Carbon material dispersed liquid, electrode composition, electrode, and all-solid-state battery

Abstract

Provided is a carbon material dispersed liquid which contains a carbon material (A), a dispersant (B), and a low-polarity solvent (C). The carbon material (A) contains a carbon material (a) that satisfies the following requirements (i) and (ii): (i) the bulk density is 0.02-0.2 g / cm3; and (ii) the specific surface area is 50 m2 / g or more. The dispersant (B) contains a polyvinyl butyral resin (b).

Description

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

[0001] This disclosure relates to carbon material dispersions, electrode compositions, electrodes, and all-solid-state batteries.

[0002] In recent years, with the spread of electric vehicles and the miniaturization, weight reduction, and performance improvement of portable devices, there has been a growing demand for secondary batteries with high energy density, as well as higher capacity. In particular, lithium-ion secondary batteries are experiencing increased demand in a wide range of fields, including portable terminals and electric vehicles. Against this backdrop, all-solid-state batteries, which are formed using solid electrolytes and are expected to offer higher capacity per unit volume and improved safety, are being investigated. In particular, bulk-type all-solid-state batteries, which form electrodes from powder materials, are attracting attention from the perspective of increasing capacity, and technologies for electrode fabrication using wet processes with sulfide-based solid electrolytes, for example, are being investigated. Fundamentally, in order to bring out the performance of an all-solid-state battery, it is important to form a sufficient conductive network within the electrodes. For this reason, in addition to the solid electrolyte that is responsible for ion conduction, carbon materials are necessary as conductive additives to impart electronic conductivity. That is, in order to form an excellent conductive network in a wet process, it is necessary to create a dispersion in which carbon materials, which are inherently prone to aggregation, are sufficiently dispersed.

[0003] Regarding carbon material dispersions for forming electrodes using such wet processes, for example, Patent Document 1 describes an electrode slurry containing a sulfide-based solid electrolyte material and a specific polar solvent. Patent Document 2 describes a method for producing a positive electrode slurry by dispersing a carbon material in a low-polarity solvent containing a binder such as styrene-butadiene rubber (SBR), and then sequentially dispersing a sulfide-based solid electrolyte and a positive electrode active material. Patent Document 3 describes obtaining a carbon material dispersion by dispersing a carbon material and a dispersant containing polyvinyl butyral in an ester-based dispersion medium. Patent Document 4 describes a dispersion containing a conductive material containing bundled carbon nanotubes, partially hydrogenated nitrile butadiene rubber (H-NBR) as a dispersant, and N-methylpyrrolidone (NMP) as a dispersion medium.

[0004] Japanese Patent Publication No. 2012-212652, Japanese Patent Publication No. 2020-145034, Japanese Patent Publication No. 2022-185480, International Publication No. 2017 / 099358

[0005] However, the electrode slurry described in Patent Document 1 has the problem that the highly reactive sulfide-based solid electrolyte is altered by polar solvents, causing the sulfide-based solid electrolyte to deteriorate. On the other hand, using a low-polarity solvent suppresses the deterioration of the sulfide-based solid electrolyte, but it becomes difficult to disperse the carbon material, resulting in a trade-off of reduced dispersibility and storage stability. Furthermore, the internal resistance of the electrode increases with the decrease in dispersibility and storage stability. The positive electrode slurry described in Patent Document 2 has the problem that the dispersibility of the carbon material is insufficient when using a binder with a thickening effect, resulting in reduced battery output characteristics. The dispersion described in Patent Document 3 uses a carbon material with a high bulk density, so the formation of a conductive network of carbon is insufficient, resulting in high internal resistance of the electrode. The dispersion described in Patent Document 4 has high solid-like physical properties, i.e., strong thixotropic properties, but it uses a highly polar solvent and cannot be applied to the dispersion of conductive materials in a low-polarity solvent.

[0006] As described above, there is room for improvement in conventional carbon material dispersions for forming electrodes in a wet process. Therefore, in view of the above circumstances, one embodiment of the present invention provides a carbon material dispersion that suppresses the degradation of sulfide-based solid electrolytes and exhibits low internal resistance and excellent electrode resistance when electrodes are formed. Another embodiment of the present invention provides a carbon material dispersion containing a low-polarity solvent that suppresses the sedimentation of carbon material over time and exhibits high conductivity and excellent cycle characteristics when electrodes are formed. Yet another embodiment of the present invention provides an electrode composition, an electrode, and an all-solid-state battery with excellent electrode resistance, using the carbon material dispersion of the above embodiment.

[0007] As a result of diligent research to solve the above problems, we have found that the above problems can be solved by the embodiments exemplified below, and have completed the present invention.

[0008] One embodiment of the present invention is a carbon material dispersion containing a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein the carbon material (A) comprises a carbon material (a) satisfying the following (i) and (ii), (i) having a bulk density of 0.02 to 0.2 g / cm ３ (ii) having a specific surface area of 50 m ２ / g or more, and the dispersant (B) comprises a polyvinyl butyral resin (b). The present invention relates to the carbon material dispersion.

[0009] Another embodiment of the present invention is a carbon material dispersion containing a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein when viscosity is measured by sequentially performing the following steps 1 to 4 while changing the shear rate, the viscosity 2 (mPa·s) measured under the condition of shear rate 1 s －１ in step 2 and the viscosity 4 (mPa·s) measured under the condition of shear rate 1 s －１ in step 4 have a change rate A (Formula 1 below) of 10% or more and 210% or less. The present invention relates to the carbon material dispersion. (Step 1) Using a rotational rheometer equipped with a cone plate (diameter 50 mm, angle 0.1°), under the conditions of 25°C and a distance between plates of 0.099 mm, change the shear rate from 1 s －１ to 1000 s －１ over 170 seconds. (Step 2) Then, change the shear rate from 1000 s －１ to 1 s －１ over 170 seconds. (Step 3) Then, stop and leave still for 10 minutes. (Step 4) Then, change the shear rate from 1 s －１ to 1000 s －１ over 170 seconds. (Formula 1) Change rate A (%) = (viscosity 4 - viscosity 2) / viscosity 2 × 100

[0010] Another embodiment of the present invention relates to an electrode composition comprising the carbon material dispersion of the above embodiment, an active material, a solid electrolyte, and a binder.

[0011] Another embodiment of the present invention relates to an electrode comprising an electrode film formed from the carbon material dispersion of the above embodiment, or an electrode composition comprising the carbon material dispersion of the above embodiment, an active material, a solid electrolyte, and a binder.

[0012] Another embodiment of the present invention relates to a method for manufacturing an electrode comprising an electrode film formed from a carbon material dispersion, comprising the steps of: preparing the carbon material dispersion of the above embodiment, or an electrode composition comprising the carbon material dispersion of the above embodiment, an active material, a solid electrolyte, and a binder; coating the carbon material dispersion or the electrode composition onto a current collector; and drying the coated carbon material dispersion or electrode composition.

[0013] Another embodiment of the present invention relates to a method for manufacturing an all-solid-state battery in which a positive electrode and a negative electrode are stacked facing each other via a separator layer made of a solid electrolyte, wherein the electrodes of the above embodiment are used as at least one of the positive electrode and the negative electrode.

[0014] According to one embodiment of the present invention, it is possible to provide a carbon material dispersion that suppresses the degradation of a sulfide-based solid electrolyte and exhibits low internal resistance and excellent electrode resistance when electrodes are formed. According to another embodiment of the present invention, it is possible to provide a carbon material dispersion containing a low-polarity solvent in which sedimentation of the carbon material over time is suppressed and which exhibits high conductivity and excellent cycle characteristics when electrodes are formed. According to yet another embodiment of the present invention, an electrode composition, an electrode, and an all-solid-state battery with excellent electrode resistance can be provided using the carbon material dispersion of the above embodiment.

[0015] Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and various modifications are possible without departing from the spirit of the invention. 1. Carbon material dispersion One embodiment of the present invention relates to a carbon material dispersion comprising a carbon material (A), a dispersant (B), and a low-polarity solvent (C). <1-1> First carbon material dispersion The first carbon material dispersion of this embodiment comprises a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein the carbon material (A) comprises a carbon material (a) satisfying the following (i) and (ii), and the dispersant (B) comprises a polyvinyl butyral resin (b). (i) Bulk density is 0.02 to 0.2 g / cm³ ３ (ii) Specific surface area of ​​50 m ２ / g or more

[0016] The first carbon material dispersion described above, by combining a carbon material (a) having a predetermined bulk density and specific surface area with a polyvinyl butyral resin (b) as a dispersant, can achieve a dispersion state in which the structural structure is maintained even in a low-polarity solvent. As a result, the internal resistance of the electrode is reduced, and due to the excellent electrode resistance, high conductivity is exhibited. Furthermore, it exhibits excellent dispersibility and storage stability even in a low-polarity solvent.

[0017] The first carbon material dispersion described above (hereinafter also referred to as the carbon material dispersion of this embodiment or simply the carbon material dispersion) will be explained in detail below. <Carbon Material (A)> [Carbon Material (a)] The carbon material (A) can be any material that functions as a conductive material in the electrode, and known carbon materials can be used. For example, one or more selected from the group consisting of carbon black, fibrous carbon such as carbon nanotubes, graphene, graphite, and fullerene can be used. On the other hand, in the carbon material dispersion of this embodiment, among the above carbon materials, (i) a bulk density of 0.02 to 0.2 g / cm³ is also used. ３ , and (ii) a specific surface area of ​​50 m ２ The invention is characterized by containing a carbon material (a) that satisfies both of the requirements of / g or more. The above bulk density and specific surface area refer to the bulk density and specific surface area of ​​the carbon material raw material used in the production of the carbon material dispersion.

[0018] The larger the specific surface area of ​​a carbon material, the smaller the primary particle size of the carbon material. A specific surface area of ​​50 m² is... ２ When the density is greater than or equal to 1 / g, the number of contact points between particles increases, which can lower the electrode resistance. Therefore, the specific surface area of ​​carbon material (a) is 50 m². ２ It is preferable that the amount is 1 / g or more. The specific surface area is preferably 58 m² from the viewpoint of electrode resistance, coating properties, and electrode adhesion. ２ / g or more, 60m ２ / g or more, 100m ２ / g or more, 200m ２ It may be 1,210 m or more. Preferably 1,210 m ２ It is less than / g and 1,200m ２ / g or less, 1,000m ２It may be less than or equal to / g. The specific surface area is, for example, 58 to 1,210 m². ２ / g, 60-1,200m ２ / g, 200-1,000m ２ / g, 58-1,000m ２ / g is also acceptable.

[0019] When the carbon material (a) is carbon black, the specific surface area is preferably 50 m². ２ / g or more, more preferably 58m ２ It is 150 m or more. ２ / g or less, more preferably 133m ２ It is less than or equal to / g. The specific surface area is, for example, 50 to 150 m². ２ / g, 50-133m ２ / g, 58-150m ２ / g, 58-133m ２ It may be / g. If the carbon material (a) is fibrous carbon, the specific surface area is preferably 200 m². ２ / g or more, more preferably 230m ２ It is 1,200 m or more. ２ / g or less, more preferably 690m ２ It is less than / g. The specific surface area is, for example, 200 to 1,200 m². ２ / g, 200-690m ２ / g, 230-1,200m ２ / g, 230-690m ２ It may also be / g. The specific surface area in this specification is the BET specific surface area obtained by the nitrogen gas adsorption method, which can be calculated by measuring the adsorption isotherm by adsorbing and desorbing nitrogen as an adsorbent molecule onto the adsorbent, and then analyzing the measured data. The specific surface area is determined by the BET method.

[0020] Bulk density is extremely important in terms of utilizing the unique structure of carbon materials in a carbon material dispersion. Even with carbon materials of the same specific surface area, the higher the bulk density, the more the carbon materials are compressed and aggregated, making it difficult to sufficiently dissolve the carbon materials in a low-polarity solvent. As a result, electrode resistance tends to increase. Conversely, if the bulk density is too low, the interaction between carbon materials is insufficient, and the carbon materials cannot sufficiently form a structure in a low-polarity solvent. As a result, electrode resistance tends to increase. On the other hand, in the carbon material dispersion of this embodiment, the bulk density is 0.02 to 0.2 g / cm³. ３ By using carbon material (a) within this range, the cohesive force of the carbon material and the size of the aggregates can be appropriately controlled. This makes it possible to optimally disperse carbon material (a) in a low-polarity solvent without breaking down its structure, thereby reducing electrode resistance and maintaining the desired conductivity.

[0021] From the viewpoint of handling, the bulk density is preferably 0.03 g / cm³. ３ The above is 0.04 g / cm³. ３ The above is also acceptable. From the viewpoint of ease of disintegration of aggregates, the bulk density is preferably 0.12 g / cm³. ３ More preferably, 0.1 g / cm³ ３ More preferably, 0.05 g / cm³ ３ The following bulk densities may be used: For example, 0.02 to 0.12 g / cm³. ３ ,0.02~0.1g / cm ３ ,0.02~0.05g / cm ３ ,0.03~0.12g / cm ３ ,0.03~0.1g / cm ３ ,0.03~0.05g / cm ３ ,0.04~0.12g / cm ３ ,0.04~0.1g / cm ３ That's fine.

[0022] If the carbon material (a) is carbon black, the bulk density is preferably 0.03 g / cm³. ３ That is all. More preferably 0.04 g / cm³ ３That is all. Preferably, 0.12 g / cm³ ３ The following is the value: 0.08 g / cm³ ３ The following may also apply: The above bulk density is, for example, 0.03 to 0.12 g / cm³. ３ ,0.04~0.12g / cm ３ ,0.03~0.08g / cm ３ ,0.04~0.08g / cm ３ This may also be the case. If the carbon material (a) is fibrous carbon, the bulk density is preferably 0.03 g / cm³. ３ More preferably, 0.04 g / cm³ ３ That is all. Preferably, 0.1 g / cm³ ３ More preferably, 0.09 g / cm³ ３ More preferably, the following is 0.05 g / cm³. ３ The following applies: For example, 0.03 to 0.1 g / cm³. ３ ,0.04~0.1g / cm ３ ,0.03~0.09g / cm ３ This may also be the case. The bulk density can be determined by placing the carbon material powder in a 30 mL stainless steel cylindrical container by free-falling it, leveling off the portion that has risen on the upper surface of the container, determining the mass of the carbon material powder, and dividing it by the volume of the container. The carbon material powder used is prepared by crushing aggregates formed during storage and passing it through a 0.5 mm sieve.

[0023] Examples of the carbon material (a) mentioned above include carbon black, fibrous carbon, graphene, graphite, and fullerene. These 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 carbon material (a) includes at least one selected from the group consisting of carbon black and fibrous carbon. From the viewpoint of availability and cost, it is preferable to include carbon black. From the viewpoint of cycle characteristics, fibrous carbon is preferably used.

[0024] The following describes materials that can be suitably used as the carbon material (a) described above. However, this does not mean that all of the materials described below meet the requirements for bulk density and specific surface area specified for the carbon material (a) above, but rather that you should select a material that meets the above requirements from the materials provided as examples. (Carbon Black) As carbon black, various types 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, especially 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, especially acetylene black made from acetylene gas. In addition, conventionally treated oxidized carbon black and hollow carbon can also be used.

[0025] Oxidation of carbon involves directly introducing (covalently bonding) oxygen-containing polar functional groups such as phenolic groups, quinone groups, carboxyl groups, and carbonyl groups to the carbon surface by treating the carbon at high temperatures in air or secondarily with nitric acid, nitrogen dioxide, ozone, etc. 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.

[0026] The smaller the primary particle diameter of carbon black, the greater the number of particles per unit mass, and the greater the number of contact points between carbon black particles, which is advantageous for lowering the internal resistance of electrodes. Therefore, the carbon black raw material used in the production of the carbon material dispersion in this embodiment is preferably 1 nm or larger, more preferably 10 nm or larger, and even more preferably 20 nm or larger, from the viewpoint of conductivity and availability. It is also preferably 100 nm or smaller, more preferably 80 nm or smaller, and even more preferably 70 nm or smaller. That is, the average primary particle diameter of the carbon black raw material is preferably 1 to 100 nm, more preferably 10 to 80 nm, and even more preferably 20 to 70 nm. In this disclosure, the average primary particle diameter is the average value of the particle diameters measured by an electron microscope for spherical particles that form aggregates (primary aggregates). The average primary particle diameter of the carbon black raw material 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 their outer diameters are measured. Next, the average primary particle size (nm) of the carbon black is calculated as the number average of the outer diameters.

[0027] In a carbon material dispersion, 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 electrodes. In this disclosure, secondary aggregates are represented by a volume-based median diameter (hereinafter also referred to as the average particle diameter (D50)). In this embodiment, from the viewpoint of conductivity, the D50 of the carbon material dispersion is preferably 0.2 μm or more, more preferably 0.3 μm or more. From the viewpoint of dispersion stability, it is preferably 5.0 μm or less, more preferably 3.0 μm or less, and may be, for example, 0.2 to 5.0 μm, 0.3 to 5.0 μm, or 0.3 to 3.0 μm. The volume-average particle diameter is the particle diameter 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 a general-purpose particle size analyzer (for example, a laser scattering type particle size analyzer such as Nikkiso's "Microtrac MT3300EXII").

[0028] (Fibrous Carbon) Fibrous carbon may be obtained by calcining petroleum-derived raw materials, or by calcining plant-derived raw materials. Examples of fibrous carbon include carbon nanotubes (hereinafter also referred to as "CNT"). Carbon nanotubes have a cylindrical shape in which planar graphite is wound, and may be single-layered, double-layered, or multi-layered, or a mixture of these. Single-walled carbon nanotubes have a structure in which one layer of graphite is wound. Double-layered or multi-layered carbon nanotubes have a structure in which two 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. Similar to carbon black, carbon nanotubes do not exist as primary particles in an isolated state, but rather form primary aggregates in the form of bundles of fibrous particles, or secondary aggregates in which multiple bundles are intertwined.

[0029] 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.

[0030] Examples of fibrous carbon forms, such as carbon nanotubes, 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.

[0031] In some embodiments, a carbon material dispersion can be obtained using fibrous carbon raw materials. The fibrous carbon raw materials have an average outer diameter of preferably 1 nm or more, more preferably 5 nm or more. They are also preferably 30 nm or less, more preferably 20 nm or less, and even more preferably 13 nm or less. The average outer diameter of the fibrous carbon raw materials can be determined as follows: First, the fibrous carbon raw materials are observed and imaged using a transmission electron microscope. Next, 300 arbitrary fibrous carbons are selected from the observation images, and the outer diameter of each is measured. Then, the average outer diameter (nm) of the fibrous carbons is calculated as the number average of the outer diameters.

[0032] As the carbon material (a), two or more types of fibrous carbon with different average outer diameters may be used in combination. When used in combination, the average outer diameter of the first fibrous carbon raw material may be 1 nm or more and less than 5 nm, and the average outer diameter of the second fibrous carbon raw material may be 5 nm or more and 30 nm or less, or 20 nm or less.

[0033] From the viewpoint of conductive network formation, the fibrous carbon raw material preferably has an average fiber length of 0.5 μm or more, more preferably 0.8 μm or more, and even more preferably 1.0 μm or more. It is also preferably 20 μm or less, and more preferably 10 μm or less. The average fiber length of the fibrous carbon can be determined as follows. First, the fibrous carbon is observed and imaged using a transmission electron microscope. Next, 300 arbitrary fibrous carbons are selected from the observation images, and the fiber length of each is measured. Then, the average fiber length (μm) of the fibrous carbon is calculated as the number average of the fiber lengths.

[0034] The aspect ratio is obtained by dividing the average fiber length by the average outer diameter. The higher the aspect ratio of the fibrous carbon raw material used, the higher the conductivity that can be achieved when electrodes are formed. From the viewpoint of conductivity, the aspect ratio of the fibrous carbon raw material is preferably 30 or more, more preferably 50 or more, and even more preferably 80 or more. It is also preferably 10,000 or less, more preferably 3,000 or less, and even more preferably 1,000 or less.

[0035] The content of carbon material (a) in the carbon material dispersion can be appropriately adjusted depending on the type of carbon material (a) used, specific surface area, surface functional group content, and other physical properties specific to the carbon material. For example, if carbon material (a) contains carbon black, the carbon black content is preferably 1% by mass or more, more preferably 5% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 50% by mass or less, and more preferably 30% by mass or less. The above content may be, for example, 1 to 50% by mass or 5 to 50% by mass. If carbon material (a) contains fibrous carbon, the carbon material (a) content is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The above content may be, for example, 1 to 10% by mass or 1 to 5% by mass. If the concentration of carbon material (a) is too low, production efficiency will be poor, and if the concentration is too high, the viscosity of the dispersion will become significantly higher, which may lead to poor dispersion and reduced handling. When the content of carbon material (a) is within the above range, the dispersion is well-dispersible, the viscosity of the dispersion is within an appropriate range, and production efficiency and handling are excellent.

[0036] The carbon material (A) may contain known carbon materials other than carbon material (a) as long as the effects of this embodiment are not impaired. The above-mentioned carbon materials can be used, but the proportion of carbon material (a) in carbon material (A) is preferably 10% by mass or more. The proportion of carbon material (a) is more preferably 50% by mass or more, and even more preferably 70% by mass or more. In some embodiments, the proportion of carbon material (a) may be 80% by mass or more, 90% by mass or more, or 100% by mass. The content of carbon material (A) in the carbon material dispersion may be the same as the content of carbon material described in the second carbon material dispersion described later.

[0037] <Dispersant (B)> In the carbon material dispersion of this embodiment, the dispersant (B) can be any material that can disperse and stabilize the carbon material (A), and known dispersants can be used. On the other hand, the carbon material dispersion of this embodiment is characterized by containing polyvinyl butyral resin (b) as a dispersant. Polyvinyl butyral resin (b) is a polymer compound consisting of three types of repeating units having acetal groups, acetyl groups, and hydroxyl groups, and exhibits excellent electrode resistance when combined with the predetermined carbon material (a) described above. Polyvinyl butyral resin (b) is not particularly limited, and various commercially available products and synthetic products can be used alone or in combination of two or more types. Furthermore, a product that has been adjusted by chemical modification methods such as acylation or urethaneization of the hydroxyl groups may be used.

[0038] [Polyvinyl butyral resin (b)] Examples of commercially available polyvinyl butyral resins include Esrec (polyvinyl butyral resin manufactured by Sekisui Chemical Co., Ltd.) and Mobital (polyvinyl butyral resin manufactured by Kuraray Co., Ltd.), and various grades can be used. Examples of such commercially available products include Esrec BL-1, BL-S, BL-10, BL-1H, BL-2H, BL-5Z, BM-1, BM-2(Z), BM-S(Z), BM-SHZ, BM-5, BH-3(Z), BH-A, BH-S, BH-6, BX-1, BX-L (polyvinyl butyral resin manufactured by Sekisui Chemical Co., Ltd.), and Esrec Mobital LPB16H, B20H, B30T, B30H, B30HH, B45M (polyvinyl butyral resin manufactured by Kuraray Co., Ltd.).

[0039] The polyvinyl butyral resin (b) preferably has a content of acetal groups (degree of acetalization) of 60 to 85% by mass. When the degree of acetalization is 60% by mass or more, the solubility in low-polarity solvents (C) is improved, and a carbon material dispersion with excellent dispersibility can be obtained. Furthermore, when the degree of acetalization is 85% by mass or less, the flexibility of the polyvinyl butyral resin (b) is improved, and the overall toughness of the electrode is excellent.

[0040] The polyvinyl butyral resin (b) preferably has a content of acetyl group-containing structural units (acetyl group content) of 20% by mass or less, and more preferably 10% by mass or less. When the acetyl group content is 20% by mass or less, both flexibility and solubility in low-polarity solvents can be achieved for the polyvinyl butyral resin (b). It is also preferably 5% by mass or more.

[0041] The polyvinyl butyral resin (b) preferably has a content of hydroxyl group-containing structural units (hydroxyl group content) of 30% by mass or less. When it is 30% by mass or less, the dispersion stability of the carbon material is improved and conductive network formation is excellent. More preferably it is 26% by mass or less, and more preferably 20% by mass or less. It is also preferably 1% by mass or more, may be 10% by mass or more, or 16% by mass or more. The content of hydroxyl group-containing structural units may be, for example, 1 to 26% by mass, 10 to 26% by mass, or 16 to 26% by mass.

[0042] From the viewpoint of excellent solubility in low-polarity solvents, the polyvinyl butyral resin (b) preferably has a weight-average molecular weight of 150,000 or less, more preferably 100,000 or less, even more preferably 80,000 or less, and particularly preferably 70,000 or less. Furthermore, from the viewpoint of dispersion stability, it is preferably 20,000 or more, more preferably 30,000 or more, and even more preferably 40,000 or more, for example, it may be 20,000 to 100,000, 30,000 to 80,000, 40,000 to 70,000, or 15,000 to 115,000, or 23,000 to 66,000. Furthermore, the polyvinyl butyral resin (b), when prepared as a 10% by mass ethanol solution, preferably has a solution viscosity of 10 mPa·s or more, more preferably 20 mPa·s or more, and even more preferably 100 mPa·s or more. Furthermore, it is preferably 500 mPa·s or less, more preferably 400 mPa·s or less, and even more preferably 300 mPa·s or less. In other words, the viscosity of the solution is preferably 10 to 500 mPa·s, more preferably 20 to 400 mPa·s, and even more preferably 100 to 300 mPa·s. The viscosity of the solution may be 10 to 352 mPa·s, or 24 to 205 mPa·s.

[0043] In this embodiment, the carbon material dispersion preferably contains 5.0% by mass or more of polyvinyl butyral resin (b) based on the mass of carbon material (a), from the viewpoint of the solubility of polyvinyl butyral resin (b) and the dispersibility of the carbon material. The content of polyvinyl butyral resin (b) may more preferably be 8.0% by mass or more, and even more preferably 10% by mass or more. Furthermore, the content may preferably be 100% by mass or less, more preferably 80% by mass or less, and even more preferably 50% by mass or less. In some embodiments, the content may be 5.0 to 100% by mass, or 10 to 50% by mass. When carbon material (a) contains carbon black, the content of polyvinyl butyral resin (b) may be 4.2 to 83.3% by mass, 4.2 to 10% by mass, or 5.0 to 10% by mass, based on the mass of carbon material (a). If the carbon material (a) contains fibrous carbon, the content of polyvinyl butyral resin (b) may be 25 to 100% by mass, based on the mass of the carbon material (a).

[0044] The dispersant (B) may contain known dispersants other than polyvinyl butyral resin (b) as long as the effects according to this embodiment are not impaired. Examples of such known dispersants include polyvinyl alcohol, polyvinylpyrrolidone, acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, styrene elastomers, and hydrogenated styrene elastomers. The proportion of polyvinyl butyral resin (b) in the dispersant (B) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

[0045] <Low Polarity Solvent (C)> The low polarity solvent (C) in the carbon material dispersion is a solvent with low polarity that does not react easily with sulfur-based solid electrolytes, and 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, and also includes 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.).

[0046] Based on the total mass of the low-polarity solvent, 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 is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0047] 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: Weighted average relative permittivity = (εr Ａ ×V Ａ +εr Ｂ ×V Ｂ ) / (V Ａ +V Ｂ )

[0048] Examples of such low-polarity solvents (C) include ester solvents having alkyl groups with four or more carbon atoms, ether solvents having alkyl groups with four or more carbon atoms, aromatic hydrocarbons, and aliphatic hydrocarbons. Because these have high hydrophobicity, using such low-polarity solvents (C) can prevent the degradation of sulfide-based solid electrolytes. Furthermore, by combining them with the aforementioned predetermined carbon material (a) and polyvinyl butyral resin (b), the dispersibility of the carbon material (a) can be improved, making it easier to achieve excellent electrode resistance. In particular, from the viewpoint of electrode resistance and dispersion stability, the low-polarity solvent (C) preferably includes at least one solvent selected from the group consisting of ester solvents having alkyl groups with four or more carbon atoms, ether solvents having alkyl groups with four or more carbon atoms, and aromatic hydrocarbons.

[0049] Examples of ester solvents having an alkyl group with four or more carbon atoms include butyl butyrate, pentyl butyrate, hexyl butyrate, butyl acetate, pentyl acetate, hexyl acetate, and butyl propionate. Examples of ether solvents having an alkyl group with 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, mesitylene, and tetralin. More preferably, the solvent is at least one solvent selected from the group consisting of ester solvents having an alkyl group with four or more carbon atoms and aromatic hydrocarbons, and even more preferably, the solvent is an ester solvent having an alkyl group with four or more carbon atoms, and particularly preferably, butyl butyrate.

[0050] The carbon material dispersion may contain a polar solvent, to the extent that it does not impair the effects of this embodiment. The content of the low-polarity solvent (C) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, and may be 100% by mass, based on the total mass of the solvent. These solvents may be used individually or in combination of two or more.

[0051] <Other Additives> The carbon material dispersion may further contain surfactants, film-forming aids, defoaming agents, leveling agents, preservatives, pH adjusters, and viscosity adjusters, to the extent that they do not impair the effects of this embodiment. Acids or alkalis can be used as pH adjusters to adjust the pH of the solvent. Examples of alkalis include amine compounds, which may be tertiary amines, secondary amines, primary amines, monoamines, diamines, triamines, tetraamines, or polyamines. By using amine compounds as pH adjusters, the zeta potential of the dispersed particles can be easily adjusted. The content of the amine compound based on the mass of the dispersion is preferably 0.1% by mass or less, and may be, for example, 0 to 0.1% by mass. The carbon material dispersion of this embodiment exhibits good dispersion stability and excellent electrode resistance and cycle characteristics because the content of the amine compound is within the above range. These optional components may be added at any time during the manufacturing process of the dispersion, such as before, during, or after the dispersion treatment of the carbon material dispersion.

[0052] <1-2> Second Carbon Material Dispersion The second carbon material dispersion of this embodiment (hereinafter also referred to as the carbon material dispersion of this embodiment or carbon material dispersion) comprises a carbon material (A), a dispersant (B), and a low-polarity solvent (C), and relates to a carbon material dispersion defined by the viscosity change rate A, as described later. The carbon material dispersion of this embodiment is a carbon material dispersion containing a carbon material, a dispersant, and a low-polarity solvent, and 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 1s －１ The viscosity 2 measured under these conditions, and the shear rate 1s in step 4. －１ The characteristic is that the rate of change A (hereinafter, formula 1) 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 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 －１Change to . (Step 2) Next, change the shear rate to 1000 s over 170 seconds －１ from 1 s －１ . (Step 3) Next, stop and stand for 10 minutes. (Step 4) Next, change the shear rate to 1 s over 170 seconds －１ from 1000 s －１ . (Formula 1) Rate of change A (%) = (viscosity 4 - viscosity 2) / viscosity 2 × 100

[0053] The thickening property of carbon material dispersions, represented by thixotropy, is expressed through the complex interaction of the contained materials (carbon material, dispersant, low-polarity solvent, etc.) and the dispersion process. Therefore, it is difficult to uniquely estimate the thickening property from specific factors, and the detailed mechanism remains unclear. However, the carbon material dispersion according to the present embodiment has a unique thickening property such that the rate of viscosity change (rate of change A) before and after standing for 10 minutes, measured according to a predetermined procedure, is 10% or more and 210% or less. It is presumed that due to such characteristics, the uniform state of the carbon material in the film is fixed by rapid mild thickening, thereby securing a conductive path and exhibiting excellent conductivity and cycle characteristics.

[0054] 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 of step 3 interposed, and two cycles of increase and decrease are performed. All viscosity measurements in steps 1 to 5 are continuously performed under the conditions of 25°C and a distance between plates of 0.099 mm using a rotational rheometer equipped with a cone plate (diameter 50 mm, angle 0.1°). (Step 1) is the step of measuring viscosity while changing the shear rate from 1 s over 170 seconds －１ to 1000 s －１ . (Step 2) is the step of measuring viscosity while continuously changing the shear rate from 1000 s over 170 seconds after step 1 －１ to 1 s －１ . (Step 3) is the step of stopping and standing for 10 minutes after step 2. (Step 4) is, after step 3, changing the shear rate from 1 s over 170 seconds －１ to 1000 s －１This 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.

[0055] The rate of change A between viscosity 2 and viscosity 4, expressed by 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.

[0056] 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%.

[0057] The rate of change A can be adjusted by the type and combination of low-polarity solvent and carbon material, as well as by the dispersion conditions, and the preferred range of the rate of change A can be appropriately adjusted by the type and combination of 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. It is also preferably 105% or less, more preferably 85% or less, and even more preferably 50% or less, 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. It is also preferably 100% or less, more preferably 80% or less, and even more preferably 40% or less, for example, 10-100%, 15-100%, 15-80%, and 15-40%.

[0058] The rate of change B between viscosity 2 and viscosity 5, expressed by 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. 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. Within the above range, it can be determined that the dispersion state after stirring has recovered to the same state as when the dispersion was prepared, resulting in excellent handling (workability) after industrial stirring.

[0059] The carbon material dispersion of this embodiment can be constructed using a known carbon material, a dispersant, and a low-polarity solvent, similar to the first carbon material dispersion described earlier, and may further contain various additives as needed. That is, the carbon material dispersion of this embodiment can be obtained by arbitrarily selecting materials from the carbon material (A), dispersant (B), and low-polarity solvent (C) exemplified earlier, and adjusting the dispersion conditions, etc. In some embodiments, it is preferable to include the carbon material (a) described above as the carbon material. It is also preferable to include polyvinyl butyral resin (b) as the dispersant. In some embodiments, the carbon material dispersion may have a combination of the carbon material (a) described above and polyvinyl butyral resin (b).

[0060] In the carbon material dispersion of this embodiment, the carbon material (A) is a conductive carbon material and functions as a conductive material within the electrode. Examples of carbon material (A) include carbon black (CB), carbon nanotubes (CNT), graphene, multilayer graphene, and graphite. One type of carbon material (A) may be used alone, or two or more types may be used in combination. In the carbon material dispersion of this embodiment (also called a conductive carbon material dispersion), at least one selected from the group consisting of carbon black and carbon nanotubes can be suitably used as the carbon material (A). Carbon black and carbon nanotubes can be selected from known materials exemplified in the description of the first carbon material dispersion above. Representative embodiments will be described below.

[0061] <Carbon Material (A)> In an example of the carbon material dispersion of this embodiment, carbon black is included as the carbon material. The smaller the primary particle diameter of the carbon black, the greater the number of particles contained per unit mass, and the greater the number of contact points between carbon black particles, which is advantageous in reducing the internal resistance of the electrode. Therefore, the carbon black raw material used in the production of the conductive carbon material dispersion preferably has an average primary particle diameter of 1 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more, from the viewpoint of conductivity and availability. It is also preferably 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, it may be 1 to 100 nm, 10 to 80 nm, 20 to 70 nm, 20 to 50 nm, or 30 to 40 nm. The average primary particle diameter is the average value of the particle diameters measured with an electron microscope, which are spherical particles that form aggregates (primary aggregates). The average primary particle diameter of the carbon black raw material 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.

[0062] Carbon black forms agglomerates (secondary aggregates) in a conductive carbon material dispersion, 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 electrodes. In this disclosure, 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, it is preferably 5 μm or less, more preferably 3 μm or less, and may be, for example, 0.2 to 5 μm, 0.3 to 5 μm, or 0.3 to 3 μm. 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 a conductive carbon material dispersion and a general particle size analyzer (for example, a laser scattering type particle size analyzer, such as Nikkiso's "Microtrac MT3300EXII").

[0063] The bulk density of carbon black raw materials tends to correlate with the degree of aggregation of carbon atoms and the wettability when in contact with a liquid medium. From this viewpoint, the bulk density of carbon black in this embodiment is preferably 0.03 g / cm³. ３ More preferably, 0.04 g / cm³ ３ That concludes the explanation. Furthermore, a preferred concentration is 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 It is also acceptable to use carbon black within the above range. By using carbon black within the above range, it becomes easier to achieve both the wettability of the carbon black in the solvent and the conductivity after dispersion.

[0064] The specific surface area of ​​carbon black raw materials tends to correlate with the average primary particle diameter and aggregation state. For example, the smaller the particle diameter, the larger the specific surface area. From this viewpoint, the BET specific surface area of ​​the carbon black in this embodiment is preferably 30 m². ２ / g or more, more preferably 40m ２ / g or more, more preferably 50m ２ It is 150 m or more. ２ / g or less, more preferably 100m ２ / g or less, more preferably 80m ２ It is less than or equal to / g. In some embodiments, the specific surface area is 30 to 150 m². 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 or aggregate state that falls within the above range for specific surface area. The specific surface area can be measured by the BET method by nitrogen adsorption.

[0065] In an example of the carbon material dispersion of this embodiment, the carbon material includes carbon nanotubes. The carbon nanotubes may be known materials, similar to the carbon nanotubes in the first carbon material dispersion described earlier. Furthermore, the carbon nanotubes used as raw materials (in this specification, carbon nanotubes before dispersion treatment are also referred to as carbon nanotube raw materials) may be carbon nanotubes manufactured by any method. Carbon nanotube raw materials can generally be manufactured by laser ablation, arc discharge, thermal CVD, plasma CVD, and combustion, but are not limited to these. The carbon nanotube raw materials may be carbon nanotubes that have undergone surface treatment. The carbon nanotube raw materials may be carbon nanotube derivatives to which functional groups such as carboxyl groups have been added. Furthermore, the carbon nanotube raw materials may be carbon nanotubes containing organic compounds, metal atoms, or substances such as fullerenes.

[0066] The average outer diameter of the carbon nanotube raw material is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. It is also 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.

[0067] In some embodiments, the specific surface area of ​​the carbon nanotube raw material 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 is less than or equal to / g. The specific surface area is 100 to 1200 m². ２ / g, 150-1000m ２ / g, 200-800m ２ / g, 230-690m ２ It 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.

[0068] The carbon purity of carbon nanotube raw materials is expressed as the carbon atom content (mass%) in the carbon nanotube raw materials. 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 materials. By setting the carbon purity within the above range, problems such as dendrite formation and short circuits caused by impurities such as metal catalysts can be prevented. High-purity treated carbon nanotube raw materials may also 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.

[0069] In some embodiments, the bulk density of the carbon nanotube raw material is preferably 0.03 g / cm³ from the viewpoint of ease of disintegration and wettability in the solvent. ３ More preferably, 0.04 g / cm³ ３ That concludes the explanation. Furthermore, a preferred concentration is 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 Alternatively, the bulk density can be 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 the container is standing, measuring the mass of the carbon nanotube raw material, and dividing it by the container volume.

[0070] The carbon nanotube raw material used in the carbon material dispersion 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 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.

[0071] 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.

[0072] The content of carbon material (A) in the carbon material dispersion can be appropriately adjusted according to the type of carbon material and its physical properties (specific surface area, amount of surface functional groups, etc.). When carbon material (A) contains carbon black, the content of conductive carbon material (A) in the carbon material dispersion is preferably 1% by mass or more, more preferably 5% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 50% by mass or less, more preferably 30% by mass or less, and may be, for example, 1 to 50% by mass or 5 to 50% by mass. When carbon material (A) contains carbon nanotubes, the content of carbon material (A) in the carbon material dispersion is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, and may be, for example, 1 to 10% by mass or 1 to 5% by mass. When the carbon material (A) content is within the above range, the dispersion exhibits excellent dispersibility, the viscosity of the dispersion is within an appropriate range, and production efficiency and handling are superior.

[0073] <Dispersant (B)> In the carbon material dispersion of this embodiment, the dispersant can be used without particular limitation as long as it can stabilize the dispersion of the carbon material (A). For example, at least one of resin-type dispersants and surfactants can be used as the dispersant. From the viewpoint of strong adsorption to the carbon material (A) and excellent dispersion stability, a resin-type dispersant is preferred as the dispersant. 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.

[0074] [Resin-type dispersants] Examples of resin-type dispersants include polymers derived from ethylenically unsaturated hydrocarbons, cellulosic derivatives, and copolymers thereof.

[0075] (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.

[0076] 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.

[0077] 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 anionically or cationically modified polyvinyl alcohol, and polyvinyl acetals modified with aldehydes (e.g., acetal modification, butyral modification) (e.g., polyvinyl acetal, polyvinyl butyral). In some embodiments, polyvinyl butyral resin can be suitably used. Specific examples of polyvinyl butyral resin may be the same as the specific example of polyvinyl butyral resin (b) in the first carbon material dispersion described above.

[0078] 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.

[0079] 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.

[0080] 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).

[0081] (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.

[0082] In a carbon material dispersion, 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. In some embodiments, 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. In other embodiments, 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 (B), exhibiting excellent dispersion stability.

[0083] The weight-average molecular weight (Mw) of the resin-type dispersant is preferably 20,000 or more. It is also 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 carbon material particles. By setting the molecular weight within the above range, sufficient steric repulsion can be obtained, which is preferable from the viewpoint of dispersion stability.

[0084] 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 carbon material (A). 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 conductive carbon material dispersion.

[0085] <Low Polarity Solvent (C)> 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. Specific examples of low polarity solvent (C) may be the same as the specific examples of low polarity solvent (C) in the first carbon material dispersion described above.

[0086] The conductive carbon material dispersion may contain solvents other than the low-polarity solvent (C) as long as the effects according to 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 conductive carbon material dispersion, and may also be 100% by mass.

[0087] The content of the low-polarity solvent (C) in the carbon material dispersion can be appropriately adjusted according to the type of carbon material and its physical properties (specific surface area, amount of surface functional groups, etc.). In some embodiments, when the carbon material (A) contains carbon black, the content of the low-polarity solvent (C) in the carbon material dispersion is preferably 70% by mass or more, more preferably 80% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 95% by mass or less, more preferably 90% by mass or less, for example, it may be 70 to 95% by mass or 80 to 90% by mass. In other embodiments, when the carbon material (A) contains carbon nanotubes, the content of the low-polarity solvent (C) in the carbon material dispersion is preferably 90% by mass or more, more preferably 93% by mass or more, based on the mass of the carbon material dispersion. It is also preferably 99% by mass or less, more preferably 98% by mass or less, for example, it may be 90 to 99% by mass or 93 to 98% by mass. Within the above range, the fluidity and dispersion stability of the carbon material dispersion are excellent.

[0088] <Other Additives> The carbon material dispersion may further contain other optional components such as surfactants, film-forming aids, defoamers, leveling agents, antioxidants, preservatives, and viscosity modifiers, to the extent that they do not impair the effects of this embodiment. The carbon material dispersion may also contain polymer components (binders), to the extent that they do not hinder the objectives of the present invention. The description of the binder can be referenced from the section on [Binder] in the <Electrode Composition (Assorted Material Slurry)> section described later. These optional components may be added at any time during the manufacturing process of the dispersion, such as before, during, or after the dispersion treatment of the carbon material dispersion.

[0089] <1-3> Physical Properties of Carbon Material Dispersion In some embodiments, the carbon material dispersion has a water content, as measured by the Karl Fischer method, preferably 1,000 ppm or less, more preferably 500 ppm or less, for example, 1,000 ppm or less, 500 ppm or less, or 0 ppm. Having a water content within the above range improves dispersion stability and suppresses measurement variations such as electrode resistance. In particular, for the second carbon material dispersion, from the viewpoint of suppressing degradation of the solid electrolyte and suppressing a decrease in lithium ion conductivity, the water content is preferably 500 ppm or less, more preferably 350 ppm or less, or 0 ppm. When the water content is within the above range, it is easy to suppress the degradation of the electrolyte and obtain a good secondary battery. In this specification, the water content was calculated as the content relative to the mass of the carbon material dispersion, based on the value measured with a Karl Fischer moisture meter.

[0090] In some embodiments, the carbon material dispersion may have a gloss value of 5 or higher, 200 or lower, or 50 or lower, for example, 5 to 200 or 5 to 50. The gloss value can be determined by the following method. First, the carbon material dispersion is coated onto a PET (polyethylene terephthalate) film so that the film thickness after drying is 3 μm, and dried in a 150°C oven for 2 minutes. The resulting coating is placed on a graphite plate with the coated surface facing upwards, and the 60° gloss value is determined using a gloss meter (BYK micro-TRI-gloss). In particular, in the first carbon material dispersion, if the gloss value of the film is within the above range, the secondary aggregates of carbon material (a) are sufficiently disintegrated, thereby reducing electrode resistance. The gloss value is related to the size of the secondary aggregates of carbon material (a) in the carbon material dispersion; the smaller the secondary aggregates, the higher the gloss value tends to be. In other words, the gloss value can be controlled by the carbon materials and their composition that make up the carbon material dispersion, as well as by the dispersion conditions such as the dispersion device and dispersion time.

[0091] 2. Method for Producing a Carbon Material Dispersion One embodiment of the present invention relates to a method for producing a carbon material dispersion according to the above embodiment. Hereinafter, unless otherwise specified, the term "carbon material dispersion" refers to both the first and second carbon material dispersions. The method for producing a carbon material dispersion is not particularly limited, but it can be obtained by mixing and dispersing at least a carbon material (A), a dispersant (B), and a low-polarity solvent (C) using a known method, and then applying appropriate shearing or impact. The mixing and dispersion may be carried out all at once or in stages. In the above production method, additional optional components may be used, and a dispersion treatment may be performed after mixing, and the dispersion treatment may be a multi-stage treatment of two or more stages. From the viewpoint of controlling the water content in the carbon material dispersion, it is preferable to carry out the dispersion treatment under a nitrogen atmosphere.

[0092] Carbon material dispersions are preferably manufactured by finely dispersing them using a dispersion device. Dispersers and mixers commonly used for pigment dispersion can be used as dispersion devices. Examples of such dispersion devices include, but are not limited to, the following: Mixers such as dispersers, homomixers, or planetary mixers; homogenizers such as M-Technique's "Clearmix" or PRIMIX's "Filmix"; paint conditioners (Red Devil), colloid mills (PUC's "PUC Colloid Mill", IKA's "magic LAB", IKA's "Colloid Mill MK"); cone mills (IKA's "Cone Mill MKO", etc.); media-type dispersers such as ball mills, sand mills (Shinmaru Enterprises' "Dino Mill", etc.), atlighters, pearl mills (Eirich's "DCP Mill", etc.), or coball mills; Wet jet mills (such as Genus PY from Genus Corporation, Starburst from Sugino Machine Co., Ltd., and Nanomizer from Nanomizer Co., Ltd.), media-less dispersers such as Crea SS-5 from M-Technique Co., Ltd., or MICROS from Nara Machinery Co., Ltd., and other roll mills, etc.

[0093] It is preferable to use a disperser that has been treated to prevent metal contamination from the disperser. For example, when using a media-type disperser, a disperser in which the agitator and vessel are made of ceramic or resin, or a disperser in which the surface of the metal agitator and vessel has been treated with tungsten carbide spraying or resin coating may be used. As the media, it is preferable to use glass beads; zirconia beads, alumina beads, or other ceramic beads. When using a roll mill, it is preferable to use ceramic rolls. The disperser may be used by using only one type of disperser, or multiple types of dispersers may be used in combination. Furthermore, when using positive or negative electrode active materials in which particles are easily broken or crushed by strong impact, media-less dispersers such as roll mills or homogenizers are preferably used.

[0094] In addition to the material selection described above, the dispersion state of a carbon material dispersion can be adjusted by controlling the dispersion conditions (dispersion equipment, dispersion process, dispersion strength, etc.). Although not particularly limited, in the production of the second carbon material dispersion, it is easy to achieve the desired viscosity change (thickening) by adjusting the dispersion conditions. This will be explained in detail below. In some embodiments, the dispersion treatment for preparing a carbon material dispersion containing carbon black is preferably carried out using a high-shear mixer, colloidal mills, media-type disperser, or a combination thereof. First, from the viewpoint of promoting wetting and dissolving coarse particles, it is preferable to 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.

[0095] In some embodiments, the dispersion process for preparing a carbon material 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. First, from the viewpoint of promoting wetting and dissolving coarse particles, the initial dispersion step is preferably performed using a high-shear mixer or colloidal mill, and then, from the viewpoint of dispersing while maintaining the aspect ratio of the carbon nanotubes, it is preferable to use a high-pressure homogenizer. The dispersibility of carbon nanotubes can be further improved by performing the high-pressure homogenizer dispersion in multiple stages using a circulating dispersion method. After dispersion with a high-pressure homogenizer, further dispersion may be performed using a media-type disperser such as a bead mill. Alternatively, by dispersing with a high-shear mixer or colloidal mill in the initial dispersion step, 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.

[0096] The dispersion apparatus used to disperse the carbon material dispersion may be equipped with a heat exchanger or a coolant supply mechanism for cooling the carbon material dispersion.

[0097] Dispersion methods using a dispersion device include batch dispersion, pass 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 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 or circulation until the desired dispersion state is achieved, and the processing volume can be increased by changing the size of the tank or the processing time. Pass dispersion is preferable to circulating dispersion because it is easier to achieve a uniform dispersion state. Circulating dispersion is preferable to pass 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.

[0098] The dispersion treatment is preferably carried out until the viscosity of the carbon material dispersion is sufficiently reduced. The viscosity of the carbon material dispersion, 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.

[0099] 3. Electrode Composition One embodiment of the present invention relates to an electrode composition. The electrode composition comprises at least the carbon material dispersion of the above embodiment, an active material, and a solid electrolyte, and may further comprise a binder. The carbon material dispersion may further comprise any additional components in addition to the above components.

[0100] [Active material] The active material is not particularly limited and may be a positive electrode active material or a negative electrode active material. As a positive electrode active material, for example, metal oxides and metal compounds such as metal sulfides that can reversibly dope or intercalate lithium ions can be used. Specific examples of such positive electrode active materials include, for example, lithium manganese composite oxide (e.g., Li ｘ Mn ２ O ４ or Li ｘ MnO ２ ), lithium nickel composite oxide (e.g., LiNiO) ２ ), lithium cobalt composite oxide (Li ｘ CoO ２ ), lithium nickel cobalt composite oxide (e.g., Li ｘ Ni １－ｙ Co ｙ O ２ ), lithium manganese cobalt composite oxide (e.g., Li ｘ MnyCo １－ｙ O ２ ), lithium nickel manganese cobalt composite oxide (e.g., Li ｘ NiyCo ｚ Mn １－ｙ－ｚ O ２ ), spinel-type lithium manganese nickel composite oxide (e.g., Li ｘ Mn ２－ｙ Ni ｙ O ４ Composite oxide powders of lithium and transition metals such as ) and lithium phosphate oxide powder having an olivine structure (e.g., Li ｘ FePO ４ Li ｘ Fe １－ｙ Mn ｙ PO ４ Li ｘ CoPO ４ ), manganese oxide, iron oxide, copper oxide, nickel oxide, vanadium oxide (e.g., V ２ O ５ , V ６ O １３ ), transition metal oxide powders such as titanium dioxide, iron sulfate (Fe ２ (SO ４ ) ３ ), TiS ２Examples include transition metal sulfide powders such as FeS. Here, x, y, and z are numbers, and 0 < x < 1, 0 < y < 1, 0 < z < 1, and 0 < y + z < 1. These positive electrode active materials may be used individually or in combination.

[0101] Examples of negative electrode active materials include metallic Li or its alloys, tin alloys, silicon alloy negative electrodes, Li, which can be reversibly doped or intercalated with lithium ions. Ｘ TiO ２ Li Ｘ Fe ２ O ３ Li Ｘ Fe ３ O ４ Li Ｘ WO ２ Examples include metal oxides such as polyacetylene and poly-p-phenylene, conductive polymers such as polyacetylene and poly-p-phenylene, artificial graphite such as high-graphitization carbon materials, or carbon material powders such as natural graphite, and resin-fired carbon materials. Here, x is a number, and 0 < x < 1. These negative electrode active materials may be used individually or in combination. In particular, when using a silicon alloy negative electrode, although the theoretical capacity is large, the volume expansion is extremely large, so it is preferable to use it in combination with artificial graphite such as high-graphitization carbon materials, carbon material powders such as natural graphite, or resin-fired carbon materials.

[0102] The surface of the active material may be coated with a buffer layer to reduce interfacial resistance with the solid electrolyte. Examples of buffer layers include oxide solid electrolytes, halide solid electrolytes, sulfide-based solid electrolytes, and oxide materials. For example, at least one type of buffer layer may be coated on the surface of the active material to a thickness of 1 to 500 nm.

[0103] [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 its constituent elements include S, and may also include Li. Furthermore, its form may be crystalline or amorphous (glass), glass ceramics obtained by crystallizing glass, or a material that is partially crystallized. For example, Li ９．５４ Si １．７４ P１．４４ S １１．７ C ｌ０．３ Li １０ GeP ２ S １２ Li ６ PS ５ C ｌ Examples include the following. Alternatively, it may be produced by mixing raw materials in any molar ratio. For example, Li ２ S-P ２ S ５ (LPS), 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 ２ S 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 ２Li 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 ５ Li ２ S-GeS ２ - ZnS, Li ２ S-GeS ２ - Al ２ S ３ These can be used individually or in combination of two or more.

[0104] [Binder] The binder is not particularly limited and can be appropriately selected depending on the purpose. Examples of binders used in electrode compositions include polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, 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.

[0105] The electrode composition can be prepared in any way using the carbon material dispersion described above. For example, methods include adding the active material, solid electrolyte, and binder to the carbon material dispersion; adding the active material and solid electrolyte to the carbon material dispersion and then adding the binder; adding the binder to the carbon material dispersion and then adding the active material and solid electrolyte; and adding the active material to the carbon material dispersion and then adding the solid electrolyte and binder. Other examples include adding the solid electrolyte to the carbon material dispersion and then adding the active material and binder; adding the active material to the carbon material dispersion, then adding the solid electrolyte and then adding the binder; and mixing the active material, solid electrolyte, and binder before adding the carbon material dispersion. The apparatus used for dispersion and mixing is not particularly limited.

[0106] In some embodiments, when the carbon material (a) in the electrode composition 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. When the carbon material (a) contains fibrous carbon, the fibrous carbon 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. In other embodiments, when carbon material (A) is used as carbon black other than the carbon material (a) or fibrous carbon such as carbon nanotubes, it is also preferable that the respective contents are within the above ranges. Two or more different carbon materials may be used as the carbon material in the electrode composition, and it is preferable that the total amount of each is within the above ranges. Furthermore, carbon materials other than carbon black and fibrous carbon may be used in combination as the carbon material constituting the electrode composition.

[0107] In some embodiments, the content of dispersant (B) in the electrode composition is preferably 0.01% by mass or more, and preferably 10% by mass or less, based on the mass of the active material. In some embodiments, the content of dispersant (b) in the electrode composition is preferably 0.01% by mass or more, and preferably 10% by mass or less, based on the mass of the active material.

[0108] The electrode composition has a solid content mass of preferably 30% by mass or more, more preferably 40% by mass or more, based on the mass of the electrode composition. It is also preferably 90% by mass or less. The electrode composition (composite 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 (C) is preferred. From the viewpoint of dispersion stability of the carbon material dispersion, the same solvent as the low-polarity solvent (C) contained in the carbon material dispersion is more preferable.

[0109] 4. Electrode Embodiment One embodiment of the present invention relates to an electrode having an electrode film formed using the carbon material dispersion or electrode composition of the above embodiment. The electrode of this embodiment includes at least one electrode film formed from the carbon material dispersion or electrode composition, and may further include a current collector. The electrode film is obtained, for example, by coating the electrode composition onto the current collector and drying it. The current collector on which the electrode film is provided is not particularly limited. Examples of materials for the current collector include conductive metals and alloys such as Al, Ni, Cu, Ti, Fe, Cr, or stainless steel. The shape of the current collector is generally a flat foil shape, but current collectors with a roughened surface, a perforated foil shape, and a mesh shape can also be used. The current collector may have a coating layer on its surface, and examples of coating layers include a carbon layer containing a conductive carbon material or binder to improve adhesion to the current collector and conductivity.

[0110] The method for coating the electrode composition onto the current collector is not particularly limited and includes, for example, die coating, roll coating, doctor coating, knife coating, dip coating, gravure coating, spray coating, screen printing, and electrostatic coating. Drying methods include, for example, drying by standing or drying using equipment such as a forced-air dryer, hot-air dryer, infrared heater, or far-infrared heater. The electrodes may be pressed after coating and drying. Examples of pressing methods include flat plate pressing and roll pressing, and adjustments such as increasing the temperature during pressing may be made.

[0111] 5. One embodiment of a solid-state battery relates to a solid-state battery equipped with the electrodes of the above embodiment. In this embodiment, the components of the drive unit are broadly divided into a positive electrode, a negative electrode, and a separator layer, and the positive electrode and negative electrode are stacked facing each other via the separator layer. In this embodiment, the positive electrode and / or negative electrode are equipped with the electrodes of the above embodiment. The separator layer placed between the positive electrode and the negative electrode 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 a solid-state 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 solid-state battery may also be equipped with an exterior such as a laminate film or a metal case, connection terminals, etc. The all-solid-state battery of the above embodiment can be manufactured by known methods, except that at least one of the positive electrode and the negative electrode is made of the electrode of the above embodiment. Accordingly, one embodiment of the present invention relates to a method for manufacturing an all-solid-state battery having a structure in which a positive electrode and a negative electrode are stacked facing each other via a separator layer made of a solid electrolyte, characterized in that in the step of forming at least one of the positive electrode and the negative electrode, the electrode composition of this embodiment is coated onto a current collector to form an electrode film.

[0112] The following are examples of the main embodiments of the present invention. [I-1] A carbon material dispersion comprising a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein the carbon material (A) comprises a carbon material (a) satisfying the following (i) and (ii), and the dispersant (B) comprises a polyvinyl butyral resin (b). (i) Bulk density of 0.02 to 0.2 g / cm³ ３ (ii) Specific surface area of ​​50 m ２ / g or more [I-2] A carbon material dispersion according to [I-1], containing 5.0 to 100% by mass of polyvinyl butyral resin (b) based on the mass of the carbon material (A). [I-3] A carbon material dispersion according to [I-1] or [I-2], wherein the amount of water in the carbon material dispersion, as measured by the Karl Fischer method, is 1000 ppm or less. [I-4] A carbon material dispersion according to any one of [I-1] to [I-3], wherein the gloss value of the film formed from the carbon material dispersion is 5 or more. [I-5] A carbon material dispersion according to any one of [I-1] to [I-4], wherein the weight-average molecular weight of the polyvinyl butyral resin (b) is 20,000 to 100,000. [I-6] A carbon material dispersion according to any one of [I-1] to [I-5], wherein the low-polarity solvent (C) comprises 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. [I-7] A carbon material dispersion according to any one of [I-1] to [I-6], wherein the low-polarity solvent (C) is butyl butyrate. [I-8] An electrode composition comprising a carbon material dispersion according to any one of [I-1] to [I-7], an active material, a solid electrolyte, and a binder. [I-9] An electrode comprising an electrode film formed from a carbon material dispersion according to any one of [I-1] to [I-7] or the electrode composition according to [I-8]. [I-10] An all-solid-state battery having the electrode according to [I-9].

[0113] The following are examples of other main embodiments of the present invention. [II-1] A conductive carbon material dispersion comprising a conductive carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein when the viscosity is measured by sequentially performing the following procedures 1 to 5 and changing the shear rate, in procedure 2 the shear rate is 1s －１ The viscosity measured under these conditions was 2 (mPa·s), and the shear rate was 1 s in step 4. －１A conductive carbon material dispersion in which the rate of change A (hereinafter, formula 1) 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 To change to (Formula 1) Rate of change A (%) = (viscosity 4 - viscosity 2) / viscosity 2 × 100 [II-2] A conductive carbon material dispersion according to [II-1] above, wherein the water content is 500 ppm or less. [II-3] A conductive carbon material dispersion according to [II-1] or [II-2], wherein the conductive carbon material (A) comprises at least one selected from the group consisting of carbon black and carbon nanotubes. [II-4] A conductive carbon material dispersion according to any one of [II-1] to [II-3], wherein the low polarity solvent (C) comprises a solvent having a relative permittivity of less than 10. [II-5] A conductive carbon material dispersion according to any one of [II-1] to [II-4], wherein the solubility of the dispersant (B) in the low polarity solvent at a temperature of 25°C is 1% by mass or more, and the weight-average molecular weight is 20,000 to 350,000. [II-6] In the above procedure 2, the shear rate is 1s －１ The viscosity 2 (mPa·s) measured under the following conditions, and the shear rate 1s in step 5 below. －１ A conductive carbon material dispersion according to any one of [II-1] to [II-5], wherein the rate of change B (hereinafter, formula 2) from 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 set 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 [II-7] A composite slurry comprising a conductive carbon material dispersion, an active material, and a solid electrolyte, as described in any one of [II-1] to [II-6]. [II-8] An electrode film, a coating film of a composite slurry, wherein the composite slurry comprises a conductive carbon material dispersion, an active material, and a solid electrolyte, as described in any one of [II-1] to [II-6]. [II-9] A secondary battery comprising a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode has the electrode film described in [II-8].

[0114] This disclosure relates to the subject matter described in Japanese Patent Application No. 2025-56901, filed on 28 March 2025, Japanese Patent Application No. 2025-134137, filed on 12 August 2025, and Japanese Patent Application No. 2025-132894, filed on 8 August 2025, all of which are incorporated herein by reference.

[0115] The present disclosure will be further described below with reference to examples and comparative examples. The present disclosure is not limited to the following examples unless it exceeds its gist. In the examples and comparative examples, "parts" and "%" mean "parts by mass" and "mass%" respectively unless otherwise specified. The amounts in the table are in parts by mass, and except for solvents, the values ​​are calculated on a non-volatile content basis. Blank spaces in the table indicate that an ingredient was not included.

[0116] <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.

[0117] The following studies were conducted as Example I and Comparative Example I. In the following description, the "I" in Example I and Comparative Example I will be omitted, and only the example and comparative example numbers will be listed. <Production of carbon material dispersion> [Example 1] Carbon material dispersion (1) 86.8 parts of butyl butyrate, 1.2 parts of polyvinyl butyral resin (BL-S, manufactured by Sekisui Chemical Co., Ltd.), and 12 parts of acetylene black (Denka Black Press product 50%), manufactured by Denka Co., Ltd. were weighed and mixed. Subsequently, 150 parts of zirconia beads were added, and the mixture was shaken in a paint shaker for 2 hours, after which the zirconia beads were removed by filtration. Molecular sieves were then added and the mixture was stirred overnight in a mix rotor to dehydrate it and obtain carbon material dispersion (1).

[0118] [Examples 2-39, Comparative Examples 1-3] Carbon material dispersions (2)-(42) Carbon material dispersions (2)-(42) were obtained in the same manner as in Example 1, except that the formulations were changed to those shown in Tables I-1 and I-2. In Examples 19 and 20, the amount of molecular sieves added was reduced and the water content was increased compared to Example 1. In Example 21, the gloss value was reduced by reducing the shaking time in the paint shaker.

[0119] <Measurement and Evaluation of Carbon Material Dispersion> The obtained carbon material dispersion was subjected to the following measurements and evaluations. The results are shown in Tables I-1 and I-2.

[0120] [Moisture Content Measurement] The moisture content of the carbon material dispersion was measured using a Karl Fischer moisture meter (MKC-710 model: manufactured by Kyoto Electronics Manufacturing Co., Ltd.). The sample was treated at 150°C under a flow of 200 mL / min of nitrogen gas, and the value measured by the Karl Fischer method was calculated as the content relative to the total mass of the carbon material dispersion. The following criteria were then used for evaluation: A: Moisture content of 500 ppm or less B: Moisture content exceeding 500 ppm and 1,000 ppm or less C: Moisture content exceeding 1,000 ppm

[0121] [Gloss Value Measurement] The obtained carbon material dispersion was coated onto a PET (polyethylene terephthalate) film to a film thickness of 3 μm after drying, and then dried in a 150°C oven for 2 minutes. The resulting coating was placed on a graphite plate with the coated surface facing upwards, and the 60° gloss value was determined using a gloss meter (BYK micro-TRI-gloss). The following criteria were then used for evaluation: A: Gloss value of 10 or higher B: Gloss value of 5 or higher and less than 10 C: Gloss value less than 5

[0122] [Dispersibility Evaluation] The initial viscosity of the obtained carbon material dispersion was measured using an E-type viscometer (TV-100 model: manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C and a rotor speed of 50 rpm. Based on the obtained initial viscosity, the dispersibility was evaluated according to the following criteria: ++: Initial viscosity is 100 mPa·s or less +: Initial viscosity is greater than 100 mPa·s

[0123] [Stability Evaluation] After storing the obtained carbon material dispersion at 25°C for 7 days, the viscosity was measured in the same manner as described in (Dispersibility Evaluation) above, and the rate of change from the initial viscosity was calculated. The appearance was also observed visually. Based on the rate of change in viscosity and the appearance results, the stability was evaluated according to the following criteria: +++: Rate of change is within 10%, and no sedimentation or separation is observed. ++: Rate of change is within 30%, and no sedimentation or separation is observed. +: Rate of change exceeds 30%, or sedimentation or separation is observed.

[0124] [Electrode Resistance Evaluation] First, electrode compositions and electrodes were prepared using the obtained carbon material dispersions (1) to (42). [In the case of carbon material dispersions (1), (2), (5) to (21), (23) to (32)] In a plastic container, nine parts by mass of a 10% solution of styrene-based elastomer resin (styrene-butadiene rubber (styrene content: 25% by mass, vinyl content: 11% by mass)) was used as a binder (diluted using the same low-polarity solvent used for the carbon material dispersion) and the electrode active material LiNi ８／１０ Mn １／１０ Co １／１０ O ２41 parts of (NMC), 7.5 parts of solid electrolyte LPS, 5 parts of the obtained carbon material dispersion, and 37.5 parts of the same low-polarity solvent used in the carbon material dispersion were weighed out and stirred at 2,000 rpm for 15 seconds using a rotation / revolution mixer (Sinky Awatori Rentaro, ARE-310). The obtained electrode composition was coated onto a 20 μm thick PET film using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes, resulting in an electrode basis weight of 20 mg / cm² per unit area. ２ The mixture was adjusted to achieve the desired result. Subsequently, a heat press was used to apply pressure at 120°C to obtain the electrodes. The preparation of the electrode composition 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.

[0125] [For carbon material dispersions (3), (4), (22), (33) to (42)] In a plastic container, measure out 8.5 parts by mass of a 10% solution of styrene-based elastomer resin (styrene-butadiene rubber (styrene content: 25% by mass, vinyl content: 11% by mass)) as a binder (diluted using the same low-polarity solvent as used in the carbon material dispersion), 41.5 parts of electrode active material NMC, 7.5 parts of solid electrolyte LPS, 6 parts of the obtained carbon material dispersion, and 36.5 parts of the same low-polarity solvent as used in the carbon material dispersion. Stir at 2,000 rpm for 15 seconds using a rotation / revolution mixer (Sinky Awatori Rentaro, ARE-310). The obtained electrode composition was coated onto a 20 μm thick PET film using an applicator, and then dried on a hot plate at 150°C ± 5°C for 25 minutes, resulting in a basis weight of 20 mg / cm² per unit area of ​​the electrode. ２ The material was adjusted to achieve the desired result. Subsequently, a heat press was used to apply pressure at 120°C to obtain the electrode. The preparation of the electrode composition and the electrode film were carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0126] [Preparation of Reference Electrode] Next, a reference electrode was prepared as follows. First, 90 parts of butyl butyrate and 10 parts of acetylene black (Denka Black Press product 50%, manufactured by Denka Co., Ltd.) were weighed and mixed. Subsequently, 150 parts of zirconia beads were added, and the mixture was shaken in a paint shaker for 2 hours, after which the zirconia beads were removed by filtration. Molecular sieves were then added and the mixture was stirred overnight in a mix rotor to dehydrate it and obtain a carbon material dispersion for reference. Using the above carbon material dispersion for reference, a reference electrode was obtained in the same manner as when the electrode for electrode resistance evaluation was prepared using carbon material dispersion (1).

[0127] The volume resistivity A of the obtained electrodes 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 relative value (%) was calculated based on the volume resistivity A of the reference electrode and evaluated according to the following criteria: +++: Relative value of 50% or less (Excellent) ++: Relative value greater than 50% and 90% or less (Good) +: Relative value greater than 90% (Poor)

[0128] [Measurement Variability Evaluation] For the obtained electrodes, the volume resistivity was measured using a 4-probe method with 5-point measurement for each electrode, in accordance with JIS-K7194, and the average volume resistivity B was calculated. The measurement variation of the volume resistivity in the electrodes was calculated using Equation 1 and evaluated according to the following criteria: (Equation 1) Measurement variation % = |Volume resistivity A - Average volume resistivity B| / Volume resistivity A × 100% +++: Measurement variation is 5% or less ++: Measurement variation is greater than 5% and 20% or less +: Measurement variation is greater than 20%

[0129] [Cycle Characteristics Evaluation] Electrode compositions were prepared using the carbon material dispersions (1) to (42) and a reference carbon material dispersion, obtained in the same manner as in the [Electrode Resistance Evaluation] described above. Next, a positive electrode was prepared in the same manner as in the [Electrode Resistance Evaluation] described above, except that the electrode composition was coated onto a 20 μm thick aluminum foil, which would serve as a current collector, using an applicator.

[0130] Next, the fabricated positive electrode was punched out to a diameter of 10 mm and used as the working electrode. The working electrode and 50 mg of LPS powder were sequentially placed in the cylindrical container of the all-solid-state battery evaluation cell and pressurized at 50 MPa to create an LPS layer on the working electrode. 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 the counter electrode. Next, the cell was assembled and fixed with bolts, and then tightened using a torque wrench to the specified pressure to obtain a positive electrode evaluation cell. The assembly of the evaluation cell was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0131] 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 200 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 can be expressed as the ratio of the 0.2C discharge capacity at the 3rd cycle to the 0.2C discharge capacity at the 200th cycle, as shown in Equation 2 below. (Equation 2) Cycle characteristics = 0.2C discharge capacity at the 200th cycle / 0.2C discharge capacity at the 3rd cycle × 100 (%) The relative value (%) was determined based on the cycle characteristics of the positive electrode evaluation cell using a reference carbon material dispersion, and evaluated according to the following criteria. ++++: Relative value of 200% or more ++++: Relative value of 150% or more and less than 200% ++: Relative value of 100 or more and less than 150% +: Relative value of less than 100%

[0132]

[0133]

[0134] The abbreviations in Tables I-1 and I-2 are shown below. (Carbon material (A)) [Carbon material (a)] ・Pressed product: Denka Black Pressed Product 50% (Manufactured by Denka Co., Ltd., Acetylene Black, specific surface area 65 m²) ２ / g, bulk density 0.08 g / cm³ ３ ) ・6A: JENOTUBE6A (manufactured by JEIO, multilayer CNT, specific surface area 690 m ２ / g, bulk density 0.042 g / cm³ ３ ) ・10B: JENOTUBE10B (manufactured by JEIO, multilayer CNT, specific surface area 230 m ２ / g, bulk density 0.05 g / cm³ ３ ) ・Li-250: Denka Black Li-250 (manufactured by Denka, acetylene black, specific surface area 58 m²) ２ / g, bulk density 0.08 g / cm³ ３ ) ・EC600J: Ketjenblack EC600J (manufactured by Lion Corporation, carbon black, specific surface area 1210 m²) ２ / g, bulk density 0.12 g / cm³ ３ ) ・Li-435: Denka Black Li-435 (manufactured by Denka, acetylene black, specific surface area 133 m²) ２ / g, bulk density 0.04 g / cm³ ３ ) ・BT1001M: LUCAN BT1001M (manufactured by LG Chemical, single-walled CNT, specific surface area 240 m²) ２ / g, bulk density 0.09 g / cm³ ３ ) ・3A: JENOTUBE3A (manufactured by JEIO, single-layer CNT, specific surface area 355 m²) ２ / g, bulk density 0.03 g / cm³ ３ ) ・TUBALL: TUBALL (manufactured by OCCIAL, single-layer CNT, specific surface area 1200 m²) ２ / g, bulk density 0.05 g / cm³ ３ ) [Carbon materials other than carbon material (a)] ・Li-400: Denka Black Li-400 (manufactured by Denka Co., Ltd., acetylene black, specific surface area 39 m²) ２ / g, bulk density 0.15 g / cm³ ３ ) ・Granular product: Denka Black (manufactured by Denka Co., Ltd., acetylene black, specific surface area 69 m²) ２ / g, bulk density 0.25 g / cm³ ３ )

[0135] (Dispersant (B)) [Dispersant (b)] ・BL-S: Esrec BL-S (manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 16%, weight-average molecular weight: 23,000, viscosity of 10% ethanol solution: 24 mP·s) ・BL-10: Esrec 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) ・BL-1: Esrec BL-1 (manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 26%, weight-average molecular weight: 19,000, viscosity of 10% ethanol solution: 25 mP·s)・BM-S: Esrec BM-S (manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 16%, weight-average molecular weight: 55,000, viscosity of 10% ethanol solution: 108 mP·s) ・BH-S: Esrec BH-S (manufactured by Sekisui Chemical Co., Ltd., repeating units containing hydroxyl groups: 16%, weight-average molecular weight: 66,000, viscosity of 10% ethanol solution: 205 mP·s) ・BH-A: Esrec 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) [Dispersants other than dispersant (b)] ・K-30: Polyvinylpyrrolidone K-30 (manufactured by Nippon Shokubai Co., Ltd., polyvinylpyrrolidone)

[0136] (Low polarity solvent (C)) • Butyl butyrate: relative permittivity 4.6 • Toluene: relative permittivity 2.5 • Dibutyl ether: n-dibutyl ether, relative permittivity 3.3 • Tetralin: 1,2,3,4-tetrahydronaphthalene, relative permittivity 2.7 • Heptane: n-heptane, relative permittivity 1.9

[0137] (pH adjuster) AMP: 2-amino-2-methyl-1-propanol

[0138] As shown in Tables I-1 and I-2, the electrode film using the carbon material dispersion of this embodiment exhibited excellent electrode resistance and cycle characteristics, and when the water content was 1,000 ppm or less, it was excellent in suppressing measurement variations in electrode resistance. Furthermore, when the amount of amine compound in the dispersion was 0 to 0.1 mass%, and when the gloss value was 5 or higher, the electrode resistance was excellent. On the other hand, Comparative Example 1, which did not meet the bulk density requirement, Comparative Example 2, which did not meet the specific surface area requirement, and Comparative Example 3, which used PVP as a dispersant, all had high volume resistivity and poor electrode performance. From these results, it can be seen that, according to the present invention, a carbon material with excellent electrode resistance can be provided by the synergistic action of a carbon material that satisfies a predetermined specific surface area and a predetermined bulk density, and a polyvinyl butyral dispersant.

[0139] The following studies were conducted as Example II and Comparative Example II. In the following descriptions, the "II" in Example II and Comparative Example II will be omitted, and only the example and comparative example numbers will be listed. <Production of conductive carbon material dispersion> [Example 1-1] Dispersion (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). Subsequently, while maintaining the same operating conditions, 15.0 parts of acetylene black (Denka Black Li-250, manufactured by Denka Co., Ltd.) were added while dispersing. After adding the entire amount, mixing was carried out until the viscosity at 60 rpm, measured with a B-type viscometer (TOKI SANGYO, VISCOMETER, MODEL: BL), was 2,000 mPa·s or less. The contents were then transferred and subjected to a circulating dispersion treatment with a residence time of 1.5 minutes (80% bead filling, peripheral speed 12 m / s) using a bead mill (Ashizawa Finetech, Star Mill LMZ) 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 dispersion (1).

[0140] [Examples 1-2, 1-3] Dispersions (2) and (3) were 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 or 2.5 minutes.

[0141] [Example 1-4] Dispersion (4) Dispersion (4) was obtained in the same manner as in Example 1-2, except that the atmosphere was changed from a dry nitrogen atmosphere to normal air.

[0142] [Example 1-5] Dispersion (5) Dispersion (5) was obtained in the same manner as in Example 1-4, except that the drying step using molecular sieves was omitted.

[0143] [Examples 1-6 to 1-8] Dispersions (6) to (8) Dispersions (6) to (8) were obtained in the same manner as in Example 1-1, except that the formulation was changed to the one shown in Table II-1.

[0144] [Example 1-9] Dispersion (9) 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 out and shaken in paint conditioner for 30 minutes. Subsequently, 15.0 parts of acetylene black (Denka Black Li-250, manufactured by Denka Co., Ltd.) and 150 parts of zirconia beads were added and shaken in paint conditioner for 30 minutes, after which the zirconia beads were removed by filtration. After further transfer to a mayonnaise bottle, molecular sieves were added and stirred overnight in a mix rotor to dehydrate and obtain dispersion (9).

[0145] [Examples 1-10] Dispersion (10) 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. 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 a dispersion (10).

[0146] [Examples 1-11 to 1-13] Dispersions (11) to (13) Dispersions (11) to (13) were obtained in the same manner as in Example 1-10, except that the formulation was changed to the one shown in Table II-1.

[0147] [Examples 1-14] Dispersion (14) 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 a dispersion (14).

[0148] [Example 1-15] Dispersion (15) Dispersion (15) was obtained in the same manner as in Example 1-14, except that the formulation composition shown in Table II-1 was changed.

[0149] [Example 1-16] Dispersion (16) 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. 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 with a residence time of 5 minutes (80% bead filling, peripheral speed 12 m / s) 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 mayonnaise bottles, molecular sieves were added and the mixture was stirred overnight with a mix rotor to dehydrate and obtain dispersion liquid (16).

[0150] [Example 1-17] Dispersion (17) Dispersion (17) was obtained in the same manner as in Example 1-16, except that the formulation composition shown in Table II-1 was changed.

[0151] [Example 1-18] Dispersion (18) JENOTUBE 6A (manufactured by JEIO, multi-walled CNT) was placed in a ceramic crucible and positioned 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 reached 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 the furnace was 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. Dispersion (18) was obtained in the same manner as in Example 1-16, except that the carbon material was changed to JENOTUBE 6A-P.

[0152] [Examples 1-19, 1-20] Dispersions (19) and (20) were obtained in the same manner as in Example 1-9, except that the compositional composition shown in Table II-1 was changed and the shaking time after the addition of carbon material was changed to 4 hours.

[0153] [Example 1-21] Dispersion (21) Under a dry nitrogen atmosphere, 95.0 parts of dispersion (1) and 37.5 parts of conductive material dispersion (10) were mixed in a disperser. After transferring the mixture to a mayonnaise bottle, molecular sieves were added and the mixture was stirred overnight in a mix rotor to dehydrate it and obtain dispersion (21).

[0154] [Comparative Example 1-1] Dispersion (22) 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 Fine Tech 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 a dispersion (22).

[0155] [Comparative Examples 1-2, 1-3] Dispersions (23) and (24) were obtained in the same manner as in Example 1-1, except that the formulation was changed to the one shown in Table II-1.

[0156] [Comparative Example 1-4] Dispersion (25) Dispersion (25) was obtained in the same manner as in Example 1-10, except that the formulation composition shown in Table II-1 was changed.

[0157] <Measurement and Evaluation of Conductive Carbon Material Dispersion> The obtained dispersion was subjected to the following measurements and evaluations. The results are shown in Table II-1.

[0158] [Moisture Content Measurement] The moisture content of the dispersion was measured using a Karl Fischer moisture meter (MKC-710 model: manufactured by Kyoto Electronics Manufacturing Co., Ltd.) under a flow of 200 mL / min of nitrogen gas at 150°C. The value measured by the Karl Fischer method was calculated as the content relative to the total mass of the conductive carbon material dispersion.

[0159] [Measurement of Change Rates A and B] The viscosity of the obtained dispersion was measured by sequentially performing the above-described procedures 1 to 5 using an Anton Paar "CP50-1" cone plate (50 mm diameter, 0.1° angle) and an Anton Paar "MCR302" 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 from the aforementioned equations 1 and 2.

[0160] [Sedimentation Evaluation] The solid content concentration of the obtained dispersion was measured and recorded as the initial solid content concentration. Next, 120 mL of the dispersion was placed in a 140 mL mayonnaise jar and stored at 25°C for 7 days. After storage, the dispersion 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 3. (Formula 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 dispersion into an aluminum dish and drying it in a 140°C oven for 1 hour.

[0161]

[0162] <Preparation of Electrode Composition> Using the dispersions obtained in Example II and Comparative Example II above, an electrode composition (composite slurry) was prepared according to the method described below. [Example 2-1] Electrode composition (1) 5.3 parts of a 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 ５11.8 parts of (LPS), 16.0 parts of the obtained dispersion (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 electrode composition (1). The work related to the preparation of the electrode composition was carried out in a glove box maintained in an argon atmosphere with a dew point of -60°C or lower.

[0163] [Examples 2-2 to 2-21, Comparative Examples 2-1 to 2-4] Electrode compositions (2) to (25) Electrode compositions were obtained in the same manner as in Example 2-1, except that the compound composition was changed to that shown in Table II-2. 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 II-2.

[0164] <Evaluation of Electrode Compositions> The following evaluations were performed using the obtained electrode compositions. The results are shown in Table II-2.

[0165] [Evaluation of Conductivity] The obtained electrode composition was coated onto 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. ２ The 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)

[0166] [Cycle Characteristic Evaluation] The obtained electrode composition 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. 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.

[0167] 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 using Equation 4 below as the ratio of the 0.2C discharge capacity at the 3rd cycle to the 0.2C discharge capacity at the 50th cycle, and evaluated according to the following criteria. (Formula 4) Cycle characteristics (%) = 0.2C discharge capacity at 200 cycles / 0.2C discharge capacity at 3 cycles × 100 <Evaluation criteria> A: Cycle characteristics of 90% or more (good) B: Cycle characteristics of 80% or more and less than 90% (usable) C: Cycle characteristics of less than 80% (unusable)

[0168]

[0169] The abbreviations in the table are shown below. <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) ・Li-400: Acetylene black (Denka Black Li-400 manufactured by Denka Co., Ltd., average primary particle size 48 nm, specific surface area 39 m²) ２ / g, bulk density 0.15 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 )

[0170] <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) • 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

[0171] <Solvents> ・Butyl butyrate (dielectric constant: 4.1) ・Tetralin: 1,2,3,4-tetrahydronaphthalene (dielectric constant: 2.8) ・NMP: N-methylpyrrolidone (dielectric constant: 32)

[0172] <Additives> ・AEPD: 2-amino-2-ethyl-1,3-propanediol

[0173] As can be seen from Tables II-1 and II-2, the conductive carbon material dispersion of this embodiment exhibited excellent sedimentation suppression due to its moderate viscosity. Furthermore, the electrode film using this dispersion exhibited particularly excellent cycle characteristics. In the examples, when the properties of the carbon material raw materials, dispersion conditions, change rate A, and water content were within a suitable range, the conductivity or cycle characteristics tended to be excellent. On the other hand, all of the comparative examples in which the change rate A was outside the predetermined range exhibited inferior cycle characteristics. Furthermore, neither sedimentation suppression nor conductivity met the required characteristics. It is also thought that electrolyte degradation occurred in comparative examples 1-1 and 2-1, which included AEPD.

[0174] As Example III, the following investigation was conducted. In the following description, the "III" in Example III will be omitted, and only the example number will be listed. [Examples 1-1 to 1-13] <Conductive carbon material dispersion and its evaluation> Dispersions (1A) to (7A), (9A) to (12A), (21A) and (22A) similar to the dispersions (1) to (7), (9) to (12), (21) and (22) obtained in Example II were obtained in the same manner as described in Example II. Furthermore, for dispersions (1A) to (7A), (9A) to (12A), (21A) and (22A), evaluations of [moisture content measurement], [gloss value measurement], [dispersibility evaluation] and [stability evaluation] were performed in the same manner as described in Example I. The evaluation criteria are the same as in Example I. The results are shown in Table III-1.

[0175] [Examples 2-1 to 2-13] <Electrode Compositions and Their Evaluation> Using the dispersions (1A) to (7A), (9A) to (12A), (21A) and (22A) obtained in Examples 1-1 to 1-13, electrode compositions (1A) to (7A), (9A) to (12A), (21A) and (22A) were prepared in the same manner as described in Example II. Next, each electrode composition was evaluated for [electrode resistance evaluation], [measurement variation evaluation], and [cycle characteristics evaluation] in the same manner as described in Example I. The evaluation criteria were the same as in Example I. The results are shown in III-2.

[0176]

[0177]

[0178] The dispersions prepared in Examples 1-1 to 1-13 each have a bulk density of 0.02 to 0.2 g / cm³ as carbon material (A). ３ Furthermore, the specific surface area is 50 m². ２ A carbon material (a) with a viscosity of 1 / g or more is used, and polyvinyl butyral resin (b) is included as a dispersant (B). As shown in Tables III-1 and III-2, it can be seen that all conductive carbon material dispersions of this embodiment having the above configuration exhibit excellent dispersibility. Furthermore, it can be seen that all electrode compositions of this embodiment exhibit excellent electrode resistance. Moreover, Examples 1-1 to 1-12 have superior cycle characteristics compared to Example 1-13. Examples 1-1 to 1-12 satisfy the specified viscosity change rate A of the conductive carbon material dispersion, but Example 1-13 does not. From this, it can be seen that improving cycle characteristics is easily achieved by constructing an electrode composition using a conductive carbon material dispersion with an appropriately adjusted viscosity change rate.

Claims

1. A carbon material dispersion comprising a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein the carbon material (A) includes a carbon material (a) satisfying the following (i) and (ii): (i) having a bulk density of 0.02 to 0.2 g / cm³ ３ (ii) Specific surface area of ​​50 m ２ A carbon material dispersion liquid in which the dispersant (B) contains polyvinyl butyral resin (b) at a concentration of 1g or more.

2. The carbon material dispersion according to claim 1, comprising 5.0 to 100% by mass of polyvinyl butyral resin (b) based on the mass of the carbon material (A).

3. The carbon material dispersion according to claim 1 or 2, wherein the water content in the carbon material dispersion, as measured by the Karl Fischer method, is 1000 ppm or less.

4. The carbon material dispersion according to any one of claims 1 to 3, wherein the gloss value of the film formed from the carbon material dispersion is 5 or more.

5. The carbon material dispersion according to any one of claims 1 to 4, wherein the polyvinyl butyral resin (b) has a weight-average molecular weight of 20,000 to 100,000.

6. The carbon material dispersion according to any one of claims 1 to 5, wherein the low-polarity solvent (C) comprises 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.

7. The carbon material dispersion according to any one of claims 1 to 6, wherein the low-polarity solvent (C) contains butyl butyrate.

8. The carbon material dispersion according to any one of claims 1 to 7, wherein the carbon material (a) is at least one selected from the group consisting of carbon black and fibrous carbon.

9. A carbon material dispersion liquid comprising a carbon material (A), a dispersant (B), and a low-polarity solvent (C), wherein when viscosity is measured by changing shear rate through sequentially performing the following steps 1 to 4, the shear rate of 1 s －１ −1, viscosity 2 (mPa·s) measured under the condition, and the shear rate of 1 s －１ −1, viscosity 4 (mPa·s) measured under the condition in step 4, satisfies that a change rate A (the following formula 1) is 10% or more and 210% or less. (Step 1) Using a rotary rheometer equipped with a cone plate (diameter: 50 mm, angle: 0.1°), the shear rate is changed from 1 s －１ −1 to 1000 s －１ −1 over 170 seconds under conditions of 25°C and an inter-plate distance of 0.099 mm. (Step 2) Next, the shear rate is changed from 1000 s －１ −1 to 1 s －１ −1 over 170 seconds. (Step 3) Next, the mixture is left to stand still for 10 minutes. (Step 4) Next, the shear rate is changed from 1 s －１ −1 to 1000 s －１ −1 over 170 seconds. (Formula 1) Change rate A (%) = (viscosity 4 − viscosity 2) / viscosity 2 × 100 10. In step 2 above, 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 carbon material dispersion according to claim 9, wherein the rate of change B (hereinafter, formula 2) 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 set to 1000 s for 170 seconds. －１ from 1s －１ To change it. (Equation 2) Rate of change B (%) = (viscosity 5 - viscosity 2) / viscosity 2 × 100 11. The carbon material dispersion according to claim 9 or 10, wherein the water content is 500 ppm or less.

12. The carbon material dispersion according to any one of claims 9 to 11, wherein the dispersant (B) has a solubility of 1% by mass or more in the low-polarity solvent under a temperature of 25°C, and a weight-average molecular weight of 20,000 to 350,000.

13. The carbon material (A) includes a carbon material (a) that satisfies the following (i) and (ii): (i) has a bulk density of 0.02 to 0.2 g / cm³ ３ (ii) Specific surface area of ​​50 m ２ A carbon material dispersion according to any one of claims 9 to 11, wherein the dispersant (B) contains polyvinyl butyral resin (b) in an amount of 1g or more.

14. An electrode composition comprising a carbon material dispersion according to any one of claims 1 to 13, an active material, a solid electrolyte, and a binder.

15. An electrode comprising an electrode film formed from a carbon material dispersion according to any one of claims 1 to 13, or from the electrode composition according to claim 14.

16. A solid-state battery having the electrode described in claim 15.

17. A method for manufacturing an electrode comprising an electrode film formed from a carbon material dispersion or an electrode composition, comprising the steps of: preparing a carbon material dispersion according to any one of claims 1 to 13, or an electrode composition according to claim 14; coating a current collector with the carbon material dispersion or the electrode composition; and drying the coated carbon material dispersion or electrode composition.

18. A method for manufacturing an all-solid-state battery having a structure in which a positive electrode and a negative electrode are stacked facing each other via a separator layer made of a solid electrolyte, wherein at least one of the positive electrode and the negative electrode is an electrode manufactured by the electrode manufacturing method described in claim 15 or claim 17.

Images