte are included in the electrolyte.

As the electrolytic solution, for example, a solution obtained by dissolving a solute in a non-aqueous solvent can be used. As the solute, an alkali metal salt, a quaternary ammonium salt, or the like can be used. Specifically, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) _{3 and the} like are preferably used. One kind of these solutes may be selected and used, or two or more kinds may be mixed and used. The content of these solutes in the electrolytic solution is preferably 0.2 mol / L or more, particularly 0.5 mol / L or more, and 2 mol / L or less, particularly 1.5 mol / L or less.

Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; cyclic ester compounds such as γ-butyrolactone; chain ethers such as 1,2-dimethoxyethane; crown ethers, 2- Cyclic ethers such as methyltetrahydrofuran, 1,2-dimethyltetrahydrofuran, 1,3-dioxolane, and tetrahydrofuran; chain carbonates such as diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate can be used. Among these, a nonaqueous solvent containing a cyclic carbonate and a chain carbonate is preferable.
One type of these solvents may be selected and used, or two or more types may be mixed and used.

  The nonaqueous electrolytic solution according to the present invention may contain various auxiliary agents such as a cyclic carbonate having an unsaturated bond in the molecule, a conventionally known overcharge inhibitor, a deoxidizer, and a dehydrator.

Examples of the cyclic carbonate having an unsaturated bond in the molecule include vinylene carbonate compounds, vinyl ethylene carbonate compounds, methylene ethylene carbonate compounds, and the like.
Examples of the vinylene carbonate compounds include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, fluoro vinylene carbonate, trifluoromethyl vinylene carbonate, and the like.
Examples of the vinyl ethylene carbonate compound include vinyl ethylene carbonate, 4-methyl-4-vinyl ethylene carbonate, 4-ethyl-4-vinyl ethylene carbonate, 4-n-propyl-4-vinyl ethylene carbonate, 5-methyl- Examples include 4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-divinylethylene carbonate, and the like.
Examples of the methylene ethylene carbonate compound include methylene ethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate, 4,4-diethyl-5-methylene ethylene carbonate, and the like.
Of these, vinylene carbonate and vinyl ethylene carbonate are preferable, and vinylene carbonate is particularly preferable.
These may be used individually by 1 type, or may use 2 or more types together.

When the non-aqueous electrolyte contains a cyclic carbonate compound having an unsaturated bond in the molecule, the proportion in the non-aqueous electrolyte is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly Preferably it is 0.3% by weight or more, most preferably 0.5% by weight or more, usually 8% by weight or less, preferably 4% by weight or less, particularly preferably 3% by weight or less.
By including in the electrolyte a cyclic carbonate having an unsaturated bond in the molecule, the cycle characteristics of the battery can be improved. Although the reason is not clear, it is presumed that a stable protective film can be formed on the surface of the negative electrode. However, when the content is small, this property is not sufficiently improved. However, if the content is too large, the gas generation amount tends to increase during high-temperature storage, so the content in the electrolyte is preferably in the above range.

Examples of the overcharge inhibitor include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; 2-fluoro Partially fluorinated products of the above aromatic compounds such as biphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; fluorine-containing compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole and 2,6-difluoroanisole Anisole compounds and the like can be mentioned.
These may be used alone or in combination of two or more.
The ratio of the overcharge inhibitor in the non-aqueous electrolyte is usually 0.1 to 5% by weight. By containing an overcharge preventing agent, rupture / ignition of the battery can be suppressed during overcharge or the like.

Other auxiliary agents include, for example, carbonate compounds such as fluoroethylene carbonate, trifluoropropylene carbonate, phenylethylene carbonate, erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, anhydrous glutar Carboxylic anhydrides such as acid, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; Ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone and tetramethylthiuram monosulfate Sulfur-containing compounds such as N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1 , 3-dimethyl-2-imidazolidinone and nitrogen-containing compounds such as N-methylsuccinimide; hydrocarbon compounds such as heptane, octane and cycloheptane; fluorobenzene, difluorobenzene, hexafluorobenzene, benzotrifluoride, etc. And fluorine-containing aromatic compounds.
These may be used alone or in combination of two or more.
The ratio of these auxiliaries in the nonaqueous electrolytic solution is usually 0.1 to 30% by weight. By containing these auxiliaries, capacity maintenance characteristics and cycle characteristics after high-temperature storage can be improved.

  Further, the non-aqueous electrolyte solution may include an organic polymer compound in the electrolyte solution, and may be a gel-like, rubber-like, or solid sheet-like solid electrolyte. In this case, specific examples of the organic polymer compound include polyether polymer compounds such as polyethylene oxide and polypropylene oxide; crosslinked polymers of polyether polymer compounds; vinyl alcohol polymers such as polyvinyl alcohol and polyvinyl butyral. Compound; insolubilized product of vinyl alcohol polymer; polyepichlorohydrin; polyphosphazene; polysiloxane; vinyl polymer such as polyvinyl pyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), Examples thereof include polymer copolymers such as poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate).

[Other components]
In addition to the electrolyte, the negative electrode, and the positive electrode, an outer can, a separator, a gasket, a sealing plate, a cell case, and the like can be used as the negative electrode for the nonaqueous electrolyte secondary battery, if necessary.
The material and shape of the separator are not particularly limited. The separator is separated so that the positive electrode and the negative electrode do not come into physical contact with each other, and preferably has high ion permeability and low electrical resistance. The separator is preferably selected from materials that are stable with respect to the electrolyte and excellent in liquid retention. Specific examples include porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene.

[Shape of non-aqueous electrolyte secondary battery]
The shape of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited. For example, a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a pellet electrode and a separator It can be made into a laminated coin type or the like.

[Method for producing non-aqueous electrolyte secondary battery]
The method for producing the nonaqueous electrolyte secondary battery of the present invention having at least an electrolyte, a negative electrode, and a positive electrode is not particularly limited and can be appropriately selected from commonly employed methods.
An example of the method for producing the nonaqueous electrolyte secondary battery of the present invention is as follows: a negative electrode is placed on an outer can, an electrolytic solution and a separator are provided thereon, a positive electrode is placed so as to face the negative electrode, a gasket, A method of assembling the battery by caulking with a sealing plate is mentioned.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples, unless the summary is exceeded.

In Examples and Comparative Examples, the composition of the formed active material layer was analyzed by the following XPS measurement.
(XPS measurement)
For the X-ray photoelectron spectroscopy measurement, an X-ray photoelectron spectrometer (“ESCA” manufactured by ULVAC-PHI) was used to place the active material layer on the sample stage so that the surface of the active material layer was flat, and the aluminum Kα ray was X-rayed. The depth profile was measured while performing Ar sputtering with the source. Spectra of Si2p (90 to 110 eV), C1s (280 to 300 eV), and O1s (525 to 545 eV) at a constant depth (for example, 200 nm) were obtained. The obtained C1s peak top was 284.5 eV, charge correction was performed, the peak areas of the Si2p, C1s, and O1s spectra were obtained, and the device sensitivity coefficient was multiplied to calculate the atomic concentrations of Si, C, and O, respectively. From the obtained atomic concentrations of Si, C, and O, a primitive concentration ratio Si / C / O (Si atomic concentration / C atomic concentration / O atomic concentration) is calculated, and the composition value Si / C / O of the active material layer is calculated. It is defined as

Moreover, evaluation of the discharge capacity of the battery produced by the Example and the comparative example was performed with the following method.
(Evaluation of discharge capacity)
The lithium cobalt positive electrode is charged to 4.2 V at a current density of 0.2 C (1 C = 80 mA), further charged to a current value of 2 mA at a constant voltage of 4.2 V, and lithium is doped into the negative electrode. After that, the charge / discharge cycle of discharging to 3 V with respect to the lithium cobalt positive electrode at a current density of 0.2 C was repeated four times to stabilize the battery capacity, and the discharge capacity was made the fourth time. Moreover, when setting it as the discharge capacity per mass, the active material mass of the negative electrode material was calculated | required by subtracting the mass of the copper foil pierced to the same area from the negative electrode mass, and calculated according to the following.
Discharge capacity (mAh / g)
= 4th cycle discharge capacity (mAh) / active material mass (g)
Active material mass (g) = Negative electrode mass (g)-Copper foil mass (g) of the same area

[Example 1]
<Formation process of release layer>
As a current collector, a film having an average surface roughness (Ra) of 0.3 μm, a tensile strength of 400 N / mm ² , a 0.2% proof stress of 380 N / mm ² and a thickness of 18 μm. Rolled copper foil with a roughened surface (about 1 m long x 60 mm wide) and 10 mm wide x 60 μm thick polyimide tape (25 μm thick polyimide film with silicone / acrylic adhesive attached as masking tape) Nitto Denko's polyimide adhesive tape) is formed in the direction perpendicular to the circumferential direction of the rotating drum (the length of the copper foil) at 100 mm intervals to form a current collecting tab on the current collector. It was affixed to 10 non-deposited portions.

<Active material vapor phase growth process>
As a target material, a mixture of Si and C (atomic ratio of Si and C is 1: 0.3) is used for 8 hours in a DC sputtering device (“HSM-52” manufactured by Shimadzu Corporation) with a rotating drum. The material was deposited to obtain a thin film active material on the current collector.
At this time, the current collector was attached to a water-cooled rotating drum with an outer circumference of about 1 m, maintained at about 25 ° C., the chamber was evacuated to 4 × 10 ⁻⁴ Pa in advance, and high-purity argon gas was allowed to flow into the chamber at 40 sccm. Then, after adjusting the opening of the main valve to an atmosphere of 1.6 Pa, film formation was performed at a power density of 7 W / cm ² and a drum rotation speed of 13 rpm. The film formation took 8 hours.
Before the thin film was formed, reverse sputtering was performed to etch the current collector surface for the purpose of removing the oxide film on the copper foil surface.

  From the scanning electron microscope (SEM) observation of the cross section of the obtained thin film active material, the film thickness of the formed thin film was about 7 μm, and the film formation speed (film thickness ÷ The vacuum deposition time was about 0.2 nm / sec.

  The composition analysis of the thin film active material by XPS revealed that the Si thin film contained 24 atomic% of the additive element C and 4 atomic% of the additive element O mixed from the atmosphere.

<Release layer and active material removal step>
After sputtering, the thin film active material was peeled off from the current collector together with a masking tape having a width of 10 mm and a thickness of 60 μm to form a current-collecting tab forming portion without an active material layer. From the appearance of the electrode, the boundary between the film-forming part of the active material and the non-film-forming part for current collection was clear.

<Production and evaluation of battery>
The electrode produced by the above method was cut out so that the active material surface had a size of 30 mm × 40 mm. At this time, the current-collecting tab adhesion portion without the active material layer was cut out to have a size of 5 mm × 5 mm outside the active material surface.
The obtained electrode was vacuum-dried at 85 ° C. for a whole day and night, transferred to a dry room, and a copper tab was welded to the bonded portion with an ultrasonic welder in a dry air atmosphere to form a negative electrode.
1 mol / L-LiPF ₆ electrolyte using a mixed solution of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3/7 (mass ratio) as an electrolyte, a polyethylene separator as a separator, and lithium cobalt oxide as a counter electrode Using the positive electrode, an aluminum laminate type battery (lithium secondary battery) in which the negative electrode and the positive electrode face each other was produced.
When the discharge capacity was evaluated using the produced battery, the discharge capacity of the negative electrode active material was 2200 mAh / g.

[Example 2]
<Formation process of release layer>
As the current collector, an inexpensive rolled copper foil having a non-roughened surface, a tensile strength of 400 N / mm ² , a 0.2% proof stress of 380 N / mm ² and a thickness of 35 μm is used, and a release layer As in Example 1, a release layer was formed using a fluororesin tape having a thickness of 100 μm (a fluororesin adhesive tape manufactured by Nitto Denko Corporation with a silicone adhesive attached to a fluororesin film).

<Roughening process of substrate surface>
As a roughening means, ferric chloride aqueous solution was used, and wet etching was performed by immersing the current collector on which the release layer was formed. It was 0.2 micrometer when the average surface roughness (Ra) after an etching was measured about the part without the peeling layer of a collector.

<Active Material Vapor Phase Growth Step, Release Layer and Active Material Removal Step>
Using the roughened current collector, the active material layer was formed, and the release layer and a part of the active material were removed in the same manner as in Example 1. When the film thickness of the thin film active material was measured in the same manner as in Example 1, it was about 7 μm.
Further, when the composition analysis of the thin film active material was performed by XPS in the same manner as in Example 1, the Si thin film contained 24 atomic% of the additive element C and 4 atomic% of the additive element O mixed from the atmosphere. .
Further, the boundary between the active material film-forming portion and the current collecting non-film-forming portion was clear from the appearance of the electrode.

<Production and evaluation of battery>
Using the electrode produced by the above method, a battery was produced in the same manner as in Example 1, and the discharge capacity was evaluated. The result was 2160 mAh / g.

[Example 3]
[Peeling layer forming step]
Carbon black (average particle size 31 μm) as filler and styrene / butadiene rubber (SBR) 0.5% by weight as polymer binder (when mixed powder of carbon black and styrene / butadiene rubber is 100% by weight) ) And 1.0% by weight of carboxymethylcellulose (CMC) were added and mixed in the form of an aqueous solution or an aqueous suspension, respectively. The mixture thus obtained was applied to a part of the current collector in the same manner as in Example 1, and then dried at 80 ° C. for 60 minutes to form a release layer having a thickness of 100 μm. After drying, the current collector was cut into a length of 60 mm and a width of 60 mm in a state including a release layer in a part thereof to obtain a sample for forming an active material.

<Active material vapor phase growth process>
The active material raw material was crushed Si, and high frequency induction heating type vacuum deposition was performed on the current collector on which the release layer was formed, using “MU-1700D high frequency induction heating apparatus” manufactured by Sekisui Medical Electronics.
At this time, the current collector was cooled with water and maintained at about 25 ° C., and the inside of the chamber was evacuated to create an atmosphere of 1 × 10 ⁻³ Pa. Then, the graphite crucible containing crushed Si was subjected to high-frequency induction heating current 9.2 A. Heated and vacuum deposited for 80 seconds. Moreover, the temperature of the upper surface of the crucible at the time of vacuum deposition measured with the radiation thermometer at this time was 1690 degreeC.
From the observation of the cross section of the obtained thin film active material by scanning electron microscope (SEM), the film thickness of the formed thin film was about 7 μm.
When the composition analysis of the thin film active material was performed by XPS, the Si thin film contained 20 atomic% of the additive element C mixed from the graphite crucible and 5 atomic% of the additive element O mixed from the atmosphere. .

<Release layer and active material removal step>
After vacuum deposition, the thin film active material formed in a vapor phase on the release layer could be easily peeled off the collector together with the release layer by wiping with a cloth soaked with ethanol. From the appearance of the electrode, the boundary between the film-forming part of the active material and the non-film-forming part for current collection was clear.

<Production and evaluation of battery>
Using the electrode produced by the above method, a battery was produced in the same manner as in Example 1 and the discharge capacity was evaluated. The result was 2250 mAh / g.

[Comparative Example 1]
<Active material vapor phase growth process>
The same operation as in Example 1 was performed except that the active material was directly formed on the current collector without forming the release layer. (No peeling layer formation, no peeling layer removal step.)

<Production and evaluation of battery>
The electrode in the state where the active material is attached to the tab bonding portion for collecting current was cut out in the same shape as in Example 1, and an attempt was made to weld the copper tab onto the active material with an ultrasonic welding machine. As a result, it was impossible to weld the battery, and it was impossible to manufacture a battery as in Example 1.

[Comparative Example 2]
<Active material vapor phase growth process>
Using a current collector that does not form a release layer, the apparatus used in Example 1 was used to form a film for 1 hour while the rotating drum was stopped, and the rotating drum was moved 1 cm while the shutter was closed (film formation was not possible). By repeating the operation of forming a film for 1 hour with the rotating drum stopped, a film formation part and an unfilmed part without an active material were formed intermittently. At this time, it took about 15 hours to form the current collector for about 1 m (for one rotation of the rotating drum). (No peeling layer formation, no peeling layer removal step.)

  From the observation of the cross section of the obtained thin film active material by scanning electron microscope (SEM), the film thickness of the formed thin film was about 7 μm. In addition, the boundary between the film-forming portion and the non-film-forming portion of the active material was unclear due to the appearance of the electrode.

<Production and evaluation of battery>
Using the electrode produced by the above method, the electrode was cut out in the same manner as in Example 1, and a copper tab was welded to the non-deposited portion to produce an electrode, and the discharge capacity was evaluated. The result was 2200 mAh / g. .

  Table 1 summarizes the physical properties and the like of the negative electrode materials used in the above Examples and Comparative Examples.

Table 1 shows the following.
The manufacturing method of Comparative Example 1 is outside the specified range of the present invention because the active material is vapor-phased on the entire surface of the current collector without forming a release layer. As a result, the current collecting tab can be welded. No battery could be produced.

  In the manufacturing method of Comparative Example 2, a Si-based active material that can be alloyed with lithium is formed in a gas phase, and the discharge capacity is high, but since it is manufactured intermittently by sputtering without forming a release layer, It was outside the specified range of the present invention, and as a result, the film formation time was long and the productivity was poor.

  On the other hand, in the production methods of Examples 1 to 3 of the present invention, after forming a release layer on a part of the substrate, the active material is vapor-phase grown, and the release layer and the release layer are formed on the substrate. Since the step of removing the active material is provided, all satisfy the specified range of the present invention. When such a manufacturing method is used, a negative electrode material that is excellent in productivity, inexpensive, and has a high discharge capacity can be obtained.

  According to the present invention, a nonaqueous electrolyte secondary battery having excellent productivity, low cost, and high discharge capacity is provided. Therefore, the present invention is applied to various fields such as electronic devices to which the nonaqueous electrolyte secondary battery is applied. It can be suitably used.

Claims (6)

  In a method for producing an electrode material for a non-aqueous electrolyte secondary battery by vapor-growing an active material on a substrate, a release layer is formed on a part of the active material layer forming surface of the substrate, and then the release on the substrate is performed. Forming an active material layer by vapor-phase growth of the active material on the layer forming surface and the non-forming surface, and thereafter removing the release layer and the active material layer on the release layer from the substrate; A method for producing a non-aqueous electrolyte secondary battery electrode material.   The method for producing an electrode material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the release layer contains a polymer binder.   The method for producing an electrode material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the release layer contains a filler.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the release layer is formed on the substrate, the surface of the substrate is roughened, and then the active material is vapor-phase grown. Method for manufacturing an electrode material.   A nonaqueous electrolyte secondary battery electrode comprising the electrode material produced by the method for producing a nonaqueous electrolyte secondary battery electrode material according to any one of claims 1 to 4.   The nonaqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the electrode (positive electrode and / or negative electrode) is the electrode for a nonaqueous electrolyte secondary battery according to claim 5. There is a nonaqueous electrolyte secondary battery.