Carbon material dispersion, electrode composition, electrode, and all-solid-state battery

Abstract

Provided is a carbon dispersion liquid that suppresses deterioration of a sulfide-based solid electrolyte and, when used to form an electrode, results in low internal resistance and excellent electrode resistance. Also provided are an electrode composition, an electrode, and an all-solid-state battery that use the carbon dispersion liquid and have excellent electrode resistance. [Solution] The above problem is solved by a carbon material dispersion liquid comprising a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein the carbon material (A) comprises a carbon material (a) that satisfies the following (i) and (ii), the dispersant (B) comprises a polyvinyl butyral resin (b), and the solvent has a relative dielectric constant of less than 10 and / or a solubility of less than 1 g of low-polarity solvent in 100 g of water at 20°C: (i) Bulk density is 0.02 to 0.2 g / cm 3 (ii) A specific surface area of ​​50 m 2 / g or more

Description

[Technical Field]

[0001] The present invention is directed to a bulk density of 0.02 to 0.2 g / cm 3 and the specific surface area is 50m 2 The present invention relates to a carbon material dispersion that suppresses deterioration of a sulfide-based solid electrolyte and has excellent electrode resistance, the carbon material dispersion comprising a carbon material (A) containing a carbon material (a) having a specific surface area of ​​1 / 2 g or more, a dispersant (B) containing a polyvinyl butyral resin (b), and a low-polarity solvent (C), the carbon material dispersion also comprising the carbon material (A), an electrode composition, an electrode, and an all-solid-state battery that use the carbon material dispersion. [Background technology]

[0002] In recent years, demand for lithium-ion secondary batteries has increased in a wide range of applications, including mobile devices and electric vehicles, and all-solid-state batteries using solid electrolytes, which offer excellent capacity and safety, are being investigated. From the perspective of achieving particularly high capacity, bulk-type all-solid-state batteries in which electrodes are formed from powder materials have attracted attention, and electrode fabrication by wet processes using sulfide-based solid electrolytes is being investigated. To maximize the performance of all-solid-state batteries, it is important to form a sufficient conductive network in the electrodes, and in addition to a solid electrolyte responsible for ionic conduction, a carbon material is required as a conductive additive to impart electronic conductivity. In other words, to form an excellent conductive network in a wet process, it is necessary to prepare a dispersion in which the carbon material, which is inherently prone to aggregation, is sufficiently dispersed.

[0003] Regarding a carbon material dispersion liquid for forming an electrode by such a wet process, for example, Patent Document 1 describes an electrode slurry containing a sulfide-based solid electrolyte material and a specific polar solvent. Patent Document 2 describes a method for producing a positive electrode slurry by dispersing a carbon material in a low-polarity solvent containing a binder such as styrene butadiene rubber (SBR), and then dispersing a sulfide-based solid electrolyte and a positive electrode active material in that order. Patent Document 3 describes a method of obtaining a carbonaceous material dispersion by dispersing a carbonaceous material and a dispersant containing polyvinyl butyral in an ester-based dispersion medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-212652 [Patent Document 2] Japanese Patent Publication No. 2020-145034 [Patent Document 3] Japanese Patent Publication No. 2022-185480 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the electrode slurry described in Patent Document 1 has a problem in that the highly reactive sulfide-based solid electrolyte is altered by the polar solvent, etc., resulting in deterioration of the sulfide-based solid electrolyte. On the other hand, using a low-polarity solvent suppresses deterioration of the sulfide-based solid electrolyte, but makes it difficult to disperse the carbon material, resulting in a trade-off in that dispersibility and storage stability are reduced. Furthermore, the internal resistance of the electrode increases as dispersibility and storage stability are reduced. The positive electrode slurry described in Patent Document 2 has a problem in that the dispersibility of the carbon material is insufficient in a binder with a thickening effect, resulting in a decrease in the output characteristics of the battery. The dispersion described in Patent Document 3 uses a carbon material with a high bulk density, which results in insufficient formation of a conductive carbon network, resulting in a problem of high internal resistance of the electrode. Therefore, an object of the present invention is to provide a carbon dispersion liquid that suppresses deterioration of a sulfide-based solid electrolyte and that, when formed into an electrode, results in low internal resistance and excellent electrode resistance.An object of the present invention is also to provide an electrode composition, an electrode, and an all-solid-state battery that use the carbon dispersion liquid and are excellent in electrode resistance. [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following embodiments, and have thus completed the present invention.

[0007] [1] The present invention relates to a carbon material dispersion comprising a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein the carbon material (A) comprises a carbon material (a) that satisfies the following (i) and (ii); the dispersant (B) comprises a polyvinyl butyral resin (b); and the low-polarity solvent (C) is a solvent having a relative dielectric constant of less than 10 and / or a solvent having a solubility of less than 1 g of low-polarity solvent in 100 g of water at 20°C: (i) Bulk density is 0.02 to 0.2 g / cm 3 (ii) A specific surface area of ​​50 m 2 / g or more

[0008] [2] The present invention relates to the carbon material dispersion liquid according to [1], which contains 5.0 to 100 mass % of a polyvinyl butyral resin (b) based on the mass of the carbon material (A).

[0009] [3] The present invention relates to the carbon material dispersion according to [1] or [2], wherein the water content in the carbon material dispersion measured by the Karl Fischer method is 1000 ppm or less.

[0010] [4] The present invention relates to the carbon material dispersion according to any one of [1] to [3], wherein a film formed from the carbon material dispersion has a gloss value of 5 or more.

[0011] [5] The present invention relates to the carbon material dispersion liquid according to any one of [1] to [4], wherein the polyvinyl butyral resin (b) has a weight average molecular weight of 20,000 to 100,000.

[0012] [6] The present invention relates to the carbon material dispersion liquid according to any one of [1] to [5], wherein the low-polarity solvent (C), which is a solvent having a relative dielectric constant of less than 10 and / or a solvent having a solubility of less than 1 g in 100 g of water at 20°C, includes at least one solvent selected from the group consisting of ester solvents having an alkyl group with 4 or more carbon atoms, ether solvents having an alkyl group with 4 or more carbon atoms, and aromatic hydrocarbons.

[0013] [7] The present invention relates to the carbon material dispersion liquid according to any one of [1] to [6], wherein the low-polarity solvent (C) is butyl butyrate.

[0014] [8] The present invention relates to an electrode composition comprising the carbon material dispersion liquid according to any one of [1] to [7], an active material, a solid electrolyte, and a binder.

[0015] [9] The present invention relates to an electrode comprising an electrode film formed from the carbon material dispersion liquid according to any one of [1] to [7] or the electrode composition according to [8].

[0016]

[10] The present invention relates to an all-solid-state battery having the electrode according to [9]. [Effects of the Invention]

[0017] The present invention can provide a carbon dispersion liquid that has excellent dispersibility in a low-polarity solvent that can suppress deterioration of a sulfide-based solid electrolyte, and that, when used to form an electrode, has low internal resistance and excellent electrode resistance. Also, an electrode composition, an electrode, and an all-solid-state battery that have excellent electrode resistance can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Carbon material dispersion> The carbon material dispersion of the present invention comprises a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein the carbon material (A) comprises a carbon material (a) that satisfies the following (i) and (ii); the dispersant (B) comprises a polyvinyl butyral resin (b); and the low-polarity solvent (C) is a solvent having a relative dielectric constant of less than 10 and / or a solvent having a solubility of less than 1 g in 100 g of water at 20°C: (i) Bulk density is 0.02 to 0.2 g / cm 3 (ii) A specific surface area of ​​50 m 2 / g or more The carbon material dispersion of the present invention combines a carbon material (a) having a predetermined bulk density and specific surface area with a polyvinyl butyral resin (b) as a dispersant, thereby achieving a dispersion state in which the structure is maintained even in a low-polarity solvent, thereby reducing the internal resistance of the electrode and improving electrode resistance. Furthermore, the carbon material dispersion exhibits excellent dispersibility and storage stability even in a low-polarity solvent. The present invention will be described in detail below.

[0019] <Carbon material (A)> The carbon material (A) in the present invention has: (i) a bulk density of 0.02 to 0.2 g / cm 3 , and (ii) a specific surface area of ​​50 m 2 It is important that the carbon material (a) contains carbon material (a) that satisfies both of the above conditions. The larger the specific surface area of ​​carbon material (a), the smaller the primary particle diameter of the carbon material. 2 When the specific surface area is 60 m / g or more, the number of contact points between particles increases, thereby reducing the electrode resistance value. 2 / g or more, more preferably 100m 2 / g or more, more preferably 200m 2 / g or more. 2 / g or less, more preferably 1,000m 2 / g or less, for example, 60 to 1,200m 2 / g, 200-1,000m 2 / g. The specific surface area in this specification refers to the BET specific surface area determined by the nitrogen gas adsorption method, and can be calculated by measuring the adsorption isotherm by adsorbing and desorbing nitrogen as adsorbed molecules onto an adsorbent and analyzing the measured data. The specific surface area is determined by the BET method.

[0020] Bulk density is extremely important from the viewpoint of utilizing the structure specific to carbon materials in carbon material dispersions. Even for carbon materials with the same specific surface area, the higher the bulk density, the more compressed the carbon materials become and the stronger the aggregation becomes, making it difficult to fully dissolve the carbon materials in a low-polarity solvent. As a result, the electrode resistance tends to be high. Furthermore, if the bulk density is too low, the interaction between the carbon materials is insufficient, and the carbon materials cannot fully form a structure in a low-polarity solvent. As a result, the electrode resistance tends to be high. On the other hand, in the present invention, a bulk density of 0.02 to 0.2 g / cm 3 By using a carbon material (a) in this range, it is possible to appropriately control the cohesive strength of the carbon material, the size of the aggregates, etc. This makes it possible to optimally disperse the carbon material (a) in a low-polarity solvent without destroying its structure, thereby reducing the electrode resistance and maintaining the required conductivity. The bulk density is preferably 0.04 g / cm from the viewpoint of handling. 3 From the viewpoint of ease of deagglomeration, it is preferable that the concentration is 0.1 g / cm 3 or less, more preferably 0.05 g / cm 3 For example, 0.02 to 0.1 g / cm 3 , 0.02~0.05g / cm 3 may be. The bulk density can be determined by allowing the carbon material powder to fall freely into a 30 mL stainless steel cylindrical container, leveling off any bulging at the top of the container, and then calculating the mass of the carbon material powder and dividing it by the volume of the container. The carbon material powder used is prepared by breaking down any agglomerates that formed during storage and passing it through a 0.5 mm sieve.

[0021] [Carbon material (a)] Examples of the carbon material (a) in the present invention include carbon black, fibrous carbon, graphene, graphite, and fullerene. These carbon materials may be used alone or in combination of two or more. Among them, from the viewpoint of electrical conductivity, the carbon material (a) preferably contains at least one selected from the group consisting of carbon black and fibrous carbon. From the viewpoints of availability and cost, it is preferable to contain carbon black. From the viewpoint of cycle characteristics, fibrous carbon is preferably used.

[0022] (carbon black) Carbon black can be produced singly or in combination of two or more types, including furnace black, which is produced by continuously pyrolyzing a gaseous or liquid raw material in a reactor, particularly ketjen black, which is made from ethylene heavy oil, channel black, which is produced by burning a raw material gas and then quenching it by applying the flame to the bottom surface of a channel steel, and thermal black, which is produced by periodically repeating combustion and pyrolysis of a gas raw material, particularly acetylene black, which is made from acetylene gas. Conventional oxidation-treated carbon black and hollow carbon can also be used.

[0023] Carbon oxidation is a process that involves treating carbon at high temperatures in air or secondary treatment with nitric acid, nitrogen dioxide, ozone, etc., to directly introduce (covalently bond) oxygen-containing polar functional groups, such as phenol groups, quinone groups, carboxyl groups, and carbonyl groups, onto the carbon surface, and is commonly performed to improve the dispersibility of carbon. However, since the conductivity of carbon generally decreases as the amount of functional groups introduced increases, it is preferable to use carbon that has not been subjected to oxidation treatment.

[0024] The smaller the primary particle diameter of carbon black, the greater the number of particles contained per unit mass, and the greater the number of contact points between carbon black particles, which is advantageous for reducing the internal resistance of electrodes. Specifically, from the standpoints of conductivity and availability, the primary particle diameter of carbon black is preferably 1 to 100 nm, more preferably 10 to 80 nm, and even more preferably 20 to 70 nm. The primary particle diameter refers to spherical particles that form aggregates (primary agglomerates), and is the average particle diameter measured using an electron microscope. The average primary particle diameter of carbon black can be determined as follows: First, carbon black is observed and photographed using a transmission electron microscope. Next, 100 spherical carbon black primary particles are randomly selected from the photograph, and the outer diameter of each is measured. Next, the average primary particle diameter (nm) of carbon black is calculated as the number average of the outer diameters.

[0025] The carbon black used in the present invention forms agglomerates (secondary aggregates) in the carbon material dispersion, which are formed by the aggregation of aggregates (primary aggregates). When the size of the secondary aggregates is larger than a predetermined value, a conductive network is easily formed, which is advantageous for reducing the internal resistance of the electrode. In the present invention, the secondary aggregates are expressed by a volume average particle diameter (D50), which is preferably 0.2 μm or more, more preferably 0.3 μm or more, from the viewpoint of electrical conductivity. Furthermore, from the viewpoint of dispersion stability, it is preferably 5 μm or less, more preferably 3 μm or less, and may be, for example, 0.2 to 5 μm, 0.3 to 5 μm, or 0.3 to 3 μm. The volume average particle diameter (D50) is the particle diameter at which the volume fraction of particles in the volume particle size distribution, starting from the finest particle diameter, reaches 50%, and can be measured using a general particle size distribution analyzer (for example, a laser scattering particle size distribution analyzer (Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd.)).

[0026] (fibrous carbon) The fibrous carbon may be obtained by firing a petroleum-derived raw material or a plant-derived raw material. Examples of the fibrous carbon include carbon nanotubes (hereinafter also referred to as "CNTs"). Carbon nanotubes have a cylindrical shape with planar graphite rolled up, and may be single-walled, double-walled, or multi-walled, or a mixture of these. Single-walled carbon nanotubes have a structure in which one layer of graphite is rolled up. Double-walled or multi-walled carbon nanotubes have a structure in which two or more layers of graphite are rolled up. Furthermore, the sidewalls of carbon nanotubes do not have to have a graphite structure. Like carbon black, carbon nanotubes do not exist as individual primary particles, but form bundled primary aggregates in which fibrous particles aggregate, and secondary aggregates in which multiple bundles are entangled.

[0027] In the present invention, the shape of the fibrous carbon is not limited. Examples of such shapes include various shapes such as needle-like, cylindrical tubular, fishbone-like (fishbone or cup stacked type), playing card-like (platelet) and coil-like. Among them, needle-like or cylindrical tubular shapes are preferable. The fibrous carbon may be used in one shape alone or in a combination of two or more shapes.

[0028] Examples of the form of the fibrous carbon in the present invention include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. The fibrous carbon may be used alone in one form, or in combination of two or more forms. The average outer diameter of the fibrous carbon is preferably 1 nm or more, more preferably 5 nm or more. It is also preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 13 nm or less. The average outer diameter of the fibrous carbon can be determined as follows. First, the fibrous carbon is observed and photographed using a transmission electron microscope. Next, 300 pieces of fibrous carbon are randomly selected from the observation photograph, and the outer diameter of each piece is measured. Next, the average outer diameter (nm) of the fibrous carbon is calculated as the number average of the outer diameters.

[0029] The carbon material (a) may be a combination of two or more types of fibrous carbon having different average outer diameters. When used in combination, the average outer diameter of the first fibrous carbon may be 1 nm or more and less than 5 nm, and the average outer diameter of the second fibrous carbon may be 5 nm or more and 30 nm or less, or may be 20 nm or less.

[0030] From the viewpoint of forming a conductive network, the average fiber length of the fibrous carbon is preferably 0.5 μm or more, more preferably 0.8 μm or more, and even more preferably 1.0 μm or more, and is preferably 20 μm or less, more preferably 10 μm or less. The average fiber length of the fibrous carbon can be determined as follows. First, the fibrous carbon is observed and photographed using a transmission electron microscope. Next, 300 pieces of fibrous carbon are randomly selected from the photograph, and the fiber length of each piece is measured. Next, the average fiber length (μm) of the fibrous carbon is calculated as the number average of the fiber lengths.

[0031] The value obtained by dividing the average fiber length by the average outer diameter is the aspect ratio. The higher the aspect ratio of fibrous carbon, the higher the conductivity that can be exhibited when an electrode is formed. From the viewpoint of conductivity, the aspect ratio of the fibrous carbon is preferably 30 or more, more preferably 50 or more, and even more preferably 80 or more. Also, it is preferably 10,000 or less, more preferably 3,000 or less, and even more preferably 1,000 or less.

[0032] The carbon material (A) may contain a known carbon material other than the carbon material (a) within a range that does not impair the effects of the present invention. The proportion of the carbon material (a) in the carbon material (A) is preferably 10% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, and may be, for example, 80% by mass or more, 90% by mass or more, or 100% by mass.

[0033] The content of the carbon material (a) in the carbon material dispersion varies depending on the type of carbon material (a) used, the specific surface area, the amount of surface functional groups, and other physical properties inherent to the carbon material, but when carbon black is contained, for example, it is preferably 1% by mass or more, more preferably 5% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 50% by mass or less, more preferably 30% by mass or less, and may be, for example, 1 to 50% by mass, or 5 to 50% by mass. When fibrous carbon is contained, the content of the carbon material (a) is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, and may be, for example, 1 to 10% by mass or 1 to 5% by mass. If the concentration of the carbon material is too low, production efficiency will be reduced, and if the concentration is too high, the viscosity of the dispersion will be significantly increased, which may result in poor dispersion and reduced handleability. If the content of the carbon material (a) is within the above range, the dispersion will be excellent in dispersibility, the viscosity of the dispersion will be in an appropriate range, and production efficiency and handleability will be excellent.

[0034] <Dispersant (B)> It is important that the dispersant (B) in the present invention contains a polyvinyl butyral resin (b). The polyvinyl butyral resin is a polymer compound consisting of three types of repeating units each having an acetal group, an acetyl group, and a hydroxyl group, and when combined with the above-described carbon material (a) of the present invention, it exhibits excellent electrode resistance. The polyvinyl butyral resin is not particularly limited, and various commercially available or synthetic products can be used alone or in combination of two or more. Furthermore, polyvinyl butyral resins in which hydroxyl groups have been modified by chemical modification such as acylation or urethanization can also be used.

[0035] [Polyvinyl butyral resin (b)] Commercially available polyvinyl butyral resins include, for example, S-LEC (a polyvinyl butyral resin manufactured by Sekisui Chemical Co., Ltd.) and Mobital (a polyvinyl butyral resin manufactured by Kuraray Co., Ltd.), and various grades can be used. Examples of such commercially available products include S-LEC BL-1, BL-S, BL-10, BL-1H, BL-2H, BL-5Z, BM-1, BM-2(Z), BM-S(Z), BM-SHZ, BM-5, BH-3(Z), BH-A, BH-S, BH-6, BX-1, and BX-L (polyvinyl butyral resins manufactured by Sekisui Chemical Co., Ltd.), and S-LEC Mobital LPB16H, B20H, B30T, B30H, B30HH, and B45M (polyvinyl butyral resins manufactured by Kuraray Co., Ltd.).

[0036] The polyvinyl butyral resin (b) preferably has a content of structural units having an acetal group (degree of acetalization) of 60 to 85% by mass. When the degree of acetalization is 60% by mass or more, the solubility in the low-polarity solvent (C) is improved, and a carbon material dispersion liquid with excellent dispersibility can be obtained. Furthermore, when the degree of acetalization is 85% by mass or less, the flexibility of the polyvinyl butyral resin (b) is improved, and the overall toughness of the electrode is excellent.

[0037] The polyvinyl butyral resin (b) preferably has a content of structural units having an acetyl group (acetyl group amount) of 20% by mass or less, more preferably 10% by mass or less. When the acetyl group amount is 20% by mass or less, the polyvinyl butyral resin (b) can achieve both flexibility and solubility in low-polarity solvents. The amount is preferably 5% by mass or more.

[0038] The polyvinyl butyral resin (b) preferably has a content of structural units having hydroxyl groups (amount of hydroxyl groups) of 30% by mass or less. When the content is 30% by mass or less, the dispersion stability of the carbon material improves and the conductive network formation is excellent. The content is more preferably 20% by mass or less. Also, the content is preferably 1% by mass or more.

[0039] From the viewpoint of excellent solubility in low-polarity solvents, the polyvinyl acetal resin (b) preferably has a weight average molecular weight of 150,000 or less, more preferably 100,000 or less, even more preferably 80,000 or less, and particularly preferably 70,000 or less. From the viewpoint of dispersion stability, the weight average molecular weight is preferably 20,000 or more, more preferably 30,000 or more, and even more preferably 40,000 or more, and may be, for example, 20,000 to 100,000, 30,000 to 80,000, or 40,000 to 70,000. Furthermore, the polyvinyl acetal resin (b) preferably has a solution viscosity of 10 to 500 mPa·s, more preferably 20 to 400 mPa·s, and even more preferably 100 to 300 mPa·s when dissolved in ethanol with a solid content concentration of 10% by mass.

[0040] From the viewpoint of the solubility of the polyvinyl butyral resin (b) and the dispersibility of the carbon material, the carbon material dispersion of the present invention contains the polyvinyl butyral resin (b) in an amount of preferably 5.0 mass% or more, more preferably 8.0 mass% or more, and even more preferably 10 mass% or more, based on the mass of the carbon material (a). The amount is also preferably 100 mass% or less, more preferably 80 mass% or less, and even more preferably 50 mass% or less, and may be, for example, 5.0 to 100 mass% or 10 to 50 mass%.

[0041] The dispersant (B) may contain a known dispersant other than the polyvinyl butyral resin (b) within a range that does not impair the effects of the present invention. Examples of such known dispersants include polyvinyl alcohol, polyvinylpyrrolidone, acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, styrene-based elastomers, and hydrogenated styrene-based elastomers.

[0042] <Low polarity solvent (C)> The low-polarity solvent (C) in the present invention is a solvent that has low polarity and is unlikely to react with the sulfur-based solid electrolyte, and is a solvent having a relative dielectric constant of less than 10 and / or a solvent having a solubility of less than 1 g in 100 g of water at 20° C., and also includes non-polar solvents. Preferably, the solvent has a relative dielectric constant of less than 10.0, more preferably 8.0 or less, and even more preferably 6.0 or less. The relative permittivity in this specification is a value measured at 20 to 25°C, and can be measured, for example, by performing a double-cylinder tube current measurement at 10 kHz using a liquid permittivity meter Model 871 (manufactured by Sanyo Trading Co., Ltd.). Among the low-polarity solvents, the proportion of the solvents having a relative dielectric constant of less than 10 and / or a solubility of less than 1 g per 100 g of water at 20°C is preferably 80 mass % or more, more preferably 90 mass % or more, and even more preferably 100 mass %. When two or more solvents are used, the dielectric constant of the mixed solvent can be calculated as the weighted average of the dielectric constants of the individual solvents based on the volume of the solvents used. That is, the dielectric constant of solvent A is εr A , the relative dielectric constant of solvent B is εr B , the volume of solvent A is V A (ml), and the volume of solvent B is V B (ml), the weighted average relative dielectric constant of the mixed solvent can be calculated by the following formula. Weighted average relative permittivity = (εr A ×V A +εr B ×V B ) / (V A +V B ) Examples of such low-polarity solvents (C) include highly hydrophobic ester-based solvents having an alkyl group with 4 or more carbon atoms, ether-based solvents having an alkyl group with 4 or more carbon atoms, aromatic hydrocarbons, and aliphatic hydrocarbons. The use of such low-polarity solvents (C) not only prevents deterioration of the sulfide-based solid electrolyte, but also improves the dispersibility of the carbon material (a) by combining the solvent with the carbon material (a) and polyvinyl butyral resin (b) of the present invention, thereby achieving excellent electrode resistance. Among these, from the viewpoint of electrode resistance and dispersion stability, it is preferable to use a solvent containing at least one solvent selected from the group consisting of ester solvents having an alkyl group with 4 or more carbon atoms, ether solvents having an alkyl group with 4 or more carbon atoms, and aromatic hydrocarbons. Examples of ester solvents having an alkyl group having 4 or more carbon atoms include butyl butyrate, pentyl butyrate, hexyl butyrate, butyl acetate, pentyl acetate, hexyl acetate, and butyl propionate. Examples of ether solvents having an alkyl group having 4 or more carbon atoms include dibutyl ether, ethyl butyl ether, tert-butyl methyl ether, and tert-butyl ethyl ether. Examples of aromatic hydrocarbons include xylene, mesitylene, and tetralin. More preferred are ester solvents having an alkyl group with 4 or more carbon atoms, and even more preferred is butyl butyrate.

[0043] The carbon material dispersion of the present invention may contain a polar solvent within a range that does not impair the effects of the present invention. The content of the low-polarity solvent (C) is preferably 50 mass % or more, more preferably 70 mass % or more, and even more preferably 90 mass % or more, based on the total mass of the solvent. These solvents may be used alone or in combination of two or more.

[0044] <Other additives> The carbon material dispersion may further contain a surfactant, a film-forming aid, an antifoaming agent, a leveling agent, an antiseptic, a pH adjuster, and a viscosity adjuster, as long as the effects of the present invention are not impaired. Acids, alkalis, etc. are used as pH adjusters, and can adjust the pH of the solvent. Examples of alkalis include amine compounds, which may be tertiary amines, secondary amines, or primary amines, or may be monoamines, diamines, triamines, tetraamines, or polyamines. The use of an amine compound as a pH adjuster can easily adjust the zeta potential of dispersed particles. The content of the amine compound based on the mass of the dispersion liquid is preferably 0.1 mass% or less, and may be, for example, 0 to 0.1 mass%. When the content of the amine compound is within the above range, the carbon material dispersion liquid of the present invention exhibits good dispersion stability and can exhibit excellent electrode resistance and cycle characteristics.

[0045] <Carbon material dispersion> The carbon material dispersion of the present invention and the electrode composition described below can be obtained by mixing and dispersing at least a carbon material (A), a dispersant (B), and a low-polarity solvent (C) using a known method, and applying appropriate shear or impact. As the apparatus used to obtain the carbon material dispersion liquid or electrode composition, a disperser or mixer that is commonly used for dispersing pigments or the like can be used. Examples of such equipment include mixers such as a Disper, Homomixer, or Planetary Mixer; homogenizers such as M-Technique's "Clearmix" or PRIMIX's "Filmix"; media-type dispersers such as a paint conditioner (Red Devil), ball mill, sand mill (Shinmaru Enterprises' "Dynomill," etc.), attritor, pearl mill (Eirich's "DCP Mill," etc.), or Coball Mill; media-less dispersers such as wet jet mills (Genus PY, Sugino Machine's "Starburst," Nanomizer, Nanomizer, etc.), M-Technique's "Clear SS-5," or Nara Kikai's "MICROS"; and other roll mills, but are not limited to these.

[0046] It is preferable to use a disperser that has been treated to prevent metal contamination from the disperser. For example, when using a media-type disperser, a disperser having an agitator and a vessel made of ceramic or resin, or a disperser having a metal agitator and a vessel whose surfaces are treated with tungsten carbide thermal spraying or resin coating, etc. may be used. As the media, glass beads; ceramic beads such as zirconia beads and alumina beads; etc. are preferably used. When using a roll mill, it is preferable to use a ceramic roll. The dispersing device may be one type alone or a combination of several types. When using a positive or negative electrode active material whose particles are likely to be broken or crushed by a strong impact, a media-less dispersing device such as a roll mill or a homogenizer is preferably used.

[0047] The carbon material dispersion of the present invention has a water content measured by the Karl Fischer method of preferably 1,000 ppm or less, more preferably 500 ppm or less, and may be, for example, 0 to 1,000 ppm or 0 to 500 ppm. When the water content is within the above range, dispersion stability is improved and measurement variations in electrode resistance and the like can be suppressed. In this specification, the water content is calculated as the content relative to the mass of the carbon material dispersion, measured using a Karl Fischer moisture meter.

[0048] The gloss value of the film formed from the carbon material dispersion of the present invention may be 5 or more, 200 or less, or 50 or less, for example, 5 to 200, or 5 to 50. When the gloss value is within the above range, secondary aggregates of the carbon material (a) are sufficiently disintegrated, thereby reducing battery resistance. The gloss value is related to the size of the secondary aggregates of the carbon material (a) in the carbon material dispersion, and the smaller the secondary aggregates, the higher the gloss value tends to be. In other words, the gloss value can be controlled by the carbon material and formulation that constitute the carbon material dispersion, as well as dispersion conditions such as the dispersion device and dispersion time. The gloss value can be determined by the following method. First, a carbon material dispersion is applied to a PET (polyethylene terephthalate) film so that the film thickness after drying is 3 μm, and dried in an oven at 150°C for 2 minutes. The obtained coated product is placed on a graphite flat plate with the coated surface facing up, and the 60° gloss value is determined using a gloss meter (micro-TRI-gloss manufactured by BYK).

[0049] <Electrode composition> The electrode composition of the present invention contains at least the carbon material dispersion, an active material, a solid electrolyte, and a binder, and may further contain an arbitrary component.

[0050] [Active material] The active material is not particularly limited and may be a positive electrode active material or a negative electrode active material. As the positive electrode active material, for example, metal oxides capable of reversibly doping or intercalating lithium ions, and metal compounds such as metal sulfides can be used. Specific examples of such positive electrode active materials include, for example, lithium manganese composite oxides (e.g., LixMn2O4 or Li x MnO2), lithium nickel composite oxides (e.g., LiNiO2), lithium cobalt composite oxides (LixCoO2), lithium nickel cobalt composite oxides (e.g., LixNi1-yCoyO2), lithium manganese cobalt composite oxides (e.g., LixMnyCo1-yO2), lithium nickel manganese cobalt composite oxides (e.g., LixNiyCozMn1-y-zO2), spinel-type lithium manganese nickel composite oxides (e.g., LixMn2-yNiyO4), etc., composite oxide powders of lithium and transition metals, lithium phosphate oxide powders having an olivine structure (e.g., LixFePO4, LixFe1-yMnyPO4, LixCoPO4), manganese oxide, iron oxide, copper oxide, nickel oxide, vanadium oxides (e.g., V2O5, V6O 13 ), transition metal oxide powders such as titanium oxide, transition metal sulfide powders such as iron sulfate (Fe2(SO4)3), TiS2, and FeS. However, x, y, and z are numbers, and 0 < x < 1, 0 < y < 1, 0 < z < 1, 0 < y + z < 1. These positive electrode active materials may be used alone or in combination of two or more.

[0051] As the negative electrode active material, for example, metallic Li or its alloy capable of reversibly doping or intercalating lithium ions, tin alloy, silicon alloy negative electrode, Li X TiO2, Li X Fe2O3, Li X Fe3O4, Li X Metal oxide systems such as WO2, conductive polymers such as polyacetylene and poly-p-phenylene, artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite, resin-fired carbon materials, etc. may be mentioned. However, x is a number and 0 < x < 1. These negative electrode active materials may be used alone or in combination of two or more. In particular, when using a silicon alloy negative electrode, although the theoretical capacity is large, the volume expansion is extremely large, so it is preferably used in combination with artificial graphite such as highly graphitized carbon materials, carbonaceous powders such as natural graphite, resin-fired carbon materials, etc.

[0052] The surface of the active material may be coated with a buffer layer in order to reduce the interfacial resistance with the solid electrolyte. Examples of the buffer layer include oxide solid electrolytes, halide solid electrolytes, sulfide solid electrolytes, and oxide materials. For example, the surface of the active material may be coated with at least one or more buffer layers with a thickness of 1 to 500 nm.

[0053] [[ID=​​​​​​​​​​​​​​​​​​​​​​As shown in the following examples, the polymer may be produced by mixing raw materials in any molar ratio. Example) Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-Al2S3, Li2S-SiS2, Li2S-Si S2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-LiI, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-Li4SiO4, Li2S-SiS2-P2O5, Li2S-B2S3, Li2S-B2 S3-Li3PO4, Li2S-GeS2, Li2S-Ga2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-ZnS, Li2S-GeS2-Al2S3. These may be used alone or in combination of two or more.

[0054] [binder] The binder is not particularly limited and can be appropriately selected depending on the purpose. Examples of binders used in electrode compositions include polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, and vinyl pyrrolidone as structural units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, and fluororesins; cellulose resins; elastomers such as styrene-butadiene rubber and fluororubber; and conductive resins such as polyaniline and polyacetylene. The binder may also be a modified product, mixture, or copolymer of these resins.

[0055] The electrode composition of the present invention can be prepared using the carbon material dispersion liquid by any method, including, for example, a method of adding an active material, a solid electrolyte, and a binder to a carbon material dispersion liquid, a method of adding an active material and a solid electrolyte to a carbon material dispersion liquid and then adding a binder, a method of adding a binder to a carbon material dispersion liquid and then adding an active material and a solid electrolyte, a method of adding an active material to a carbon material dispersion liquid and then adding a solid electrolyte and a binder, a method of adding an active material to a carbon material dispersion liquid and then adding a solid electrolyte, a method of adding an active material to a carbon material dispersion liquid and then adding a binder, and a method of mixing an active material, a solid electrolyte, and a binder and then adding a carbon material dispersion liquid. The apparatus used for dispersion and mixing is not particularly limited.

[0056] When the carbon material (a) in the electrode composition contains carbon black, the content of carbon black is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 20% by mass or less, based on the mass of the active material. When the carbon material (a) contains fibrous carbon, the content of fibrous carbon is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 10% by mass or less, based on the mass of the active material. As the carbon material for the electrode composition, two or more different materials may be used, and the total amount of each is preferably within the above range. Furthermore, the carbon material for the electrode composition of the present invention may be a carbon material other than carbon black and fibrous carbon in combination.

[0057] The content of the dispersant (b) in the electrode composition is preferably 0.01 mass % or more and preferably 10 mass % or less, based on the mass of the active material.

[0058] The electrode composition of the present invention has a solid content by mass based on the mass of the electrode composition of preferably 30 mass % or more, more preferably 40 mass % or more, and preferably 90 mass % or less.

[0059] <Electrode> The electrode of the present invention includes at least one electrode film formed from a carbon material dispersion or an electrode composition, and may further include a current collector. The electrode film can be obtained, for example, by coating the electrode composition on a current collector and drying it. The shape and material of the current collector are not particularly limited, and examples thereof include conductive metals and alloys such as Al, Ni, Cu, Ti, Fe, Cr, and stainless steel. The current collector may have a coating layer on its surface, and examples of the coating layer include a carbon layer containing conductive carbon or a binder that improves adhesion to the current collector and conductivity.

[0060] The method for applying the electrode composition to the current collector is not particularly limited, and examples thereof include die coating, roll coating, doctor coating, knife coating, dip coating, gravure coating, spray coating, screen printing, and electrostatic painting. Examples of the drying method include leaving the composition to dry or drying using equipment such as a blower dryer, a warm air dryer, an infrared heater, or a far-infrared heater. The electrode may be subjected to a pressing treatment after coating and drying. Examples of the pressing treatment include plate pressing and roll pressing, and adjustments such as increasing the temperature during pressing may be made.

[0061] <All-solid-state battery> In an all-solid-state battery, the components of the driving part are roughly divided into a positive electrode, a negative electrode, and a separator layer, and the positive electrode and the negative electrode are stacked so as to face each other with the separator layer interposed therebetween. The positive electrode and / or the negative electrode are the electrodes, and the separator layer placed therebetween is made of a solid electrolyte and may contain a binder. The method for stacking the components of the driving section of an all-solid-state battery is not particularly limited. For example, a positive electrode, a negative electrode, and a separator layer may be formed and stacked, or a separator layer may be formed on the surface of a positive electrode and / or a negative electrode, and then the paired positive electrode or negative electrode may be stacked. Pressing may be performed during stacking, and adjustments such as increasing the temperature during pressing may be made. Pressing may be performed after all the components have been stacked, or pressing may be performed after the components have been stacked. In addition to the components of the drive unit, the all-solid-state battery may further include an exterior such as a laminate film or a metal case, a connection terminal, and the like. [Example]

[0062] The present invention will be explained in more detail below with reference to examples and comparative examples. The present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified. The blending amounts in the tables are in parts by mass, and amounts other than the solvent are calculated as non-volatile contents. Note that blank spaces in the tables indicate that no ingredients were blended.

[0063] <Production of carbon material dispersion> [Example 1] Carbon material dispersion (1) 86.8 parts of butyl butyrate, 1.2 parts of polyvinyl butyral resin (BL-S, manufactured by Sekisui Chemical Co., Ltd.), and 12 parts of acetylene black (Denka Black pressed product 50%, manufactured by Denka Co., Ltd.) were weighed and mixed. Next, 150 parts of zirconia beads were added, and the mixture was shaken for 2 hours using a paint shaker. The zirconia beads were then removed by filtration. Molecular sieves were then added, and the mixture was stirred overnight using a mix rotor to dehydrate, yielding a carbon material dispersion (1).

[0064] [Examples 2 to 22, Comparative Examples 1 to 3] Carbon material dispersions (2) to (25) Carbon material dispersions (2) to (25) were obtained in the same manner as in Example 1, except that the blending compositions were changed to those shown in Table 1.

[0065] <Measurement and evaluation of carbon material dispersion liquid> The carbon material dispersion thus obtained was subjected to the following measurements and evaluations, and the results are shown in Table 1.

[0066] [Moisture content measurement] The water content of the carbon material dispersion was measured by a Karl Fischer moisture meter (MKC-710 model: manufactured by Kyoto Electronics Manufacturing Co., Ltd.) by treating a sample at 150°C under a nitrogen gas flow of 200 mL / min, and the value measured by the Karl Fischer method was calculated as the content relative to the total mass of the carbon material dispersion. A: Moisture content is 500 ppm or less B: Moisture content is over 500 ppm and less than 1000 ppm C: Moisture content exceeds 1000 ppm

[0067] [Gloss value measurement] The obtained carbon material dispersion was applied to a PET (polyethylene terephthalate) film so that the film thickness after drying would be 3 μm, and then dried for 2 minutes in an oven at 150° C. The obtained coating was placed on a graphite plate with the coated side facing up, and the 60° gloss value was measured using a gloss meter (BYK micro-TRI-gloss). A: Gloss value is 10 or more B: Gloss value is 5 or more and less than 10 C: Gloss value less than 5

[0068] [Dispersibility evaluation] The initial viscosity of the obtained carbon material dispersion was measured using an E-type viscometer (TV-100 model: manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C and a rotor rotation speed of 50 rpm. Based on the obtained initial viscosity, the dispersibility was evaluated according to the following criteria. ++: Initial viscosity is 100 mPa·s or less +: Initial viscosity exceeds 100 mPa·s

[0069] [Stability evaluation] The obtained carbon material dispersion was stored at 25°C for 7 days, and then the viscosity was measured in the same manner as described above (Evaluation of Dispersibility), and the rate of change from the initial viscosity was calculated. The appearance was also visually observed. Based on the rate of change in viscosity and the results of appearance, the stability was evaluated according to the following criteria. +++: The rate of change is within 10% and no sedimentation or separation is observed. ++: The rate of change is within 30% and no sedimentation or separation is observed +: The rate of change exceeds 30%, or sedimentation or separation is observed.

[0070] [Electrode resistance evaluation] First, the obtained carbon material dispersions (1) to (25) were used to prepare electrode compositions and electrodes. [In the case of carbon material dispersions (1), (2), (5) to (21), and (23) to (25)] Nine parts of a 10% by weight solution of styrene-based elastomer resin as a binder (diluted with the same low-polarity solvent as used in the carbon material dispersion), 41 parts of the electrode active material NMC, 7.5 parts of the solid electrolyte LPS, 5 parts of the resulting carbon material dispersion, and 37.5 parts of the same low-polarity solvent as used in the carbon material dispersion were weighed into a plastic container and stirred at 2,000 rpm for 15 seconds using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The resulting electrode composition was applied to a 20 μm-thick PET film using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes to adjust the electrode weight per unit area to 20 mg / cm2. The electrode was then pressurized at 120°C using a heat press to obtain an electrode. The preparation of the electrode composition and the preparation of the electrode were carried out in a glove box kept in an argon atmosphere with a dew point of -60°C or less.

[0071] [In the case of carbon material dispersions (3), (4), and (22)] 8.5 parts of a 10% by weight solution of styrene-based elastomer resin as a binder (diluted with the same low-polarity solvent as used in the carbon material dispersion), 41.5 parts of the electrode active material NMC, 7.5 parts of the solid electrolyte LPS, 6 parts of the resulting carbon material dispersion, and 36.5 parts of the same low-polarity solvent as used in the carbon material dispersion were weighed into a plastic container and stirred at 2,000 rpm for 15 seconds using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The resulting electrode composition was applied to a 20 μm-thick PET film using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes to adjust the electrode weight per unit area to 20 mg / cm2. The electrode was then pressurized at 120°C using a heat press to obtain an electrode. The preparation of the electrode composition and the preparation of the electrode film were carried out in a glove box kept in an argon atmosphere with a dew point of -60°C or less.

[0072] [Preparation of reference electrode] Next, a reference electrode was prepared as follows. First, 90 parts of butyl butyrate and 10 parts of acetylene black (50% Denka Black Press, manufactured by Denka Co.) were weighed and mixed. Next, 150 parts of zirconia beads were added, and the mixture was shaken for 2 hours using a paint shaker. The zirconia beads were then removed by filtration. Molecular sieves were then added, and the mixture was stirred overnight using a mix rotor to dehydrate, yielding a reference carbon material dispersion. A reference electrode was obtained using the above-mentioned reference carbon material dispersion liquid in the same manner as in the case of producing an electrode for evaluating electrode resistance using carbon material dispersion liquid (1).

[0073] The volume resistivity A of the obtained electrode was measured by one-point measurement using a four-probe method using a Loresta GP (manufactured by Nitto Seiko Analytech Co., Ltd.) in accordance with JIS-K7194. The relative value (%) based on the volume resistivity A of the reference electrode was determined and evaluated according to the following criteria. +++: Relative value is 50% or less (excellent) ++: Relative value is over 50% and under 90% (good) +: Relative value is over 90% (bad)

[0074] [Measurement variation evaluation] The volume resistivity of the obtained electrode was measured by a four-probe method using a Loresta GP (manufactured by Nitto Seiko Analytech Co., Ltd.) at five points in accordance with JIS-K7194, and the average volume resistivity B was calculated. The measurement variation of the volume resistivity of the electrode was evaluated using Equation 1 according to the following criteria. (Equation 1) Measurement variation % = |Volume resistivity A - average volume resistivity B| / volume resistivity A × 100% +++: Measurement variation is 5% or less ++: Measurement variation is more than 5% and less than 20% +: Measurement variation exceeds 20%

[0075] [Cycle characteristic evaluation] In the same manner as in [Evaluation of electrode resistance], electrode compositions were prepared using the obtained carbon material dispersions (1) to (25) and the reference carbon material dispersion. Next, a positive electrode was prepared in the same manner as in [Evaluation of electrode resistance], except that the electrode composition was applied to a 20 μm-thick aluminum foil as a current collector using an applicator.

[0076] Next, the fabricated positive electrode was punched out to a diameter of 10 mm and used as the working electrode. The working electrode and 50 mg of LPS powder were placed in a cylindrical container for an all-solid-state battery evaluation cell, and a pressure of 50 MPa was applied to create an LPS layer on the working electrode. On the opposite side of the LPS layer, metal indium foil and metal lithium foil were placed in that order as counter electrodes. The cell was then assembled and secured with bolts, and then tightened using a torque wrench to the specified pressure, resulting in a positive electrode evaluation cell. The assembly of the evaluation cell was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0077] The resulting positive electrode evaluation cell was placed in a thermostatic chamber at 25°C and subjected to charge / discharge measurements using a charge / discharge device (Hokuto Denko Corporation, SM-8). A constant-current, constant-voltage charge (cutoff current: 0.02C) was performed at a charge rate of 0.2C with a charge cutoff voltage of 4.2V, followed by a constant-current discharge at a discharge rate of 0.2C with a discharge cutoff voltage of 2.5V. This procedure was repeated 200 times. 1C was defined as the current value required to charge or discharge the theoretical capacity of the positive electrode in 1 hour. The cycle characteristics can be expressed as the ratio of the 3rd 0.2C discharge capacity to the 200th 0.2C discharge capacity, using the following equation: (Equation 2) Cycle characteristics = 200th 0.2C discharge capacity / 3rd 0.2C discharge capacity × 100 (%) The relative value (%) was determined based on the cycle characteristics of a positive electrode evaluation cell using a standard carbon material dispersion liquid, and the results were evaluated according to the following criteria. ++++: Relative value is 200% or more +++: Relative value is 150% or more and less than 200% ++: Relative value is 100 or more and less than 150% +: Relative value is less than 100%

[0078] [Table 1]

[0079] The abbreviations in Table 1 are as follows: (Carbon material (A)) Pressed product: Denka Black Pressed product 50% (Denka Co., Ltd., acetylene black, specific surface area 65m 2 / g, bulk density 0.08g / cm 3 ) 6A:JENOTUBE6A (manufactured by JEIO, multilayer CNT, specific surface area 690m 2 / g, bulk density 0.042g / cm 3 ) 10B:JENOTUBE10B (manufactured by JEIO, multilayer CNT, specific surface area 230m 2 / g, bulk density 0.05g / cm 3 ) Li-250: Denka Black Li-250 (manufactured by Denka Co., Ltd., acetylene black, specific surface area 58 m 2 / g, bulk density 0.08g / cm 3 ) Li-400: Denka Black Li-400 (manufactured by Denka Co., Ltd., acetylene black, specific surface area 39 m 2 / g, bulk density 0.15g / cm 3 ) Granular product: Denka Black (manufactured by Denka Co., Ltd., acetylene black, specific surface area 69 m 2 / g, bulk density 0.25g / cm 3 ) EC600J: Ketjenblack EC600J (manufactured by Lion Corporation, carbon black, specific surface area 1210 m 2 / g, bulk density 0.12g / cm 3 )

[0080] (Dispersant (B)) BL-S: S-LEC BL-S (manufactured by Sekisui Chemical Co., Ltd., hydroxyl-containing repeating units: 16%, average molecular weight: 23,000, viscosity of 10% ethanol solution: 24 mP·s) BL-10: S-LEC BL-10 (manufactured by Sekisui Chemical Co., Ltd., hydroxyl-containing repeating units: 19%, average molecular weight: 15,000, viscosity of 10% ethanol solution: 10 mP·s) BL-1: S-LEC BL-1 (manufactured by Sekisui Chemical Co., Ltd., hydroxyl group-containing repeating units: 26%, average molecular weight: 19,000, viscosity of 10% ethanol solution: 25 mP·s) BM-S: S-LEC BM-S (manufactured by Sekisui Chemical Co., Ltd., hydroxyl group-containing repeating units: 16%, average molecular weight: 55,000, viscosity of 10% ethanol solution: 108 mP·s) BH-S: S-LEC BH-S (manufactured by Sekisui Chemical Co., Ltd., hydroxyl-containing repeating units: 16%, average molecular weight: 66,000, viscosity of 10% ethanol solution: 205 mP·s) BH-A: S-LEC BH-A (manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 18%, average molecular weight: 115,000, viscosity of 10% ethanol solution: 352 mP·s) K-30: Polyvinylpyrrolidone K-30 (Nippon Shokubai Co., Ltd., polyvinylpyrrolidone)

[0081] (Low polarity solvent (C)) Butyl butyrate: relative dielectric constant 4.6 Toluene: relative dielectric constant 2.5 Dibutyl ether: n-dibutyl ether, relative dielectric constant 3.3 Tetralin: 1,2,3,4-tetrahydronaphthalene, relative dielectric constant 2.7 Heptane: n-heptane, relative dielectric constant 1.9

[0082] (pH adjuster) AMP: 2-amino-2-methyl-1-propanol

[0083] According to Table 1, it is presumed that the carbon material dispersion of the present invention is excellent in dispersibility and storage stability, and that the carbon material is deaggregated, resulting in a uniform and stable dispersion state. Furthermore, an electrode film using the carbon material dispersion is excellent in electrode resistance and cycle characteristics, and when the water content is 1000 ppm or less, it is excellent in suppressing the measurement variation of the electrode resistance. Furthermore, when the amount of the amine compound in the dispersion is 0 to 0.1 mass %, and the gloss value is 5 or more, the electrode resistance is excellent. On the other hand, Comparative Example 1, which does not satisfy the bulk density requirement, Comparative Example 2, which does not satisfy the specific surface area requirement, and Comparative Example 3, which uses PVP as a dispersant, all exhibit high volume resistivity and poor electrode performance. From the above results, it is apparent that the present invention can provide a carbon material having excellent electrode resistance by synergistically combining a carbon material having a predetermined specific surface area and a predetermined bulk density with a polyvinyl butyral dispersant.

Claims

1. A carbon material dispersion comprising a carbon material (A), a dispersant (B), and a low-polarity solvent (C), The carbon material (A) includes a carbon material (a) that satisfies the following (i) and (ii): (i) Bulk density is 0.02 to 0.2 g / cm ３ (ii) A specific surface area of ​​50 m ２ / g or more the carbon material (a) is carbon black, the dispersant (B) contains a polyvinyl butyral resin (b), The low-polarity solvent (C) is a solvent having a relative dielectric constant of less than 10 and / or a low-polarity solvent having a relative dielectric constant of less than 10 and ... The solvent has a solubility of less than 1 g per 100 g. Carbon material dispersion.

2. The polyvinyl butyral resin (b) is added in an amount of 5.0 to 100% by mass based on the mass of the carbon material (A). The carbon material dispersion liquid according to claim 1 , containing 100% by mass of the carbon material.

3. The water content in the carbon material dispersion liquid measured by the Karl Fischer method is 1000p The carbon material dispersion according to claim 1, wherein the average particle size is 100 μm or less.

4. The carbon material according to claim 1, wherein the gloss value of the film formed from the carbon material dispersion is 5 or more. Material dispersion.

5. The polyvinyl butyral resin (b) was dissolved in ethanol at a solids concentration of 10% by mass.

2. The carbon material dispersion according to claim 1, wherein the solution viscosity when the carbon material dispersion is 10 to 500 mPa·s.

6. The solvent having a relative dielectric constant of less than 10 and / or solubility in 100 g of water at 20°C The low polarity solvent (C), which is a solvent having a viscosity of less than 1 g, is an ester having an alkyl group having 4 or more carbon atoms. ether solvents, ether solvents having an alkyl group with 4 or more carbon atoms, and aromatic hydrocarbons The carbon material dispersion according to claim 1 , further comprising at least one solvent selected from the group consisting of:

7. The carbon material dispersion according to claim 1 , wherein the low-polarity solvent (C) is butyl butyrate.

8. An electrode composition comprising the carbon material dispersion according to any one of claims 1 to 7, an active material, a solid electrolyte, and a binder.

9. A method for manufacturing an electrode having an electrode film formed from a carbon material dispersion liquid, comprising the steps of: preparing the carbon material dispersion liquid described in any one of claims 1 to 7; applying the carbon material dispersion liquid onto a current collector; and drying the applied carbon material dispersion liquid.

10. A method for manufacturing an electrode having an electrode film formed from an electrode composition, comprising the steps of preparing the electrode composition described in claim 8, applying the electrode composition onto a current collector, and drying the applied electrode composition.

11. A method for manufacturing an all-solid-state battery in which a positive electrode and a negative electrode are stacked so as to face each other via a separator layer made of a solid electrolyte, characterized in that an electrode manufactured by the electrode manufacturing method described in claim 9 is used for at least one of the positive electrode and the negative electrode.

12. A method for manufacturing an all-solid-state battery in which a positive electrode and a negative electrode are stacked so as to face each other via a separator layer made of a solid electrolyte, characterized in that an electrode manufactured by the electrode manufacturing method described in claim 10 is used for at least one of the positive electrode and the negative electrode.

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