Electrode composition for all-solid-state secondary battery, electrode slurry using said composition, electrode battery, and method for producing said composition

Abstract

Provided is a composition for all-solid-state secondary batteries that can exhibit high electronic conductivity with a small amount of conductive material added in electrodes containing solid electrolytes, where improving ionic conductivity is an issue. [Solution] The above-mentioned problem is solved by an electrode composition for an all-solid-state secondary battery, which contains a low-polarity solvent, 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, and a conductive carbon material, and which is characterized by satisfying the following condition (1) or (2): (1) The sedimentation rate calculated by the following formula (I) is 10% or more and 90% or less. Sedimentation rate % = (100 - (B / A) × 100) (I) A: Mass of solid content of the surface liquid of the electrode composition immediately after shaking B: Solid mass of the surface liquid of the electrode composition after standing at 25°C for 7 days (2) When 10 mL of electrode composition is placed in a No. 2 standard bottle, the bottle is tilted 180°, and then left for 10 seconds. The residual rate determined by the amount of electrode composition remaining in the bottle is 90% or more.

Description

[Technical Field]

[0001] The present invention relates to an electrode composition for an all-solid-state secondary battery. [Background technology]

[0002] As laptops become smaller and lighter, smart devices become more powerful, and electric vehicles become more widespread, there is a demand for batteries with high capacity in limited spaces. Lithium-ion secondary batteries (LIBs), which have the characteristics of high energy density and high voltage, are used as batteries in many devices. In particular, for mobility applications where driving range, charging time, and battery life are issues, development of all-solid-state lithium-ion secondary batteries (all-solid-state LIBs), which use solid-state electrolytes as ion conductors, is gaining momentum. Compared to LIBs that use conventional liquid electrolytes, all-solid-state LIBs have battery properties such as higher capacity, faster charging, and higher cycle characteristics. In addition, since they do not use flammable electrolytes, they can reduce the risk of fire and improve safety. These advantages raise expectations for the practical application of electric vehicles equipped with all-solid-state LIBs.

[0003] In all-solid-state LIBs, the electrolyte, which is the conductor of lithium ions, is solid, so contact between solid electrolytes (forming a solid interface) is important to increase ionic conductivity in the electrodes. On the other hand, the active material, solid electrolyte, binder, etc. contained in the electrodes are usually insulating materials, so the addition of conductive materials is essential to ensure the electronic conductivity in the electrodes necessary for charge-discharge reactions.

[0004] To address the above issues, optimization of the dispersion design of conductive material compositions has been proposed. For example, Patent Document 1 describes a method for preparing a dispersion using a conductive paste containing conductive carbon, polyvinyl butyral, and amino alcohol. Patent Document 2 discloses an example of producing a conductive paste of conductive carbon using an acrylic resin, which is a polymerizable unsaturated monomer polymer having a polar group, as a dispersant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2022 / 030636 [Patent Document 2] Patent No. 7136682 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 contains an amino alcohol as an additive, and Patent Document 2 also contains an acrylic resin having a polar group as a dispersant. Both of these materials are used to improve dispersibility, but because they contain polar groups, they react with the sulfur-based solid electrolyte, raising concerns about an increase in interfacial resistance due to aggregation or deterioration of the electrolyte.

[0007] An object of the present invention is to provide a composition for an all-solid-state secondary battery that can exhibit high electronic conductivity in an electrode for an all-solid-state secondary battery, which requires improved electronic conductivity to improve battery performance. [Means for solving the problem]

[0008] 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.

[0009] [1] The present invention relates to an electrode composition for an all-solid-state secondary battery, which contains a low-polarity solvent that 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 a conductive carbon material, and which is characterized by satisfying the following condition (1) or (2): (1) The sedimentation rate calculated by the following formula (I) is 10% or more and 90% or less. Sedimentation rate % = (100 - (B / A) × 100) (I) A: Mass of solid content of the surface liquid of the electrode composition immediately after shaking B: Solid mass of the surface liquid of the electrode composition after standing at 25°C for 7 days (2) When 10 mL of electrode composition is placed in a No. 2 standard bottle, the bottle is tilted 180°, and then left for 10 seconds. The residual rate determined by the amount of electrode composition remaining in the bottle is 90% or more.

[0010] [2] The present invention relates to the electrode composition for an all-solid-state secondary battery according to [1], further comprising a dispersant.

[0011] [3] The present invention relates to an electrode composition for an all-solid-state secondary battery according to [1] or [2], wherein the solvent having a relative dielectric constant of less than 10 and / or the low-polarity solvent having a solubility of less than 1 g in 100 g of water at 20°C contains at least one selected from the group consisting of ester compounds, aromatic hydrocarbons, and aliphatic hydrocarbons.

[0012] [4] The present invention relates to the electrode composition for an all-solid-state secondary battery according to any one of [1] to [3], wherein the conductive carbon material includes at least one material selected from the group consisting of carbon black, fibrous carbon, and graphene-based materials.

[0013] [5] The present invention relates to an electrode slurry for an all-solid-state secondary battery, comprising at least the electrode composition for an all-solid-state secondary battery according to any one of [1] to [4], an active material, a solid electrolyte, a binder, and a solvent.

[0014] [6] The present invention relates to an electrode for an all-solid-state secondary battery, comprising a coating film of the electrode slurry for an all-solid-state secondary battery according to [5].

[0015] [7] The present invention relates to an all-solid-state secondary battery including the electrode for an all-solid-state secondary battery according to [6].

[0016] [8] The present invention relates to a method for producing an electrode composition for an all-solid-state secondary battery according to any one of [1] to [4], the method comprising: a step of dispersing, using a media-less disperser, a mixture containing a conductive carbon material and a low-polarity solvent, the low-polarity solvent being a solvent having a relative dielectric constant of less than 10 and / or a solvent having a solubility of less than 1 g per 100 g of water at 20°C, to prepare a pretreatment liquid; and a step of dispersing the pretreatment liquid using a media-type disperser and / or a media-less disperser. [Effects of the Invention]

[0017] According to an embodiment of the present invention, a composition for an all-solid-state secondary battery having excellent electrical conductivity can be provided. According to still another embodiment of the present invention, an electrode and an all-solid-state secondary battery having high electronic conductivity can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an electrode composition for an all-solid-state secondary battery according to an embodiment of the present invention will be described in detail. The present invention is not limited to the following embodiment, and the present invention also includes embodiments that are implemented within the scope of the present invention.

[0019] In this specification, carbon black may be referred to as "CB" and carbon nanotubes as "CNT." Polyvinyl alcohol may be referred to as "PVA" and polyvinyl butyral as "PVB." In this specification, a carbon black dispersion may be simply referred to as a "CB dispersion," and a carbon nanotube dispersion may be simply referred to as a "CNT dispersion." Furthermore, an electrode composition for an all-solid-state secondary battery may be referred to as an "electrode composition" or a "composition." An electrode slurry for an all-solid-state secondary battery may be referred to as an "electrode slurry," and an electrode for an all-solid-state secondary battery may be referred to as an "electrode."

[0020] <Electrode composition for all-solid-state secondary batteries> The electrode composition for an all-solid-state secondary battery of the present invention contains a conductive carbon material and a predetermined low-polarity solvent, and optionally contains a dispersant. The electrode composition may contain optional components such as wetting agents, surfactants, pH adjusters, wetting and penetrating agents, leveling agents, other additives, other conductive materials, and other polymeric components, as needed, within the scope of the present invention. The optional components can be added at any timing, such as before preparing the dispersion, during dispersion, after dispersion, or a combination thereof.

[0021] The electrode composition for an all-solid-state secondary battery of the present invention satisfies the following condition (1) or (2): It is characterized by: (1) The sedimentation rate calculated by the following formula (I) is 10% or more and 90% or less. Sedimentation rate % = (100 - (B / A) × 100) (I) A: Solid mass (%) of the surface liquid of the electrode composition immediately after shaking B: Solid mass (%) of the surface liquid of the electrode composition after standing at 25°C for 7 days (2) When 10 mL of electrode composition is placed in a No. 2 standard bottle, the bottle is tilted 180°, and then left for 10 seconds. The residual rate determined by the amount of electrode composition remaining in the bottle is 90% or more.

[0022] Unlike common polar solvents, dispersion of conductive carbon materials in low-polarity solvents is prone to over-dispersion and excessive aggregation, making it difficult to maintain an appropriate dispersion state. By satisfying the above conditions, the electrode composition for all-solid-state secondary batteries of the present invention allows the conductive carbon material to have interparticle interactions in the low-polarity solvent, and when formed into a coating film (hereinafter also referred to as an electrode film), the conductive carbon material particles form a secondary structure, thereby exhibiting high conductivity. The above can be achieved by appropriately selecting the type and ratio of the conductive carbon material, dispersant, and low-polarity solvent, as well as the dispersion process.

[0023] The sedimentation property of the electrode composition for an all-solid-state secondary battery can be evaluated, for example, by the following method. 10 mL of the electrode composition surface liquid (above half the liquid phase) was placed in a No. 2 standard bottle (20 mL capacity), and 1.5 g was taken with a 2 mL plastic dropper and transferred to a Menthol can. The solvent was then evaporated in a hot air oven, and the solid mass (%) of the surface liquid was determined. The sedimentation rate was calculated using the following formula: Sedimentation rate % = (100 - (B / A) x 100) A: The solid mass (%) of the surface liquid measured on a sample immediately after shaking the standard bottle up and down at a speed of 3 times / second with a shaking amplitude of 30 cm. B: The solid mass (%) of the surface liquid measured on the sample after leaving the sample at 25°C for 7 days in the atmosphere When the sedimentation rate is 10% or more and 90% or less, the conductive carbon material has interparticle interactions in a low-polarity solvent. When the sedimentation rate exceeds 90%, the composition becomes unstable and tends to become excessively aggregated. On the other hand, when it is less than 10%, the interactions between the carbon materials are weak and tend to become over-dispersed, which may make it difficult for the conductive carbon materials to form a secondary structure when formed into an electrode film. The sedimentation rate is preferably 15% or more, more preferably 20% or more. It is also preferably 80% or less, more preferably 70% or less, and may be, for example, 15% or more and 80% or less, or 20% or more and 70% or less.

[0024] The gel state of the electrode composition for an all-solid-state secondary battery can be evaluated, for example, by the method of measuring the residual rate by the following 180° tilt test. 10 mL of electrode composition is placed in a No. 2 standard bottle (volume 20 mL), tilted 180°, and left for 10 seconds. The remaining amount of composition (mL) in the bottle is used to calculate the residual rate using the following formula. Residual rate % = (residual amount / 10) × 100 The sample used to measure the residual rate is prepared by shaking the standard bottle containing the sample up and down at a speed of 3 times per second with a shaking amplitude of 30 cm and then leaving it to stand in the atmosphere at 25°C for 7 days. When the residual rate is 90% or more, the conductive carbon material enters a gel state, resulting in particle-to-particle interactions. This gelation differs from a typical gel state, resulting in a reversible dispersion of the conductive carbon material. A reversible dispersion is a state in which fluidity is restored when force is applied, such as in a shaking test, even if fluidity is lost due to gelation. For example, this refers to a state in which the change in solution viscosity between the solution immediately after shaking a standard bottle containing the sample up and down at a speed of 3 times per second with a 30 cm swing amplitude and the solution immediately after performing a similar shaking test after leaving the sample to gel is less than 10%.

[0025] The dispersibility of the conductive carbon material in an electrode composition for an all-solid-state secondary battery can be evaluated by the median diameter (μm) determined using a laser diffraction / scattering particle size distribution analyzer. The median diameter (μm) determined using a laser diffraction / scattering particle size distribution analyzer can be used to estimate the particle size of the conductive carbon material agglomerated particles from the scattered light intensity distribution of the particles. The median diameter (μm) is preferably 0.4 μm or more, and is preferably 5.0 μm or less, and more preferably 2.0 μm or less. By setting the median diameter within the above range, the amount of agglomerated conductive carbon material is reduced, and the conductive carbon material is not excessively pulverized, allowing for the production of an electrode composition for an all-solid-state secondary battery in an appropriately dispersed state. This allows for the formation of an efficient conductive network.

[0026] The viscosity of the electrode composition for an all-solid-state secondary battery of the present invention, measured using an E-type viscometer at 60 rpm at 25°C, is preferably 10 mPa·s or more, more preferably 10,000 mPa·s or less, more preferably 2,000 mPa·s or less, and even more preferably 1,000 mPa·s or less, and may be, for example, 10 mPa·s or more and 10,000 mPa·s or less, 10 mPa·s or more and 2,000 mPa·s or less, or 10 mPa·s or more and 1,000 mPa·s or less.

[0027] The TI value of an electrode composition for an all-solid-state secondary battery can be calculated by dividing the viscosity (mPa·s) at 6 rpm measured at 25°C using an E-type viscometer by the viscosity (mPa·s) at 60 rpm. The TI value is preferably 1.0 or greater, and is preferably 10.0 or less, more preferably 5.0 or less, and even more preferably 3.0 or less. For example, it may be 1.0 or greater and 10.0 or less, 1.0 or greater and 5.0 or less, or 1.0 or greater and 3.0 or less. The higher the TI value, the greater the structural viscosity due to the entanglement of the conductive carbon material, dispersant, and other resin components, or the intermolecular forces thereof. The lower the TI value, the smaller the structural viscosity. By setting the TI value within the above range, it is possible to suppress the entanglement of the conductive carbon material, dispersant, and other resin components while allowing these intermolecular forces to act appropriately.

[0028] The solid content of the electrode composition for an all-solid-state secondary battery is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, for example, 0.2 to 40% by mass, 0.3 to 30% by mass, or 0.5 to 20% by mass.

[0029] <Conductive carbon materials> Examples of conductive carbon materials in the present invention include carbon black, fibrous carbon, graphene, graphite, and fullerene. These conductive carbon materials may be used alone or in combination of two or more. Among them, from the viewpoint of conductivity, it is preferable that the conductive carbon material contains at least one selected from the group consisting of carbon black and fibrous carbon. Furthermore, from the viewpoint of conductivity, it is preferable to use carbon black or fibrous carbon.

[0030] [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 may also be used.

[0031] 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, carboxy 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.

[0032] 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 the electrode. Specifically, from the viewpoints of conductivity and availability, the diameter is preferably 1 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. The diameter is also preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 70 nm or less, and may be, for example, 1 to 100 nm, 10 to 80 nm, or 20 to 70 nm. Here, the primary particle size refers to spherical particles that form aggregates (primary agglomerates), and is the average particle size measured using an electron microscope. The average primary particle size of carbon black can be determined as follows: First, carbon black is observed and photographed using a transmission electron microscope. Next, 100 spherical primary carbon black particles are randomly selected from the photograph, and the outer diameter of each is measured. Next, the average primary particle size (nm) of carbon black is calculated as the number average of the outer diameters.

[0033] The carbon black used in the present invention forms agglomerates (secondary aggregates) formed by the aggregation of aggregates (primary aggregates). When the size of the secondary aggregates is larger than a certain level, 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. It is also 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 size referred to here is the particle size at which the volume proportion of particles in the volume particle size distribution is 50% when the volume proportion of particles is accumulated from the smallest particle size, and is measured using a general particle size distribution analyzer, for example, a laser scattering particle size distribution analyzer ("Microtrac MT3300EXII" manufactured by Nikkiso Co., Ltd.).

[0034] [Fiber carbon] The fibrous carbon may be obtained by firing a petroleum-derived raw material, or may be obtained by firing a plant-derived raw material. Examples of the fibrous carbon include carbon nanotubes.

[0035] In the present invention, carbon nanotubes have a cylindrical shape in which planar graphite is wound, 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 wound. Double-walled or multi-walled carbon nanotubes have a structure in which two or more layers of graphite are wound. In addition, the sidewalls of carbon nanotubes do not have to have a graphite structure.

[0036] 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.

[0037] 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.

[0038] The carbon material 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. When used in combination, the mass ratio of the first fibrous carbon to the second fibrous carbon may be 1:10 to 1:100, or 1:10 to 1:50.

[0039] 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.

[0040] 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.

[0041] Generally, the larger the specific surface area of the conductive carbon material used in the present invention, the smaller the primary particle diameter of the conductive carbon material, which increases the number of contact points between particles and is advantageous for reducing the internal resistance of the electrode. Specifically, from the viewpoints of conductivity, coating suitability, and electrode adhesion, the specific surface area (BET) determined by the nitrogen adsorption method is set to 20 m 2 / g or more is desirable. The nitrogen adsorption method involves measuring the adsorption isotherm by having the adsorbent adsorb and desorb nitrogen as an adsorbed molecule, and then analyzing the measured data to calculate the specific surface area, pore volume, and pore diameter. The specific surface area can be determined using the BET method.

[0042] The content of the conductive carbon material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, based on the total amount of the electrode composition for an all-solid-state secondary battery. It is also preferably 20% by mass or less, and more preferably 10% by mass or less. By adjusting the content within the above range, the conductive carbon material can be present in a favorable state while maintaining its structure. It is more preferably 0.1 to 20% by mass, and even more preferably 0.5 to 10% by mass. It is also preferable to appropriately adjust the content of the conductive carbon material so as to obtain an electrode composition with appropriate fluidity or viscosity, depending on the specific surface area of the conductive carbon material, its affinity for the dispersion medium, the dispersibility of the dispersant, etc.

[0043] <Low polarity solvent> The low-polarity solvent 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 per 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 the solvents having 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 include highly hydrophobic (ester or ether) solvents having an alkyl group with 4 or more carbon atoms, aromatic hydrocarbons, and aliphatic hydrocarbons. The above-mentioned solvents can prevent deterioration of the sulfide-based solid electrolyte, which occurs when polar solvents such as water, alcohol, and N-methyl-2-pyrrolidone are used. Furthermore, by combining them with the above-mentioned dispersant, the dispersibility of the carbon material can be improved. The content of the low-polarity solvent is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the solvent. These solvents may be used alone or in combination of two or more. Examples of (ester or ether) solvents having an alkyl group with 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 with 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, toluene, and tetralin. More preferred are ester solvents having an alkyl group with 4 or more carbon atoms, and even more preferred is butyl butyrate.

[0044] <Dispersant> The electrode composition for an all-solid-state secondary battery of the present invention may further contain a dispersant. The dispersant is not particularly limited as long as it can stabilize the dispersion of the conductive carbon material in the electrode composition for an all-solid-state secondary battery. Although either a resin-type dispersant or a surfactant can be used as the dispersant, a resin-type dispersant is preferred because it has a strong adsorption force to the conductive carbon material and provides good dispersion stability. Depending on the properties required for dispersing the conductive carbon material, an appropriate type of dispersant can be used in an appropriate amount.

[0045] Examples of resin-type dispersants that can be used include (meth)acrylic polymers, polymers derived from ethylenically unsaturated hydrocarbons, cellulose derivatives, and copolymers thereof. Examples of polymers derived from ethylenically unsaturated hydrocarbons include polyvinyl alcohol resins, polyvinylpyrrolidone resins, polyacrylonitrile resins, and nitrile rubbers. Examples of polyvinyl alcohol resins include polyvinyl alcohol, modified polyvinyl alcohols having functional groups other than hydroxyl groups (e.g., acetyl groups, sulfo groups, carboxy groups, carbonyl groups, and amino groups), polyvinyl alcohols modified with various salts, other anion- or cation-modified polyvinyl alcohols, and polyvinyl acetals (e.g., polyvinyl acetoacetal and polyvinyl butyral) modified with aldehydes (e.g., acetoacetal-modified or butyral-modified). Polyacrylonitrile resins may be polyacrylonitrile homopolymers, polyacrylonitrile copolymers, or modified versions thereof. Preferred examples include polyacrylonitrile resins having at least one selected from the group consisting of active hydrogen groups such as hydroxy groups, carboxy groups, primary amino groups, secondary amino groups, and mercapto groups, basic groups, and alkyl groups derived from (meth)acrylic acid alkyl esters or α-olefins. For example, the acrylonitrile copolymer described in JP 2020-163362 A can be used. Nitrile rubbers include acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, styrene-based elastomers, and hydrogenated styrene-based elastomers. Cellulose derivatives include cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethylhydroxyethyl cellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, and copolymers thereof. Polymers in which other substituents have been introduced into a portion of these polymers, modified polymers, etc. may also be used. Among these, polyvinyl acetal, acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, styrene-based elastomers, and hydrogenated styrene-based elastomers are preferred from the viewpoints of solubility in low-polarity solvents and dispersion stability. From the viewpoint of the balance of affinity between the dispersed substance and the dispersion medium, the weight-average molecular weight of the resin-type dispersant is preferably 500,000 or less, more preferably 300,000 or less, and preferably 3,000 or more, and more preferably 5,000 or more. The resin-type dispersants may be used alone or in combination of two or more.

[0046] The content of the dispersant is preferably 5 to 300 mass %, more preferably 10 to 200 mass %, and even more preferably 15 to 100 mass %, based on the total amount of the conductive carbon material. The content of the dispersant is preferably 0.1 to 10 mass %, more preferably 0.5 to 5 mass %, based on the total amount of the electrode composition for an all-solid-state secondary battery.

[0047] <Method of manufacturing electrode composition for all-solid-state secondary battery> The electrode composition of the present invention is preferably produced by dispersing a conductive carbon material, a low-polarity solvent, and optionally a dispersant using a dispersing device to finely disperse the material. The dispersion treatment may be carried out by arbitrarily adjusting the timing of adding the materials used, or by carrying out a multi-stage treatment of two or more steps.

[0048] Examples of the dispersion device include a kneader, a two-roll mill, a three-roll mill, a planetary mixer, a ball mill, a horizontal sand mill, a vertical sand mill, an annular bead mill, an attritor, a high-shear mixer, a high-pressure homogenizer, and an ultrasonic homogenizer. From the viewpoint of promoting wetting of the conductive carbon material and dissolving coarse particles, the electrode composition for an all-solid-state secondary battery of the present invention preferably includes a step of dispersing a mixture containing a low-polarity solvent and a conductive carbon material using a media-less disperser such as a high-shear mixer or a colloid mill to prepare a pretreatment liquid (hereinafter also referred to as a pretreatment step), and a step of dispersing the pretreatment liquid using a media-type disperser and / or a media-less disperser (hereinafter also referred to as a dispersion step). Furthermore, when a media-type disperser such as a bead mill is used, excessive dispersion may occur, which may result in over-dispersion, so it may be preferable to shorten the treatment time or use a milder treatment intensity.

[0049] <Electrode slurry for all-solid-state secondary batteries> The electrode slurry for an all-solid-state secondary battery in the present invention contains at least the above-mentioned electrode composition, active material, solid electrolyte, binder, and solvent, and may further contain optional components such as a dispersant.

[0050] [Electrode active material] The electrode active material is a material that causes a battery reaction required to extract electrical energy, and is not particularly limited. As the positive electrode active material, for example, a metal oxide capable of reversibly doping or intercalating lithium ions, a metal compound such as a metal sulfide, etc., can be used. Specific examples of such a positive electrode active material include lithium manganese composite oxides (e.g., LixMn2O4 or Li xComposite oxide powders of lithium and transition metals such as manganese dioxide (MnO2), lithium nickel composite oxide (e.g., LiNiO2), lithium cobalt composite oxide (LixCoO2), lithium nickel cobalt composite oxide (e.g., LixNi1-yCoyO2), lithium manganese cobalt composite oxide (e.g., LixMnyCo1-yO2), lithium nickel manganese cobalt composite oxide (e.g., LixNiyCozMn1-y-zO2), spinel-type lithium manganese nickel composite oxide (e.g., LixMn2-yNiyO4), etc., lithium phosphate 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 ), etc., 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] Examples of the negative electrode active material include metal Li or its alloy (such as metal In), tin alloy, silicon alloy negative electrode, which can reversibly dope or intercalate lithium ions, X Li X TiO2, Li X Fe2O3, Li X WO2 and other metal oxide systems, conductive polymers such as polyacetylene and poly-p-phenylene, artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite. 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. Therefore, 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] [Solid electrolyte] As the solid electrolyte, a sulfide-based solid electrolyte can be used, and an oxide solid electrolyte or a halide solid electrolyte may also be used in part. The sulfide-based solid electrolyte is not particularly limited, and may contain elements such as S and Li. Crystals, non-crystals (glass), glass ceramics obtained by crystallizing glass, and partially crystallized ones may also be used. Examples of sulfide-based solid electrolytes include Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 , Li 10 GeP2S 12 , Li6PS5C l 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.

[0053] [binder] The binder is not particularly limited and can be appropriately selected depending on the purpose. Examples of binder resins used in secondary battery 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, vinyl pyrrolidone, or the like 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 be a modified product, mixture, or copolymer of these resins.

[0054] The content of the binder in the electrode composition for secondary batteries is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, based on the mass of the active material, and is preferably 20% by mass or less, more preferably 10% by mass or less.

[0055] <Electrode for all-solid-state secondary battery> An electrode for an all-solid-state secondary battery can be produced by applying the above-mentioned electrode slurry to a substrate such as a current collector and removing volatile components. The material and shape of the current collector are not particularly limited and can be appropriately selected from those suitable for various secondary batteries. Examples of materials for the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. While flat foils are generally used, those with a roughened surface, perforated foils, and mesh-like shapes are also acceptable. The thickness of the current collector is preferably about 0.5 to 30 μm.

[0056] The method for producing an electrode using the electrode slurry is not particularly limited, and known methods can be used. Specific examples include die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic coating. Drying methods after coating include, but are not limited to, standing to dry, blowing dryers, hot air dryers, infrared heaters, and far-infrared heaters.

[0057] After the electrode slurry is applied, it may be rolled using a lithographic press, a calender roll, etc. Heating may be performed during pressing.

[0058] <All-solid-state secondary battery> In an all-solid-state secondary battery, the components of the driving section are broadly divided into a positive electrode, a negative electrode, and a separator layer, and are stacked so that the positive electrode and the negative electrode face each other with the separator layer interposed therebetween. The positive electrode and / or the negative electrode are the electrode film, 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 in an all-solid-state secondary battery is not particularly limited. For example, a positive electrode, a negative electrode, and a separator layer may be formed separately and then 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. Furthermore, a pressing process may be performed during stacking, and further 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 when the components are stacked together. 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.

[0059] The all-solid-state secondary battery of the present invention can be suitably used as a battery for electric vehicles such as electric cars and hybrid cars, and portable electronic devices such as personal computers and smartphones. [Example]

[0060] The present invention will be explained in more detail below with reference to examples. The present invention is not limited to the following examples as long as it does not depart from the gist of the invention. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass." Furthermore, in the examples, "copolymer A" may be referred to as "copolymer" or "dispersant." Furthermore, in the examples, a "dispersant-containing liquid" containing a "dispersant" and a solvent may be referred to as a "dispersant solution."

[0061] <Production of dispersants> [Production of Copolymer 1] Hydrogenated NBR (nitrile rubber) A stainless steel polymerization reactor was charged with 20 parts acrylonitrile, 80 parts 1,3-butadiene, 3 parts potassium soap oleate, 0.3 parts azobisisobutyronitrile, 0.6 parts t-dodecyl mercaptan, and 200 parts ion-exchanged water. Under a nitrogen atmosphere, polymerization was carried out at 45°C for 20 hours with stirring, and terminated at a conversion of 90%. Unreacted monomer was removed by vacuum stripping to obtain an acrylonitrile-conjugated diene rubber latex with a solids concentration of approximately 30%. Subsequently, ion-exchanged water was added to the latex to adjust the total solids concentration to 12%. The mixture was then placed in a 1 L autoclave equipped with a stirrer, and nitrogen gas was purged for 10 minutes to remove dissolved oxygen. A catalyst solution prepared by dissolving 75 mg of palladium acetate as a hydrogenation catalyst in 180 mL of ion-exchanged water containing 4 times the molar amount of nitric acid relative to the palladium was added to the autoclave. The autoclave was purged twice with hydrogen gas, and then the contents of the autoclave were heated to 50°C under a pressure of 3 MPa with hydrogen gas, and a hydrogenation reaction was carried out for 6 hours. The contents were then returned to room temperature, a nitrogen atmosphere was created inside the autoclave, and the solids were dried to recover Copolymer 1. The hydrogenation rate of Copolymer 1 was 99.5%, and the weight-average molecular weight (Mw) was 200,000. In the acrylonitrile-conjugated diene rubber, the content of conjugated diene monomer units was 80%, and the content of nitrile group-containing monomer units was 20%, based on the mass of the acrylonitrile-conjugated diene rubber. The contents of these monomer units and structural units were determined from the amounts of monomers used.

[0062] <Production of electrode composition for all-solid-state secondary battery> [Example 1-1] Electrode composition 1 for all-solid-state secondary battery While stirring 86.0 parts of butyl butyrate as a solvent with a mixer, 1.0 parts of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) as a dispersant was added and stirred to dissolve. Next, while circulating in a colloid mill (Magic Lab; manufactured by Shinmaru Enterprises), 13.0 parts of acetylene black (Li-250; manufactured by Denka Co., Ltd.) as a conductive material was added little by little, and after the entire amount was added, circulation dispersion was carried out for 1 hour to prepare a pretreatment solution. The prepared pretreatment solution was subjected to a circulation dispersion treatment in a bead mill (Dyno Mill MULTILAB; manufactured by Shinmaru Enterprises) filled with zirconia beads with a diameter of 1 mm at a peripheral speed of 10 m / s and a residence time of 10 minutes to prepare an electrode composition 1 for an all-solid-state secondary battery.

[0063] [Examples 1-2 to 1-5] Electrode Compositions 2 to 5 for All-Solid-State Secondary Batteries All-solid-state secondary battery electrode compositions 2 to 5 were obtained in the same manner as in Example 1-1, except that the materials, compositions, and processing conditions were changed according to Table 1.

[0064] [Examples 1-6] Electrode composition 6 for all-solid-state secondary battery While stirring 86.0 parts of butyl butyrate as a solvent with a mixer, 1.0 parts of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) as a dispersant was added and stirred to dissolve. Next, a Silverson (L5M-A, manufactured by Silverson) equipped with a square-hole high-shear screen was used to circulate the mixture. 13.0 parts of acetylene black (Li-250; manufactured by Denka Co., Ltd.) as a conductive material were added little by little. After the entire amount was added, the mixture was circulated at a speed of 6000 rpm until the mixture was uniform, forming a pretreatment solution. The resulting pretreatment solution was subjected to a circulatory dispersion treatment using a bead mill (Dyno Mill MULTILAB; manufactured by Shinmaru Enterprises) filled with 1 mm diameter zirconia beads at a peripheral speed of 10 m / s and a residence time of 10 minutes to produce electrode composition 6 for all-solid-state secondary batteries.

[0065] [Examples 1-7] Electrode composition 7 for all-solid-state secondary batteries While stirring 43.0 parts of butyl butyrate as a solvent in a mixer, 1.0 parts of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) as a dispersant was added and stirred and dissolved. Next, the dispersant solution and 13.0 parts of acetylene black (Li-250; manufactured by Denka Co., Ltd.) as a conductive material were added to a planetary mixer (Hibismix 2P-03 model; manufactured by Plamix Co., Ltd.) and stirred at a rotation speed (revolution) of 60 rpm for 60 minutes to obtain a pretreated powder. 43.0 parts of butyl butyrate were circulated in a bead mill (Dyno Mill MULTILAB; manufactured by Shinmaru Enterprises Co., Ltd.) filled with zirconia beads with a diameter of 1 mm, and the pretreated powder was added little by little. After the entire amount was added, a circulation-type dispersion treatment was performed at a peripheral speed of 10 m / s and a residence time of 10 minutes to produce electrode composition 7 for all-solid-state secondary batteries.

[0066] [Examples 1-8] Electrode composition 8 for all-solid-state secondary batteries While stirring 86.0 parts of butyl butyrate as a solvent with a mixer, 1.0 parts of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) as a dispersant was added and stirred and dissolved. Next, the dispersant solution was circulated in a bead mill (Dyno Mill MULTILAB; manufactured by Shinmaru Enterprises) filled with zirconia beads having a diameter of 0.5 mm. Next, 13.0 parts of acetylene black (Li-250; manufactured by Denka Co., Ltd.) as a conductive material was added little by little. After the entire amount was added, a circulation dispersion treatment was performed at a peripheral speed of 8 m / s and a residence time of 8 minutes to prepare an electrode composition 8 for an all-solid-state secondary battery.

[0067] [Examples 1-9] Electrode composition 9 for all-solid-state secondary battery While stirring 96.8 parts of butyl butyrate as a solvent with a mixer, 1.0 parts of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) as a dispersant was added and stirred to dissolve. Next, while circulating in a colloid mill (Magic Lab; manufactured by Shinmaru Enterprises), 2.2 parts of carbon nanotubes (JENOTUBE10B; manufactured by JEIO) as a conductive material were added little by little. After the entire amount was added, circulation dispersion was carried out for 1 hour to prepare a pretreatment solution. The prepared pretreatment solution was subjected to a circulation dispersion treatment in a bead mill (Dyno Mill MULTILAB; manufactured by Shinmaru Enterprises) filled with 1 mm diameter zirconia beads at a peripheral speed of 10 m / s and a residence time of 30 minutes to prepare electrode composition 9 for all-solid-state secondary batteries.

[0068] [Examples 1-10 to 1-12] Electrode Compositions 10 to 12 for All-Solid-State Secondary Batteries All-solid-state secondary battery electrode compositions 10 to 12 were obtained in the same manner as in Examples 1-9, except that the materials, compositions, and processing conditions were changed according to Table 1.

[0069] [Comparative Example 1-1] Electrode composition 13 for all-solid-state secondary battery While stirring 86.0 parts of butyl butyrate as a solvent with a mixer, 1.0 parts of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) as a dispersant was added and stirred and dissolved. Next, the dispersant solution was circulated in a bead mill (Dyno Mill MULTILAB; manufactured by Shinmaru Enterprises) filled with zirconia beads having a diameter of 2 mm. Next, 13.0 parts of acetylene black (Li-250; manufactured by Denka Co., Ltd.) were added little by little. After the entire amount was added, a circulation-type dispersion treatment was performed at a peripheral speed of 14 m / s and a residence time of 20 minutes to prepare an electrode composition 13 for an all-solid-state secondary battery.

[0070] [Comparative Example 1-2] Electrode composition 14 for all-solid-state secondary battery An electrode composition 14 for an all-solid-state secondary battery was obtained in the same manner as in Example 1-1, except that the materials, composition, and processing conditions were changed according to those shown in Table 1.

[0071] [Comparative Example 1-3] Electrode composition 15 for all-solid-state secondary battery Acetylene black (Li-250, manufactured by Denka Co., Ltd.) was processed five times in a dry bead mill filled with 10 mm diameter alumina beads to obtain a pretreated powder. Next, 86.5 parts of butyl butyrate as a solvent was stirred in a mixer, while 0.5 parts of polyvinyl butyral (BL-S, manufactured by Sekisui Chemical Co., Ltd.) as a dispersant was added and stirred and dissolved. The dispersant solution was circulated in a bead mill (Dyno Mill MULTILAB, manufactured by Shinmaru Enterprises Co., Ltd.) filled with 1 mm diameter zirconia beads, and 13.5 parts of pretreated powder produced in a dry bead mill as a conductive material was added little by little. After the entire amount was added, a circulation dispersion process was performed at a peripheral speed of 10 m / s and a residence time of 10 minutes to produce an electrode composition 15 for an all-solid-state secondary battery.

[0072] [Comparative Example 1-4] Electrode composition 16 for all-solid-state secondary battery An electrode composition 16 for an all-solid-state secondary battery was obtained in the same manner as in Example 1-9, except that the materials, composition, and processing conditions were changed according to those shown in Table 1.

[0073] [Comparative Example 1-5] Electrode composition 17 for all-solid-state secondary battery An electrode composition 17 for an all-solid-state secondary battery was obtained in the same manner as in Comparative Example 1-1, except that the materials, composition, and processing conditions were changed according to those shown in Table 1.

[0074] <Measurement of electrode composition for all-solid-state secondary batteries> [Initial viscosity] The initial viscosity (mPa·s) of the obtained electrode composition for an all-solid-state secondary battery 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.

[0075] [Settling rate] 1.5 g of the surface liquid (above half the liquid phase) of the electrode composition placed in 10 mL of a No. 2 standard bottle (capacity 20 mL) was sucked up with a 2 mL plastic dropper and transferred to a Menthol can. The solvent was then evaporated in a hot air oven, and the solids mass (%) of the surface liquid was determined. The sedimentation rate was calculated using the determined solids mass (%) according to the following formula. Sedimentation rate % = (100-(B / A) x 100) A: A sample immediately after shaking a standard bottle up and down at a speed of 3 times per second with a shaking amplitude of 30 cm. Solid mass (%) of the surface liquid measured B: The solid content of the surface liquid measured on the sample after leaving the above sample at 25°C for 7 days in the atmosphere mass(%)

[0076] [Residual rate after 180° tilt test] 10 mL of the electrode composition was placed in a No. 2 standard bottle (20 mL capacity), tilted 180°, and left for 10 seconds. The residual rate was calculated based on the amount of composition remaining in the bottle (mL), with a residual rate of 90% or more being rated A and a residual rate of less than 90% being rated B. The sample used to measure the residual rate was one that had been shaken up and down with a shaking amplitude of 30 cm at a speed of 3 times per second 30 or more times, and then left to stand in the atmosphere at 25°C for 7 days.

[0077] [Table 1]

[0078] The abbreviations used in Table 1 are as follows: Li-250: Denka Black Li-250 (manufactured by Denka Co., Ltd., acetylene black) Li-400: Denka Black Li-400 (manufactured by Denka Co., Ltd., acetylene black) EC200L: Lionite 200L (Ketjenblack, manufactured by Lion) ·10B:JENOTUBE10B (manufactured by JEIO, multilayer CNT) ·6A:JENOTUBE6A (manufactured by JEIO, multilayer CNT) PVB: Polyvinyl butyral BL-S (manufactured by Sekisui Chemical Co., Ltd.) Vinyl chloride and acetate: Solvine A (manufactured by Nissin Chemical Co., Ltd.)

[0079] <Fabrication of positive electrodes for all-solid-state batteries> [Example 2-1] Positive electrode 1 A positive electrode was produced using the electrode composition produced in the example. 8.5 parts of a 10% by weight butyl butyrate solution of styrene-based elastomer resin as a binder, 41 parts of the electrode active material NMC, 7.5 parts of the solid electrolyte LPS, 5 parts of electrode composition 1, and 38 parts of butyl butyrate were weighed into a plastic container and stirred at 2,000 rpm for 3 minutes using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The positive electrode slurry was applied to a 20 μm-thick aluminum foil current collector using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes. Subsequently, pressure treatment was performed at 120°C using a heat press to obtain positive electrode 1. The electrode slurry preparation and electrode fabrication procedures were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below. Solid concentration

[0080] [Examples 2-2 to 2-8] Positive Electrodes 2 to 8 Positive electrodes 2 to 8 were obtained in the same manner as in Example 2-1, except that electrode composition 1 was changed to electrode compositions 2 to 8.

[0081] [Example 2-9] Positive electrode 9 8.5 parts of a 10% by weight butyl butyrate solution of styrene-based elastomer resin as a binder, 41.5 parts of the electrode active material NMC, 8.5 parts of the solid electrolyte LPS, 6.8 parts of electrode composition 9, and 35.7 parts of butyl butyrate were weighed into a plastic container and stirred at 2,000 rpm for 3 minutes using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The resulting positive electrode slurry was applied to a 20 μm-thick aluminum foil current collector using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes. Subsequently, pressure treatment was performed at 120°C using a heat press to obtain positive electrode 9. The electrode slurry preparation and electrode fabrication procedures were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0082] [Example 2-10] Positive electrode 10 The same procedure as in Example 2-9 was repeated except that electrode composition 9 was changed to electrode composition 10. An electrode 10 was obtained.

[0083] [Example 2-11] Positive electrode 11 8.5 parts of a 10% by mass solids styrene-based elastomer resin tetralin solution as a binder, 41.5 parts of the electrode active material NMC, 7.5 parts of the solid electrolyte LPS, 4.5 parts of electrode composition 11, and 38.0 parts of tetralin were weighed into a plastic container and stirred at 2,000 rpm for 3 minutes using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The resulting positive electrode slurry was applied to a 20 μm-thick aluminum foil current collector using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes. Subsequently, pressure treatment was performed at 120°C using a heat press to obtain positive electrode 11. The electrode slurry preparation and electrode fabrication procedures were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0084] [Example 2-12] Positive electrode 12 A positive electrode 12 was obtained in the same manner as in Example 2-11, except that electrode composition 11 was changed to electrode composition 12.

[0085] [Comparative Examples 2-1 to 2-3] Positive Electrodes 13 to 15 Positive electrodes 13 to 15 were obtained in the same manner as in Example 2-1, except that electrode composition 1 was changed to electrode compositions 13 to 15.

[0086] [Comparative Example 2-4] Positive electrode 16 A positive electrode 16 was obtained in the same manner as in Example 2-9, except that electrode composition 9 was changed to electrode composition 16.

[0087] [Comparative Example 2-5] Positive electrode 17 A positive electrode 17 was obtained in the same manner as in Example 2-11, except that the electrode composition 11 was changed to the electrode composition 17.

[0088] <Evaluation of positive electrodes for all-solid-state batteries> [Electrode resistance] The volume resistivity of the positive electrodes 1 to 8, 14, and 15 was measured by the four-probe method using a Loresta GP (manufactured by Nitto Seiko Analytech Co., Ltd.) in accordance with JIS-K7194. For the resistance measurement, a measurement electrode was used in which the coating substrate used in the preparation of each electrode was changed from aluminum foil to a PET substrate. The relative value (%) based on the volume resistivity of electrode 13 prepared in Comparative Example 2-1 was determined and evaluated according to the following criteria. ◎: 50% or less (excellent) ○: Over 50% and under 90% (good) ×: Over 90% (defective)

[0089] The volume resistivity of positive electrodes 9 to 12 and 17 was measured in the same manner as above. For the resistance measurement, a measurement electrode was used in which the coating substrate used in the preparation of each electrode was changed from aluminum foil to a PET substrate. The relative value (%) based on the volume resistivity of electrode 16 prepared in Comparative Example 2-4 was determined and evaluated according to the following criteria. ◎: 50% or less (excellent) ○: Over 50% and under 90% (good) ×: Over 90% (defective)

[0090] [Cycle characteristics] (Assembly of a cell for evaluating the positive electrode of an all-solid-state secondary battery) Positive electrodes 1 to 17 were punched out to a diameter of 10 mm and used as working electrodes. The working electrode and 50 mg of LPS powder were placed in a cylindrical container for all-solid-state battery evaluation cells, and a pressure of 50 MPa was applied to create an LPS layer on the working electrode. Metal indium foil and metal lithium foil were placed in that order as counter electrodes on the opposite side of the LPS layer from the working electrode. The cells were then assembled and secured with bolts, and then tightened to the specified pressure using a torque wrench to obtain positive electrode evaluation cells 1 to 17. The assembly of the evaluation cells was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0091] (evaluation) The prepared positive electrode evaluation cell was placed in a constant temperature room at 25°C, and a charge / discharge device (Hokuto Denko Corporation, S00 (%)

[0092] For the positive electrode evaluation cells 1 to 8, 14, and 15, the relative values (%) were calculated based on the cycle characteristics of the positive electrode evaluation cell 13, and evaluated according to the following criteria. ◎: 200% or more (excellent) ○: 150% or more, less than 200% (good) ×: Less than 150% (defective)

[0093] For positive electrode evaluation cells 9 to 12 and 17, the relative values (%) were calculated based on the cycle characteristics of positive electrode evaluation cell 16, and evaluated according to the following criteria. ◎: 200% or more (excellent) ○: 150% or more, less than 200% (good) ×: Less than 150% (defective)

[0094] <Preparation of negative electrode film for all-solid-state batteries> [Example 3-1] Negative electrode 1 A negative electrode was produced using the electrode composition produced in the example. 8.5 parts of a 10% by weight butyl butyrate solution of styrene-based elastomer resin as a binder, 36.9 parts of artificial graphite as electrode active material, 1.1 parts of silicon monoxide (SiO4), 7.5 parts of LPS solid electrolyte, 5 parts of electrode composition 1, and 38 parts of butyl butyrate were weighed into a plastic container and stirred at 2,000 rpm for 3 minutes using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The resulting negative electrode slurry was applied to a 20 μm-thick copper foil current collector using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes. Subsequently, pressure treatment was performed at 120°C using a heat press to obtain negative electrode 1. The electrode slurry preparation and electrode fabrication procedures were carried out in a glove box maintained under an argon atmosphere with a dew point of -60°C or below.

[0095] [Examples 3-2 to 3-8] Negative electrodes 2 to 8 Negative electrodes 2 to 8 were obtained in the same manner as in Example 3-1, except that electrode composition 1 was changed to electrode compositions 2 to 8.

[0096] [Example 3-9] Negative electrode film 9 8.5 parts of a 10% by weight butyl butyrate solution of styrene-based elastomer resin as a binder, 36.9 parts of artificial graphite as an electrode active material, 1.1 parts of silicon monoxide (SiO4), 8.5 parts of LPS solid electrolyte, 6.8 parts of electrode composition 9, and 35.7 parts of butyl butyrate were weighed into a plastic container and stirred at 2,000 rpm for 3 minutes using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The resulting negative electrode slurry was applied to a 20 μm-thick copper foil current collector using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes. Subsequently, pressure treatment was performed at 120°C using a heat press to obtain negative electrode film 9. The electrode slurry preparation and electrode fabrication procedures were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0097] [Example 3-10] Negative electrode film 10 A negative electrode 10 was obtained in the same manner as in Example 3-9, except that electrode composition 9 was changed to electrode composition 10.

[0098] [Example 3-11] Negative electrode film 11 8.5 parts of a 10% by weight solids styrene-based elastomer resin tetralin solution as a binder, 37.35 parts of electrode active material artificial graphite, 37.35 parts of silicon monoxide (SiO4), 7.5 parts of solid electrolyte LPS, 4.5 parts of electrode composition 11, and 38.0 parts of tetralin were weighed into a plastic container and stirred at 2,000 rpm for 3 minutes using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). The resulting negative electrode slurry was applied to a 20 μm-thick copper foil current collector using an applicator and then dried on a hot plate at 150°C ± 5°C for 25 minutes. Subsequently, pressure treatment was performed at 120°C using a heat press to obtain negative electrode 11. The electrode slurry preparation and electrode fabrication procedures were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0099] [Example 3-12] Negative electrode film 12 A negative electrode 12 was obtained in the same manner as in Example 3-11, except that electrode composition 11 was changed to electrode composition 12.

[0100] [Comparative Examples 3-1 to 3-3] Negative Electrodes 13 to 15 Negative electrodes 13 to 15 were obtained in the same manner as in Example 3-1, except that electrode composition 1 was changed to electrode compositions 13 to 15.

[0101] [Comparative Example 3-4] Negative electrode 16 A negative electrode 16 was obtained in the same manner as in Example 3-11, except that the electrode composition 11 was changed to the electrode composition 16.

[0102] [Comparative Example 3-5] Negative electrode 17 A negative electrode 17 was obtained in the same manner as in Example 3-11, except that electrode composition 11 was changed to electrode composition 17.

[0103] <Evaluation of negative electrodes for all-solid-state batteries> [Cycle characteristics] (Assembly of negative electrode cells for all-solid-state secondary batteries) Negative electrodes 1 to 17 were punched out to a diameter of 10 mm and used as working electrodes. The working electrode and 50 mg of LPS powder were placed in a cylindrical container for all-solid-state battery evaluation cells, 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 cells were then assembled and secured with bolts, and then tightened to the specified pressure using a torque wrench to obtain negative electrode evaluation cells 1 to 17. The assembly of the evaluation cells was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or below.

[0104] (Cycle characteristics evaluation) The negative electrode evaluation cell was placed in a thermostatic chamber at 25°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Corporation). 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 0.05V, followed by a constant-current discharge at a discharge rate of 0.2C with a discharge cutoff voltage of 1.5V. This procedure was repeated 25 times. 1C was defined as the current value required to charge or discharge the theoretical capacity of the negative electrode in 1 hour. The cycle characteristics can be expressed as the ratio of the 3rd 0.2C discharge capacity to the 25th 0.2C discharge capacity, using the following formula: (Formula 1) Cycle characteristics = 25th 0.2C discharge capacity / 3rd 0.2C discharge capacity × 100 (%)

[0105] For negative electrode evaluation cells 1 to 8, 14, and 15, the relative values (%) were calculated based on the cycle characteristics of negative electrode evaluation cell 13, and evaluated according to the following criteria. ◎: 180% or more (excellent) ○: 130% or more, less than 180% (good) ×: Less than 130% (poor)

[0106] For negative electrode evaluation cells 9 to 12 and 17, the relative values (%) were calculated based on the cycle characteristics of negative electrode evaluation cell 16, and evaluated according to the following criteria. ◎: 180% or more (excellent) ○: 130% or more, less than 180% (good) ×: Less than 130% (poor)

[0107] [Table 2]

[0108] As shown in Table 2, the Examples exhibited superior electrode resistance and battery characteristics (cycle characteristics) compared to the Comparative Examples. It is presumed that the carbon material contained in the electrode composition of the Examples maintained its structure, which allowed for the uniform formation of conductive paths within the electrode, leading to reduced electrode resistance and improved cycle characteristics. On the other hand, in the comparative example, the collapse of the structure and excessive aggregation due to the over-dispersion state caused the formation of conductive paths in the electrode to become non-uniform, which is presumed to have led to an increase in electrode resistance and a deterioration in cycle characteristics. From the above, it was demonstrated that the electrode composition produced by the production method of the present invention can exhibit excellent battery characteristics.

Claims

1. A solvent with a relative dielectric constant of less than 10 and / or a solubility in 100 g of water at 20°C Electrode composition for all-solid-state secondary battery containing less than 1 g of low-polarity solvent and conductive carbon material The all-solid-state secondary battery battery is characterized in that it satisfies the following conditions (1) or (2): Polar composition. (1) The sedimentation rate calculated by the following formula (I) is 10% or more and 90% or less. Sedimentation rate %=(100−(B / A)×100) (I) A: solid mass of the surface layer liquid of the electrode composition immediately after shaking B: Solid mass of the surface layer liquid of the electrode composition after standing at 25°C for 7 days (2) 10 mL of electrode assembly composition was placed in a No. 2 standard bottle, tilted 180°, and left for 10 seconds. The remaining rate of the electrode composition in the bottle is 90% or more.

2. The electrode composition for an all-solid-state secondary battery according to claim 1 , further comprising a dispersant.

3. The solvent having a relative dielectric constant of less than 10 and / or a solubility in 100 g of water at 20°C The low polarity solvent, which is a solvent with a viscosity of less than 1 g, is selected from ester compounds, aromatic hydrocarbons, and aliphatic 3. The all-solid composition according to claim 1, comprising at least one selected from the group consisting of hydrocarbons. Electrode composition for secondary batteries.

4. The conductive carbon material is composed of carbon black, fibrous carbon, and a graphene-based material. The electrode set for an all-solid-state secondary battery according to claim 1 or 2, comprising at least one selected from the group consisting of Finished product.

5. The electrode composition for an all-solid-state secondary battery according to claim 1 or 2, the active material, the solid electrolyte, and the binder and a solvent.

6. 6. A method for producing an electrode for an all-solid-state secondary battery, comprising: a step of preparing the electrode slurry for an all-solid-state secondary battery according to claim 5; a step of applying the electrode slurry onto a current collector; and a step of removing volatile components from the applied electrode slurry.

7. A method for manufacturing an all-solid-state secondary battery in which a positive electrode and a negative electrode are stacked so as to face each other via a separator layer made of an all-solid-state electrolyte, characterized in that an electrode for an all-solid-state secondary battery manufactured by the method for manufacturing an electrode for an all-solid-state secondary battery described in claim 6 is used for at least one of the positive electrode and the negative electrode.

8. 3. The method for producing an electrode composition for an all-solid-state secondary battery according to claim 1 or 2, wherein the electrode composition has a relative dielectric constant of 1 Solvents with a solubility of less than 0.0 and / or a solvent with a solubility of less than 1 g in 100 g of water at 20°C A mixture containing a low polarity solvent and a conductive carbon material is dispersed in a media-less disperser. a step of preparing a treatment liquid, and dispersing the pretreatment liquid in a media-type disperser and / or a media-less disperser. and dispersing the composition using a disperser.

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