Electrode composition for all-solid-state secondary batteries, electrode slurry, electrode for batteries, all-solid-state secondary battery, and production methods for same

Abstract

The problem is addressed by an electrode composition for all-solid-state secondary batteries which comprises a conductive carbon material and a solvent that has a dielectric constant of less than 10 and / or a low-polarity solvent that has a solubility of less than 1 g with respect to 100 g of water at 20°C, said electrode composition being characterized by satisfying the following condition (1) or (2). (1) A sedimentation rate determined by the following expression (I) is 10-90%. (I): Sedimentation rate %=(100-(B / A)×100), wherein A is the mass of solid content in a surface-layer liquid of the electrode composition immediately after shaking, and B is the mass of the solid content in the surface-layer liquid of the electrode composition after the electrode composition has been left to stand at 25°C for 7 days. (2) A residual ratio determined from the residual amount of the electrode composition in a No. 2 standard bottle is not less than 90%, when 10 mL of the electrode composition is placed in the bottle and the bottle is tilted 180° and then left to stand for 10 seconds.

Description

All-solid-state secondary battery electrode composition, electrode slurry, battery electrode, and all-solid-state secondary battery, and methods for manufacturing the same.

[0001] This disclosure relates to an electrode composition for all-solid-state secondary batteries, its use, and a method for manufacturing the same. More specifically, this disclosure relates to an electrode composition for all-solid-state secondary batteries, an electrode slurry using the electrode composition, an electrode for a battery, and an all-solid-state secondary battery, as well as a method for manufacturing the same.

[0002] With the miniaturization and weight reduction of laptops, the increased performance of smart devices, and the spread of electric vehicles, there is a growing demand for batteries with high capacity in limited spaces. For example, lithium-ion secondary batteries (LIBs) have the characteristics of high energy density and high voltage, and are used as batteries in many devices. In particular, in mobility applications where driving range, charging time, and battery life are challenges, the development of all-solid-state lithium-ion secondary batteries (all-solid-state LIBs), which use a solid electrolyte as an ion conductor, is becoming more active. Compared to conventional LIBs that use liquid electrolytes, all-solid-state LIBs offer battery characteristics such as high capacity, rapid charging, and high cycle characteristics, as well as improved safety by reducing the risk of ignition because they do not use flammable electrolytes. Due to these advantages, the practical application of electric vehicles equipped with all-solid-state LIBs is expected.

[0003] In all-solid-state lithium-ion batteries (LIBs), the electrolyte, which acts as a conductor of lithium ions, is solid. Therefore, contact between solid electrolytes (formation of solid interfaces) is crucial to enhance ionic conductivity within the electrodes. On the other hand, the active material, solid electrolyte, and binder contained within the electrodes are typically insulating materials. Consequently, the addition of conductive materials is essential to ensure the electron conduction within the electrodes necessary for charge and discharge reactions.

[0004] To address the above issues, optimization of the design of conductive material compositions dispersions has been proposed. For example, Patent Document 1 describes a method for producing 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 polar groups, as a dispersant.

[0005] International Publication No. 2022 / 030636, Patent No. 7136682

[0006] However, the method described in Patent Document 1 includes an amino alcohol as an additive, and Patent Document 2 includes an acrylic resin having polar groups as a dispersant. While both of these materials are used to improve dispersibility, their polar groups cause them to react with sulfur-based solid electrolytes, raising concerns about increased interfacial resistance due to electrolyte aggregation and alteration.

[0007] Therefore, in one embodiment of the present invention, the objective is to provide an electrode composition for an all-solid-state secondary battery that can exhibit high electronic conductivity, in an electrode for an all-solid-state secondary battery where improved electronic conductivity is required to improve battery performance.

[0008] As a result of diligent research to solve the above problems, we have found that the above problems can be solved by the embodiments shown below, and have completed the present invention. That is, the embodiments of the present invention relate to the following. However, the present invention is not limited to the embodiments shown below, but includes various embodiments.

[0009] One embodiment of the present invention relates to an electrode composition for an all-solid-state secondary battery comprising a low-polarity solvent which has a relative permittivity of less than 10 and / or a solvent which has a solubility of less than 1 g in 100 g of water at 20°C, and a conductive carbon material, characterized in that it satisfies the following conditions (1) or (2). (1) The settling rate determined by the following formula (I) is 10% or more and 90% or less Settling rate % = (100 - (B / A) × 100) ... (I) A: Mass of solids in the surface liquid of the electrode composition immediately after shaking B: Mass of solids in the surface liquid of the electrode composition after standing at 25°C for 7 days (2) The residual rate determined by the amount of electrode composition remaining in a No. 2 standard bottle after placing 10 mL of the electrode composition in the bottle and leaving it for 10 seconds after tilting it 180° is 90% or more

[0010] Another embodiment of the present invention relates to an electrode composition for an all-solid-state secondary battery, comprising a conductive carbon material (A), a dispersant (B), and a low-polarity solvent (C), and characterized in that it satisfies the following conditions (2) and (3). (2) The residual rate, determined by the amount of electrode composition remaining in a No. 2 standard bottle after placing 10 mL of the electrode composition in the bottle and leaving it for 10 seconds after tilting it 180°, is 90% or more. (3) When the viscosity is measured by sequentially performing the following procedures 1 to 4 and changing the shear rate, in procedure 2 the shear rate is 1 s －１ The viscosity measured under these conditions was 2 (mPa·s), and the shear rate was 1 s in step 4. －１ The rate of change A (Equation 1 below) from the viscosity 4 (mPa·s) measured under the following conditions is 10% or more and 210% or less. (Procedure 1) Using a rotary rheometer equipped with a cone plate (diameter 50 mm, angle 0.1°), the shear rate was set to 1 s per 170 seconds under the conditions of 25°C and a plate distance of 0.099 mm. －１ from 1000s －１ Change to this. (Step 2) Next, change the shear rate to 1000 s in 170 seconds. －１ from 1s －１ Change to this. (Step 3) Then, let it stand for 10 minutes. (Step 4) Then, increase the shear rate to 1 s in 170 seconds. －１ from 1000s －１ It is changed to this. (Formula 1): Rate of change A (%) = (viscosity 4 - viscosity 2) / viscosity 2 × 100

[0011] Another embodiment of the present invention relates to an electrode slurry for an all-solid-state secondary battery, comprising at least the electrode composition, active material, solid electrolyte, binder, and solvent of the above embodiment.

[0012] Another embodiment of 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 of the above embodiment.

[0013] Another embodiment of the present invention relates to an all-solid-state secondary battery, including electrodes for the all-solid-state secondary battery of the above embodiment.

[0014] Another embodiment of the present invention relates to a method for producing an electrode composition for an all-solid-state secondary battery, comprising the steps of: preparing a pretreatment solution by dispersing a mixture containing a solvent with a relative permittivity of less than 10 and / or a low-temperature solvent having a solubility of less than 1 g in 100 g of water at 20°C and a conductive carbon material in a medialess disperser; and dispersing the pretreatment solution in a media-type disperser and / or a medialess disperser.

[0015] According to one embodiment of the present invention, a composition for an all-solid-state secondary battery with excellent conductivity can be provided. According to yet another embodiment of the present invention, an electrode and an all-solid-state secondary battery having high electronic conductivity can be provided.

[0016] The following describes in detail an electrode composition for an all-solid-state secondary battery, which is one embodiment of the present invention, and its use. However, the present invention is not limited to the following embodiments, and the present invention also includes various embodiments that are implemented without changing the essence of the invention. In this specification, numerical ranges specified using "~" include the numerical values ​​written before and after "~" as the lower and upper limits. Furthermore, unless otherwise specified, each of the components described in this specification may be used independently, one by one, or two or more may be used in combination.

[0017] 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, carbon black dispersions may be simply referred to as "CB dispersions" and carbon nanotube dispersions as simply "CNT dispersions". Furthermore, electrode compositions for all-solid-state secondary batteries may be referred to as "electrode compositions" or simply "compositions". Electrode slurry for all-solid-state secondary batteries may be referred to as "electrode slurry" and electrodes for all-solid-state secondary batteries may be referred to as "electrodes".

[0018] <Electrode Composition for All-Solid-State Secondary Battery> The electrode composition for all-solid-state secondary battery of this embodiment comprises a conductive carbon material and a predetermined low-polarity solvent, and optionally contains a dispersant. The electrode composition may optionally contain other additives such as wetting agents, surfactants, pH adjusters, wetting penetrating agents, leveling agents, other conductive materials, and other polymer components, as long as they do not hinder the objectives of the present invention. Optional components can be added at any time, such as before the preparation of the electrode composition, during dispersion, after dispersion, or in combination thereof. The electrode composition for all-solid-state secondary battery of this embodiment will be described in more detail below.

[0019] 1. Electrode Composition for All-Solid-State Secondary Battery 1-1. First Electrode Composition for All-Solid-State Secondary Battery The first electrode composition for all-solid-state secondary battery of this embodiment is characterized by satisfying the following conditions (1) or (2). (1) The settling rate determined by the following formula (I) is 10% or more and 90% or less Settling rate % = (100 - (B / A) × 100) ... (I) A: Mass of solids in the surface liquid of the electrode composition immediately after shaking (%) B: Mass of solids in the surface liquid of the electrode composition after standing at 25°C for 7 days (%) (2) The residual rate determined by the amount of electrode composition remaining in the bottle after placing 10 mL of the electrode composition in a No. 2 standard bottle, tilting it 180°, and leaving it for 10 seconds is 90% or more

[0020] Unlike general polar solvents, the dispersion of conductive carbon materials in low-polarity solvents is prone to overdispersion and excessive aggregation, making it difficult to maintain an appropriate dispersion state. The electrode composition for all-solid-state secondary batteries of this embodiment satisfies either condition (1) or (2) above, allowing the conductive carbon material to have interparticle interactions in a low-polarity solvent. When formed into a coating film (hereinafter also referred to as an electrode film), the conductive carbon materials form a secondary structural structure, resulting in high conductivity. The above conditions can be achieved by appropriately selecting the type and ratio of conductive carbon material, dispersant, low-polarity solvent, and dispersion process.

[0021] In the above-described first electrode composition for all-solid-state secondary batteries, the settling properties can be evaluated, for example, by the following method. 1.5 g of the surface liquid (the upper half of the liquid phase) of the electrode composition, which has been placed in a 10 mL No. 2 standard bottle (capacity 20 mL), is drawn up with a 2 mL polydropper and transferred to a Mentholatum can. The solvent is then vaporized in a hot air oven to determine the solid content mass (%) of the surface liquid, and the settling rate is calculated using the following formula (I). In some embodiments, the settling rate preferably satisfies condition (1) specified for the above-described first electrode composition for all-solid-state secondary batteries, i.e., the settling rate is 10% or more and 90% or less. Sedimentation rate % = (100 - (B / A) × 100) ... (I) A: Solid content mass (%) of the surface liquid measured in a sample immediately after shaking a standard bottle up and down 30 times or more at a speed of 3 times / second with a swing width of 30 cm B: Solid content mass (%) of the surface liquid measured in a sample after standing the above sample in air at 25°C for 7 days If the sedimentation rate is 10% or more and 90% or less, the conductive carbon material will have interparticle interactions in a low-polarity solvent. If the sedimentation rate exceeds 90%, the composition will be in an unstable dispersion state and will be prone to excessive aggregation. On the other hand, if the sedimentation rate is less than 10%, the interaction between carbon materials will be weak and will be prone to overdispersion, which may make it difficult for the conductive carbon materials to form a secondary structural structure when used as an electrode film. The sedimentation rate is preferably 15% or more, more preferably 20% or more. Furthermore, the settling rate is 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.

[0022] The gelation state of the electrode composition for all-solid-state secondary batteries can be evaluated, for example, by the residual rate measurement method using the 180° tilt test described below. 10 mL of the electrode composition is placed in a No. 2 standard bottle (capacity 20 mL), tilted 180°, and left for 10 seconds. The residual rate is calculated from the amount of composition remaining in the bottle (mL) using the following formula: Formula: Residual rate % = (Residual amount / 10) × 100 The sample used for measuring the residual rate is prepared by shaking the standard bottle containing the sample up and down at a speed of 3 times / second with a swing amplitude of 30 cm at least 30 times, and then letting it stand in the air at 25°C for 7 days. In some embodiments, the residual rate preferably satisfies condition (2) specified for the first electrode composition for all-solid-state secondary batteries described above, i.e., the residual rate is 90% or more. When the residual rate is 90% or more, a gel state is formed, and the conductive carbon material has interparticle interactions. The gelation here differs from a general gel state, as it has a reversible dispersion state of the conductive carbon material. A reversible dispersion state 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, it refers to a state in which the change in solution viscosity between the solution viscosity immediately after shaking a standard bottle containing a sample up and down at a speed of 3 times per second with a shaking amplitude of 30 cm, and the solution viscosity immediately after performing the same shaking test after the sample has been allowed to stand and become a gel, is less than 10%.

[0023] The dispersibility of conductive carbon material in electrode compositions for all-solid-state secondary batteries can be evaluated by the median diameter (μm) determined by a laser diffraction / scattering particle size analyzer. The median diameter (μm) determined by the laser diffraction / scattering particle size analyzer allows for the estimation of the particle size of aggregated conductive carbon material particles based on the scattered light intensity distribution by the particles. The median diameter (μm) is preferably 0.4 μm or greater, preferably 5.0 μm or less, and more preferably 2.0 μm or less. By setting the median diameter within this range, the amount of aggregated conductive carbon material is reduced, and the conductive carbon material is not excessively refined, resulting in an electrode composition for all-solid-state secondary batteries with an appropriate dispersion state. This enables the formation of an efficient conductive network.

[0024] The electrode composition for all-solid-state secondary batteries has a viscosity of 10 mPa·s or more, measured at 60 rpm at 25°C using an E-type viscometer. Furthermore, the viscosity is 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. For example, it may be between 10 mPa·s and 10,000 mPa·s, between 10 mPa·s and 2,000 mPa·s, or between 10 mPa·s and 1,000 mPa·s.

[0025] The TI value of the electrode composition for all-solid-state secondary batteries can be calculated from the viscosity (mPa·s) at 6 rpm measured at 25°C using an E-type viscometer, divided by the viscosity (mPa·s) at 60 rpm. The TI value is preferably 1.0 or higher, preferably 10.0 or lower, more preferably 5.0 or lower, and even more preferably 3.0 or lower. For example, it may be between 1.0 and 10.0, between 1.0 and 5.0, or between 1.0 and 3.0. A higher TI value indicates greater structural viscosity due to entanglement of conductive carbon material, dispersant, and other resin components, or their intermolecular forces, while a lower TI value indicates lower structural viscosity. By setting the TI value within the above range, it is possible to suppress entanglement of conductive carbon material, dispersant, and other resin components while allowing these intermolecular forces to act appropriately.

[0026] The solid content of the electrode composition for all-solid-state secondary batteries 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. Furthermore, the above solid content is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, and may be, for example, 0.2 to 40% by mass, 0.3 to 30% by mass, or 0.5 to 20% by mass.

[0027] <Conductive Carbon Materials> In this embodiment, examples of conductive carbon materials include carbon black, fibrous carbon, graphene, graphite, and fullerene. These conductive carbon materials may be used individually or in combination of two or more. In particular, from the viewpoint of conductivity, it is preferable that the conductive carbon material includes at least one selected from the group consisting of carbon black and fibrous carbon. Furthermore, the use of carbon black or fibrous carbon is preferred from the viewpoint of conductivity.

[0028] [Carbon Black] Various types of carbon black can be used individually or in combination of two or more, such as furnace black produced by continuously thermally decomposing gaseous or liquid raw materials in a reactor, particularly Ketjenblack made from ethylene heavy oil, channel black produced by burning raw material gas and rapidly cooling the bottom surface of channel steel with the flame, thermal black obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, particularly acetylene black made from acetylene gas. In addition, conventionally treated oxidized carbon black and hollow carbon can also be used.

[0029] Oxidation of carbon involves treating carbon at high temperatures in air, or secondarily treating it 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 to the carbon surface. This process 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 undergone oxidation treatment.

[0030] The smaller the primary particle diameter of carbon black, the greater the number of particles per unit mass, and the greater the contact points between carbon black particles, which is advantageous for lowering the internal resistance of electrodes. Specifically, from the viewpoint of conductivity and availability, the primary particle diameter of carbon black is preferably 1 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. Furthermore, the above primary particle diameter is 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. However, the primary particle diameter referred to here is the spherical particle that forms an aggregate (primary aggregate), and is the average value of the particle diameter measured by an electron microscope. The average primary particle diameter of carbon black can be determined as follows. First, carbon black is observed and imaged using a transmission electron microscope. Next, 100 arbitrary spherical carbon black primary particles are selected from the observation image, 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.

[0031] The carbon black used in this embodiment forms agglomerates (secondary aggregates) which are formed by the aggregation of aggregates (primary aggregates). A size of secondary aggregates greater than a predetermined value facilitates the formation of a conductive network, which is advantageous in reducing the internal resistance of the electrodes. In this embodiment, the secondary aggregates are expressed by the volume-average particle diameter (D50), which is preferably 0.2 μm or more, more preferably 0.3 μm or more. Furthermore, the volume-average particle diameter 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 referred to here is the particle diameter at which the volume percentage of the particles becomes 50% when the volume percentage of the particles is accumulated from the finest to the largest in the volume particle size distribution, and is measured with a general particle size analyzer, for example, a laser scattering type particle size analyzer ("Microtrac MT3300EXII" manufactured by Nikkiso Co., Ltd.).

[0032] [Fibrous carbon] Fibrous carbon may be obtained by calcining petroleum-derived raw materials, or it may be obtained by calcining plant-derived raw materials. Examples of fibrous carbon include carbon nanotubes.

[0033] In this embodiment, the carbon nanotube has a cylindrical shape formed by winding planar graphite, and may be single-layer, double-layer, or multi-layer, or a mixture of these. A single-layer carbon nanotube has a structure in which one layer of graphite is wound. A double-layer or multi-layer carbon nanotube has a structure in which two or more layers of graphite are wound. Furthermore, the sidewalls of the carbon nanotube do not have to be made of graphite.

[0034] In this embodiment, the shape of the fibrous carbon is not limited. Examples of such shapes include needle-shaped, cylindrical tubular, fishbone-shaped (fishbone or cup stacked type), playing card-shaped (platelet), and coil-shaped. Among these, needle-shaped or cylindrical tubular shapes are preferred. The fibrous carbon may be used alone in one shape, or in combination of two or more shapes.

[0035] In this embodiment, examples of fibrous carbon forms include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. 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. Furthermore, the above average outer diameter is 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 imaged using a transmission electron microscope. Next, 300 arbitrary fibrous carbons are selected from the observation images, and their outer diameters are measured. Then, the average outer diameter (nm) of the fibrous carbon is calculated as the number average of the outer diameters.

[0036] In the carbon material, two or more types of fibrous carbon having different average outer diameters may be used in combination. 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. Further, 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 may be 1:10 to 1:50.

[0037] 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 still more preferably 1.0 µm or more. Further, the average fiber length is preferably 20 µm or less, more preferably 10 µm or less. The average fiber length of fibrous carbon can be determined as follows. First, fibrous carbon is observed and imaged using a transmission electron microscope. Next, in the observed photograph, 300 arbitrary fibrous carbons are selected, and the fiber length of each is measured. Then, the average fiber length (µm) of fibrous carbon is calculated as the number average of the fiber lengths.

[0038] A value obtained by dividing the average fiber length by the average outer diameter is the aspect ratio. Fibrous carbon with a higher aspect ratio can exhibit higher conductivity when an electrode is formed. From the viewpoint of conductivity, the aspect ratio of fibrous carbon is preferably 30 or more, more preferably 50 or more, and still more preferably 80 or more. Further, the aspect ratio is preferably 10,000 or less, more preferably 3,000 or less, and still more preferably 1,000 or less.

[0039] Regarding the specific surface area of the conductive carbon material used in the present embodiment, generally, the larger the value, the smaller the primary particle diameter of the conductive carbon material. This increases the number of contact points between particles, which 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 20 m ２ It is desirable to use one having / g or more. In the nitrogen adsorption method, an adsorption isotherm is measured by adsorbing and desorbing nitrogen as adsorbate molecules onto an adsorbent, the measured data is analyzed, and the specific surface area, pore volume and pore diameter are calculated. The specific surface area is determined by the BET method.

[0040] 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 the all-solid-state secondary battery. Furthermore, the content is preferably 20% by mass or less, and more preferably 10% by mass or less. By setting the content within the above range, the conductive carbon material can be present in a good state while maintaining its structure. The content is more preferably 0.1 to 20% by mass, and even more preferably 0.5 to 10% by mass. Furthermore, it is preferable to appropriately adjust the content of the conductive carbon material so that an electrode composition with appropriate fluidity or viscosity can be obtained, depending on the specific surface area of ​​the conductive carbon material, its affinity to the dispersion medium, the dispersibility of the dispersant, etc.

[0041] <Low Polarity Solvents> The low polarity solvents in this embodiment are solvents with low polarity that do not react easily with sulfur-based solid electrolytes, solvents with a relative permittivity of less than 10, and / or solvents with a solubility of less than 1 g in 100 g of water at 20°C, and also include nonpolar solvents. Preferably, the solvent has a relative permittivity 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 measuring the double cylindrical tube current at 10 kHz using a liquid dielectric constant meter Model 871 (manufactured by Sanyo Trading Co., Ltd.). The proportion of solvents with a relative permittivity of less than 10, and / or solvents with a solubility of less than 1 g in 100 g of water at 20°C, in the low polarity solvent is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. When using two or more solvents, the relative permittivity of the mixed solvent can be calculated as the weighted average of the relative permittivity of the individual solvents, based on the volume of each solvent used. That is, if the relative permittivity of solvent A is εr Ａ The relative permittivity of solvent B is εr Ｂ The volume of solvent A is V Ａ (ml), the volume of solvent B is V Ｂ When the volume is (ml), the weighted average relative permittivity of the mixed solvent can be calculated using the following formula: Formula: Weighted average relative permittivity = (εrＡ ×V Ａ +εr Ｂ ×V Ｂ ) / (V Ａ +V Ｂ Examples of such low-polarity solvents include highly hydrophobic solvents having an alkyl group with four or more carbon atoms (ester-based or ether-based), aromatic hydrocarbons, aliphatic hydrocarbons, etc. Using the above solvents can prevent the degradation of sulfide-based solid electrolytes that occurs when polar solvents such as water, alcohol, or N-methyl-2-pyrrolidone are used. Furthermore, by combining them with the aforementioned dispersants, the dispersibility of carbon materials 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, and may be 100% by mass. These solvents may be used individually or in combination of two or more. For example, examples of solvents having an alkyl group with four or more carbon atoms (ester-based or ether-based) include butyl butyrate, pentyl butyrate, hexyl butyrate, butyl acetate, pentyl acetate, hexyl acetate, and butyl propionate. Examples of ether-based solvents having an alkyl group with four 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 preferably, an ester solvent having an alkyl group with four or more carbon atoms is used, and even more preferably, butyl butyrate.

[0042] <Dispersant> The above-described first electrode composition for all-solid-state secondary batteries may further contain a dispersant. The dispersant is not particularly limited as long as it can disperse and stabilize the conductive carbon material in the electrode composition for all-solid-state secondary batteries. Either a resin-type dispersant or a surfactant can be used as the dispersant, but a resin-type dispersant is preferred because it has strong adsorption to the conductive carbon material and provides good dispersion stability. Depending on the properties required for the dispersion of the conductive carbon material, a suitable type of dispersant can be used in a suitable amount.

[0043] As resin-type dispersants, (meth)acrylic polymers, polymers derived from ethylenically unsaturated hydrocarbons, cellulose derivatives, copolymers thereof, etc., can be used. 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 alcohol having functional groups other than hydroxyl groups (e.g., acetyl groups, sulfo groups, carboxyl groups, carbonyl groups, amino groups), polyvinyl alcohol modified with various salts, other anionically or cationically modified polyvinyl alcohol, and polyvinyl acetals (polyvinyl acetal, polyvinyl butyral, etc.) modified with aldehydes (acetal modification or butyral modification, etc.). The polyacrylonitrile resin may be a homopolymer of polyacrylonitrile, a copolymer of polyacrylonitrile, or a modified version thereof. Preferably, the polyacrylonitrile resin has at least one selected from the group consisting of active hydrogen groups such as hydroxyl groups, carboxyl groups, primary amino groups, secondary amino groups, and mercapto groups, basic groups, alkyl groups introduced from (meth)acrylate or α-olefins, etc. For example, the acrylonitrile copolymer described in Japanese Patent Application Publication No. 2020-163362 can be used. Examples of nitrile rubbers include acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, styrene elastomers, and hydrogenated styrene elastomers. Examples of cellulose derivatives include cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, ethyl hydroxyethylcellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, or copolymers thereof. Polymers in which other substituents have been introduced into some of these polymers, or modified polymers, 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 viewpoint of solubility in low-polarity solvents and dispersion stability. The weight-average molecular weight of the resin-type dispersant is preferably 500,000 or less, more preferably 300,000 or less, more preferably 3,000 or more, and more preferably 5,000 or more, from the viewpoint of affinity balance between the dispersed material and the dispersion medium. The resin-type dispersant may be used alone or in combination of two or more types.

[0044] The dispersant content is preferably 5 to 300% by mass, more preferably 10 to 200% by mass, and even more preferably 15 to 100% by mass, based on the total amount of conductive carbon material. The dispersant content is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total amount of electrode composition for all-solid-state secondary batteries.

[0045] <Method for Manufacturing Electrode Composition for All-Solid-State Secondary Battery> The electrode composition described above, which is one embodiment of the present invention, is preferably manufactured by finely dispersing a conductive carbon material, a low-polarity solvent, and a dispersant as needed, using a dispersion apparatus. The dispersion process may be carried out in two or more multi-stage processes, with the timing of the addition of the materials used being arbitrarily adjusted.

[0046] Examples of dispersion devices include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, annular bead mills, attritors, high-shear mixers, high-pressure homogenizers, and ultrasonic homogenizers. The electrode composition for all-solid-state secondary batteries of this embodiment preferably includes a step of preparing a pretreatment solution by dispersing a mixture containing a low-polarity solvent and a conductive carbon material in a media-less disperser such as a high-shear mixer or colloid mill (hereinafter also referred to as the pretreatment step), and a step of dispersing the pretreatment solution in a media-type disperser and / or a media-less disperser (hereinafter also referred to as the dispersion step), from the viewpoint of promoting wetting of the conductive carbon material and dissolving coarse particles. Furthermore, when using a media-type disperser such as a bead mill, there is a risk of overdispersion due to excessive dispersion, so it may be preferable to shorten the processing time or make the processing intensity milder.

[0047] Although not particularly limited, for example, the above-mentioned first electrode composition for a solid-state secondary battery can be easily produced by a manufacturing method that includes the steps of: preparing a pretreatment solution by dispersing a mixture containing a solvent with a relative permittivity of less than 10 and / or a low-polarity solvent having a solubility of less than 1 g in 100 g of water at 20°C and a conductive carbon material in a medialess disperser; and dispersing the pretreatment solution in a media-type disperser and / or a medialess disperser.

[0048] 2-2. Second Electrode Composition for Solid-State Secondary Battery As a preferred specific example of the electrode composition for solid-state secondary battery of this embodiment, an electrode composition for solid-state secondary battery that satisfies the conditions (2) of the first electrode composition for solid-state secondary battery described above, in addition to the conditions (3) described later, is mentioned. That is, the second electrode composition for solid-state secondary battery of this embodiment comprises a conductive carbon material, a dispersant, and a low-polarity solvent, and is characterized by satisfying the following conditions (2) and (3). (2) The residual rate determined by the amount of electrode composition remaining in the bottle after placing 10 mL of the electrode composition in a No. 2 standard bottle and leaving it for 10 seconds after tilting it 180° is 90% or more. (3) When the viscosity is measured by sequentially performing the following procedures 1 to 4 and changing the shear rate, in procedure 2 the shear rate is 1 s －１The viscosity 2 measured under these conditions, and the shear rate 1s in step 4. －１ The rate of change A (Equation 1 below) from the viscosity 4 measured under the following conditions is 10% or more and 210% or less. (Procedure 1) Using a rotary rheometer equipped with a cone plate (diameter 50 mm, angle 0.1°, CP50-1), the shear rate is set to 1 s per 170 seconds under the conditions of 25°C and a plate distance of 0.099 mm. －１ from 1000s －１ Change to this. (Step 2) Next, change the shear rate to 1000 s in 170 seconds. －１ from 1s －１ Change to this. (Step 3) Then, let it stand for 10 minutes. (Step 4) Then, increase the shear rate to 1 s in 170 seconds. －１ from 1000s －１ It is changed to this. (Formula 1): Rate of change A (%) = (viscosity 4 - viscosity 2) / viscosity 2 × 100

[0049] The viscosity of electrode compositions for all-solid-state secondary batteries (hereinafter also referred to as electrode compositions or dispersions), typified by thixotropy, is manifested by the complex interactions of the contained materials (conductive carbon material, dispersant, low-polarity solvent, etc.) and the dispersion process. Therefore, it is difficult to uniquely estimate viscosity from specific factors, and the detailed mechanism is unknown. However, the electrode composition of this embodiment has a unique viscosity, with a viscosity change rate (change rate A) before and after standing for 10 minutes, measured according to a predetermined procedure, being between 10% and 210%. It is believed that this unique viscosity allows for rapid, mild viscosity increase, which fixes the uniform state of the conductive carbon material within the film, thereby ensuring conductive paths and resulting in excellent conductivity and cycleability.

[0050] The measurements in steps 1 to 5 are hysteresis loop measurements in which the shear force is continuously increased and then continuously decreased, with the interval in step 3 in between, and the cycle of increase and decrease is performed twice. The viscosity measurements in steps 1 to 5 are all performed continuously under conditions of 25°C and a plate distance of 0.099 mm using a rotary rheometer equipped with a cone plate (diameter 50 mm, angle 0.1°). (Step 1) is performed with a shear rate of 1 s over 170 seconds. －１ from 1000s －１This is a process of measuring viscosity while changing the temperature. (Step 2) is performed immediately after Step 1, by changing the shear rate to 1000 s for 170 seconds. －１ from 1s －１ This is a process of measuring viscosity while changing the temperature. (Step 3) is a process of letting it stand for 10 minutes after step 2. (Step 4) is a process of changing the shear rate to 1 s for 170 seconds after step 3. －１ from 1000s －１ This is a process of measuring viscosity while changing the temperature. (Step 5) is performed immediately after Step 4, and the shear rate is changed to 1000 s over 170 seconds. －１ from 1s －１ This is a process of taking measurements while changing the value.

[0051] The rate of change A between viscosity 2 and viscosity 4, expressed by the above (Equation 1), represents the change in viscosity before and after standing for 10 minutes, and a larger value means a greater increase in viscosity. Viscosity 2 decreases as the shear rate decreases in step 2, 1s －１ This refers to the viscosity (mPa·s) measured at that time. Viscosity 4 is the shear rate 1s in step 4. －１ This refers to the viscosity (mPa·s) at the start of the measurement.

[0052] It is important that the rate of change A is between 10% and 210%, and preferably 15% or more from the viewpoint of suppressing sedimentation of carbon material. Also, from the viewpoint of handling, it is preferably 180% or less. The rate of change A may be, for example, 15 to 180%.

[0053] The rate of change A can be adjusted by the type and combination of the low-polarity solvent and carbon material, as well as the dispersion conditions, and the preferred range of the rate of change A can be appropriately adjusted by the type and combination of the low-polarity solvent and carbon material. For example, in the case of a combination of butyl butyrate and carbon black, the rate of change A is preferably 20% or more, more preferably 30% or more, and even more preferably 35% or more. Furthermore, the rate of change A is preferably 105% or less, more preferably 85% or less, and even more preferably 50% or less, and may be, for example, 20-105%, 20-85%, 20-50%, 35-85%, and 35-50%. In the case of a combination of tetralin and carbon nanotubes, the rate of change A is preferably 10% or more, more preferably 15% or more. Furthermore, the rate of change A is preferably 100% or less, more preferably 80% or less, and even more preferably 40% or less, and may be, for example, 10-100%, 15-100%, 15-80%, and 15-40%.

[0054] The rate of change B between viscosity 2 and viscosity 5, expressed by the following (Equation 2), represents the change in viscosity before and after 10 minutes of standing and hysteresis loop measurement. A value closer to 0 indicates a smaller change. (Equation 2): Rate of change B (%) = (Viscosity 5 - Viscosity 2) / Viscosity 2 × 100 The above viscosity 5 decreases in step 5 as the shear rate decreases for 1 s －１ This refers to the viscosity (mPa·s) measured at that point. The rate of change B is preferably -4% or more, more preferably -3% or more, preferably 4% or less, more preferably 2% or less, and may be, for example, -4% or more and 4% or less. When the rate of change B is within the above range, it can be determined that the dispersion state after stirring has recovered to the same state as when the electrode composition (dispersion) was prepared, resulting in excellent handling (workability) after industrial stirring.

[0055] The second electrode composition described above can be manufactured using the same materials as those previously exemplified as constituent materials of the first electrode composition. Although not particularly limited, typical constituent materials of the second electrode composition will be described again below. <Conductive carbon material (A)> The second electrode composition described above includes a conductive carbon material (A). The conductive carbon material (A) functions as a conductive material in the electrode. Examples of conductive carbon material (A) include carbon black (CB), carbon nanotubes (CNT), graphene, multilayer graphene, and graphite. One type of conductive carbon material (A) may be used alone, or two or more types may be used in combination. From the viewpoint of conductive performance, it is preferable that the conductive carbon material (A) includes at least one selected from the group consisting of carbon black and carbon nanotubes.

[0056] [Carbon Black (CB)] Examples of carbon black include furnace black, which is produced by continuously thermally decomposing gaseous or liquid raw materials in a reactor, particularly Ketjenblack made from ethylene heavy oil, channel black, which is produced by burning raw material gas and rapidly cooling the bottom surface of channel steel with the flame to precipitate the black, and thermal black, which is obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, particularly acetylene black made from acetylene gas. Oxidized carbon black and hollow carbon can also be used. These carbon blacks may be used individually or in combination of two or more types.

[0057] Oxidation of carbon is a process that directly introduces (covalently bonds) oxygen-containing polar functional groups such as phenol groups, quinone groups, carboxyl groups, and carbonyl groups to the carbon surface, and is generally performed to improve the dispersibility of carbon. Examples of oxidation treatments include treating carbon at high temperatures in air, and secondarily treating it with nitric acid, nitrogen dioxide, ozone, etc. Since the conductivity of carbon black tends to decrease with the introduction of functional groups, it is preferable to use unoxidized carbon black in this embodiment.

[0058] The smaller the primary particle diameter of carbon black, the greater the number of particles per unit mass, and the greater the contact points between carbon black particles, which is advantageous for lowering the internal resistance of the electrode. Therefore, from the viewpoint of conductivity and availability, the average primary particle diameter of the carbon black raw material used in the manufacture of the electrode composition is preferably 1 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. Alternatively, the average primary particle diameter may be 100 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, and particularly preferably 50 nm or less, for example, 1 to 100 nm, 10 to 80 nm, 20 to 70 nm, 20 to 50 nm, or 30 to 40 nm. The above average primary particle diameter refers to the spherical particles that form aggregates (primary aggregates), and is the average value of the particle diameters measured with an electron microscope. The average primary particle diameter of the carbon black raw material (carbon black before dispersion treatment) can be determined as follows. First, the carbon black raw material is observed and imaged using a transmission electron microscope. Next, 100 arbitrary spherical carbon black primary particles are selected from the observation photographs, and their outer diameters are measured. Then, the average primary particle diameter (nm) of the carbon black raw material is calculated as the number average of the outer diameters.

[0059] In the electrode composition, carbon black forms agglomerates (secondary aggregates) formed by the aggregation of aggregates (primary aggregates). A size of secondary aggregates greater than a predetermined value facilitates the formation of a conductive network, which is advantageous in reducing the internal resistance of the electrode. In this specification, the size of the secondary aggregates is expressed as the median diameter (D50) based on volume. From the viewpoint of conductivity, D50 is preferably 0.2 μm or more, more preferably 0.3 μm or more. From the viewpoint of dispersion stability, D50 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. D50 is the particle size at which, in the volume particle size distribution, the volume percentage of particles from the finest to the smallest is accumulated to reach 50%. D50 can be measured using an electrode composition with a general particle size distribution analyzer (for example, a laser scattering type particle size distribution analyzer such as Nikkiso's "Microtrac MT3300EXII").

[0060] The bulk density of the carbon black raw material tends to correlate with the degree of aggregation of carbon atoms and its wettability when in contact with a liquid medium. In this embodiment, the bulk density of the carbon black raw material is preferably 0.03 g / cm³. ３ More preferably, 0.04 g / cm³ ３ That concludes the explanation. Furthermore, the above bulk density is preferably 0.15 g / cm³. ３ More preferably, 0.10 g / cm³ ３ The following are examples, for instance, 0.03 to 0.15 g / cm³. ３ ,0.04~0.10g / cm ３ Alternatively, the following may be used: By using raw materials whose bulk density falls within the above range, both the wettability of carbon black in the solvent and its conductivity after dispersion can be achieved.

[0061] The specific surface area of ​​carbon black raw materials tends to correlate with the average primary particle size and aggregation state. For example, the smaller the particle size, the larger the specific surface area. In this embodiment, the BET specific surface area of ​​the carbon black is preferably 30 m². ２ / g or more, more preferably 40m ２ / g or more, more preferably 50m２ It is 150 m² or more. Furthermore, the BET specific surface area is preferably 150 m². ２ / g or less, more preferably 100m ２ / g or less, more preferably 80m ２ It is less than or equal to / g, for example, 30 to 150m ２ / g, 40-100m ２ / g, 50-80m ２ / g, 58-68m ２ It may also be / g. From the viewpoint of conductivity, it is preferable to use raw materials with particle size and aggregation state that fall within the above range for specific surface area. The specific surface area can be measured by the BET method using nitrogen adsorption.

[0062] [Carbon Nanotubes (CNTs)] Carbon nanotubes have a cylindrical shape formed by winding planar graphite. Carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes, or a mixture of both. Single-walled carbon nanotubes have a structure in which one layer of graphite is wound. Multi-walled carbon nanotubes have a structure in which two or three or more layers of graphite are wound. Furthermore, the sidewalls of carbon nanotubes do not have to be of a graphite structure. For example, carbon nanotubes having sidewalls with an amorphous structure can also be used as carbon nanotubes.

[0063] The shape of carbon nanotubes is not particularly limited. Examples of such shapes include needle-shaped, cylindrical, fishbone-shaped (fishbone or cup-stacked), and coil-shaped forms. Carbon nanotubes may have a single shape or a combination of two or more shapes. Examples of carbon nanotube forms include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. However, they are not limited to these. Carbon nanotubes may have these forms individually or in combination of two or more.

[0064] The electrode composition of this embodiment can be obtained using a carbon nanotube raw material. The carbon nanotube raw material may be any carbon nanotube manufactured by any method. Generally, the carbon nanotube raw material can be manufactured by laser ablation, arc discharge, thermal CVD, plasma CVD, and combustion, but is not limited to these methods. The carbon nanotube raw material may be a surface-treated carbon nanotube. The carbon nanotube raw material may be a carbon nanotube derivative to which a functional group such as a carboxyl group has been added. Furthermore, the carbon nanotube raw material may be a carbon nanotube containing an organic compound, a metal atom, or a substance such as a fullerene.

[0065] The average outer diameter of the carbon nanotube raw material (carbon nanotubes before dispersion treatment) is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. Furthermore, the above average outer diameter is preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 15 nm or less. The average outer diameter of the carbon nanotube raw material can be calculated by first observing and imaging the carbon nanotube raw material using a transmission electron microscope, selecting 300 arbitrary carbon nanotubes from the observation images, measuring the outer diameter of each, and calculating the average value.

[0066] The specific surface area of ​​carbon nanotube raw materials is 100 m². ２ Preferably, it is 150m or more per gram. ２ It is more preferable that it be 200m or more per g. ２ It is even more preferable that the amount is 1 / g or more. Furthermore, the specific surface area is 1200 m². ２ It is preferable that it be less than or equal to 1000m ２ It is more preferable that it be less than or equal to 800m ２ It is even more preferable that the amount be less than or equal to 100 to 1200 m ２ / g, 150-1000m ２ / g, 200-800m ２ / g, 230-690m ２It may also be / g. The specific surface area of ​​the carbon nanotube raw material is calculated by the BET method using nitrogen adsorption measurement. When the average outer diameter, average fiber length, aspect ratio, and specific surface area are within the above range, it becomes easier to form conductive paths that have developed in the electrode.

[0067] The carbon purity of the carbon nanotube raw material is expressed as the carbon atom content (mass%) in the carbon nanotube raw material. The carbon purity is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more, based on 100% by mass of the carbon nanotube raw material. By setting the carbon purity within the above range, it is possible to prevent problems such as dendrite formation and short circuits caused by impurities such as metal catalysts. Carbon nanotube raw materials that have undergone high-purity treatment may be used for the purpose of removing or reducing impurities such as metal catalysts and increasing carbon purity. The method of high-purity treatment is not particularly limited, and known methods can be used.

[0068] From the viewpoint of ease of disintegration of aggregates and wettability in solvents, the bulk density of the carbon nanotube raw material is preferably 0.03 g / cm³. ３ More preferably, 0.04 g / cm³ ３ That concludes the explanation. Furthermore, the above bulk density is preferably 0.15 g / cm³. ３ More preferably, 0.10 g / cm³ ３ The following are examples, for instance, 0.03 to 0.15 g / cm³. ３ ,0.04~0.10g / cm ３ ,0.04~0.07g / cm ３ It may also be done in the following way. The bulk density described above is determined by filling a predetermined volume of top-opening container with carbon nanotube raw material by free-falling until it overflows, leveling off the raised portion on the top surface while it is standing, measuring the mass of the carbon nanotube raw material, and dividing it by the container volume.

[0069] The carbon nanotube raw material used in the electrode composition may be pre-treated, and the pre-treatment method is not particularly limited, and may include surface treatment using chemicals, heat treatment, or grinding. The grinding treatment may be wet grinding or dry grinding, and may be media grinding or grinding without media. Dry grinding is preferred due to the ease of controlling the physical properties of the carbon nanotube raw material, and a combination of dry grinding and media grinding is even more preferable. Examples of grinding devices include bead mills, ball mills, and attrition mills. The components introduced into the grinding device may consist only of untreated carbon nanotube raw material, and optional components such as lubricants, dispersants, and surface treatment agents may be added. Dry grinding is preferred, but if necessary, a liquid medium may be introduced into the grinding device along with the untreated carbon nanotube raw material. When using a grinding device, the grinding treatment may be any of the following methods: batch type, continuous dispersion, or circulating dispersion, but continuous dispersion grinding is preferred due to the ease of controlling the physical properties of the carbon nanotube raw material. In continuous dispersion grinding processes, the desired carbon nanotube raw material can be obtained by controlling the mass of untreated carbon nanotube raw material per unit time, the type and diameter of the grinding media, and the amount of material fed into the grinding device.

[0070] The heat treatment conditions, such as the heat treatment temperature and time, can be appropriately determined depending on the type of carbon nanotube raw material and the type of metal derived from the catalyst metal contained in the carbon nanotube raw material. The heat treatment temperature is preferably the temperature at which all metals—aluminum, magnesium, cobalt, iron, copper, zinc, nickel, chromium, manganese, and molybdenum—begin to melt. Furthermore, since the catalyst metals used in the production of carbon nanotube raw materials are at the nanoscale, and due to the nanoscale effect, their melting temperature is lower than that of bulk metals, a heat treatment temperature lower than that of bulk metals is also acceptable. An inert atmosphere may be used during heat treatment; examples of inert atmospheres include nitrogen, argon, vacuum, and combinations thereof. For example, an inert atmosphere can be obtained by introducing an inert gas such as nitrogen gas into the apparatus used during heat treatment and replacing the inside of the apparatus with the inert gas. The heat treatment can then be carried out while maintaining a vacuum by reducing the pressure inside the apparatus.

[0071] The content of conductive carbon material (A) in the electrode composition can be appropriately adjusted according to the type and physical properties (specific surface area, amount of surface functional groups, etc.) of the conductive carbon material. When conductive carbon material (A) contains carbon black, the content of conductive carbon material (A) in the electrode composition is preferably 1% by mass or more, more preferably 5% by mass or more, based on the mass of the electrode composition. Furthermore, the above content is 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 conductive carbon material (A) contains carbon nanotubes, the content of conductive carbon material (A) in the electrode composition 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 electrode composition. Furthermore, the above content is 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. When the content of conductive carbon material (A) is within the above range, the dispersibility is excellent, the viscosity of the electrode composition (dispersion) is within an appropriate range, and production efficiency and handling are excellent.

[0072] <Dispersant (B)> The electrode composition of this embodiment includes a dispersant. The dispersant can be used without particular limitation as long as it can disperse and stabilize the conductive carbon material (A), and for example, at least one of resin-type dispersants and surfactants can be used. From the viewpoint of strong adsorption to the conductive carbon material (A) and excellent dispersion stability, a resin-type dispersant is preferred. The type and amount of the dispersant can be appropriately adjusted according to the required characteristics. One type of dispersant may be used alone, or two or more types may be used in combination.

[0073] [Resin-type dispersants] Examples of resin-type dispersants include polymers derived from ethylenically unsaturated hydrocarbons, cellulosic derivatives, and copolymers thereof.

[0074] (Polymers derived from ethylenically unsaturated hydrocarbons) Examples of polymers derived from ethylenically unsaturated hydrocarbons include (meth)acrylic resins, polyvinyl alcohol resins, polyvinylpyrrolidone resins, polyacrylonitrile resins, and rubbers.

[0075] Examples of (meth)acrylic resins include methyl polyacrylate, ethyl polyacrylate, butyl polyacrylate, polymethyl methacrylate, polyethyl methacrylate, polytart-butyl methacrylate, copolymer of ethylene-methyl acrylate, and copolymer of ethylene-ethyl acrylate.

[0076] Examples of polyvinyl alcohol-based resins include polyvinyl alcohol, modified polyvinyl alcohol having functional groups other than hydroxyl groups (e.g., acetyl groups, sulfo groups, carboxyl groups, carbonyl groups, amino groups), polyvinyl alcohol modified with various salts, other anionic or cationic modified polyvinyl alcohol, and polyvinyl acetals modified with aldehydes (e.g., acetacetal modification, butyral modification) (e.g., polyvinyl acetal, polyvinyl butyral).

[0077] Examples of polyvinylpyrrolidone resins include Luvitec K17, K30, K80, K85, K90, and K90HM manufactured by BASF Japan, K15, K30, K90, and K120 manufactured by Ashland, and polyvinylpyrrolidone K30, K85, and K90 manufactured by Nippon Shokubai Co., Ltd.

[0078] Examples of polyacrylonitrile resins include polyacrylonitrile homopolymers, polyacrylonitrile copolymers, and modified versions thereof, and more preferably, polyacrylonitrile resins having alkyl groups in their side chains. Examples of the alkyl groups include alkyl (meth)acrylates and alkyl groups derived from α-olefins, and as such polyacrylonitrile resins having alkyl groups in their side chains, for example, the acrylonitrile copolymer described in Japanese Patent Application Publication No. 2020-163362 can be used.

[0079] Examples of rubbers include acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, styrene elastomers, and hydrogenated styrene elastomers. Examples of styrene elastomers and hydrogenated styrene elastomers include modified versions of any of the following: styrene-ethylene-butylene block copolymer (SEB), styrene-ethylene-propylene block copolymer (SEP), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-butylene-styrene-styrene block copolymer (SEBSS), styrene-isobutylene-styrene block copolymer (SIBS), and styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS).

[0080] (Cellulose derivatives) Examples of cellulose derivatives include cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, ethyl hydroxyethylcellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, and copolymers thereof.

[0081] In the electrode composition, the affinity between the low-polarity solvent (C) and the dispersant (B), and the affinity between the conductive carbon material (A) and the dispersant (B) contribute to dispersion stabilization. Therefore, it is preferable to appropriately select the dispersant (B) according to the type of low-polarity solvent (C) described later. For example, when the low-polarity solvent (C) is an ester-based solvent having an alkyl group with 4 or more carbon atoms, the dispersant is preferably a polyvinyl alcohol-based resin, and more preferably polyvinyl butyral. Furthermore, the polyvinyl butyral is preferably a solution viscosity of 10 to 500 mPa·s when prepared as a 10% by mass ethanol solution, more preferably 20 to 400 mPa·s, and even more preferably 100 to 300 mPa·s. When the low-polarity solvent (C) is an aromatic solvent, the dispersant is preferably a styrene-based resin, and more preferably a styrene-ethylene-butylene-styrene block copolymer. From the viewpoint of increasing affinity with the low-polarity solvent (C), the dispersant (B) preferably has a solubility of 0.8% by mass or more, more preferably 1% by mass or more, in the low-polarity solvent (C) at 25°C. On the other hand, from the viewpoint of increasing affinity with the conductive carbon material (A), the dispersant (B) preferably has a solubility of 50% by mass or less, in the low-polarity solvent (C) at 25°C. When the solubility of the dispersant (B) in the low-polarity solvent (C) is within the above range, it is presumed that the dispersant (B) reaches an equilibrium state between adsorption to the conductive carbon material (A) and dissolution to the low-polarity solvent (C), exhibiting excellent dispersion stability.

[0082] The weight-average molecular weight (Mw) of the resin-type dispersant is preferably 20,000 or more. Furthermore, Mw is preferably 350,000 or less, more preferably 110,000 or less, and may be, for example, 20,000 to 350,000 or 20,000 to 110,000. Since ionization hardly occurs in low-polarity solvents, steric repulsion of the dispersant adsorbed on the particles is necessary for the dispersion stabilization of conductive carbon material particles. By setting the molecular weight within the above range, sufficient steric repulsion is obtained, which is preferable from the viewpoint of dispersion stability.

[0083] The content of the dispersant (B) is preferably 5 to 300% by mass, more preferably 10 to 200% by mass, and even more preferably 15 to 100% by mass, based on the mass of the conductive carbon material (A). Furthermore, the content of the dispersant is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the mass of the electrode composition.

[0084] <Low Polarity Solvent (C)> The low polarity solvent (C) is a solvent with low polarity that does not react easily with sulfur-based solid electrolytes, has a relative permittivity of less than 10, and / or has a solubility of less than 1 g in 100 g of water at 20°C, and also includes nonpolar solvents. Preferably, it contains a solvent with a relative permittivity of less than 10.0, more preferably 8.0 or less, and even more preferably 6.0 or less, and the content of the solvent is preferably 100% by mass based on the mass of the low polarity solvent (C). The relative permittivity in this specification is a value measured at 20 to 25°C, and can be measured, for example, by measuring the double cylindrical tube current at 10 kHz using a liquid dielectric constant meter Model 871 (manufactured by Sanyo Trading Co., Ltd.).

[0085] Examples of such low-polarity solvents (C) include ester solvents having a highly hydrophobic alkyl group with 4 or more carbon atoms, ether solvents having an alkyl group with 4 or more carbon atoms, aromatic hydrocarbons, and aliphatic hydrocarbons. By using a low-polarity solvent (C), the degradation of sulfide-based solid electrolytes can be prevented. A single low-polarity solvent (C) may be used, or two or more may be used in combination.

[0086] In particular, from the viewpoint of electrode resistance and dispersion stability, the solvent preferably includes at least one solvent selected from the group consisting of ester solvents having an alkyl group having 4 or more carbon atoms, ether solvents having an alkyl group having 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 preferably, the solvent is an ester solvent having an alkyl group having 4 or more carbon atoms, and even more preferably, butyl butyrate.

[0087] The electrode composition of this embodiment may contain solvents other than the low-polarity solvent (C) as long as the effects of this embodiment are not impaired. The content of the low-polarity solvent (C) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total amount of solvent in the electrode composition, and may also be 100% by mass.

[0088] The content of the low-polarity solvent (C) in the electrode composition can be appropriately adjusted according to the type and physical properties (specific surface area, amount of surface functional groups, etc.) of the conductive carbon material. When the conductive carbon material (A) contains carbon black, the content of the low-polarity solvent (C) in the electrode composition is preferably 70% by mass or more, more preferably 80% by mass or more, based on the mass of the electrode composition. Furthermore, the above content is preferably 95% by mass or less, more preferably 90% by mass or less, and may be, for example, 70 to 95% by mass or 80 to 90% by mass. When the conductive carbon material (A) contains carbon nanotubes, the content of the low-polarity solvent (C) in the electrode composition is preferably 90% by mass or more, more preferably 93% by mass or more, based on the mass of the electrode composition. Furthermore, the above content is preferably 99% by mass or less, more preferably 98% by mass or less, and may be, for example, 90 to 99% by mass or 93 to 98% by mass. When the above content is within the range, the fluidity and dispersion stability of the electrode composition are excellent.

[0089] <Other Additives> The electrode composition of this embodiment may further contain other optional components such as surfactants, film-forming aids, defoaming agents, leveling agents, antioxidants, preservatives, and viscosity modifiers, to the extent that they do not impair the effects of this embodiment. The electrode composition may also contain polymer components (binders) to the extent that they do not hinder the objectives of the present invention. The description of binders can be referred to in the section on <Mixed Slurry> under [Binder]. These optional components may be added at any time during the manufacturing process of the electrode composition, such as before, during, or after the dispersion treatment of the electrode composition.

[0090] <Method for Manufacturing the Electrode Composition> The method for manufacturing the second electrode composition described above is not particularly limited, but it can be obtained by mixing at least a conductive carbon material (A) raw material, a dispersant (B), and a low-polarity solvent (C) all at once or in separate parts. Any components may be used, and a dispersion treatment may be performed after mixing. The dispersion apparatus used for the dispersion treatment is not particularly limited. As the dispersion apparatus, a disperser commonly used for pigment dispersion, etc., can be used. Such dispersion devices include, for example, mixers such as dispersers, homomixers, and planetary mixers; homogenizers such as M-Technic's "Clearmix," PRIMIX's "Filmix," and Silverson's "Abramix" and "High Shear Mixer"; paint conditioners (Red Devil); colloid mills (PUC's "PUC Colloid Mill," IKA's "Magic LAB," IKA's "Colloid Mill MK"); cone mills (IKA's "Corn Mill MKO," etc.); ball mills, sand mills (Shinmaru Enterprises' "Dyno Mill," etc.), attritors, pearl mills (Eirich's "DCP Mill," etc.), bead mills (Ashizawa Finetech's "Star Mill LMZ," etc.), and media-type dispersers such as coball mills; Examples include high-pressure homogenizers such as the "Starburst" manufactured by Sugino Machine Co., Ltd. and the "Pressure Homogenizer" manufactured by SMT Co., Ltd.; media-less dispersers such as the "Nanomizer" manufactured by Nanomizer Co., Ltd., the "CREA SS-5" manufactured by M-Technique Co., Ltd., and the "MICROS" manufactured by Nara Machinery Co., Ltd.; and other roll mills, but are not limited to these.

[0091] The dispersion device should preferably be treated to prevent metal contamination from the device. For example, when using a media-type dispersion device, a dispersion device in which the agitator and vessel are made of ceramic or resin, or a dispersion device in which the surface of the metal agitator and vessel is treated with tungsten carbide spraying or resin coating, etc., can be used. As the media, glass beads; zirconia beads, alumina beads, and other ceramic beads are preferably used. When using a roll mill, it is preferable to use ceramic rolls.

[0092] The second electrode composition of this embodiment can exhibit the viscosity defined in this embodiment by controlling the dispersion conditions (dispersion apparatus, dispersion process, dispersion intensity, etc.) in addition to the material selection described above. In some embodiments, the dispersion treatment for preparing the electrode composition containing carbon black is preferably carried out using a high-shear mixer, colloidal mills, media-type disperser, or a combination thereof. For example, from the viewpoint of promoting wetting and dissolving coarse particles, it is preferable to first disperse using a high-shear mixer or colloidal mill in the initial dispersion step, and then disperse using a media-type disperser such as a bead mill to homogenize the dispersion state.

[0093] In some embodiments, the dispersion process for preparing an electrode composition (dispersion) containing carbon nanotubes is preferably carried out using a high-shear mixer, colloidal mills, a high-pressure homogenizer, a media-type disperser, or a combination thereof. For example, in the initial stage of dispersion, it is preferable to use a high-shear mixer or colloidal mill to promote wetting and dissolve coarse particles, and then to use a high-pressure homogenizer to disperse while maintaining the aspect ratio of the carbon nanotubes. The dispersibility of carbon nanotubes can be further improved by performing the high-pressure homogenization in multiple stages by circulating dispersion. After dispersion with a high-pressure homogenizer, further dispersion may be carried out using a media-type disperser such as a bead mill. Alternatively, by dispersing with a high-shear mixer or colloidal mill in the initial stage of dispersion, then dispersing with a media-type disperser such as a bead mill, and then further dispersing with a high-pressure homogenizer, the dispersion state can be made uniform while maintaining the fiber length. When using a high-pressure homogenizer, the pressure is preferably 25 to 120 MPa, and more preferably 30 to 100 MPa.

[0094] The dispersion apparatus used to disperse the second electrode composition may include a heat exchanger and a coolant supply mechanism for cooling the electrode composition.

[0095] Dispersion methods using a dispersion device include batch dispersion, pass-through dispersion, and circulating dispersion. Any of these methods may be used, or two or more methods may be combined. Batch dispersion is a method of dispersion using only the dispersion device itself, without using piping or other equipment. It is preferable for small-scale production because it is easy to handle. Pass-through dispersion is a dispersion method in which the dispersion device is equipped with a tank to supply the liquid to be dispersed via piping and a tank to receive the liquid to be dispersed, and the liquid is dispersed by passing it through the dispersion device. Circulating dispersion is a method in which the liquid to be dispersed, after passing through the dispersion device, is returned to the tank to supply the liquid and dispersed while being circulated. In all cases, dispersion progresses as the processing time increases, so it is sufficient to repeat the pass-through or circulation until the desired dispersion state is achieved, and the processing volume can be increased by changing the size of the tanks or the processing time. Pass-through dispersion is preferable to circulating dispersion because it is easier to achieve a uniform dispersion state. Circulating dispersion is preferable to pass-through dispersion because the work and manufacturing equipment are simpler. In the dispersion process, the disintegration of aggregated particles, the loosening of conductive materials, wetting, stabilization, etc., proceed sequentially or simultaneously, and the final dispersion state differs depending on how these processes proceed. Therefore, it is preferable to control the dispersion state in each dispersion process by using various evaluation methods.

[0096] The dispersion process is preferably carried out until the viscosity of the electrode composition is sufficiently reduced. The viscosity of the second electrode composition, as measured using a B-type viscometer at 25°C and 60 rpm, is preferably 10 mPa·s or more and 10,000 mPa·s or less, more preferably 10 mPa·s or more and 5,000 mPa·s or less, even more preferably 10 mPa·s or more and 2,000 mPa·s or less, and particularly preferably 10 mPa·s or more and 1,000 mPa·s or less.

[0097] <Moisture Content> The second electrode composition of this embodiment preferably has a moisture content of 500 ppm or less, from the viewpoint of suppressing degradation of the solid electrolyte and suppressing a decrease in lithium ion conductivity. More preferably, the moisture content is 350 ppm or less. By keeping the moisture content below the above value, the degradation of the electrolyte is suppressed, and a good secondary battery can be obtained. From the viewpoint of moisture management, the above dispersion treatment is preferably carried out under a nitrogen atmosphere.

[0098] 2. Electrode slurry for all-solid-state secondary batteries An electrode slurry for an all-solid-state secondary battery according to an embodiment of the present invention includes at least the electrode composition, active material, solid electrolyte, binder and solvent of the above-described embodiment, and may further include optional components such as a dispersant. The electrode composition of the above embodiment may be either the first or the second electrode composition. Hereinafter, unless otherwise specified, the description of the electrode composition means that it may be either the first or the second electrode composition.

[0099] [Electrode Active Material] The electrode active material is a substance that causes a battery reaction necessary for extracting electrical energy, and is not particularly limited. The electrode 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 compounds such as metal oxides capable of reversibly doping or intercalating lithium ions and metal sulfides can be used. Specific examples of such a positive electrode active material include, for example, lithium manganese composite oxide (for example Li ｘ Mn ２ O ４ or Li ｘ MnO ２ ), lithium nickel composite oxide (for example LiNiO ２ ), lithium cobalt composite oxide (Li ｘ CoO ２ ), lithium nickel cobalt composite oxide (for example Li ｘ Ni １－ｙ Co ｙ O ２ ), lithium manganese cobalt composite oxide (for example Li ｘ Mn ｙ Co １－ｙ O ２ ), lithium nickel manganese cobalt composite oxide (for example Li ｘ Ni ｙ Co ｚ Mn １－ｙ－ｚ O ２ ), spinel-type lithium manganese nickel composite oxide (for example Li ｘ Mn ２－ｙ Ni ｙ O ４ ), composite oxide powders of lithium and transition metals such as the above, and lithium phosphate oxide powders having an olivine structure (for example Liｘ FePO ４ , Li ｘ Fe １－ｙ Mn ｙ PO ４ , Li ｘ CoPO ４ ), manganese oxide, iron oxide, copper oxide, nickel oxide, vanadium oxides (e.g., V ２ O ５ , V ６ O １３ ), transition metal oxide powders such as titanium oxide, iron sulfate (Fe ２ (SO ４ ) ３ ), TiS ２ and transition metal sulfide powders such as FeS, etc. Wherein, x, y and z are numbers satisfying 0 < x < 1, 0 < y < 1, 0 < z < 1, and 0 < y+z < 1. One or a combination of a plurality of these positive electrode active materials may be used.

[0100] Examples of negative electrode active materials include metallic Li capable of reversibly doping or intercalating lithium ions or alloys thereof (such as metallic In), tin alloy, silicon alloy negative electrodes, Li Ｘ TiO ２ , Li Ｘ Fe ２ O ３ , Li Ｘ Fe ３ O ４ , Li Ｘ WO ２ and other metal oxide-based materials, conductive polymers such as polyacetylene and poly-p-phenylene, artificial graphite such as highly graphitized carbon materials, carbonaceous powders such as natural graphite, and resin-fired carbon materials. Wherein, x is a number satisfying 0 < x < 1. One or a combination of a plurality of these negative electrode active materials may be used. Particularly when a silicon alloy negative electrode is used, although it has a large theoretical capacity, its 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, and the like.

[0101] [Solid Electrolyte] As the solid electrolyte, a sulfide-based solid electrolyte can be used, and oxide solid electrolytes and halide solid electrolytes may also be used in part. The sulfide-based solid electrolyte is not particularly limited, and may contain S and Li. Furthermore, crystalline, amorphous (glass), glass ceramics obtained by crystallizing glass, or materials that are partially crystallized may be used. As an example of a sulfide-based solid electrolyte, Li ９．５４ Si １．７４ P １．４４ S １１．７ C ｌ０．３ Li １０ GeP ２ S １２ Li ６ PS ５ C ｌ These are examples. Furthermore, sulfide-based solid electrolytes may be produced by mixing raw materials in any molar ratio, and specific examples include the following: Li ２ S-P ２ S ５ Li ２ S-P ２ S ５ -LiCl, Li ２ S-LiI-P ２ S ５ Li ２ S-LiI-Li ２ O-P ２ S ５ Li ２ S-LiBr-P ２ S ５ Li ２ S-Li ２ O-P ２ S ５ Li ２ S-Li ３ PO ４ -P ２ S ５ Li ２ S-P ２ S ５ -P ２ O ５ Li ２ S-P ２ S ５ -SiS ２ Li ２ S-P ２S ５ -SiS ２ -LiCl、Li ２ S-P ２ S ５ -SnS、Li ２ S-P ２ S ５ -Al ２ S ３ 、Li ２ S-Al ２ S ３ 、Li ２ S-SiS ２ 、Li ２ S-SiS ２ -Al ２ S ３ 、Li ２ S-SiS ２ -P ２ S ５ 、Li ２ S-SiS ２ -LiI、Li ２ S-SiS ２ -P ２ S ５ -LiI、Li ２ S-SiS ２ -Li ４ SiO ４ 、Li ２ S-SiS ２ -P ２ O ５ 、Li ２ S-B ２ S ３ 、Li ２ S-B ２ S ３ -Li ３ PO ４ 、Li ２ S-GeS ２ 、Li ２ S-Ga ２ S ３ 、Li ２ S-GeS ２ -Ga ２ S ３ 、Li ２ S-GeS ２ -P ２ S ５ 、Li ２ S-GeS ２ -Sb ２ S ５Li ２ S-GeS ２ - ZnS, Li ２ S-GeS ２ - Al ２ S ３ These may be used individually or in combination of two or more types.

[0102] [Binder] There are no particular restrictions on the binder, and it can be appropriately selected according to the purpose. Examples of binder resins used in electrode compositions for secondary batteries 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, vinylpyrrolidone, etc. as constituent units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, 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 form or mixture of these resins, or a copolymer.

[0103] The binder content in the electrode slurry 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. Furthermore, the above content is preferably 20% by mass or less, more preferably 10% by mass or less.

[0104] The electrode slurry for secondary batteries (also called composite slurry) of this embodiment can be prepared by any method using the electrode composition of the above embodiment. For example, methods include adding an active material, a solid electrolyte, and a binder to the electrode composition; adding the active material and solid electrolyte to the electrode composition and then adding the binder; adding the binder to the electrode composition and then adding the active material and solid electrolyte; adding the active material to the electrode composition and then adding the solid electrolyte and binder; adding the solid electrolyte to the electrode composition and then adding the active material and binder; adding the active material to the electrode composition and then adding the solid electrolyte and then adding the binder; and mixing the active material, solid electrolyte, and binder before adding the electrode composition. The method of dispersing and mixing the above is not particularly limited, and known methods can be selected.

[0105] While not particularly limited, for example, in the electrode composition of this embodiment (the first or second electrode composition described above), if the conductive carbon material or conductive carbon material (A) contains carbon black, the carbon black content 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. One type of carbon black may be used alone, or two or more types may be used in combination. In the electrode composition of this embodiment (the first or second electrode composition described above), if the conductive carbon material or conductive carbon material (A) contains carbon nanotubes, the carbon nanotube content 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. One type of carbon nanotube may be used alone, or two or more types may be used in combination. In the composite slurry formed using the electrode composition of this embodiment, a carbon material other than carbon black and carbon nanotubes may be used in combination as the conductive carbon material or conductive carbon material (A) contained in the composite slurry.

[0106] The content of the dispersant (B) in the composite slurry formed using the second electrode composition described above is preferably 0.01% by mass or more, and preferably 10% by mass or less, based on the mass of the active material. The content of the dispersant in the composite slurry formed using the first electrode composition described above may also be within the same range as described above.

[0107] The asphalt slurry of this embodiment preferably has a solid content concentration of 30% by mass or more, more preferably 40% by mass or more. Furthermore, the solid content concentration is preferably 90% by mass or less. The asphalt slurry may further contain a solvent to adjust the solid content concentration. From the viewpoint of reactivity with the solid electrolyte, a low-polarity solvent is preferred. From the viewpoint of dispersion stability of the electrode composition, a low-polarity solvent contained in the first or second electrode composition, or the same solvent as low-polarity solvent (C), is more preferable.

[0108] 3. Electrodes for All-Solid-State Secondary Batteries An electrode for an all-solid-state secondary battery, which is one embodiment of the present invention, is a coating film (electrode film) of the electrode slurry described above, and may further include a current collector. The electrode film described above can be made by coating the electrode slurry onto a substrate such as a current collector and removing volatile components. An electrode for an all-solid-state secondary battery can be obtained, for example, by coating an asphalt slurry onto a current collector and drying it. The material and shape of the current collector are not particularly limited, and one suitable for various secondary batteries can be appropriately selected. For example, the material of the current collector can be a metal or alloy such as aluminum, copper, nickel, titanium, or stainless steel. Other examples include metals such as iron and chromium or alloys containing these. As for the shape of the current collector, a flat foil is generally used, but it may also be a foil with a roughened surface, a perforated foil, or a mesh. The thickness of the current collector is preferably about 0.5 to 30 μm. In some embodiments, a coating layer may be provided on the surface of the current collector. Examples of coating layers include a carbon layer containing conductive carbon or a binder that improves adhesion to the current collector and conductivity.

[0109] There are no particular restrictions on the method for preparing electrodes using electrode slurry, and known methods can be used. Specifically, examples include die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, or electrostatic coating. For drying after coating, methods such as standing drying, forced-air drying, hot-air drying, infrared heating, and far-infrared heating can be used, but are not limited to these.

[0110] After coating the electrode slurry, rolling may be performed using a flatbed press, calender roll, or the like. Heating may also be performed during pressing.

[0111] 4. One embodiment of an all-solid-state secondary battery relates to an all-solid-state secondary battery. The components of the drive unit of the all-solid-state secondary battery are broadly classified into a positive electrode, a negative electrode, and a separator layer, and the positive electrode and negative electrode are stacked facing each other with the separator layer in between. The positive electrode and / or negative electrode are the electrode films, and the separator layer placed between them is made of a solid electrolyte and may contain a binder. There are no particular limitations on the method of stacking the components of the drive unit in an all-solid-state secondary battery. For example, the positive electrode, negative electrode, and separator layer may be formed and stacked separately, or a separator layer may be formed on the surface of the positive electrode and / or negative electrode and the paired positive or negative electrode may be stacked. Furthermore, a press treatment may be performed during stacking, and adjustments such as increasing the temperature during pressing may be made. Pressing may be performed after all components have been stacked, or pressing may be performed at each stage when the components have been stacked. In addition to the components of the drive unit, the all-solid-state secondary battery may also be equipped with an exterior such as a laminate film or a metal case, connection terminals, etc.

[0112] The all-solid-state secondary battery of this embodiment can be suitably used as a battery for electric vehicles such as electric cars and hybrid vehicles, as well as for portable electronic devices such as personal computers and smartphones.

[0113] The following are examples of the main embodiments of the present invention. However, the present invention is not limited to the following description and includes various embodiments. <1> An electrode composition for an all-solid-state secondary battery comprising a low-polarity solvent which has a relative permittivity of less than 10 and / or a solvent which has a solubility of less than 1 g in 100 g of water at 20°C, and a conductive carbon material, characterized in that it satisfies the following conditions (1) or (2). (1) The settling rate obtained by the following formula (I) is 10% or more and 90% or less Settling rate % = (100 - (B / A) × 100) ... (I) A: Mass of solids in the surface liquid of the electrode composition immediately after shaking B: Mass of solids in the surface liquid of the electrode composition after standing at 25°C for 7 days (2) No. 1. The residual rate determined by the amount of electrode composition remaining in the bottle after placing 10 mL of electrode assembly material in a standard bottle, tilting it 180°, and leaving it for 10 seconds is 90% or more. <2> The electrode composition for all-solid-state secondary batteries according to <1> above, further comprising a dispersant. <3> The electrode composition for all-solid-state secondary batteries according to <1> or <2> above, wherein the solvent having a relative permittivity of less than 10 and / or a low-polarity solvent having a solubility of less than 1 g in 100 g of water at 20°C is at least one selected from the group consisting of ester compounds, aromatic hydrocarbons, and aliphatic hydrocarbons. <4> The electrode composition for all-solid-state secondary batteries according to any one of <1> to <3> above, wherein the conductive carbon material comprises at least one selected from the group consisting of carbon black, fibrous carbon, and graphene-based materials. <5> The electrode composition for all-solid-state secondary batteries comprising a conductive carbon material (A), a dispersant (B), and a low-polarity solvent (C), and characterized by satisfying the following conditions (2) and (3). (2) No. (2) When 10 mL of electrode assembly material is placed in a standard bottle and tilted 180° and left for 10 seconds, the residual rate determined by the amount of electrode composition remaining in the bottle is 90% or more. (3) When the viscosity is measured by sequentially performing the following steps 1 to 4 and changing the shear rate, in step 2 the shear rate is 1 s －１ The viscosity measured under these conditions was 2 (mPa·s), and the shear rate was 1 s in step 4. －１The rate of change A (Equation 1 below) from the viscosity 4 (mPa·s) measured under the following conditions is 10% or more and 210% or less. (Procedure 1) Using a rotary rheometer equipped with a cone plate (diameter 50 mm, angle 0.1°), the shear rate was set to 1 s per 170 seconds under the conditions of 25°C and a plate distance of 0.099 mm. －１ from 1000s －１ Change to this. (Step 2) Next, change the shear rate to 1000 s in 170 seconds. －１ from 1s －１ Change to this. (Step 3) Then, let it stand for 10 minutes. (Step 4) Then, increase the shear rate to 1 s in 170 seconds. －１ from 1000s －１ Change to (Equation 1): Rate of change A (%) = (viscosity 4 - viscosity 2) / viscosity 2 × 100 <6> In the above procedure 2, the shear rate is 1 s －１ The viscosity 2 (mPa·s) measured under the following conditions, and the shear rate 1s in step 5 below. －１ The electrode composition for all-solid-state secondary batteries described in <5> above, wherein the rate of change B (formula 2 below) with respect to the viscosity 5 (mPa·s) measured under the conditions is -4% or more and 4% or less. (Procedure 5) Following the above procedure 4, the shear rate is increased to 1000 s for 170 seconds. －１ from 1s －１To change to (Equation 2): Rate of change B (%) = (viscosity 5 - viscosity 2) / viscosity 2 × 100 <7> An electrode composition for an all-solid-state secondary battery according to <5> or <6> above, wherein the water content is 500 ppm or less. <8> An electrode composition for an all-solid-state secondary battery according to any one of <5> to <7> above, wherein the low-polarity solvent (C) is a solvent with a relative permittivity of less than 10, and / or a solvent with a solubility of less than 1 g in 100 g of water at 20°C. <9> 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 <8> above, an active material, a solid electrolyte, a binder, and a solvent. <10> 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 <9> above. <11> An all-solid-state secondary battery comprising the electrode for an all-solid-state secondary battery according to <10> above. <12> A method for producing an electrode composition for an all-solid-state secondary battery according to any one of <1> to <4> and <8> above, comprising the steps of: dispersing a mixture containing a solvent with a relative permittivity of less than 10 and / or a low-polarity solvent having a solubility of less than 1 g in 100 g of water at 20°C and a conductive carbon material in a medialess disperser to produce a pretreatment solution; and dispersing the pretreatment solution in a media-type disperser and / or a medialess disperser. <13> A method for producing an electrode for an all-solid-state secondary battery, comprising the steps of: preparing an electrode slurry for an all-solid-state secondary battery containing at least the electrode composition for an all-solid-state secondary battery according to any one of <1> to <8> above, an active material, a solid electrolyte, a binder and a solvent; coating the electrode slurry onto a current collector; and removing volatile components from the coated electrode slurry. <14> A method for manufacturing an all-solid-state secondary battery, wherein a positive electrode and a negative electrode are stacked facing each other via a separator layer made of an all-solid-state electrolyte, characterized in that an electrode manufactured by the method for manufacturing an electrode for an all-solid-state secondary battery described in <13> above is used as at least one of the positive electrode and the negative electrode.

[0114] This disclosure relates to the subject matter described in Japanese Patent Application No. 2025-056900, filed on 28 March 2025, and Japanese Patent Application No. 2025-132894, filed on 8 August 2025, all of which are incorporated herein by reference.

[0115] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples unless it exceeds the gist of the invention. Unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "mass percent". 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".

[0116] The following studies were conducted as Example I and Comparative Example I. In the following description, the details of Example I and Comparative Example I will be omitted, and only the example and comparative example numbers will be listed. <Production of Dispersant> [Production of Copolymer 1] Hydrogenated NBR (Nitrile Rubber) 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 were added to a stainless steel polymerization reactor. Polymerization was carried out at 45°C for 20 hours with stirring under a nitrogen atmosphere, and the polymerization was terminated when the conversion rate reached 90%. Unreacted monomers were removed by vacuum stripping to obtain an acrylonitrile-conjugated diene rubber latex with a solid content of approximately 30%. Next, deionized water was added to the latex to adjust the total solid content concentration to 12%, and the mixture was placed in a 1 L autoclave with a stirrer. Nitrogen gas was then flowed through the mixture for 10 minutes to remove dissolved oxygen from the contents. 75 mg of palladium acetate was dissolved in 180 mL of deionized water containing 4 molar amounts of nitric acid relative to the palladium to prepare a catalyst solution, which was then added to the autoclave. After purging the autoclave twice with hydrogen gas, the contents of the autoclave were heated to 50°C under a hydrogen gas pressure of 3 MPa, and the hydrogenation reaction was carried out for 6 hours. After that, the contents were allowed to return to room temperature, the autoclave was subjected to a nitrogen atmosphere, 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 content of these monomer units and structural units was determined from the amount of monomer used.

[0117] <Manufacturing of Electrode Composition for All-Solid-State Secondary Batteries> [Example 1-1] Electrode Composition 1 for All-Solid-State Secondary Batteries 86.0 parts of butyl butyrate as a solvent was stirred in a mixer, and 1.0 part of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) was added as a dispersant and stirred until dissolved. Next, 13.0 parts of acetylene black (Li-250; manufactured by Denka Co., Ltd.) was added little by little while circulating in a colloid mill (Magic Lab; manufactured by Shinmaru Enterprises Co., Ltd.) as a conductive material, and after the entire amount had been added, circulating dispersion was carried out for 1 hour to prepare a pretreatment solution. The prepared pretreatment solution was subjected to circulating dispersion treatment in a bead mill (Dyno Mill MULTILAB; manufactured by Shinmaru Enterprises Co., Ltd.) filled with zirconia beads with a diameter of 1 mmΦ at a peripheral speed of 10 m / s and a residence time of 10 minutes to prepare Electrode Composition 1 for All-Solid-State Secondary Batteries.

[0118] [Examples 1-2 to 1-5] All-solid-state secondary battery electrode compositions 2 to 5 were obtained in the same manner as in Example 1, except that they were modified according to the materials, composition and processing conditions shown in Table 1.

[0119] [Examples 1-6] Electrode composition 6 for all-solid-state secondary batteries 86.0 parts of butyl butyrate was stirred in a mixer as a solvent, and 1.0 part of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) was added as a dispersant and stirred until dissolved. Next, a square-hole high-sear screen was attached to a Silverson (L5M-A, manufactured by SILVERSON) and circulated while 13.0 parts of acetylene black (Li-250: manufactured by Denka Co., Ltd.) was added little by little as a conductive material. After the entire amount had been added, the mixture was circulated and dispersed at a speed of 6000 rpm until the mixture was uniform to obtain a pretreatment solution. The prepared pretreatment solution was subjected to a circulating dispersion treatment at a peripheral speed of 10 m / s and residence time of 10 minutes in a bead mill (Dynomill Multilab: manufactured by Shinmaru Enterprises) filled with zirconia beads with a diameter of 1 mmΦ to produce electrode composition 6 for all-solid-state secondary batteries.

[0120] [Examples 1-7] Electrode composition 7 for all-solid-state secondary batteries 43.0 parts of butyl butyrate were added to a mixer while stirring, and 1.0 part of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) was added as a dispersant and stirred until 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 type; manufactured by Plamix Co., Ltd.), and the mixture was stirred at a rotation speed (revolution) of 60 rpm for 60 minutes to obtain a pre-treated powder. 43.0 parts of butyl butyrate were circulated in a bead mill (Dinomill Multilab; manufactured by Shinmaru Enterprises Co., Ltd.) filled with zirconia beads with a diameter of 1 mmΦ, and the pre-treated powder was added little by little. After the entire amount had been added, a circulating 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.

[0121] [Examples 1-8] Electrode composition 8 for all-solid-state secondary battery 86.0 parts of butyl butyrate was stirred in a mixer as a solvent, and 1.0 part of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) was added as a dispersant and stirred until dissolved. Next, the dispersant solution was circulated in a bead mill (Dinomill Multilab: manufactured by Shinmaru Enterprises) filled with zirconia beads with a diameter of 0.5 mmΦ. Then, 13.0 parts of acetylene black (Li-250: manufactured by Denka Co., Ltd.) was added little by little as a conductive material, and after the entire amount had been added, a circulating dispersion treatment was performed at a peripheral speed of 8 m / s and a residence time of 8 minutes to prepare electrode composition 8 for all-solid-state secondary battery.

[0122] [Examples 1-9] Electrode composition 9 for all-solid-state secondary batteries 96.8 parts of butyl butyrate was stirred in a mixer as a solvent, and 1.0 part of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) was added as a dispersant and stirred until dissolved. Next, 2.2 parts of carbon nanotubes (JENOTUBE10B; manufactured by JEIO) were added little by little while circulating in a colloid mill (Magic Lab; manufactured by Shinmaru Enterprises) as a conductive material, and after the entire amount had been added, the mixture was circulated and dispersed for 1 hour to prepare a pretreatment solution. The prepared pretreatment solution was subjected to a circulating dispersion treatment in a bead mill (Dyno Mill Multilab; manufactured by Shinmaru Enterprises) filled with zirconia beads with a diameter of 1 mmΦ 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.

[0123] [Examples 1-10 to 1-12] All-solid-state secondary battery electrode compositions 10 to 12 were obtained in the same manner as in Example 1-9, except that the materials, composition, and processing conditions were modified according to those shown in Table 1.

[0124] [Comparative Example 1-1] Electrode composition 13 for all-solid-state secondary battery 86.0 parts of butyl butyrate was stirred in a mixer as a solvent, and 1.0 part of polyvinyl butyral (BL-S; manufactured by Sekisui Chemical Co., Ltd.) was added as a dispersant and stirred until dissolved. Next, the dispersant solution was circulated in a bead mill (Dinomill Multilab: manufactured by Shinmaru Enterprises) filled with zirconia beads with a diameter of 2 mmΦ. Then, 13.0 parts of acetylene black (Li-250: manufactured by Denka Co., Ltd.) were added in small amounts, and after the entire amount had been added, a circulating dispersion treatment was performed at a peripheral speed of 14 m / s and a residence time of 20 minutes to prepare the electrode composition 13 for all-solid-state secondary battery.

[0125] [Comparative Example 1-2] All-solid-state secondary battery electrode composition 14 All-solid-state secondary battery electrode composition 14 was obtained in the same manner as in Example 1-1, except that it was modified according to the materials, composition and processing conditions shown in Table 1.

[0126] [Comparative Example 1-3] Electrode Composition 15 for All-Solid-State Secondary Battery Acetylene black (Li-250: manufactured by Denka Co., Ltd.) was processed in five passes in a dry bead mill filled with alumina beads with a diameter of 10 mmΦ to obtain a pre-treated powder. Next, 86.5 parts of butyl butyrate was added as a solvent in a mixer while stirring, and 0.5 parts of polyvinyl butyral (BL-S: manufactured by Sekisui Chemical Co., Ltd.) was added as a dispersant and stirred until dissolved. The dispersant solution was circulated in a bead mill (Dinomill Multilab: manufactured by Shinmaru Enterprises) filled with zirconia beads with a diameter of 1 mmΦ, and 13.5 parts of the pre-treated powder prepared in the dry bead mill was added little by little as a conductive material. After the entire amount had been added, a circulating dispersion treatment was performed at a peripheral speed of 10 m / s and a residence time of 10 minutes to prepare the electrode composition 15 for all-solid-state secondary battery.

[0127] [Comparative Example 1-4] All-solid-state secondary battery electrode composition 16 All-solid-state secondary battery electrode composition 16 was obtained in the same manner as in Example 1-9, except that it was modified according to the materials, composition and processing conditions shown in Table 1.

[0128] [Comparative Example 1-5] All-solid-state secondary battery electrode composition 17 All-solid-state secondary battery electrode composition 17 was obtained in the same manner as in Comparative Example 1-1, except that it was modified according to the materials, composition and processing conditions shown in Table 1.

[0129] <Measurement of Electrode Composition for All-Solid-State Secondary Battery> [Initial Viscosity] The initial viscosity (mPa·s) of the obtained electrode composition for 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.

[0130] [Sedimentation Rate] 1.5 g of the surface liquid (the upper half of the liquid phase) of the electrode composition, which was placed in a 10 mL No. 2 standard bottle (capacity 20 mL), was drawn up using a 2 mL poly pipette and transferred to a Mentholatum can. The solvent was then vaporized in a hot air oven, and the solid content mass (%) of the surface liquid was determined. The sedimentation rate was calculated using the determined solid content mass (%) by the following formula (I). Sedimentation rate % = (100 - (B / A) × 100) ... (I) A: Solid content mass (%) of the surface liquid measured immediately after shaking the standard bottle up and down 30 times or more at a speed of 3 times / second with a swing amplitude of 30 cm. B: Solid content mass (%) of the surface liquid measured after the above sample was left to stand in the air at 25°C for 7 days.

[0131] [Residual Rate by 180° Tilt Test] 10 mL of electrode composition was placed in a No. 2 standard bottle (capacity 20 mL), tilted 180°, and left for 10 seconds. The residual rate was calculated based on the amount of composition remaining in the bottle (mL), and those with a residual rate of 90% or more were classified as "A," and those with a residual rate of less than 90% were classified as "B." The samples used for measuring the residual rate were prepared by shaking the standard bottle containing the sample up and down at a speed of 3 times / second with a swing amplitude of 30 cm at least 30 times, and then letting it stand in the air at 25°C for 7 days.

[0132]

[0133] The abbreviations used in Table 1 are as follows: ・Li-250: Denka Black Li-250 (manufactured by Denka, acetylene black) ・Li-400: Denka Black Li-400 (manufactured by Denka, acetylene black) ・EC200L: Lionite 200L (manufactured by Lion, Ketjen black) ・10B: JENOTUBE 10B (manufactured by JEIO, multilayer CNT) ・6A: JENOTUBE 6A (manufactured by JEIO, multilayer CNT) ・PVB: Polyvinyl butyral BL-S (manufactured by Sekisui Chemical Co., Ltd.) ・Vinyl chloride: Solvine A (manufactured by Nisshin Chemical Co., Ltd.)

[0134] <Preparation of Positive Electrode for All-Solid-State Battery> [Example 2-1] Positive Electrode 1 A positive electrode was prepared using the electrode composition prepared in the example. 8.5 parts of a 10% by mass butyl butyrate solution of styrene-based elastomer resin as a binder, 41 parts of NMC as the electrode active material, 7.5 parts of LPS as the 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 rotation / revolution mixer (Awatori Rentaro, ARE-310, manufactured by Thinky). The positive electrode slurry was coated onto a 20 μm thick aluminum foil, which would serve as the current collector, using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. After that, a heat press was used to perform a pressurized treatment at 120°C to obtain positive electrode 1. The work related to the preparation of the electrode slurry and the electrode was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0135] [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.

[0136] [Example 2-9] Positive electrode 9 In a plastic container, 8.5 parts of a 10% by mass butyl butyrate solution of styrene-based elastomer resin as a binder, 41.5 parts of electrode active material NMC, 8.5 parts of solid electrolyte LPS, 6.8 parts of electrode composition 9, and 35.7 parts of butyl butyrate were weighed out and stirred at 2,000 rpm for 3 minutes using a rotation / revolution mixer (Sinky Awatori Rentaro, ARE-310). The obtained positive electrode slurry was coated onto a 20 μm thick aluminum foil, which would serve as the current collector, using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. After that, a heat press was used to perform a pressurized treatment at 120°C to obtain the positive electrode 9. The work related to the preparation of the electrode slurry and the electrode was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0137] [Example 2-10] Positive electrode 10 A positive electrode 10 was obtained in the same manner as in Example 2-9, except that electrode composition 9 was changed to electrode composition 10.

[0138] [Example 2-11] Positive electrode 11 8.5 parts of a 10% by mass tetralin solution of styrene-based elastomer resin as a binder, 41.5 parts of NMC as the electrode active material, 7.5 parts of LPS as the solid electrolyte, 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 rotation / revolution mixer (Awatori Rentaro, ARE-310, manufactured by Thinky). The obtained positive electrode slurry was coated onto a 20 μm thick aluminum foil, which would serve as the current collector, using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. After that, a heat press was used to perform a pressurized treatment at 120°C to obtain the positive electrode 11. The work related to the preparation of the electrode slurry and the electrode was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0139] [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.

[0140] [Comparative Examples 2-1 to 2-3] Positive electrode electrodes 13 to 15 Positive electrode 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.

[0141] [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 replaced with electrode composition 16.

[0142] [Comparative Example 2-5] Positive electrode 17 A positive electrode 17 was obtained in the same manner as in Example 2-11, except that electrode composition 11 was changed to electrode composition 17.

[0143] <Evaluation of Positive Electrodes for All-Solid-State Batteries> [Electrode Resistivity] Volume resistivity was measured for positive electrodes 1-8, 14, and 15 using the four-probe method with a Rolester GP (manufactured by Nitto Seikou Analytech Co., Ltd.) in accordance with JIS-K7194. For resistance measurement, measuring electrodes were used in which the coating substrate during the manufacture of each electrode was changed from aluminum foil to a PET substrate. The relative value (%) was determined based on the volume resistivity of electrode 13 manufactured in Comparative Example 2-1 and evaluated according to the following criteria: ◎: 50% or less (Excellent) ○: Greater than 50% and 90% or less (Good) ×: Greater than 90% (Poor)

[0144] The volume resistivity of positive electrodes 9-12 and 17 was measured in the same manner as described above. For resistance measurement, measuring electrodes were used in which the coating substrate used during the manufacture of each electrode was changed from aluminum foil to a PET substrate. The relative value (%) was determined based on the volume resistivity of electrode 16 manufactured in Comparative Example 2-4 and evaluated according to the following criteria: ◎: 50% or less (Excellent) ○: Greater than 50% and 90% or less (Good) ×: Greater than 90% (Poor)

[0145] [Cycle Characteristics] (Assembly of Cells for Evaluation of All-Solid-State Secondary Battery Cathodes) Cathode electrodes 1 to 17 were punched out to a diameter of φ10 mm and used as working electrodes. An LPS layer was created on the working electrode by sequentially placing the working electrode and 50 mg of LPS powder into the cylindrical container of the all-solid-state battery evaluation cell and pressurizing it at 50 MPa. On the opposite side of the working electrode, with the LPS layer in between, metallic indium foil and metallic lithium foil were sequentially placed as counter electrodes. Next, the cell was assembled and fixed with bolts, and then tightened using a torque wrench to the specified pressure to obtain the cathode 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 lower.

[0146] (Evaluation) The fabricated cathode evaluation cell was placed in a constant temperature room at 25°C, and a charge / discharge device (manufactured by Hokuto Denko Co., Ltd., S00 (%)) was used.

[0147] For positive electrode evaluation cells 1-8, 14, and 15, relative values ​​(%) were calculated based on the cycle characteristics of 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% (Poor)

[0148] For positive electrode evaluation cells 9-12 and 17, 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% (Poor)

[0149] <Preparation of Negative Electrode Film (Negative Electrode) for All-Solid-State Batteries> [Example 3-1] Negative Electrode 1 A negative electrode was prepared using the electrode composition prepared in the example. 8.5 parts of a 10% by mass butyl butyrate solution of styrene-based elastomer resin as a binder, 36.9 parts of artificial graphite as the electrode active material, 4.1 parts of silicon monoxide SiO, 7.5 parts of 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 rotation / revolution mixer (Awatori Rentaro, ARE-310, manufactured by Thinky). The obtained negative electrode slurry was coated onto a 20 μm thick copper foil, which would serve as the current collector, using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. After that, a heat press was applied at 120°C to obtain negative electrode 1. Furthermore, the preparation of the electrode slurry and the preparation of the electrodes were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0150] [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.

[0151] [Example 3-9] Negative electrode 9 In a plastic container, 8.5 parts of a 10% by mass butyl butyrate solution of styrene-based elastomer resin as a binder, 36.9 parts of artificial graphite as the electrode active material, 4.1 parts of silicon monoxide SiO, 8.5 parts of solid electrolyte LPS, 6.8 parts of electrode composition 9, and 35.7 parts of butyl butyrate were weighed out and stirred at 2,000 rpm for 3 minutes using a rotation / revolution mixer (Awatori Rentaro, ARE-310, manufactured by Thinky). The obtained negative electrode slurry was coated onto a 20 μm thick copper foil, which would serve as the current collector, using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. After that, a heat press was used to perform a pressurized treatment at 120°C to obtain the negative electrode 9. The work related to the preparation of the electrode slurry and the electrode was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0152] [Example 3-10] Negative electrode 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.

[0153] [Example 3-11] Negative electrode 11 8.5 parts of a 10% by mass tetralin solution of styrene-based elastomer resin as a binder, 37.35 parts of artificial graphite as the electrode active material, 4.15 parts of silicon monoxide SiO, 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 rotation / revolution mixer (Sinky Awatori Rentaro, ARE-310). The obtained negative electrode slurry was coated onto a 20 μm thick copper foil, which would serve as the current collector, using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. After that, a heat press was used to perform a pressurized treatment at 120°C to obtain the negative electrode 11. The work related to the preparation of the electrode slurry and the electrode was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0154] [Example 3-12] Negative electrode 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.

[0155] [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.

[0156] [Comparative Example 3-4] Negative electrode 16 A negative electrode 16 was obtained in the same manner as in Example 3-11, except that electrode composition 11 was changed to electrode composition 16.

[0157] [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.

[0158] <Evaluation of Negative Electrode for All-Solid-State Batteries> [Cycle Characteristics] (Assembly of Cell for Evaluation of Negative Electrode for All-Solid-State Secondary Battery) Negative electrodes 1 to 17 were punched out to a diameter of φ10 mm and used as working electrodes. An LPS layer was created on the working electrode by sequentially placing the working electrode and 50 mg of LPS powder into the cylindrical container of the cell for evaluation of the all-solid-state battery negative electrode and pressurizing it at 50 MPa. On the opposite side of the working electrode, with the LPS layer in between, metallic indium foil and metallic lithium foil were sequentially placed as counter electrodes. Next, the cell was assembled and fixed with bolts, and then tightened using a torque wrench to the specified pressure 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 lower.

[0159] (Cycle Characteristic Evaluation) The negative electrode evaluation cell was placed in a constant temperature room at 25°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). Constant current constant voltage charging (cutoff current: 0.02C current) was performed at a charge rate of 0.2C with a charge termination voltage of 0.05V, followed by constant current discharge at a discharge rate of 0.2C with a discharge termination voltage of 1.5V. This operation was repeated 25 times. 1C was defined as the current value required to charge or discharge the theoretical capacity of the negative electrode in one hour. The cycle characteristic can be expressed as the ratio of the 0.2C discharge capacity at the 3rd cycle to the 0.2C discharge capacity at the 25th cycle, as shown below (Equation II). (Equation II): Cycle characteristic = 0.2C discharge capacity at the 25th cycle / 0.2C discharge capacity at the 3rd cycle × 100 (%)

[0160] For negative electrode evaluation cells 1-8, 14, and 15, 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)

[0161] For negative electrode evaluation cells 9-12 and 17, 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)

[0162]

[0163] As shown in Table 2, the example demonstrated superior electrode resistance and battery characteristics (cycle characteristics) compared to the comparative example. It is presumed that the carbon material contained in the electrode composition of the example maintained its structure, allowing for the uniform formation of conductive paths within the electrode, which led to a reduction in electrode resistance and an improvement in cycle characteristics. On the other hand, in the comparative example, it is presumed that the formation of conductive paths within the electrode became uneven due to the collapse of the structure caused by overdispersion or excessive aggregation, leading to an increase in electrode resistance and a deterioration in cycle characteristics. From the above, it has been shown that the electrode composition produced by the manufacturing method of the present invention can exhibit superior battery characteristics.

[0164] The second electrode composition for a solid-state secondary battery of this embodiment was examined in the following Example II and Comparative Example II. In the following description, the descriptions of Example II and Comparative Example II are omitted, and only the example and comparative example numbers are listed.

[0165] <Measurement of Weight-Average Molecular Weight (Mw)> The weight-average molecular weight (Mw) was measured using gel permeation chromatography (GPC) equipped with an RI detector. An HLC-8420GPC (manufactured by Tosoh Corporation) was used as the instrument, with two separation columns connected in series, and "TSK-GEL SUPER HZM-M" used as the packing material for both columns in a double-row configuration. The measurement was performed at an oven temperature of 40°C, using THF solution as the eluent, and a flow rate of 0.35 ml / min. The sample was dissolved in a solvent consisting of 1% by mass of the above eluent, and 20 μl was injected. All molecular weights were calculated on a polystyrene basis.

[0166] <Manufacturing of Electrode Composition for All-Solid-State Secondary Batteries (Electrode Composition)> [Example 1-1] Electrode Composition (1) Under a dry nitrogen atmosphere, 84.0 parts of butyl butyrate and 1.0 part of polyvinyl butyral resin (Eslec BL-S, manufactured by Sekisui Chemical Co., Ltd.) were weighed and mixed and dissolved at 12,000 rpm and a GAP of 450 μm using the MK unit of a colloid mill (magic LAB, manufactured by IKA Corporation). Subsequently, while maintaining the same operating conditions, 15.0 parts of acetylene black (Denka Black Li-250, manufactured by Denka Corporation) were added while dispersing. After the entire amount was added, mixing was carried out until the viscosity at 60 rpm, as measured by a B-type viscometer (VISCOMETER, MODEL: BL, manufactured by TOKI SANGYO), was 2,000 mPa·s or less. The contents were pumped and subjected to a circulating dispersion treatment (80% bead filling, peripheral speed 12 m / s) with a residence time of 1.5 minutes using a bead mill (Star Mill LMZ, manufactured by Ashizawa Finetech Co., Ltd.) filled with 1.0 mm diameter zirconia beads. After transferring the contents to a mayonnaise bottle, molecular sieves were added and the mixture was stirred overnight with a mix rotor to dehydrate it and obtain electrode composition (1).

[0167] [Example 1-2] Electrode composition (2) Under a dry nitrogen atmosphere, 97.0 parts of butyl butyrate and 1.0 part of polyvinyl butyral resin (Eslec BL-S, manufactured by Sekisui Chemical Co., Ltd.) were weighed out, and a square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and the mixture was mixed and dissolved at a speed of 8,000 rpm. Subsequently, while maintaining the same operating conditions, 2.0 parts of JENOTUBE 10B (manufactured by JEIO, multilayer CNT) were added while dispersing and stirring. Batch dispersion was performed in the high-shear mixer until the dispersed particle size was 250 μm or less using a grind gauge with a maximum groove depth of 300 μm. The contents were pumped and subjected to a circulating dispersion treatment (80% bead filling, peripheral speed 12 m / s) with a residence time of 15 minutes using a bead mill (Star Mill LMZ, manufactured by Ashizawa Finetech Co., Ltd.) filled with 1.0 mm diameter zirconia beads. After transferring the contents to a mayonnaise bottle, molecular sieves were added and the mixture was stirred overnight with a mix rotor to dehydrate it and obtain electrode composition (2).

[0168] [Examples 1-3 to 1-5] Electrode compositions (3) to (5) were obtained by the same method as in Example 1-2, except that the compound composition was changed to that shown in Table 3.

[0169] [Examples 1-6] Electrode composition (6) Under a dry nitrogen atmosphere, 97.0 parts of tetralin and 1.5 parts of styrene-ethylene-butylene-styrene block copolymer (Septon 8004, manufactured by Kuraray) were weighed out and mixed and dissolved at a speed of 8,000 rpm in a high-shear mixer (L5M-A, manufactured by SILVERSON) fitted with a square-hole high-shear screen. Subsequently, while maintaining the same operating conditions, 1.5 parts of JENOTUBE 6A (manufactured by JEIO, multilayer CNT) were added while dispersing. Batch dispersion was performed in the high-shear mixer using a grind gauge with a maximum groove depth of 300 μm until the dispersed particle size was 250 μm or less. The contents were pumped and subjected to a circulating dispersion treatment (80% bead filling, peripheral speed 12 m / s) with a residence time of 25 minutes using a bead mill (Star Mill LMZ, manufactured by Ashizawa Finetech Co., Ltd.) filled with 1.0 mm diameter zirconia beads. After transferring the contents to a mayonnaise bottle, molecular sieves were added and the mixture was stirred overnight with a mix rotor to dehydrate it and obtain electrode composition (6).

[0170] [Example 1-7] Electrode composition (7) An electrode composition (9) was obtained in the same manner as in Example 1-6, except that the compound composition was changed to the one shown in Table 3.

[0171] [Examples 1-8] Electrode composition (8) Under a dry nitrogen atmosphere, 97.0 parts of tetralin and 1.0 part of styrene-ethylene-butylene-styrene block copolymer (Septon 8004, manufactured by Kuraray) were weighed out, and a square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and the mixture was mixed and dissolved at a speed of 8,000 rpm. Subsequently, while maintaining the same operating conditions, 2.0 parts of JENOTUBE 10B (manufactured by JEIO, multilayer CNT) were added while dispersing and stirring. Batch dispersion was performed in the high-shear mixer using a grind gauge with a maximum groove depth of 300 μm until the dispersed particle size was 250 μm or less. The contents were pumped and subjected to a circulating dispersion treatment (80% bead filling, peripheral speed 12 m / s) with a residence time of 5 minutes using a bead mill (Star Mill LMZ, manufactured by Ashizawa Fine Tech Co., Ltd.) filled with 1.0 mm diameter zirconia beads. Subsequently, the dispersion liquid was supplied via piping to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine Co., Ltd.) and subjected to a pass-type dispersion treatment. The dispersion treatment was performed using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 40 MPa, and the treatment was performed in 15 passes. After further transfer to a mayonnaise bottle, molecular sieves were added and the mixture was stirred overnight in a mix rotor to dehydrate it and obtain electrode composition (8).

[0172] [Example 1-9] Electrode composition (9) Electrode composition (9) was obtained in the same manner as in Example 1-8, except that the compound composition shown in Table 3 was changed.

[0173] [Example 1-10] Electrode composition (10) JENOTUBE 6A (manufactured by JEIO, multilayer CNT) was placed in a ceramic crucible and placed in a firing furnace. The furnace was evacuated to less than 1 Torr and then heated to 1000°C. 0.3 L / min of carbon tetrachloride gas was introduced until the pressure inside the furnace was 90 Torr, and then the temperature inside the furnace was raised to 1600°C and held for 1 hour. Subsequently, the heater was stopped and the pressure was slowly reduced to 1 Torr, and then allowed to cool to room temperature. The pressure inside the furnace was released and the highly purified carbon nanotubes (JENOTUBE 6A-P) were recovered from the crucible. Electrode composition (10) was obtained in the same manner as in Example 1-8, except that the carbon material was changed to JENOTUBE 6A-P.

[0174] [Comparative Example 1-1] Electrode Composition (11) Under a dry nitrogen atmosphere, 82.5 parts of butyl butyrate, 1.5 parts of polyvinyl butyral resin (Eslec BL-S, manufactured by Sekisui Chemical Co., Ltd.), and 1.0 part of 2-amino-2-ethyl-1,3-propanediol were weighed and mixed and dissolved at 12,000 rpm and a GAP of 450 μm using the MK unit of magic LAB (manufactured by IKA Corporation). Subsequently, while maintaining the same operating conditions, 15.0 parts of acetylene black (Denka Black Li-250, manufactured by Denka Corporation) were added while dispersing. After the entire amount was added, stirring was carried out until the viscosity at 60 rpm, as measured by a B-type viscometer (VISCOMETER, MODEL: BL, manufactured by TOKI SANGYO), was 2,000 mPa·s or less. The contents were pumped and subjected to a circulating dispersion treatment with a residence time of 0.5 minutes (bead filling amount 80%, peripheral speed 12 m / s) using a bead mill (Star Mill LMZ, manufactured by Ashizawa Finetech Co., Ltd.) filled with 1.0 mmφ zirconia beads. After transferring the contents to a mayonnaise bottle, molecular sieves were added and the mixture was stirred overnight with a mix rotor to dehydrate it and obtain the electrode composition (11).

[0175] [Comparative Examples 1-2 to 1-5] Electrode compositions (12) to (15) Electrode compositions (12) to (15) were obtained in the same manner as in Example 1-1, except that the compound composition was changed to that shown in Table 3.

[0176] [Comparative Example 1-6] Electrode composition (16) An electrode composition (16) was obtained in the same manner as in Example 1-2, except that the compound composition was changed to the one shown in Table 3.

[0177] [Comparative Example 1-7] Electrode composition (17) An electrode composition (17) was obtained in the same manner as in Example 1-1, except that the residence time in the bead mill was changed to 0.5 minutes.

[0178] <Measurement and Evaluation of Electrode Composition> The obtained electrode composition was subjected to the following measurements and evaluations. The results are shown in Table 3.

[0179] [Moisture Content Measurement] The moisture content of the electrode composition was measured using a Karl Fischer moisture meter (MKC-710 model: manufactured by Kyoto Electronics Manufacturing Co., Ltd.) under a nitrogen gas flow of 200 mL / min at 150°C. The value measured by the Karl Fischer method was calculated as the content relative to the total mass of the electrode composition.

[0180] [Measurement of change rates A and B] For the obtained electrode composition, the viscosity was measured by sequentially performing the above-described procedures 1 to 5 using an Anton Paar "CP50-1" (diameter 50 mm, angle 0.1°) as a cone plate and an Anton Paar "MCR302" as a rotary rheometer, while varying the shear rate. Shear rate 1s in procedure 2 －１ Viscosity 2 (mPa·s), shear rate 1s in step 4. －１ Viscosity 4 (mPa·s), shear rate 1s in step 5. －１ Using a viscosity of 5 (mPa·s), the rates of change A and B were calculated using the aforementioned (Equation 1) and (Equation 2).

[0181] [Sedimentation Evaluation] The solid content concentration of the obtained electrode composition was measured and recorded as the initial solid content concentration. Next, 120 mL of the electrode composition was placed in a 140 mL mayonnaise jar and stored at 25°C for 7 days. After storage, the electrode composition was sampled from the mayonnaise jar at approximately 1 cm from the liquid surface, and the solid content concentration was measured and recorded as the solid content concentration over time. Using the obtained value, the sedimentation change rate was calculated using the following formula (Equation 3). (Equation 3): Sedimentation change rate (%) = (Solid content concentration over time - Initial solid content concentration) / Initial solid content concentration × 100 Note that the solid content concentration can be determined from the weight of the residual after weighing 1 g of the electrode composition into an aluminum dish and drying it in a 140°C oven for 1 hour.

[0182] [Residual Rate by 180° Tilt Test] 10 mL of electrode composition was placed in a No. 2 standard bottle (capacity 20 mL), tilted 180°, and left for 10 seconds. The residual rate was calculated based on the amount of composition remaining in the bottle (mL), and those with a residual rate of 90% or more were classified as "A," and those with a residual rate of less than 90% were classified as "B." The samples used for measuring the residual rate were prepared by shaking the standard bottle containing the sample up and down at a speed of 3 times / second with a swing amplitude of 30 cm at least 30 times, and then letting it stand in the air at 25°C for 7 days.

[0183] The abbreviations in Table 3 below are as follows: <Conductive carbon materials> ・Li-250: Acetylene black (Denka Black Li-250 manufactured by Denka Co., Ltd., average primary particle size 37 nm, specific surface area 58 m²) ２ / g, bulk density 0.08 g / cm³ ３ ) ・10B: Multilayer CNT (JENOTUBE 10B manufactured by JEIO, average outer diameter 10 nm, average fiber length 100-200 μm, bundle shape, specific surface area 230 m²) ２ / g, carbon purity 95% or higher, bulk density 0.05 g / cm³ ３ ) 6A: Multilayer CNT (JENOTUBE 6A manufactured by JEIO, average outer diameter 6 nm, specific surface area 690 m ２ / g, carbon purity 97% or higher, bulk density 0.042 g / cm³ ３ ) ・6A-P: Multilayer CNT (Pre-heat treated product of JENOTUBE 6A manufactured by JEIO, average outer diameter 8 nm, specific surface area 450 m²) ２ / g, carbon purity 99% or higher, bulk density 0.07 g / cm³ ３ )

[0184] <Dispersants> ・Eslec BL-S: Polyvinyl butyral resin (Eslec BL-S manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 16%, weight-average molecular weight: 23,000, viscosity in 10% ethanol solution: 24 mP·s) ・Eslec BM-SZ: Polyvinyl butyral resin (Eslec BM-SZ manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 16%, weight-average molecular weight: 55,000, viscosity in 10% ethanol solution: 140 mP·s) ・Eslec BH-S: Polyvinyl butyral resin (Eslec BH-S manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 16%, weight-average molecular weight: 66,000, viscosity in 10% ethanol solution: 205 mP·s)・S-Lec BL-10: Polyvinyl butyral resin (S-Lec BL-10 manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 19%, weight-average molecular weight: 15,000, viscosity of 10% ethanol solution: 10 mP·s) ・S-Lec BH-A: Polyvinyl butyral resin (S-Lec BH-A manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 18%, weight-average molecular weight: 115,000, viscosity of 10% ethanol solution: 352 mP·s) ・Septon 8004: Styrene-ethylene-butylene-styrene block copolymer (manufactured by Kuraray Co., Ltd., weight-average molecular weight 110,000) ・Septon 8006: Styrene-ethylene-butylene-styrene block copolymer (manufactured by Kuraray Co., Ltd., weight-average molecular weight 280,000) ・Solvine C: Vinyl chloride-vinyl acetate copolymer (manufactured by Nisshin Chemical Industry Co., Ltd.) • PVP: Polyvinylpyrrolidone (Polyvinylpyrrolidone K-30, manufactured by Nippon Shokubai Co., Ltd., weight-average molecular weight: 40,000) • Polyethylene: Sigma-Aldrich, product code 427772, weight-average molecular weight: 4,000

[0185] <Solvents> ・Butyl butyrate (dielectric constant: 4.1) ・Tetralin: 1,2,3,4-tetrahydronaphthalene (dielectric constant: 2.8) ・NMP: N-methylpyrrolidone (dielectric constant: 32)

[0186] <Additives> ・AEPD: 2-amino-2-ethyl-1,3-propanediol

[0187]

[0188]

[0189] <Preparation of composite slurry> A composite slurry was prepared using the obtained electrode composition. [Example 2-1] Composite slurry (1) 5.3 parts of butyl butyrate solution with a solid content of 15% by mass of styrene-butadiene rubber (styrene content: 25% by mass, vinyl content: 11% by mass) as a binder, and electrode active material LiNi ８／１０ Mn １／１０ Co １／１０ O ２ (NMC) 64.8 parts, solid electrolyte Li ２ S-P ２ S ５ 11.8 parts of (LPS), 16.0 parts of the obtained electrode composition (1), and 2.0 parts of butyl butyrate were weighed out and stirred at 2,000 rpm for 2 minutes using a rotation / revolution mixer (Sinky Awatori Rentaro, ARE-310) to obtain a composite slurry (1). The work related to the preparation of the composite slurry was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0190] [Examples 2-2 to 2-10, Comparative Examples 2-1 to 2-7] Mixture Slurries (2) to (17) Mixture slurries were obtained in the same manner as in Example 2-1, except that the compound composition was changed as shown in Table 4. The solvent used to dilute the styrene-butadiene rubber (styrene content: 25% by mass, vinyl content: 11% by mass) to a solid content concentration of 15% by mass was the solvent listed in Table 4.

[0191] <Evaluation of Asphalt Slurry> The following evaluation was performed using the obtained asphalt slurry. The results are shown in Table 4.

[0192] [Evaluation of Conductivity] The obtained mixture slurry was applied to a 20 μm thick polyethylene terephthalate (PET) film using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. The coating amount was 20 mg / cm² per unit area. ２The material was adjusted to achieve the desired result. Subsequently, a heat press was used to apply pressure at 120°C to obtain the electrode film. The work related to the preparation of the electrode film was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower. The volume resistivity of the obtained electrode film was measured using a four-probe method at one point with a Rolester GP (manufactured by Nitto Seikou Analytech Co., Ltd.) in accordance with JIS-K7194. The following criteria were used for evaluation: <Evaluation Criteria> A: Volume resistivity less than 5 Ω·cm (Good) B: Volume resistivity 5 Ω·cm or more and less than 15 Ω·cm (Usable) C: Volume resistivity 15 Ω·cm or more (Unusable)

[0193] [Cycle Characteristics Evaluation] The obtained asphalt slurry was applied to a 20 μm thick aluminum foil, which would serve as the current collector, using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes. The coating amount was 20 mg / cm² per unit area. ２ The electrodes were adjusted accordingly. Then, a heat press was used to apply pressure at 120°C to obtain the positive electrode. The work related to the preparation of the electrode film was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower. Next, the prepared 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 sequence into the cylindrical container of the all-solid-state battery evaluation cell, and an LPS layer was created on the working electrode by applying pressure at 50 MPa. On the opposite side of the working electrode, with the LPS layer in between, metallic indium foil and metallic lithium foil were placed in sequence as the counter electrode. Next, the cell was assembled and fixed with bolts, and then tightened to the specified pressure using a torque wrench to obtain the positive electrode evaluation cell. The work related to 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 lower.

[0194] The obtained positive electrode evaluation cell was placed in a constant temperature room at 25°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). Constant current constant voltage charging (cutoff current: 0.02C current) was performed at a charge rate of 0.2C with a charge termination voltage of 4.2V, followed by constant current discharge at a discharge rate of 0.2C with a discharge termination voltage of 2.5V. This operation was repeated 50 times. 1C was defined as the current value required to charge or discharge the theoretical capacity of the positive electrode in one hour. The cycle characteristics were calculated as the ratio of the 0.2C discharge capacity at the 3rd cycle to the 0.2C discharge capacity at the 50th cycle using the following formula (Equation 4), and evaluated according to the following criteria. (Formula 4): Cycle performance (%) = 0.2C discharge capacity at 50th cycle / 0.2C discharge capacity at 3rd cycle × 100 <Evaluation criteria> A: Cycle performance of 90% or more (good) B: Cycle performance of 80% or more and less than 90% (usable) C: Cycle performance of less than 80% (unusable)

[0195]

[0196] As can be seen from Tables 3 and 4, the electrode compositions of this embodiment (Examples 1-1 to 1-10) exhibited excellent sedimentation suppression due to their moderate viscosity. Furthermore, the electrode films formed from the composite slurry using these electrode compositions exhibited particularly excellent cycle characteristics. In the examples, when the properties of the carbon material raw materials, dispersion conditions, change rate A, and moisture content were within a suitable range, there was a tendency for excellent conductivity or cycle characteristics. On the other hand, in Comparative Examples 2-1 to 2-7, which used the electrode compositions of Comparative Examples 1-1 to 1-7, where the residual rate was outside the predetermined range, at least one of the conductivity and cycle characteristics was inferior to that of the above examples. In particular, in Comparative Examples 2-1 to 2-6, which used the electrode compositions of Comparative Examples 1-1 to 1-6, where the residual rate was outside the predetermined range and the change rate A was also outside the predetermined range, the cycle characteristics deteriorated. Furthermore, neither sedimentation suppression nor conductivity met the required physical properties. In Comparative Example 2-1, which used the electrode composition of Comparative Example 1-1 containing AEPD, it is thought that electrolyte degradation also occurred.

Claims

1. An electrode composition for an all-solid-state secondary battery comprising a low-polarity solvent which has a relative permittivity of less than 10 and / or a solvent which has a solubility of less than 1 g in 100 g of water at 20°C and a conductive carbon material, characterized in that it satisfies the following conditions (1) or (2): (1) The settling rate determined by the following formula (I) is 10% or more and 90% or less Settling rate % = (100 - (B / A) × 100) ... (I) A: Mass of solids in the surface liquid of the electrode composition immediately after shaking B: Mass of solids in the surface liquid of the electrode composition after standing at 25°C for 7 days (2) The residual rate determined by the amount of electrode composition remaining in a No. 2 standard bottle after placing 10 mL of the electrode composition in the bottle and leaving it for 10 seconds after tilting it 180° 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 electrode composition for an all-solid-state secondary battery according to claim 1 or 2, wherein the low-polarity solvent, which has a relative permittivity of less than 10 and / or a solubility of less than 1 g in 100 g of water at 20°C, comprises at least one selected from the group consisting of ester compounds, aromatic hydrocarbons and aliphatic hydrocarbons.

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

5. An electrode composition for an all-solid-state secondary battery, comprising a conductive carbon material (A), a dispersant (B), and a low-polarity solvent (C), characterized in that it satisfies the following conditions (2) and (3). (2) The residual rate determined by the amount of electrode composition remaining in a No. 2 standard bottle after placing 10 mL of the electrode composition in the bottle and leaving it for 10 seconds after tilting it 180° is 90% or more. (3) When the viscosity is measured by sequentially performing the following steps 1 to 4 and changing the shear rate, in step 2 the shear rate is 1 s －１ The viscosity measured under these conditions was 2 (mPa·s), and the shear rate was 1 s in step 4. －１ The rate of change A (Equation 1 below) from the viscosity 4 (mPa·s) measured under the following conditions is 10% or more and 210% or less. (Procedure 1) Using a rotary rheometer equipped with a cone plate (diameter 50 mm, angle 0.1°), the shear rate was set to 1 s per 170 seconds under the conditions of 25°C and a plate distance of 0.099 mm. －１ From 1000s －１ Change to this. (Step 2) Next, change the shear rate to 1000 s in 170 seconds. －１ from 1s －１ Change to this. (Step 3) Then, let it stand for 10 minutes. (Step 4) Then, increase the shear rate to 1 s in 170 seconds. －１ From 1000s －１ It is changed to this. (Formula 1): Rate of change A (%) = (viscosity 4 - viscosity 2) / viscosity 2 × 100 6. In the above step 2, viscosity 2 (mPa·s) measured at a shear rate of 1 s －１ and viscosity 5 (mPa·s) measured at a shear rate of 1 s －１ in the following step 5, the rate of change B (the following mathematical formula 2) is -4% or more and 4% or less, the electrode composition for an all-solid-state secondary battery according to claim 5. (Step 5) After the above step 4, the shear rate is changed from 1000 s －１ to 1 s －１ over 170 seconds. (Mathematical formula 2): Rate of change B (%) = (viscosity 5 - viscosity 2) / viscosity 2 × 100 7. The electrode composition for all-solid-state secondary batteries according to claim 5 or 6, wherein the moisture content is 500 ppm or less.

8. The electrode composition for an all-solid-state secondary battery according to any one of claims 5 to 7, wherein the low-polarity solvent (C) is a solvent with a relative permittivity of less than 10 and / or a solvent with a solubility of less than 1 g in 100 g of water at 20°C.

9. An electrode slurry for an all-solid-state secondary battery comprising at least the electrode composition for an all-solid-state secondary battery, an active material, a solid electrolyte, a binder, and a solvent according to any one of claims 1 to 8.

10. An electrode for an all-solid-state secondary battery, comprising a coating film of the electrode slurry for an all-solid-state secondary battery described in claim 9.

11. An all-solid-state secondary battery comprising an electrode for an all-solid-state secondary battery as described in claim 10.

12. A method for producing an electrode composition for an all-solid-state secondary battery according to any one of claims 1 to 4 and 8, comprising the steps of: preparing a pretreatment solution by dispersing a mixture containing a solvent with a relative permittivity of less than 10 and / or a low-polarity solvent having a solubility of less than 1 g in 100 g of water at 20°C and a conductive carbon material in a medialess disperser; and dispersing the pretreatment solution in a media-type disperser and / or a medialess disperser.

13. A method for manufacturing an electrode for an all-solid-state secondary battery, comprising the steps of: preparing an electrode slurry for an all-solid-state secondary battery containing at least an electrode composition for an all-solid-state secondary battery, an active material, a solid electrolyte, a binder, and a solvent according to any one of claims 1 to 8; coating the electrode slurry onto a current collector; and removing volatile components from the coated electrode slurry.

14. A method for manufacturing an all-solid-state secondary battery, wherein a positive electrode and a negative electrode are stacked facing each other via a separator layer made of an all-solid-state electrolyte, characterized in that an electrode manufactured by the method for manufacturing an electrode for an all-solid-state secondary battery described in claim 13 is used as at least one of the positive electrode and the negative electrode.

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