Binder particles for all-solid-state batteries, composition for all-solid-state batteries, functional layer for all-solid-state batteries, and all-solid-state batteries

Abstract

The purpose of the present invention is to provide binder particles for an all-solid-state battery that enable attainment of an all-solid-state battery having superior battery characteristics even if the all-solid-state battery is manufactured using a dry process. The binder particles for an all-solid-state battery of the present invention are characterized by: being constituted by a polymer; having an agglomeration rate of 1% to less than 30%; and having a volume average particle diameter D50 of 10 to 100 μｍ, inclusive. A composition for an all-solid-state battery of the present invention is characterized by containing the binder particles for an all-solid-state battery and solid electrolyte particles. A functional layer for an all-solid-state battery of the present invention is characterized by being formed from the composition for an all-solid-state battery. Additionally, an all-solid-state battery of the present invention is characterized by comprising the functional layer for an all-solid-state battery.

Description

[Technical Field]

[0001] The present invention relates to binder particles for an all-solid-state battery, a composition for an all-solid-state battery, a functional layer for an all-solid-state battery, and an all-solid-state battery. [Background technology]

[0002] In recent years, demand for batteries such as lithium-ion batteries has been increasing for a variety of applications, including not only portable terminals such as personal digital assistants and portable electronic devices, but also small home power storage devices, electric motorcycles, electric vehicles, and hybrid electric vehicles.

[0003] With the expansion of such applications, further improvements in the safety of batteries are required. To ensure the safety of batteries, for example, a method of preventing leakage of an organic electrolyte solution obtained by dissolving an electrolyte in an organic solvent is effective. Meanwhile, techniques for producing batteries (all-solid-state batteries) in which all components are solid, including a solid electrolyte layer instead of a flammable organic electrolyte solution, have also been studied.

[0004] Specifically, all-solid-state batteries typically have a solid electrolyte layer between a positive electrode and a negative electrode. A binder is typically used in the fabrication of all-solid-state batteries. The binder is used, for example, in the solid electrolyte layer or in the electrode active material layer of an electrode formed by providing an electrode active material layer on a current collector, to bind components such as solid electrolyte particles and electrode active material together and prevent these components from being detached from battery components such as the electrode. For example, Patent Documents 1 to 3 describe forming an electrode active material layer by applying a slurry composition for an electrode layer containing an electrode active material, solid electrolyte particles, a predetermined binder, and a solvent (dispersion medium) onto a current collector and drying it. They also describe forming a solid electrolyte layer by applying a slurry composition for a solid electrolyte layer containing solid electrolyte particles, a predetermined binder, and a solvent (dispersion medium) onto an electrode active material layer and drying it. [Prior art documents] [Non-patent literature]

[0005] [Patent Document 1] Patent No. 6459691 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-088486 [Patent Document 3] International Publication No. 2016 / 136090 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional technology, which uses a slurry composition containing a solvent (dispersion medium) to form an electrode active material layer or a solid electrolyte layer (hereinafter, these layers may be collectively referred to as "functional layers"), requires good dispersion of the compounded components in the slurry composition, and has room for improvement in that operations such as coating and drying are complicated. Here, one possible technology that can solve such problems is to form a functional layer by dry-mixing (dry blending) the components that make up the functional layer and molding the resulting composition using a molding method such as hot pressing. However, according to the investigations of the present inventors, when an all-solid-state battery is manufactured by a dry process using the conventional binder, the binder particles have poor fluidity, resulting in aggregation (blocking), and the adhesion between the electrode active material particles and the solid electrolyte particles in the electrode active material layer and the solid electrolyte layer is not necessarily sufficient. Therefore, in an all-solid-state battery manufactured using the binder, the electrode active material particles and the solid electrolyte particles cannot be sufficiently bound together, and the battery characteristics such as the output characteristics and the cycle characteristics may be insufficient.

[0007] Therefore, an object of the present invention is to provide binder particles for an all-solid-state battery, a composition for an all-solid-state battery, and a functional layer for an all-solid-state battery, which can provide an all-solid-state battery with excellent battery characteristics even when the all-solid-state battery is manufactured by a dry process, and an all-solid-state battery with excellent battery characteristics. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to achieve the above object, and as a result, have found that the above object can be achieved by using binder particles for an all-solid-state battery having a specific aggregation degree and a specific average particle diameter, thereby completing the present invention.

[0009] The present invention advantageously solves the above-mentioned problems, and the binder particles for an all-solid-state battery of the present invention are characterized by being composed of a polymer, having a degree of aggregation of 1% or more and less than 30%, and having a volume average particle diameter D50 of 10 μm or more and 100 μm or less. By using binder particles for an all-solid-state battery having such a specific degree of aggregation and specific average particle diameter, even when the functional layer is produced by a dry process, it is possible to satisfactorily bind the electrode active material particles and solid electrolyte particles in the functional layer, and the battery characteristics of the resulting all-solid-state battery can be improved. In the present invention, the "degree of aggregation" of the binder particles for an all-solid-state battery can be measured by the method described in the examples below. In the present invention, the "volume average particle diameter D50" of the binder particles for an all-solid-state battery means a particle diameter at which the cumulative volume calculated from the small diameter side in the particle size distribution (volume basis) measured by a laser diffraction method becomes 50%, and can be measured by the method described in the examples below.

[0010] Furthermore, in the binder particles for an all-solid-state battery of the present invention, the glass transition temperature of the polymer is preferably 50° C. or higher and 120° C. or lower. By having the glass transition temperature of the polymer be 50° C. or higher and 120° C. or lower, in an all-solid-state battery produced using the binder particles for an all-solid-state battery, it is possible to more effectively prevent the binder particles for an all-solid-state battery from excessively agglomerating and thereby reducing adhesion, and it is also possible to more effectively prevent the binder particles for an all-solid-state battery from becoming too hard and thereby reducing strength. As a result, it is possible to further improve the battery characteristics of the all-solid-state battery. In the present invention, the "glass transition temperature" of the polymer contained in the binder particles for an all-solid-state battery can be measured by the method described in the examples below.

[0011] In addition, in the binder particles for an all-solid-state battery of the present invention, the polymer preferably contains an ethylenically unsaturated acid monomer unit, and the content of the ethylenically unsaturated acid monomer unit in the polymer is preferably 1.5% by mass or more and less than 10% by mass. If the polymer contains the ethylenically unsaturated acid monomer unit in the above-mentioned proportion, the battery characteristics of the all-solid-state battery can be further improved.

[0012] Furthermore, in the binder particles for all-solid-state batteries of the present invention, the polymer contains alkyl acrylate ester monomer units having an alkyl chain with four or more carbon atoms and alkyl methacrylate ester monomer units having an alkyl chain with four or fewer carbon atoms, and the content of the alkyl acrylate ester monomer units having an alkyl chain with four or more carbon atoms in the polymer is preferably 5% to 40% by mass, and the content of the alkyl methacrylate ester monomer units having an alkyl chain with four or fewer carbon atoms in the polymer is preferably 5% to 40% by mass. When the polymer contains alkyl acrylate ester monomer units having an alkyl chain with four or more carbon atoms in the above-mentioned proportion, the binder particles for all-solid-state batteries can be more effectively bonded to electrode active material particles and solid electrolyte particles in all-solid-state batteries produced using the binder particles for all-solid-state batteries. This further improves the battery characteristics of the all-solid-state batteries. Furthermore, if the polymer contains the methacrylic acid alkyl ester monomer units having an alkyl chain with 4 or less carbon atoms in the above ratio, in an all-solid-state battery manufactured using the binder particles for an all-solid-state battery, the binder particles for an all-solid-state battery can better adhere to the electrode active material particles and the solid electrolyte particles, and the binder particles can be more effectively prevented from becoming too hard and causing a decrease in strength, thereby further improving the battery characteristics of the solid-state battery.

[0013] Furthermore, in the binder particles for an all-solid-state battery of the present invention, the polymer preferably contains at least one monomer unit selected from the group consisting of nitrile group-containing monomer units and aromatic vinyl monomer units. When the polymer contains at least one monomer unit selected from the group consisting of nitrile group-containing monomer units and aromatic vinyl monomer units, the binder particles for an all-solid-state battery can be more effectively prevented from excessive aggregation, resulting in a decrease in adhesion, and the binder particles for an all-solid-state battery can be more effectively prevented from becoming too hard, resulting in a decrease in strength. This further improves the battery characteristics of the all-solid-state battery.

[0014] Furthermore, in the binder particles for an all-solid-state battery of the present invention, the polymer preferably contains a crosslinkable monomer unit, and the content of the crosslinkable monomer unit in the polymer is preferably 0.1% by mass or more and less than 2.0% by mass. When the polymer contains the crosslinkable monomer unit in the above-mentioned proportion, the polymer is appropriately crosslinked and the binder particles have an appropriate amount of gel structure, which makes it possible to more effectively prevent excessive aggregation of the binder particles for an all-solid-state battery and more effectively prevent a decrease in strength due to the binder particles for an all-solid-state battery becoming too hard. As a result, the battery characteristics of the all-solid-state battery can be further improved.

[0015] Furthermore, the present invention aims to advantageously solve the above-mentioned problems, and provides a composition for an all-solid-state battery of the present invention, which is characterized by containing any of the binder particles for an all-solid-state battery described above and solid electrolyte particles. The composition for an all-solid-state battery containing the binder particles for an all-solid-state battery described above can satisfactorily form a functional layer, allowing the all-solid-state battery to exhibit excellent battery characteristics.

[0016] The composition for an all-solid-state battery of the present invention preferably further contains an electrode active material. If the composition for an all-solid-state battery contains an electrode active material, an electrode active material layer can be formed well, and the all-solid-state battery can exhibit excellent battery characteristics.

[0017] Furthermore, the composition for an all-solid-state battery of the present invention preferably further contains a conductive auxiliary. When the composition for an all-solid-state battery containing an electrode active material further contains a conductive auxiliary, the conductivity of the obtained electrode can be improved, and the battery characteristics of the all-solid-state battery can be further improved.

[0018] Furthermore, the present invention aims to advantageously solve the above-mentioned problems, and the functional layer for an all-solid-state battery of the present invention is characterized in that it is formed using any of the above-mentioned compositions for an all-solid-state battery. A functional layer formed using a composition for an all-solid-state battery containing the above-mentioned binder particles for an all-solid-state battery can cause the all-solid-state battery to exhibit excellent battery characteristics.

[0019] Furthermore, the present invention aims to advantageously solve the above-mentioned problems, and the all-solid-state battery of the present invention is characterized by including the above-mentioned functional layer for an all-solid-state battery. An all-solid-state battery including the functional layer for an all-solid-state battery manufactured using the above-mentioned binder particles for an all-solid-state battery has excellent battery characteristics. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide binder particles for an all-solid-state battery, a composition for an all-solid-state battery, and a functional layer for an all-solid-state battery, which can provide an all-solid-state battery with excellent battery characteristics even when the all-solid-state battery is manufactured by a dry process, and an all-solid-state battery with excellent battery characteristics. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail. The binder particles for an all-solid-state battery of the present invention (hereinafter also simply referred to as "binder particles") are used in the production of an all-solid-state battery (for example, in the formation of a functional layer). The composition for an all-solid-state battery of the present invention contains at least the binder particles for an all-solid-state battery of the present invention and solid electrolyte particles, and is used to form a functional layer included in an all-solid-state battery. The functional layer for an all-solid-state battery of the present invention is formed from the composition for an all-solid-state battery of the present invention. The all-solid-state battery of the present invention comprises the functional layer for an all-solid-state battery of the present invention.

[0022] (binder particles) The binder particles of the present invention are composed of a polymer, have a degree of aggregation of 1% or more and less than 30%, and a volume average particle diameter D50 of 10 μm or more and 100 μm or less. The binder particles of the present invention are particles that exist in a particulate state in a gas phase, and usually exist as an aggregate of multiple particles. The binder particles may contain additives, impurities mixed in during the manufacturing process, etc. However, the binder particles usually do not contain an active material or a solid electrolyte.

[0023] (Properties of binder particles) <Cohesion degree> The degree of aggregation of the binder particles of the present invention must be 1% or more and less than 30%, preferably 1.5% or more, more preferably 2% or more, even more preferably 10% or more, and preferably 20% or less, more preferably 15% or less. When the degree of aggregation of the binder particles is 1% or more and less than 30%, good aggregation resistance (blocking resistance) is exhibited, allowing for uniform dry blending with electrode active material particles and / or solid electrolyte particles, and the binder particles adhere well to the electrode active material particles and / or solid electrolyte particles. If the degree of aggregation of the binder particles is less than 1%, good adhesion with the electrode active material particles and / or solid electrolyte particles is impaired, resulting in poor cycle performance of the all-solid-state battery. On the other hand, if the degree of aggregation of the binder particles is 30% or more, the binder particles will excessively aggregate, reducing fluidity (dispersibility) during dry blending. This reduces adhesion with the electrode active material particles and / or solid electrolyte particles, resulting in poor cycle performance. The degree of aggregation of the binder particles can be controlled, for example, by adjusting the glass transition temperature of the polymer described below and / or the content ratio of crosslinkable monomer units contained in the polymer.

[0024] <Volume average particle size D50> The volume average particle diameter D50 of the binder particles of the present invention must be 10 μm or more and 100 μm or less, preferably 15 μm or more, more preferably 20 μm or more, even more preferably 50 μm or more, and preferably 90 μm or less, more preferably 85 μm or less, and even more preferably 80 μm or less. If the volume average particle diameter D50 is less than 10 μm, the adhesion area (particle coverage area) with the electrode active material particles and solid electrolyte particles increases excessively, resulting in increased resistance. This results in a decrease in the output characteristics of the all-solid-state battery. On the other hand, if the volume average particle diameter D50 exceeds 100 μm, the adhesion area with the electrode active material particles and solid electrolyte particles decreases, resulting in decreased adhesion. This results in a decrease in the cycle characteristics of the all-solid-state battery. The volume average particle diameter D50 can be adjusted to a desired range by adjusting the amount of an emulsifier or the amount of a monomer in the polymer synthesis method described below. Alternatively, the volume average particle diameter D50 can be adjusted to a desired range by using a particle size distribution adjustment method described below.

[0025] <Moisture content> The water content of the binder particles of the present invention is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 2,000 ppm or less, and particularly preferably 1,000 ppm or less. If the water content exceeds 10,000 ppm, the binder particles are likely to aggregate (block) due to the water, which may result in a decrease in the output characteristics and / or cycle characteristics of the all-solid-state battery. The moisture content of the binder particles can be measured by the method described in the Examples below.

[0026] (polymer) <Glass transition temperature> The glass transition temperature of the polymer constituting the binder particles of the present invention is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 75°C or higher, and is preferably 120°C or lower, more preferably 110°C or lower, and even more preferably 100°C or lower. If the glass transition temperature of the polymer is 50°C or higher, it is possible to more effectively prevent a deterioration in the cycle characteristics of the all-solid-state battery due to excessive aggregation of the binder particles, which would reduce adhesion to the electrode active material or solid electrolyte particles. Furthermore, if the glass transition temperature of the polymer is 120°C or lower, it is possible to more effectively prevent a deterioration in the cycle characteristics due to a reduction in strength caused by the binder particles becoming too hard.

[0027] <Composition> The composition of the polymer is not particularly limited and can be any composition that can be used as a binder for an all-solid-state battery. The polymer can contain, for example, at least one monomer unit selected from the group consisting of an ethylenically unsaturated acid monomer unit, an acrylic acid alkyl ester monomer unit having an alkyl chain with four or more carbon atoms, a methacrylic acid alkyl ester monomer unit having an alkyl chain with four or less carbon atoms, a nitrile group-containing monomer unit, and an aromatic vinyl monomer unit, as well as other monomer units. In the present invention, when a polymer "contains a monomer unit," it means that "a polymer obtained using the monomer contains a structural unit (repeating unit) derived from the monomer."

[0028] <<Ethylenically unsaturated acid monomer unit>> The ethylenically unsaturated acid monomer unit that can be contained in the polymer is a repeating unit derived from an ethylenically unsaturated acid monomer, contains an ethylenically unsaturated bond, and has an acidic group. Examples of the acidic group include a -COOH group (carboxylic acid group); a -SO group (sulfonic acid group); and a -PO H group (phosphoric acid group). Therefore, as the ethylenically unsaturated acid monomer, an acidic group-containing monomer such as a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, or a monomer having a phosphoric acid group can be used. Furthermore, examples of the acidic group-containing monomer include, for example, a monomer that can generate the above-mentioned acidic group upon hydrolysis. Specific examples of such acidic group-containing monomers include acid anhydrides that can generate a carboxylic acid group upon hydrolysis. These monomers may be used either alone or in combination of two or more kinds in any ratio.

[0029] Examples of monomers having a carboxylic acid group include monocarboxylic acids, dicarboxylic acids, dicarboxylic acid anhydrides, and derivatives thereof. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, crotonic acid, 2-ethylacrylic acid, and isocrotonic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, and methylmaleic acid. Examples of dicarboxylic acid anhydrides include maleic anhydride, acrylic anhydride, methylmaleic anhydride, and dimethylmaleic anhydride. Among these, acrylic acid, methacrylic acid, and itaconic acid are preferred.

[0030] Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, 2-(N-acryloyl)amino-2-methyl-1,3-propane-disulfonic acid, etc. Among these, 2-acrylamido-2-methylpropanesulfonic acid is preferred.

[0031] Examples of the monomer having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate.

[0032] The content of the ethylenically unsaturated acid monomer units in the polymer is preferably 1.5% by mass or more, more preferably 1.7% by mass or more, even more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more, based on 100% by mass of all monomer units constituting the polymer. It is also preferably less than 10% by mass, more preferably 8% by mass or less, and even more preferably 6% by mass or less. When the content of the ethylenically unsaturated acid monomer units in the polymer is equal to or greater than the lower limit, aggregation of binder particles is prevented, adhesion to electrode active material particles and solid electrolyte particles is further improved, and cycle characteristics are further improved. On the other hand, when the content of the ethylenically unsaturated acid monomer units in the polymer is equal to or less than the upper limit, reaction between the ethylenically unsaturated acid monomer units and the solid electrolyte is prevented, which prevents an increase in resistance due to the reaction between the two, thereby further improving the output characteristics of the all-solid-state battery.

[0033] <<Acrylic acid alkyl ester monomer unit having an alkyl chain with 4 or more carbon atoms>> The acrylic acid alkyl ester monomer unit having an alkyl chain with 4 or more carbon atoms is a repeating unit derived from an acrylic acid alkyl ester monomer having an alkyl chain with 4 or more carbon atoms. Examples of alkyl acrylate monomers having an alkyl chain with 4 or more carbon atoms that can form alkyl acrylate monomer units having an alkyl chain with 4 or more carbon atoms include n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate (n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, etc.), nonyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, undecyl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, and stearyl acrylate. Of these, butyl acrylate and 2-ethylhexyl acrylate are preferred. These compounds may be used either alone or in combination of two or more in any ratio.

[0034] The content of acrylic acid alkyl ester monomer units having an alkyl chain of 4 or more carbon atoms in the polymer is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 19% by mass or more, and preferably 40% by mass or less, preferably 30% by mass or less, and even more preferably 25% by mass or less, based on 100% by mass of all monomer units constituting the polymer. When the content of acrylic acid alkyl ester monomer units having an alkyl chain of 4 or more carbon atoms in the polymer is equal to or greater than the above-mentioned lower limit, deterioration of cycle characteristics due to reduced adhesion to the solid electrolyte particles can be more effectively prevented. On the other hand, when the content is equal to or less than the above-mentioned upper limit, deterioration of cycle characteristics due to reduced adhesion to the electrode active material or solid electrolyte particles caused by aggregation of binder particles can be more effectively prevented.

[0035] <<Methacrylic acid alkyl ester monomer unit having an alkyl chain with 4 or less carbon atoms>> The methacrylic acid alkyl ester monomer unit having an alkyl chain with 4 or less carbon atoms is a repeating unit derived from a methacrylic acid alkyl ester monomer having an alkyl chain with 4 or less carbon atoms. Examples of methacrylic acid alkyl ester monomers having an alkyl chain containing 4 or less carbon atoms that can form methacrylic acid alkyl ester monomer units having an alkyl chain containing 4 or less carbon atoms include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and isobutyl methacrylate. Among these, methyl methacrylate and ethyl methacrylate are preferred, and methyl methacrylate is more preferred. These compounds may be used alone or in combination of two or more in any ratio.

[0036] The content of methacrylic acid alkyl ester monomer units having an alkyl chain containing 4 or less carbon atoms in the polymer is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 9% by mass or more, even more preferably 11.5% by mass or more, and preferably 40% by mass or less, preferably 25% by mass or less, and even more preferably 20% by mass or less, based on 100% by mass of all monomer units constituting the polymer. When the content of methacrylic acid alkyl ester monomer units having an alkyl chain containing 4 or less carbon atoms in the polymer is equal to or greater than the lower limit, deterioration of cycle characteristics due to aggregation of binder particles and reduced adhesion to the electrode active material and solid electrolyte particles can be more effectively prevented. When the content is equal to or less than the upper limit, deterioration of cycle characteristics due to excessive hardness of the binder particles and reduced strength can be more effectively prevented.

[0037] <<At least one monomer unit selected from the group consisting of nitrile group-containing monomer units and aromatic vinyl monomer units>> The at least one monomer unit selected from the group consisting of nitrile group-containing monomer units and aromatic vinyl monomer units is a repeating unit derived from at least one monomer selected from the group consisting of nitrile group-containing monomers and aromatic vinyl monomers.

[0038] -Nitrile group-containing monomer unit- Examples of nitrile group-containing monomers capable of forming nitrile group-containing monomer units include α,β-ethylenically unsaturated nitrile monomers. Specifically, the α,β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α,β-ethylenically unsaturated compound having a nitrile group. Examples include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. Among these, acrylonitrile and methacrylonitrile are preferred as nitrile group-containing monomers from the viewpoint of satisfactorily increasing the glass transition temperature of the polymer. These compounds can be used alone or in combination of two or more.

[0039] -Aromatic vinyl monomer unit- Examples of aromatic vinyl compounds that can form aromatic vinyl monomer units include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, divinylbenzene, N,N-dimethyl-p-aminoethylstyrene, 2,4-dimethylstyrene, N,N-diethyl-p-aminoethylstyrene, 2,4-diethylstyrene, vinylnaphthalene, and vinylanthracene. Among these, styrene is particularly preferred from the viewpoint of satisfactorily increasing the glass transition temperature of the polymer. These compounds may be used alone or in combination of two or more in any ratio.

[0040] The content of at least one monomer unit selected from the group consisting of nitrile group-containing monomer units and aromatic vinyl monomer units in the polymer is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 66.25% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, based on 100% by mass of all monomer units constituting the polymer. When the content of at least one monomer unit selected from the group consisting of nitrile group-containing monomer units and aromatic vinyl monomer units in the polymer is equal to or greater than the lower limit, the glass transition temperature of the polymer can be improved, and deterioration in cycle performance due to reduced adhesion between the binder particles and the electrode active material or solid electrolyte particles can be prevented. When the content is equal to or less than the upper limit, deterioration in cycle performance due to reduced strength due to excessive hardness of the binder particles can be prevented.

[0041] <<Crosslinkable monomer unit>> The crosslinkable monomer unit is a repeating unit derived from a crosslinkable monomer. The crosslinkable monomer capable of forming the crosslinkable monomer unit can be any monomer capable of forming a crosslinked structure upon polymerization (excluding the compounds described above as "monomer"). Specific examples include monofunctional monomers having a thermally crosslinkable crosslinkable group and one ethylenically unsaturated bond per molecule, and polyfunctional monomers having two or more ethylenically unsaturated bonds per molecule. Examples of the thermally crosslinkable crosslinkable group contained in the monofunctional monomer include an epoxy group, an N-methylolamide group, an oxetanyl group, an oxazoline group, and combinations thereof.

[0042] The cross-linking monomer may be either hydrophobic or hydrophilic. In the present invention, a crosslinkable monomer being "hydrophobic" means that the crosslinkable monomer does not contain a hydrophilic group, and a crosslinkable monomer being "hydrophilic" means that the crosslinkable monomer contains a hydrophilic group. Here, the "hydrophilic group" in the crosslinkable monomer refers to a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a phosphate group, an epoxy group, a thiol group, an aldehyde group, an amide group, an oxetanyl group, or an oxazoline group.

[0043] Examples of hydrophobic crosslinkable monomers include polyfunctional (meth)acrylates such as allyl (meth)acrylate, ethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate; polyfunctional allyl / vinyl ethers such as dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, and tetraallyloxyethane; and divinylbenzene. Examples of hydrophilic crosslinkable monomers include vinyl glycidyl ether, allyl glycidyl ether, N-methylolacrylamide, acrylamide, and allyl methacrylamide. Among these, allyl methacrylate, ethylene dimethacrylate, and allyl glycidyl ether are preferred as the crosslinkable monomer. These may be used alone or in combination of two or more.

[0044] The content of the crosslinkable monomer units in the polymer, when the amount of all monomer units is taken as 100% by mass, is preferably 0.1% by mass or more, more preferably 0.15% by mass or more, even more preferably 0.2% by mass or more, even more preferably 0.25% by mass or more, and is preferably less than 2.0% by mass, more preferably less than 1.0% by mass, and even more preferably less than 0.5% by mass. When the content of the crosslinkable monomer units in the polymer is equal to or greater than the above-mentioned lower limit, the polymer has an appropriate amount of gel structure, which can more effectively prevent excessive aggregation of the binder particles, which reduces adhesion to the electrode active material and solid electrolyte particles and leads to a deterioration in the cycle characteristics of the all-solid-state battery. On the other hand, when the content is equal to or less than the above-mentioned upper limit, it can more effectively prevent a deterioration in cycle characteristics due to a decrease in strength caused by the binder particles becoming too hard.

[0045] <<Other monomer units>> The other monomer units other than the above-described monomer units are not particularly limited, and examples thereof include repeating units derived from known monomers copolymerizable with the above-described monomers, such as hydroxyl group-containing monomer units and conjugated diene monomer units. Examples of monomers having a hydroxyl group that can form a hydroxyl group-containing monomer unit include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-butene-1-ol, and 5-hexene-1-ol; alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconate; and esters of ethylenically unsaturated carboxylic acids having the general formula: CH═CR 1 -COO-(C q H 2q O) p -H (wherein p is an integer of 2 to 9, q is an integer of 2 to 4, R 1represents a hydrogen atom or a methyl group) and (meth)acrylic acid esters; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; alkyl ethers such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, and (meth)allyl-6-hydroxyhexyl ether. mono(meth)allyl ethers of alkylene glycol; polyoxyalkylene glycol mono(meth)allyl ethers such as diethylene glycol mono(meth)allyl ether and dipropylene glycol mono(meth)allyl ether; mono(meth)allyl ethers of halogen- and hydroxy-substituted (poly)alkylene glycols such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether and (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyhydric phenols such as eugenol and isoeugenol and halogen-substituted products thereof; (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether; etc. These may be used alone or in combination of two or more in any ratio.

[0046] -Conjugated diene monomer unit- Examples of conjugated diene monomers capable of forming conjugated diene monomer units include aliphatic conjugated diene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadiene, substituted and side-chain conjugated hexadienes, etc. These may be used alone or in combination of two or more in any ratio.

[0047] The content of the other repeating units in the polymer used in the present invention is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less, when the total amount of all repeating units in the polymer is 100% by mass.

[0048] <Gel structure> The polymer preferably has a gel structure, and more specifically, a gel fraction of 90% or more. A gel fraction of 90% or more allows the polymer to have an appropriate amount of gel structure, thereby more effectively preventing deterioration in the cycle characteristics of the all-solid-state battery due to excessive aggregation of binder particles, which reduces adhesion to the electrode active material and solid electrolyte particles. The gel fraction is an indicator of whether the polymer has a gel structure, and is a value indicating the weight ratio of components that are insoluble in organic solvents due to bonding or entanglement of polymer chains to the total weight. The gel fraction can be controlled, for example, by adjusting the amount of the crosslinkable monomer used. The gel fraction can be determined, for example, by immersing a film obtained by pressing binder particles under pressure in tetrahydrofuran (THF) for 24 hours, filtering the film through a 200-mesh stainless steel wire mesh, drying the filtered wire mesh at 100°C for 1 hour, and dividing the increase in weight of the wire mesh by the weight of the film.

[0049] <Method of polymer synthesis> The polymer used in the present invention may be synthesized by any method, and may be obtained, for example, by polymerizing a monomer composition containing the above-mentioned monomers. The polymerization may be carried out in the presence of an optional chain transfer agent (molecular weight modifier). Here, the content ratio of each monomer in the monomer composition used for synthesizing the polymer can be determined according to the content ratio of each repeating unit in the polymer.

[0050] The polymerization method is not particularly limited, and any of solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. The polymerization reaction may be carried out in any of ionic polymerization, radical polymerization, living radical polymerization, etc. The case where emulsion polymerization is used as the polymerization method will be explained below.

[0051] [Emulsion polymerization method] The emulsion polymerization can be carried out in a conventional manner. In addition, during the emulsion polymerization, commonly used polymerization auxiliary materials such as an emulsifier, a polymerization initiator, and a chain transfer agent can be used.

[0052] Any emulsifier can be used as long as it can produce the desired copolymer, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, anionic surfactants such as alkylbenzene sulfonates, aliphatic sulfonates, sulfates of higher alcohols, α-olefin sulfonates, and alkyl ether sulfates are preferably used.

[0053] The amount of emulsifier is optional as long as the desired polymer is obtained, and is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the total of the monomers in the monomer composition.

[0054] Any polymerization initiator can be used in the polymerization reaction as long as it can produce the desired polymer, and examples thereof include sodium persulfate (NaPS), ammonium persulfate (APS), and potassium persulfate (KPS).

[0055] Furthermore, during polymerization, the polymerization system may contain a chain transfer agent. Examples of the chain transfer agent include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan; xanthogen compounds such as dimethyl xanthogen disulfide and diisopropyl xanthogen disulfide; terpinolene; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide; phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrabromide; thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, diphenylethylene, and α-methylstyrene dimer. Among these, alkyl mercaptans are preferred, and t-dodecyl mercaptan is more preferred, from the viewpoint of suppressing side reactions. These may be used alone or in combination of two or more in any ratio.

[0056] When a chain transfer agent is used, the amount of the chain transfer agent used is preferably 0.1 parts by mass or more, more preferably 0.15 parts by mass or more, and preferably 0.6 parts by mass or less, more preferably 0.5 parts by mass or less, per 100 parts by mass of the total of the monomers in the monomer composition.

[0057] In addition, examples of solvents that can be used when employing emulsion polymerization include aqueous solvents. Here, the aqueous solvent is a solvent containing water and is not flammable. Note that, as long as the effects of the present invention are not impaired and the copolymer can be obtained, water may be used as the main solvent and mixed with an aqueous solvent other than water. Examples of aqueous solvents other than water include ketones, alcohols, glycols, glycol ethers, and ethers.

[0058] In addition, seed polymerization may be carried out using seed particles. The polymerization conditions can also be selected arbitrarily depending on the polymerization method, the type of polymerization initiator, and the like.

[0059] The synthesized polymer is preferably a particulate polymer dispersed in a solvent, and a polymer that remains particulate even after drying.

[0060] <Granulation of binder particles> The binder particles of the present invention can be obtained by granulating a polymer by a conventionally known method. The granulation method is not particularly limited, but preferably includes step (A) of granulating a raw material slurry containing the polymer by any granulation method, and optionally includes step (B) of adjusting the properties of the obtained particles, and other steps.

[0061] <<Process (A)>> Step (A) is a step of obtaining binder particles by granulating a raw material slurry containing a polymer using a known granulation method, such as spray drying granulation, tumbling bed granulation, compression granulation, stirring granulation, extrusion granulation, crushing granulation, fluidized bed granulation, fluidized bed multifunctional granulation, pulse combustion drying, and melt granulation. Among these, in step (A), it is preferable to granulate the raw material slurry using a nozzle-type or atomizer-type spray dryer, and it is more preferable to granulate the raw material slurry using an atomizer-type spray dryer. The granulation conditions can be adjusted appropriately according to the desired properties of the binder particles.

[0062] <<Process (B)>> Step (B) is a step for adjusting the properties of the particles obtained in step (A) described above. Specifically, in step (B), the average particle diameter D50 of the binder particles can be adjusted using a known particle size distribution adjustment method, such as pulverization or classification.

[0063] <<Other processes>> Other steps include, but are not limited to, a step of mixing the polymer with other polymers as optional components, additives such as plasticizers, and / or a solvent to prepare a raw material slurry before step (A). The solvent is not particularly limited, and water or the like can be used. When the above-mentioned polymer is mixed in the state of a solution or aqueous dispersion, the solvent of the solution or aqueous dispersion may be used as the solvent. As a means for dispersing or dissolving the above-mentioned components in a solvent, for example, a mixing device such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, or a planetary mixer can be used. The solid content and viscosity of the raw material slurry can be adjusted appropriately depending on the granulation conditions.

[0064] (Composition for all-solid-state batteries) The composition for an all-solid-state battery of the present invention contains at least the binder particles of the present invention and solid electrolyte particles, and optionally further contains an electrode active material (positive electrode active material or negative electrode active material) and / or additives such as a conductive aid, a reinforcing material, etc. The amount of solvent in the composition for an all-solid-state battery of the present invention is 0.1 mass % or less.

[0065] The composition for an all-solid-state battery of the present invention, which does not contain an electrode active material, is a composition for a solid electrolyte layer that can be used to form a solid electrolyte layer of an all-solid-state battery. Specifically, the composition for a solid electrolyte layer contains at least the binder particles of the present invention and solid electrolyte particles, and optionally further contains additives that exhibit various functions, such as a reinforcing material.

[0066] The composition for an all-solid-state battery of the present invention, which contains a positive electrode active material, is a composition for a positive electrode active material layer that can be used to form a positive electrode active material layer of an all-solid-state battery. Specifically, the composition for a positive electrode active material layer contains at least the binder particles of the present invention, a positive electrode active material, and solid electrolyte particles, and optionally further contains additives that exhibit various functions, such as a conductive aid and a reinforcing material.

[0067] The composition for an all-solid-state battery of the present invention, which contains a negative electrode active material, is a composition for a negative electrode active material layer that can be used to form a negative electrode active material layer of an all-solid-state battery. Specifically, the composition for a negative electrode active material layer contains at least the binder particles of the present invention, a negative electrode active material, and solid electrolyte particles, and optionally further contains additives that exhibit various functions, such as a conductive aid and a reinforcing material.

[0068] <Solid electrolyte particles> Solid electrolyte particles are usually particulate because they have been crushed, but they are irregularly shaped rather than perfectly spherical. The size of fine particles is generally measured by irradiating the particles with laser light and measuring the scattered light, but in this case the particle diameter is a value assuming that each particle is spherical. When multiple particles are measured together, the proportion of particles with a corresponding particle diameter can be expressed as a particle size distribution. The solid electrolyte particles that form the solid electrolyte layer are often expressed as an average particle diameter, measured using this method.

[0069] The average particle diameter of the solid electrolyte particles is preferably 0.3 μm or more and 5.0 μm or less from the viewpoint of ion conduction resistance in the solid electrolyte layer. The average particle diameter of the solid electrolyte particles is a volume-average particle diameter, and refers to the particle diameter (D50) at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured by laser diffraction method becomes 50%.

[0070] In the case of an all-solid-state lithium secondary battery, the solid electrolyte particles are not particularly limited as long as they have lithium ion conductivity, but preferably contain a crystalline inorganic lithium ion conductor or an amorphous inorganic lithium ion conductor.

[0071] Crystalline inorganic lithium ion conductors include Li3N and LISICON (Li 14 Zn(GeO4)4), perovskite-type Li 0.5 La 0.5 TiO3, LIPON(Li 3+y PO 4-x N x ), Thio-LISICON(Li 3.25 Ge0.25 P 0.75 S4) and others.

[0072] Examples of amorphous inorganic lithium ion conductors include those containing S (sulfur atoms) and having ion conductivity (sulfide solid electrolyte materials). When the all-solid-state battery composition of the present invention is used in an all-solid-state lithium secondary battery, the sulfide solid electrolyte material used may be one obtained by using a raw material composition containing LiS and a sulfide of an element of Groups 13 to 15. Examples of methods for synthesizing a sulfide solid electrolyte material using such a raw material composition include an amorphization method. Examples of amorphization methods include mechanical milling and melt quenching, with mechanical milling being preferred. Mechanical milling allows processing at room temperature, simplifying the manufacturing process.

[0073] Examples of the elements of Groups 13 to 15 include Al, Si, Ge, P, As, and Sb. Specific examples of sulfides of elements of Groups 13 to 15 include Al2S3, SiS2, GeS2, P2S3, P2S5, As2S3, and Sb2S3. Among these, sulfides of Groups 14 and 15 are preferably used. In particular, sulfide solid electrolyte materials obtained using raw material compositions containing Li2S and sulfides of elements of Groups 13 to 15 are preferably Li2S-P2S5 materials, Li2S-SiS2 materials, Li2S-GeS2 materials, or Li2S-Al2S3 materials, and more preferably Li2S-P2S5 materials. These materials have excellent Li-ion conductivity.

[0074] Furthermore, the sulfide solid electrolyte material preferably has bridging sulfur, because the presence of bridging sulfur increases ionic conductivity. Note that "having bridging sulfur" can also be determined by taking into consideration, for example, the results of Raman spectroscopy, the raw material composition ratio, and the results of NMR measurement.

[0075] The molar fraction of Li2S in the Li2S-P2S5 material or Li2S-Al2S3 material is preferably in the range of, for example, 50% or more and 74% or less, particularly in the range of 60% or more and 74% or less, from the viewpoint of more reliably obtaining a sulfide solid electrolyte material having bridging sulfur.

[0076] The sulfide solid electrolyte material may be sulfide glass, or may be crystallized sulfide glass obtained by heat-treating the sulfide glass. The sulfide glass can be obtained, for example, by the amorphization method described above. The crystallized sulfide glass can be obtained, for example, by heat-treating the sulfide glass.

[0077] In particular, sulfide solid electrolyte materials, such as Li7P3S 11 It is preferable to use a crystallized sulfide glass represented by the formula: Li7P3S. This is because it has particularly excellent Li ion conductivity. 11 For example, Li2S and P2S5 are mixed in a molar ratio of 70:30 and amorphized in a ball mill to synthesize sulfide glass. The sulfide glass obtained is then heat-treated at a temperature of 150°C to 360°C to synthesize Li7P3S. 11 can be synthesized.

[0078] In addition, as the amorphous inorganic lithium ion conductor, a material containing O (oxygen atom) and having ion conductivity (oxide solid electrolyte material) can also be used. Examples of oxide solid electrolyte materials include LiN, LISICON (Li 14 Zn(GeO4)4), perovskite type (e.g., Li 0.5 La 0.5 TiO3), garnet type (e.g. Li7La3Zr2O 12 ), LIPON(Li3+yPO4-xNx), Thio-LISICON(Li 3.25 Ge 0.25 P 0.75 S4) and others.

[0079] <Cathode active material> In the case of an all-solid-state lithium secondary battery, the positive electrode active material is a compound capable of absorbing and releasing lithium ions. Positive electrode active materials are broadly classified into those made of inorganic compounds and those made of organic compounds.

[0080] Examples of inorganic cathode active materials include transition metal oxides, composite oxides of lithium and transition metals, and transition metal sulfides. Examples of the transition metals include Fe, Co, Ni, and Mn. Specific examples of inorganic compounds used in cathode active materials include lithium-containing composite metal oxides such as LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiFePO4, and LiFeVO4; transition metal sulfides such as TiS2, TiS3, and amorphous MoS2; Cu2V2O3, amorphous VO-P2O5, MoO3, VO5, and VO. 13 These compounds may be partially element-substituted.

[0081] Examples of the positive electrode active material made of an organic compound include polyaniline, polypyrrole, polyacene, disulfide-based compounds, polysulfide-based compounds, N-fluoropyridinium salts, etc. The positive electrode active material may be a mixture of the above inorganic compounds and organic compounds.

[0082] The average particle size of the positive electrode active material used in the present invention is usually 0.1 μm to 50 μm, preferably 1 μm to 20 μm, from the viewpoint of improving battery characteristics such as load characteristics and charge / discharge cycle characteristics, obtaining a solid electrolyte secondary battery with large charge / discharge capacity, and facilitating handling of the composition for the positive electrode active material layer and handling during production of the positive electrode. The average particle size can be determined by measuring the particle size distribution by laser diffraction.

[0083] <Negative electrode active material> Examples of negative electrode active materials include carbon allotropes such as graphite and coke. The negative electrode active materials made of carbon allotropes can also be used in the form of mixtures or coatings with metals, metal salts, oxides, etc. Other examples of negative electrode active materials include oxides and sulfates of silicon, tin, zinc, manganese, iron, nickel, etc.; metallic lithium; lithium alloys such as Li-Al, Li-Bi-Cd, and Li-Sn-Cd; lithium transition metal nitrides; and silicon. In the case of metal materials, metal foils or metal plates can be used as electrodes, but particulate forms are also acceptable.

[0084] When the negative electrode active material is particulate, the average particle size of the negative electrode active material is usually 1 μm or more and 50 μm or less, preferably 15 μm or more and 30 μm or less, from the viewpoint of improving battery characteristics such as initial efficiency, load characteristics, and charge / discharge cycle characteristics.

[0085] <Conductive additive> The conductive additive is not particularly limited as long as it can impart conductivity, but typical examples include carbon powders such as acetylene black, carbon black, and graphite, and fibers and foils of various metals.

[0086] <Reinforcing material> As the reinforcing material, various inorganic and organic spherical, plate-like, rod-like or fibrous fillers can be used.

[0087] <Content of binder particles in composition for solid electrolyte layer> The content of the binder particles of the present invention in the composition for a solid electrolyte layer is preferably 0.1 part by weight or more, more preferably 0.5 part by weight or more, and is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, and particularly preferably 5 parts by weight or less, relative to 100 parts by weight of the solid electrolyte particles. By setting the content of the binder particles of the present invention within the above range, it is possible to maintain the binding strength between the solid electrolyte particles while suppressing an increase in the resistance of the solid electrolyte layer due to the inhibition of lithium ion migration.

[0088] <Content of binder particles in the composition for positive electrode active material layer> The content of the binder particles of the present invention in the composition for a positive electrode active material layer is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and is preferably 10 parts by weight or less, more preferably 7 parts by weight or less, relative to 100 parts by weight of the positive electrode active material, from the viewpoint of preventing the electrode active material from falling off from the electrode without inhibiting the battery reaction. When the content of the binder particles of the present invention is within the above range, the positive electrode active material can be prevented from falling off from the electrode without inhibiting the battery reaction.

[0089] <Mass Ratio of Positive Electrode Active Material to Solid Electrolyte Particles in Positive Electrode Active Material Composition> The mass ratio of the positive electrode active material to the solid electrolyte particles is preferably 90:10 to 50:50 (positive electrode active material:solid electrolyte particles), and more preferably 60:40 to 80:20 (positive electrode active material:solid electrolyte particles). This range of the mass ratio of the positive electrode active material can prevent a decrease in the mass of the positive electrode active material in the battery due to a too small mass ratio of the positive electrode active material, resulting in a decrease in the battery's capacity. Furthermore, a too small mass ratio of the solid electrolyte particles can prevent sufficient conductivity from being obtained, preventing effective use of the positive electrode active material, resulting in a decrease in the battery's capacity.

[0090] <Content of binder particles in composition for negative electrode active material layer> When the negative electrode active material is in particulate form, the content of the binder particles of the present invention in the composition for a negative electrode active material layer is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 5 parts by mass or less, more preferably 4 parts by mass or less, relative to 100 parts by mass of the negative electrode active material, from the viewpoint of preventing the electrode active material from falling off from the electrode without inhibiting the battery reaction.

[0091] <Mass Ratio of Negative Electrode Active Material to Solid Electrolyte Particles in Composition for Negative Electrode Active Material Layer> The mass ratio of the negative electrode active material to the solid electrolyte particles is preferably 90:10 to 50:50 (negative electrode active material:solid electrolyte particles), more preferably 60:40 to 80:20 (negative electrode active material:solid electrolyte particles). This range of mass ratio of the negative electrode active material can prevent a phenomenon in which the mass of the negative electrode active material in the battery is reduced due to a too low mass ratio of the negative electrode active material, leading to a decrease in battery capacity. Furthermore, a phenomenon in which the mass ratio of the solid electrolyte particles is too low due to insufficient conductivity and ineffective use of the negative electrode active material, leading to a decrease in battery capacity, can be prevented.

[0092] <Method of manufacturing a composition for an all-solid-state battery> The method for producing the all-solid-state battery composition of the present invention is not particularly limited. For example, powders of the above-mentioned components may be dry-mixed by any method. Examples of dry-mixing methods include methods using a mixing device such as a stirring device, a shaking device, or a rotary device. Also included are methods using a dispersion kneading device such as a homogenizer, a ball mill, a bead mill, a planetary mixer, a sand mill, a roll mill, or a planetary kneader. From the viewpoint of suppressing aggregation of powder particles, methods using a planetary mixer, a ball mill, or a bead mill are preferred.

[0093] (All-solid-state battery) The all-solid-state battery of the present invention includes a positive electrode having a positive electrode active material layer on a current collector, a negative electrode having a negative electrode active material layer on a current collector, and a solid electrolyte layer between these positive and negative electrode active material layers, and at least one layer, preferably all layers, of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contain the binder particles of the present invention.

[0094] <Solid electrolyte layer> The solid electrolyte layer can be formed by a powder compaction method in which a powder of the above-described solid electrolyte layer composition is pressed under pressure. For example, the solid electrolyte layer can be formed by placing a powder of the above-described solid electrolyte layer composition on the surface of a positive electrode active material layer or a negative electrode active material layer, and pressing the resulting laminate in the thickness direction. Alternatively, a solid electrolyte layer formed in the same manner on any release substrate can be peeled off and attached to the positive electrode active material layer or the negative electrode active material layer. The method for placing the solid electrolyte layer composition on the electrode active material layer or the release substrate is not particularly limited, and for example, electrostatic screen printing can be used.

[0095] The amount of powder of the solid electrolyte layer composition to be pressed under pressure is not particularly limited, and is an amount such that the thickness of the solid electrolyte layer after pressing is usually 5 μm or more and 50 μm or less, preferably 8 μm or more and 20 μm or less.

[0096] From the viewpoint of good battery characteristics, the pressure to be applied is preferably 5 MPa or more, more preferably 7 MPa or more, and preferably 700 MPa or less, more preferably 500 MPa or less. The method of applying pressure is not particularly limited, and examples thereof include plate pressing, roll pressing, and CIP (Cold Isostatic Press).

[0097] <Cathode active material layer> The positive electrode active material layer can be formed by a powder compaction method in which a powder of the above-described positive electrode active material layer composition is pressed under pressure. For example, the positive electrode active material layer can be formed by placing the powder of the above-described positive electrode active material layer composition on the surface of a current collector or a solid electrolyte layer described below, and pressing the resulting laminate under pressure in the thickness direction. Alternatively, a positive electrode active material layer formed in the same manner on any release substrate can be peeled off and attached to the current collector or solid electrolyte layer. The method for placing the positive electrode active material layer composition on the current collector, solid electrolyte layer, or release substrate is not particularly limited, and for example, electrostatic screen printing can be used.

[0098] The amount of powder of the positive electrode active material layer composition to be pressed is not particularly limited, but is usually an amount such that the thickness of each active material layer after pressing is generally 5 μm or more and 300 μm or less, preferably 10 μm or more and 250 μm or less.

[0099] The pressure and pressing method may be the same as those for the solid electrolyte layer composition described above.

[0100] <Negative electrode active material layer> When the negative electrode active material is particulate, the negative electrode active material layer can be formed by a powder compaction method in which a powder of the above-described composition for a negative electrode active material layer is pressed under pressure. For example, the negative electrode active material layer can be formed by placing the powder of the above-described composition for a negative electrode active material layer on the surface of a current collector or a solid electrolyte layer described below, and pressing the resulting laminate under pressure in the thickness direction. Alternatively, a negative electrode active material layer formed in the same manner on any release substrate can be peeled off and attached to the current collector or solid electrolyte layer. The method for placing the composition for a negative electrode active material layer on the current collector, solid electrolyte layer, or release substrate is not particularly limited, and for example, electrostatic screen printing can be used.

[0101] The amount of powder of the composition for the negative electrode active material layer to be pressed is not particularly limited, but is an amount such that the thickness of the negative electrode active material layer after pressing is usually 5 μm or more and 300 μm or less, preferably 10 μm or more and 250 μm or less.

[0102] The pressure and pressing method may be the same as those for the solid electrolyte layer composition described above.

[0103] <Current collector> The current collectors used to form the positive and negative electrode active material layers are not particularly limited as long as they are electrically conductive and electrochemically durable. However, from the viewpoint of heat resistance, metal materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum are preferred. Among these, aluminum is particularly preferred for the positive electrode, and copper is particularly preferred for the negative electrode. The shape of the current collector is not particularly limited, but a sheet-like material with a thickness of approximately 0.001 to 0.5 mm is preferred. The current collector is preferably roughened before use to enhance the adhesive strength with the positive and negative electrode active material layers. Examples of surface roughening methods include mechanical polishing, electrolytic polishing, and chemical polishing. Mechanical polishing uses abrasive cloths and paper with abrasive particles attached, grinding stones, emery buffs, and wire brushes equipped with steel wires. An intermediate layer may be formed on the surface of the current collector to enhance the adhesive strength and electrical conductivity between the current collector and the positive and negative electrode active material layers.

[0104] (Manufacturing method of all-solid-state batteries) The positive electrode in the all-solid-state battery is obtained by forming a positive electrode active material layer on a current collector. When the negative electrode and / or the solid electrolyte layer are formed using the composition for an all-solid-state battery of the present invention, a known positive electrode may be used as the positive electrode.

[0105] In the case where the negative electrode active material is a metal foil or a metal plate, the negative electrode may be used as it is. Alternatively, when the negative electrode active material is particulate, the negative electrode active material layer may be formed on a current collector separate from the current collector for the positive electrode. When the positive electrode and / or the solid electrolyte layer are formed using the composition for an all-solid-state battery of the present invention, a known negative electrode may be used as the negative electrode.

[0106] The solid electrolyte layer in an all-solid-state battery is obtained by forming a solid electrolyte layer on a positive electrode active material layer or a negative electrode active material layer. When the positive electrode and / or the negative electrode are formed using the composition for an all-solid-state battery of the present invention, a known solid electrolyte layer may be used as the solid electrolyte layer.

[0107] The all-solid-state battery can be manufactured by preparing the positive electrode, the negative electrode, and the solid electrolyte layer by any method and in any order, without any particular limitation. Specifically, all-solid-state batteries can be manufactured by, for example, (1) a method of preparing a laminate consisting of a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, and then bonding current collectors to both sides of the laminate; (2) a method of bonding a positive electrode, a negative electrode, and a solid electrolyte layer that have been prepared separately; (3) a method of forming a solid electrolyte layer on one electrode, and then bonding the other electrode; or (4) a method of preparing a laminate consisting of a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer on one current collector, and then bonding the other current collector.

[0108] The all-solid-state battery element obtained as described above is then placed in a battery container either as is or rolled or folded depending on the battery shape, and the container is sealed to obtain an all-solid-state battery. If necessary, an expanded metal, a fuse, an overcurrent protection element such as a PTC element, a lead plate, etc. may be placed in the battery container to prevent pressure buildup inside the battery and overcharging and discharging. The battery may be in any shape, such as a coin type, button type, sheet type, cylindrical type, prismatic type, or flat type.

[0109] By using the binder particles for an all-solid-state battery or the composition for an all-solid-state battery of the present invention, it is possible to obtain a functional layer for an all-solid-state battery that can provide an all-solid-state battery having good battery characteristics even in a dry system, and an all-solid-state battery having good battery characteristics. [Example]

[0110] The present invention will be described below with reference to examples, but the present invention is not limited thereto. Each property was evaluated by the following method. In the examples, parts and percentages are by mass unless otherwise specified.

[0111] <Measurement of cohesion> Using a powder tester (manufactured by Hosokawa Micron Corporation), sieves with 250 μm, 150 μm, and 75 μm meshes were stacked on the top, middle, and bottom tiers, respectively. 2 g of the binder particles produced in the Examples and Comparative Examples were placed on the top sieve with 250 μm mesh, and vibration was applied at a vibration amplitude of 1 mm for 60 seconds. After vibration was stopped, the degree of cohesion was calculated using the following equations 1 to 3. 1. (Weight of binder particles on a 250 μm sieve / 2 g) x 100 2. (Weight of binder particles on a 150 μm sieve / 2 g) x 100 x (3 / 5) 3. (Weight of binder particles on a 75 μm sieve / 2 g) x 100 x (1 / 5) The degree of aggregation (%) was calculated by adding up the values calculated by the above formulas 1 to 3. The lower the degree of aggregation, the better the fluidity.

[0112] <Particle size measurement> The volume-based cumulative particle size distribution of the binder particles produced in the examples and comparative examples was measured in a dry state using a laser diffraction / scattering particle size distribution analyzer ("Microtrac MT3200II" manufactured by Nikkiso Co., Ltd.) with the dispersion air pressure set to 0.02 MPa during measurement. The particle diameter at which the cumulative volume calculated from the small diameter side in the measured particle size distribution becomes 50% was defined as the volume average particle diameter D50 of the binder particles.

[0113] <Measurement of glass transition temperature> A 10 mg sample of powdered binder particles produced in the Examples and Comparative Examples was weighed into an aluminum pan and measured using a differential scanning calorimetry (DSC) analyzer (manufactured by SII NanoTechnology, product name "EXSTAR DSC6220") under the conditions specified in JIS Z8703, with a temperature range of -100°C to 200°C and a heating rate of 20°C / min. A differential scanning calorimetry (DSC) curve was obtained. An empty aluminum pan was used as a reference. During this heating process, the temperature at which the differential signal (DDSC) peaked was determined as the glass transition temperature. Since multiple peaks were measured, the temperature with the largest displacement peak was determined as the glass transition temperature of the binder particles.

[0114] <Measurement of moisture content> 0.2 g of the binder particles produced in the examples and comparative examples was weighed into a measuring container and left to stand for 24 hours at a temperature of 25° C. and a dew point temperature of −60° C. Thereafter, the moisture content of the binder particles was measured using a coulometric titration moisture meter by the Karl Fischer method (JIS K-0068 (2001) moisture evaporation method, evaporation temperature 150° C.).

[0115] (Evaluation of battery characteristics) <Evaluation of output characteristics> Three-cell all-solid-state secondary batteries manufactured in the examples and comparative examples were charged to 4.2 V at a constant current of 0.1 C and then discharged to 3.0 V at 0.1 C to determine the 0.1 C discharge capacity. Next, they were charged to 4.2 V at 0.1 C and then discharged to 3.0 V at 2 C to determine the 2 C discharge capacity. The average value of the 0.1 C discharge capacity of the three cells was designated as discharge capacity a, and the average value of the 2 C discharge capacity of the three cells was designated as discharge capacity b. The ratio of discharge capacity b to discharge capacity a (capacity ratio) = discharge capacity b / discharge capacity a × 100 (%) was calculated and evaluated according to the following criteria: A higher capacity ratio indicates better output characteristics. A: Capacity ratio is 80% or more B: Capacity ratio is 70% or more but less than 80% C: Capacity ratio is 50% or more and less than 70% D: Capacity ratio is less than 50%

[0116] <Evaluation of cycle characteristics> The all-solid-state secondary batteries produced in the examples and comparative examples were charged at 45°C from 3 V to 4.2 V at 0.1 C, and then discharged at 0.1 C from 4.2 V to 3 V, for 50 cycles. The ratio of the 0.1 C discharge capacity at the 50th cycle to the 0.1 C discharge capacity at the first cycle was calculated as a percentage to define the capacity retention rate, which was evaluated according to the following criteria. A higher capacity retention rate indicates less discharge capacity loss and better high-temperature cycle characteristics. A: Capacity retention rate is 90% or more B: Capacity retention rate is 80% or more but less than 90% C: Capacity retention rate is 70% or more but less than 80% D: Capacity retention rate is less than 70%

[0117] Example 1 <Preparation of Polymer> A reactor equipped with a mechanical stirrer and a condenser was charged with 85 parts of ion-exchanged water and 0.2 parts of sodium dodecylbenzenesulfonate under a nitrogen atmosphere, and the mixture was heated to 55°C with stirring. 0.3 parts of potassium persulfate as a 5.0% aqueous solution was then added to the reactor. Next, in a separate vessel equipped with a mechanical stirrer, under a nitrogen atmosphere, 66.25 parts of acrylonitrile (AN) as a nitrile group-containing monomer, 3 parts of methacrylic acid (MAA) as an ethylenically unsaturated acid monomer, 19 parts of butyl acrylate (BA) as an acrylic acid alkyl ester monomer having an alkyl chain of 4 or more carbon atoms, 11.5 parts of methyl methacrylate (MMA) as a methacrylic acid alkyl ester monomer having an alkyl chain of 4 or less carbon atoms, and 0.25 parts of allyl methacrylate (AMA) as a crosslinkable monomer, 0.6 parts of sodium dodecylbenzenesulfonate, 0.035 parts of tertiary dodecyl mercaptan, 0.4 parts of polyoxyethylene lauryl ether, and 80 parts of ion-exchanged water were added, and the mixture was stirred and emulsified to prepare a monomer mixture. Then, this monomer mixture was added to the reactor at a constant rate over 5 hours while being stirred and emulsified, and the reaction was continued until the polymerization conversion rate reached 95%, thereby obtaining an aqueous dispersion of the polymer.

[0118] <Granulation and classification of binder particles> The obtained aqueous dispersion of the polymer was spray-dried using a spray dryer (manufactured by Niro, GEA) under the following conditions: atomizer: rotating disk type (diameter: 150 mm), rotation speed: 11,000 rpm, hot air temperature (outlet temperature): 100°C, to prepare binder particles. The obtained particles were then classified using a predetermined mesh to obtain binder particles with an average particle diameter D50 adjusted to 50 μm. The degree of aggregation of the obtained binder particles was 10%, the water content was 3500 ppm, and the glass transition temperature of the polymer was 86°C.

[0119] <Preparation of positive electrode active material layer> 70 parts of lithium cobalt oxide (number average particle diameter: 11.5 μm) as positive electrode active material particles, 25.5 parts of sulfide glass consisting of Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) as solid electrolyte particles, 2.5 parts of acetylene black as a conductive additive, and 2 parts of the binder particles obtained as described above were mixed in a planetary mixer for 30 minutes to prepare a positive electrode active material layer composition. 8.5 mg of the obtained composition for a positive electrode active material layer was filled into a cylindrical mold having a diameter of 10 mm, and then pressed at 200 MPa in the thickness direction of the layer to produce a positive electrode active material layer.

[0120] <Preparation of solid electrolyte layer> In a glove box under an argon gas atmosphere (water concentration 0.6 mass ppm, oxygen concentration 1.8 mass ppm), 100 parts of sulfide glass consisting of Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle size: 0.9 μm) as solid electrolyte particles were mixed with 2 parts of the binder particles obtained as described above, and the mixture was mixed for 30 minutes using a planetary mixer to prepare a composition for a solid electrolyte layer. 50 mg of the obtained composition for a solid electrolyte layer was filled into the mold and placed on the positive electrode active material layer, and then pressed in the thickness direction of the layer at 200 MPa to produce a solid electrolyte layer.

[0121] <Preparation of negative electrode active material layer> 65 parts of graphite (number average particle diameter: 20 μm) as negative electrode active material particles, 31.5 parts of sulfide glass consisting of Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) as solid electrolyte particles, 1.5 parts of acetylene black as a conductive additive, and 2 parts of the binder particles obtained as described above were mixed and mixed for 30 minutes using a planetary mixer to prepare a composition for a negative electrode active material layer. 5.5 mg of the obtained composition for a negative electrode active material layer was filled into the mold and placed on the solid electrolyte layer, and then pressed in the thickness direction of the layer at 200 MPa to produce a negative electrode active material layer.

[0122] <Manufacturing of all-solid-state secondary batteries> The laminate obtained as described above, consisting of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, was removed from the mold. Aluminum foil as a positive electrode current collector, the laminate, and copper foil as a negative electrode current collector were arranged in this order within the mold. Then, a pressure of 200 MPa was applied in the thickness direction of the layers to produce an all-solid-state battery. Furthermore, the all-solid-state battery produced as described above was left standing in a thermostatic chamber set at 120°C for 3 hours under pressure of 60.0 MPa to impart adhesive strength between the binder particles and the active material particles and solid electrolyte particles. After heating, the all-solid-state battery was cooled to room temperature (25°C).

[0123] Example 2 A polymer was produced in the same manner as in Example 1, except that 19 parts of 2-ethylhexyl acrylate (2EHA) was used instead of 19 parts of butyl acrylate (BA) as the alkyl acrylate monomer having an alkyl chain of 4 or more carbon atoms. The resulting polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 38 μm. The resulting binder particles had a degree of agglomeration of 10%, a moisture content of 3600 ppm, and a glass transition temperature of 90°C. Furthermore, using these binder particles, compositions for all-solid-state batteries (composition for positive electrode active material layer, composition for solid electrolyte layer, composition for negative electrode active material layer) were prepared, and all-solid-state batteries were manufactured, in the same manner as in Example 1.

[0124] Example 3 A polymer was produced in the same manner as in Example 1, except that 66.25 parts of styrene (St) was used as the aromatic vinyl monomer instead of 66.25 parts of acrylonitrile (AN) as the nitrile group-containing monomer. The resulting polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 50 μm. The resulting binder particles had a degree of aggregation of 10%, a water content of 3300 ppm, and a glass transition temperature of 83°C. Using these binder particles, compositions for all-solid-state batteries (compositions for a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer) were prepared and all-solid-state batteries were produced in the same manner as in Example 1.

[0125] Example 4 Except for adjusting the average particle size D50 of the binder particles to 85 μm, the preparation of polymers, binder particles, and compositions for all-solid-state batteries (composition for positive electrode active material layer, composition for solid electrolyte layer, composition for negative electrode active material layer), and the production of all-solid-state batteries were carried out in the same manner as in Example 1. The degree of aggregation of the obtained binder particles was 12%, the water content was 4000 ppm, and the glass transition temperature of the polymer was 86° C.

[0126] Example 5 Except for adjusting the average particle size D50 of the binder particles to 16 μm, the preparation of polymers, binder particles, and compositions for all-solid-state batteries (composition for positive electrode active material layer, composition for solid electrolyte layer, composition for negative electrode active material layer), and the production of all-solid-state batteries were carried out in the same manner as in Example 1. The degree of aggregation of the obtained binder particles was 9.5%, the water content was 4100 ppm, and the glass transition temperature of the polymer was 86° C.

[0127] Example 6 A polymer was produced in the same manner as in Example 1, except that the amounts of methacrylic acid (MAA), butyl acrylate (BA), methyl methacrylate (MMA), acrylonitrile (AN), and allyl methacrylate (AMA) were changed to 2.5 parts, 24 parts, 19 parts, 54.3 parts, and 0.2 parts, respectively. The resulting polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 55 μm. The resulting binder particles had a degree of aggregation of 20%, a moisture content of 4200 ppm, and a glass transition temperature of 81°C. Using these binder particles, compositions for all-solid-state batteries (compositions for positive electrode active material layers, solid electrolyte layer compositions, and negative electrode active material layer compositions) were prepared and all-solid-state batteries were produced in the same manner as in Example 1.

[0128] Example 7 A polymer was produced in the same manner as in Example 1, except that the amounts of methacrylic acid (MAA), allyl methacrylate (AMA), butyl acrylate (BA), methyl methacrylate (MMA), and acrylonitrile (AN) were changed to 5 parts, 0.4 parts, 10 parts, 7 parts, and 77.6 parts, respectively. The resulting polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 45 μm. The resulting binder particles had a degree of aggregation of 1.5%, a moisture content of 4500 ppm, and a glass transition temperature of 94°C. Using these binder particles, compositions for all-solid-state batteries (compositions for positive electrode active material layers, solid electrolyte layer compositions, and negative electrode active material layer compositions) were prepared and all-solid-state batteries were produced in the same manner as in Example 1.

[0129] Example 8 A polymer was produced in the same manner as in Example 1, except that the amounts of butyl acrylate (BA), methyl methacrylate (MMA), and acrylonitrile (AN) were changed to 37 parts, 15 parts, and 44.75 parts, respectively. The resulting polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 53 μm. The resulting binder particles had a degree of aggregation of 25%, a water content of 3800 ppm, and a glass transition temperature of 68°C. Furthermore, compositions for all-solid-state batteries (composition for a positive electrode active material layer, a composition for a solid electrolyte layer, and a composition for a negative electrode active material layer) were prepared, and all-solid-state batteries were produced, in the same manner as in Example 1.

[0130] Example 9 A polymer was produced in the same manner as in Example 1, except that the amount of methacrylic acid (MAA) charged was 5 parts, the amount of butyl acrylate (BA) charged was 9 parts, and the amount of methyl methacrylate (MMA) charged was 5 parts, and 80.75 parts of methacrylonitrile (MAN) was used instead of 66.25 parts of acrylonitrile (AN). The obtained polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 60 μm. The obtained binder particles had a degree of aggregation of 25%, a moisture content of 3900 ppm, and a glass transition temperature of 110°C. Furthermore, using the binder particles, all-solid-state battery compositions (composition for positive electrode active material layer, composition for solid electrolyte layer, composition for negative electrode active material layer) were prepared and all-solid-state batteries were produced in the same manner as in Example 1.

[0131] Example 10 Instead of sulfide glass consisting of Li2S and P2S5 as solid electrolyte particles, garnet-type Li7La3Zr2O was used as the oxide solid electrolyte. 12 Except for using 100 parts of the above, a polymer and compositions for all-solid-state batteries (composition for positive electrode active material layer, composition for solid electrolyte layer, composition for negative electrode active material layer) were prepared, and an all-solid-state battery was manufactured in the same manner as in Example 1. The obtained binder particles had a degree of aggregation of 10%, an average particle diameter D50 of 50 μm, a water content of 4200 ppm, and a glass transition temperature of the polymer of 86°C.

[0132] (Comparative Example 1) A polymer was produced in the same manner as in Example 1, except that the amounts of methacrylic acid (MAA), allyl methacrylate (AMA), butyl acrylate (BA), methyl methacrylate (MMA), and acrylonitrile (AN) were changed to 9 parts, 1.9 parts, 5 parts, 5 parts, and 79.1 parts, respectively. The resulting polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 55 μm. The resulting binder particles had a degree of aggregation of 0.5%, a water content of 3600 ppm, and a glass transition temperature of 105°C. Using these binder particles, compositions for all-solid-state batteries (compositions for positive electrode active material layers, solid electrolyte layer compositions, and negative electrode active material layer compositions) were prepared and all-solid-state batteries were produced in the same manner as in Example 1.

[0133] (Comparative Example 2) A polymer was produced in the same manner as in Example 1, except that the amounts of methacrylic acid (MAA), allyl methacrylate (AMA), butyl acrylate (BA), methyl methacrylate (MMA), and acrylonitrile (AN) were changed to 1.5 parts, 0.1 parts, 40 parts, 15 parts, and 43.4 parts, respectively. The resulting polymer was then granulated and classified in the same manner as above to produce binder particles having an average particle size D50 of 48 μm. The resulting binder particles had a degree of aggregation of 45%, a moisture content of 4000 ppm, and a glass transition temperature of 63°C. Using these binder particles, compositions for all-solid-state batteries (compositions for positive electrode active material layers, solid electrolyte layer compositions, and negative electrode active material layer compositions) were prepared and all-solid-state batteries were produced in the same manner as in Example 1.

[0134] (Comparative Example 3) Except for adjusting the average particle size D50 of the binder particles to 8 μm, the preparation of polymers, binder particles, and compositions for all-solid-state batteries (composition for positive electrode active material layer, composition for solid electrolyte layer, and composition for negative electrode active material layer), and the production of all-solid-state batteries were carried out in the same manner as in Example 1. The degree of aggregation of the obtained binder particles was 9%, the water content was 4200 ppm, and the glass transition temperature of the polymer was 86° C.

[0135] Comparative Example 4 Except for adjusting the average particle size D50 of the binder particles to 170 μm, the preparation of polymers, binder particles, and compositions for all-solid-state batteries (composition for positive electrode active material layer, composition for solid electrolyte layer, and composition for negative electrode active material layer), and the production of all-solid-state batteries were carried out in the same manner as in Example 1. The degree of aggregation of the obtained binder particles was 13%, the water content was 4100 ppm, and the glass transition temperature of the polymer was 86° C.

[0136] [Table 1] The meanings of the abbreviations in Table 1 are as follows: MAA: methacrylic acid, BA: butyl acrylate, MMA: methyl methacrylate, 2EHA: 2-ethylhexyl acrylate, AN: acrylonitrile, MAN: methacrylonitrile, St: styrene, AMA: allyl methacrylate

[0137] The results in Table 1 show that the all-solid-state batteries manufactured by a dry process using the binder particles of Examples 1 to 10, each of which has a degree of aggregation and a volume average particle diameter D50 within a specific range, are excellent in both output characteristics and cycle characteristics. In contrast, the all-solid-state batteries manufactured by a dry process using the binder particles of Comparative Examples 1 and 2, each of which has a degree of aggregation outside the specific range, and the all-solid-state batteries manufactured by a dry process using the binder particles of Comparative Examples 3 and 4, each of which has a volume average particle diameter D50 outside the specific range, are inferior in both output characteristics and cycle characteristics. [Industrial Applicability]

[0138] According to the present invention, it is possible to provide binder particles for an all-solid-state battery, a composition for an all-solid-state battery, and a functional layer for an all-solid-state battery, which can provide an all-solid-state battery with excellent battery characteristics even when the all-solid-state battery is manufactured by a dry process, and an all-solid-state battery with excellent battery characteristics.

Claims

1. Binder particles for an all-solid-state battery, comprising a polymer, The degree of aggregation is 1% or more and less than 30%, and the volume average particle diameter D50 is 10 μm or more and 100 μm or less, The binder particles for an all-solid-state battery, wherein the polymer contains at least one monomer unit selected from the group consisting of a nitrile group-containing monomer unit and an aromatic vinyl monomer unit.

2. Binder particles for an all-solid-state battery, comprising a polymer, The degree of aggregation is 1% or more and less than 30%, and the volume average particle diameter D50 is 10 μm or more and 100 μm or less, the polymer contains an acrylic acid alkyl ester monomer unit having an alkyl chain with 4 or more carbon atoms and a methacrylic acid alkyl ester monomer unit having an alkyl chain with 4 or less carbon atoms, the polymer contains 5% by mass or more and 40% by mass or less of alkyl acrylate ester monomer units having an alkyl chain with 4 or less carbon atoms, and the polymer contains 5% by mass or more and 40% by mass or less of alkyl methacrylate ester monomer units having an alkyl chain with 4 or less carbon atoms.

3. the polymer contains an acrylic acid alkyl ester monomer unit having an alkyl chain with 4 or more carbon atoms and a methacrylic acid alkyl ester monomer unit having an alkyl chain with 4 or less carbon atoms, 2. The binder particle for an all-solid-state battery according to claim 1, wherein a content ratio of the acrylic acid alkyl ester monomer units having an alkyl chain with 4 or more carbon atoms in the polymer is 5% by mass or more and 40% by mass or less, and a content ratio of the methacrylic acid alkyl ester monomer units having an alkyl chain with 4 or less carbon atoms in the polymer is 5% by mass or more and 40% by mass or less.

4. The binder particles for an all-solid-state battery according to any one of claims 1 to 3, wherein the polymer has a glass transition temperature of 50°C or higher and 120°C or lower.

5. the polymer comprises ethylenically unsaturated acid monomer units, The binder particles for an all-solid-state battery according to any one of claims 1 to 4, wherein the content of the ethylenically unsaturated acid monomer unit in the polymer is 1.5% by mass or more and less than 10% by mass.

6. the polymer comprises crosslinkable monomer units, The binder particles for an all-solid-state battery according to any one of claims 1 to 5, wherein a content ratio of the crosslinkable monomer unit in the polymer is 0.1 mass% or more and less than 2.0 mass%.

7. The binder particles for an all-solid-state battery according to any one of claims 1 to 6, and solid electrolyte particles.

8. The composition for an all-solid-state battery according to claim 7 , further comprising an electrode active material.

9. The composition for an all-solid-state battery according to claim 8 , further comprising a conductive additive.

10. A functional layer for an all-solid-state battery, formed from the composition for an all-solid-state battery according to any one of claims 7 to 9.

11. An all-solid-state battery comprising the functional layer for an all-solid-state battery according to claim 10.

Images