Binder for all-solid-state battery, electrode, electrolyte layer, and all-solid-state battery

Abstract

Provided are: a binder for an all-solid-state battery, the binder containing a polymer (A) that includes two or more structural units selected from the group consisting of a structural unit (a1) derived from ethylene, a structural unit (a2) derived from an alpha-olefin having 3-20 carbon atoms, and a structural unit (a3) derived from a non-conjugated polyene, wherein the polymer (A) includes 77 mass% or more of the structural unit (a1) when 100 mass% is defined as the total of the structural unit (a1) derived from ethylene, the structural unit (a2) derived from an alpha-olefin having 3-20 carbon atoms, and the structural unit (a3) derived from a non-conjugated polyene; and an electrode, an electrolyte layer, and an all-solid-state battery that include the binder for an all-solid-state battery.

Description

Binder, electrodes, electrolyte layer, and all-solid-state battery for solid-state batteries

[0001] This disclosure relates to a resin useful as a binder for the electrodes and electrolyte layers of a rechargeable all-solid-state battery used in power supplies for portable electronic devices, in-vehicle applications, and power storage, and to an all-solid-state battery utilizing the said resin. This application claims priority under Japanese Patent Application No. 2024-192135, filed in Japan on October 31, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, lithium-ion batteries have been widely used as power sources for electronic devices such as mobile phones and laptop computers, as well as for electric vehicles and power storage. Lithium-ion batteries primarily consist of a positive electrode and a negative electrode containing materials capable of intercalating and deintercalating lithium, and an electrolyte. As electrolytes, non-aqueous electrolytes for batteries containing lithium salts and non-aqueous solvents, and solid electrolytes such as sulfide-based solid electrolytes are used. Recently, all-solid-state batteries using solid electrolytes have attracted attention due to their higher safety features.

[0003] All-solid-state batteries are batteries in which a solid electrolyte layer is placed between a positive electrode layer and a negative electrode layer. Generally, the positive and negative electrode layers are formed as laminates in which the electrode active material and the current collector are stacked by applying a slurry in which the electrode active material is dispersed in a liquid medium to a current collector and drying it. A small amount of binder (binding agent) is used in this slurry to improve the adhesion of the active material to the current collector. For example, Patent Document 1 describes a binder with a strong binding force and an average particle size (D ５０Patent Document 2 describes using a granular first binder with a particle size of 0.01 μm to 10 μm to form a cluster complex with the electrode active material, solid electrolyte, and conductive material, and using a second binder that does not react with the sulfide-based solid electrolyte to uniformly disperse this cluster complex. Patent Document 2 describes using a rubber-based binder to improve the mechanical properties such as the elasticity and rigidity of the electrode layer. Patent Document 3 describes using a non-polar binder resin, taking into consideration that a sulfide-based solid electrolyte and a non-polar solvent are used when manufacturing a slurry for forming the electrode active material layer. Patent Document 4 describes that by using a polymer containing 35 to 75% by mass of repeating units derived from ethylene and 20 to 55% by mass of repeating units derived from an α-olefin compound as a binder, an electrode for an all-solid-state secondary battery with excellent adhesion and ionic conductivity can be produced.

[0004] Japanese Patent Publication No. 2017-135094, Japanese Patent Publication No. 2019-527919, Japanese Patent Publication No. 2022-518316, Japanese Patent Publication No. 2024-81858

[0005] For binders used in all-solid-state batteries, it is desirable that they be soluble in low-polarity solvents, have excellent binding properties, exhibit low reactivity with sulfide solid electrolytes, and, when used as a binder for electrodes and electrolytes, provide all-solid-state batteries with excellent electrode strength and battery characteristics.

[0006] One embodiment of this disclosure aims to solve the problem of providing a polymer suitable as a binder for the electrodes and electrolyte layers of an all-solid-state battery. Another embodiment of this disclosure aims to solve the problem of providing an electrode, an electrolyte layer, or an all-solid-state battery containing the polymer as a binder for an all-solid-state battery.

[0007] As a result of diligent research to solve the above problems, the present inventors have discovered that by using a polymer (A) containing two or more structural units selected from the group consisting of structural units derived from ethylene (a1), structural units derived from α-olefins having 3 to 20 carbon atoms (a2), and structural units derived from non-conjugated polyenes (a3), and in which the proportion of the structural unit (a1) is within a specific range, as a binder for the battery or electrolyte layer of an all-solid-state battery, an all-solid-state battery with excellent electrode strength and battery characteristics can be obtained, thus completing the present invention.

[0008] The means for solving the above problems include the following embodiments: [1] A binder for all-solid-state batteries containing a polymer (A) comprising two or more structural units selected from the group consisting of structural units derived from ethylene (a1), structural units derived from α-olefins having 3 to 20 carbon atoms (a2), and structural units derived from non-conjugated polyenes (a3), wherein the polymer (A) contains 77% by mass or more of the structural units derived from ethylene (a1), the structural units derived from α-olefins having 3 to 20 carbon atoms (a2), and the structural units derived from non-conjugated polyenes (a3), with the total being 100% by mass. [2] The binder for all-solid-state batteries according to [1], wherein the weight-average molecular weight (Mw) of the polymer (A) is 100,000 or more. [3] The binder for all-solid-state batteries according to [1] or [2], wherein the polymer (A) is a copolymer comprising structural units (a1) derived from ethylene and structural units (a2) derived from an α-olefin having 3 to 20 carbon atoms, or a copolymer comprising structural units (a1) derived from ethylene, structural units (a2) derived from an α-olefin having 3 to 20 carbon atoms, and structural units (a3) ​​derived from a non-conjugated polyene. [4] The binder for all-solid-state batteries according to any one of [1] to [3], wherein the polymer (A) comprises structural units (a1) derived from ethylene and structural units (a2) derived from an α-olefin having 3 to 20 carbon atoms, and when the total of structural units (a1) derived from ethylene, structural units (a2) derived from an α-olefin having 3 to 20 carbon atoms, and structural units (a3) ​​derived from a non-conjugated polyene is 100% by mass, the ratio of structural units (a2) derived from an α-olefin having 3 to 20 carbon atoms is greater than 0% by mass and 23% by mass or less.[5] A binder for all-solid-state batteries according to any one of [1] to [4], wherein the polymer (A) comprises structural units (a1) derived from ethylene, structural units (a2) derived from a carbon-3 to carbon-20 α-olefin, and structural units (a3) ​​derived from a non-conjugated polyene, and when the total of the structural units (a1) derived from ethylene, the structural units (a2) derived from a carbon-3 to carbon-20 α-olefin, and the structural units (a3) ​​derived from a non-conjugated polyene is 100% by mass, the ratio of structural units (a2) derived from a carbon-3 to carbon-20 α-olefin is 5% by mass or more and 18% by mass or less, and the ratio of structural units (a3) ​​derived from a non-conjugated polyene is 5% by mass or more and 18% by mass or less. [6] An electrode comprising the binder for all-solid-state batteries according to any one of [1] to [5]. [7] An electrolyte layer comprising the binder for all-solid-state batteries according to any one of [1] to [5]. [8] A solid-state battery comprising any of the solid-state battery binders described in [1] to [5] above.

[0009] According to the present invention, a binder for all-solid-state batteries is available that is soluble in low-polarity solvents, has excellent binding properties, has low reactivity with sulfide solid electrolytes, and when used as a binder for electrodes and electrolyte layers, provides all-solid-state batteries with excellent electrode strength and battery characteristics. The present invention also provides electrodes, an electrolyte layer, and an all-solid-state battery using the binder for all-solid-state batteries.

[0010] In this specification, the terms “polymer” and “(co)polymer” are used to encompass homopolymers and copolymers, unless otherwise specified. In this specification, “~” indicating a numerical range means that the numbers before and after it are included as the lower and upper limits. In this specification, the units described before or after “~” indicating a numerical range mean the same unit, unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. Also, in this specification, unless otherwise specified, each component in a composition or each constituent unit in a polymer may be included alone or in combination of two or more. In this specification, the amount of each component in a composition or each constituent unit in a polymer means the total amount of the multiple substances or constituent units present in the composition or polymer, unless otherwise specified, if there are multiple substances or constituent units corresponding to each component or each constituent unit in the composition. The present disclosure will now be described in detail.

[0011] [Binder for All-Solid-State Batteries (First Embodiment)] A binder for all-solid-state batteries according to one embodiment of the present disclosure contains a polymer (A) containing two or more structural units selected from the group consisting of structural units derived from ethylene (a1), structural units derived from α-olefins having 3 to 20 carbon atoms (a2), and structural units derived from non-conjugated polyenes (a3). Hereinafter, structural units derived from ethylene (a1) will also be referred to as "structural unit (a1)", structural units derived from α-olefins having 3 to 20 carbon atoms (a2) will also be referred to as "structural unit (a2)", and structural units derived from non-conjugated polyenes (a3) ​​will also be referred to as "structural unit (a3)". The polymer (A) contains 77% by mass or more of structural unit (a1) when the total of structural unit (a1), structural unit (a2), and structural unit (a3) ​​is 100% by mass. Hereinafter, the sum of structural units (a1), (a2), and (a3) ​​will also be referred to as "the sum of structural units (a1), (a2), and (a3)." Polymer (A) is soluble in low-polarity solvents, has excellent binding properties, and has low reactivity with sulfide solid electrolytes. By using the binder for all-solid-state batteries according to this disclosure, which contains polymer (A), as a binder for the electrode or electrolyte layer, an all-solid-state battery with excellent electrode strength and battery characteristics can be obtained.

[0012] The reason why the binder for all-solid-state batteries described herein exhibits such effects is not clear, but the following mechanism is presumed. Since the solvent used to form a slurry by adding it to the positive electrode active material, negative electrode active material, and solid electrolyte is required to have low reactivity with these materials, nonpolar solvents are generally used. Structural unit (a1) is low polarity, while structural units (a2) and (a3) ​​are relatively polar; therefore, the more structural units (a1) there are, the better the affinity of the polymer with the nonpolar solvent. In other words, when polymer (A) having 77% by mass or more of structural units (a1) is used as a binder, the dispersibility of the binder in the slurry is improved, the dispersion state of the binder in the electrode and solid electrolyte layer becomes more uniform, the strength of the electrode and solid electrolyte layer is increased, and they become less prone to cracking. Furthermore, because electrodes and solid electrolyte layers using polymer (A) as a binder have high uniformity, the ion conductivity is improved, resulting in an all-solid-state battery with excellent battery characteristics.

[0013] <Polymer (A)> The polymer (A) contained in the binder for all-solid-state batteries according to this disclosure contains two or more structural units selected from the group consisting of structural unit (a1), structural unit (a2), and structural unit (a3). When the total of structural unit (a1), structural unit (a2), and structural unit (a3) ​​of polymer (A) is taken as 100% by mass, structural unit (a1) is present in 77% by mass or more. Polymer (A) may be a polymer containing structural unit (a1) and structural unit (a2), a polymer containing structural unit (a1) and structural unit (a3), or a polymer containing structural unit (a1), structural unit (a2), and structural unit (a3). As for the polymer (A) contained in the binder for all-solid-state batteries according to this disclosure, from the viewpoint of obtaining an all-solid-state battery with better electrode strength and battery characteristics when used as a binder for the electrodes or solid electrolyte layer of an all-solid-state battery, a polymer containing structural unit (a1) and structural unit (a2), or a polymer containing structural unit (a1), structural unit (a2), and structural unit (a3) ​​is preferred.

[0014] Hereafter, the "percentage of structural unit (a1) when the total of structural units (a1), structural unit (a2), and structural unit (a3) ​​contained in the polymer is set to 100% by mass ([mass of structural unit (a1) contained in the polymer] / [total mass of structural units (a1), structural unit (a2), and structural unit (a3) ​​contained in the polymer] × 100)" may be referred to as the "percentage of structural unit (a1)". Similarly, the "percentage of structural unit (a2) when the total of structural units (a1), structural unit (a2), and structural unit (a3) ​​contained in the polymer is set to 100% by mass ([mass of structural unit (a2) contained in the polymer] / [total mass of structural units (a1), structural unit (a2), and structural unit (a3) ​​contained in the polymer] × 100)" is called the "percentage of structural unit (a2) (%)", and the "percentage of structural unit (a3) ​​when the total of structural units (a1), structural unit (a2), and structural unit (a3) ​​contained in the polymer is set to 100% by mass ([mass of structural unit (a3) ​​contained in the polymer] / [total mass of structural units (a1), structural unit (a2), and structural unit (a3) ​​contained in the polymer] × 100)" is called the "percentage of structural unit (a3) ​​(%)". The percentage of each structural unit in the polymer can be calculated from the percentage (mass ratio) of monomer raw materials used in polymer synthesis.

[0015] The structural unit (a1) is ethylene (CH ２ CH ２ The ethylene group (-CH) has an open C=C bond. ２ CH ２ -)

[0016] The structural unit (a2) is a structural unit derived from an α-olefin having 3 to 20 carbon atoms, and is an alkylene group having 3 to 20 carbon atoms in which the C═C bond in the α-olefin having 3 to 20 carbon atoms is opened. Examples of the α-olefin having 3 to 20 carbon atoms include linear or branched α-olefins having 3 to 20 carbon atoms such as propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, vinylcyclohexane. As the α-olefin, an α-olefin having 3 to 10 carbon atoms, for example, a linear or branched α-olefin having 3 to 10 carbon atoms is preferable, propylene, 1-butene, 1-hexene and 1-octene are more preferable, propylene and 1-butene are even more preferable, and 1-butene is particularly preferable. These α-olefins can be used alone or in combination of two or more. That is, when the polymer (A) contains the structural unit (a2), the structural unit (a2) contained in the polymer (A) may be one kind or two or more kinds.

[0017] The structural unit (a3) is a structural unit derived from a non-conjugated polyene, and is composed of a group in which one of the non-conjugated C═C bonds in the non-conjugated polyene is opened. As the non-conjugated polyene, a compound having two or more non-conjugated C═C bonds can be used without limitation. For example, non-conjugated cyclic polyenes, non-conjugated chain polyenes, etc. described later, and they can be used alone or in combination of two or more. That is, when the polymer (A) contains the structural unit (a3), the structural unit (a3) contained in the polymer (A) may be one kind or two or more kinds.

[0018] (Non-conjugated cyclic polyene) The non-conjugated cyclic polyene is, for example, a compound represented by the following general formula [IV].

[0019]

[0020] In the formula [IV], n is an integer of 0 to 2, and R 10 , R 11 , R 12 and R 13R is an atom or substituent selected from a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, a halogen atom, and a halogen-containing group, and each may be the same or different, and the hydrocarbon group may have a double bond, 10 From R 13 Any two substituents up to R may be bonded to each other to form a ring, and the ring may contain a double bond, 10 and R 11 And, or R 12 and R 13 And may form an alkylidene group, R 10 and R 12 toga, or R 11 and R 13 R may be bonded to each other to form a double bond, and at least one of the following requirements (i) to (iv) is satisfied: (i) R 10 From R 13 At least one of them is a hydrocarbon group having one or more double bonds. (ii) R 10 From R 13 Any two substituents up to R are bonded to each other to form a ring, and the ring contains a double bond. (iii) R 10 and R 11 And, or R 12 and R 13 (iv) R 10 and R 12 toga, or R 11 and R 13 These two elements are bonded to each other, forming a double bond.

[0021] In the above general formula [IV], R 10 , R 11 , R 12 and R 13 The specific examples of hydrocarbon groups having 1 to 20 carbon atoms, silicon-containing groups, nitrogen-containing groups, oxygen-containing groups, halogen atoms, and halogen-containing groups listed are as follows:

[0022] Examples of hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups having 1 to 20 carbon atoms, cyclic saturated hydrocarbon groups having 3 to 20 carbon atoms, chain-like unsaturated hydrocarbon groups having 2 to 20 carbon atoms, cyclic unsaturated hydrocarbon groups having 3 to 20 carbon atoms, alkylene groups having 1 to 20 carbon atoms, arylene groups having 6 to 20 carbon atoms, aryl groups, and substituted aryl groups.

[0023] Examples of alkyl groups having 1 to 20 carbon atoms include linear saturated hydrocarbon groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decanyl groups, and branched saturated hydrocarbon groups such as isopropyl, isobutyl, s-butyl, t-butyl, t-amyl, neopentyl, 3-methylpentyl, 1,1-diethylpropyl, 1,1-dimethylbutyl, 1-methyl-1-propylbutyl, 1,1-dipropylbutyl, 1,1-dimethyl-2-methylpropyl, 1-methyl-1-isopropyl-2-methylpropyl, and cyclopropylmethyl groups. The number of carbon atoms in the alkyl group is preferably 1 to 6.

[0024] Examples of cyclic saturated hydrocarbon groups having 3 to 20 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, norborneyl, 1-adamantyl, and 2-adamantyl groups, as well as groups in which the hydrogen atoms of a cyclic saturated hydrocarbon group are replaced by hydrocarbon groups having 1 to 17 carbon atoms, such as 3-methylcyclopentyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 4-cyclohexylcyclohexyl, and 4-phenylcyclohexyl groups. The number of carbon atoms in the cyclic saturated hydrocarbon group is preferably 5 to 11.

[0025] Examples of chain-like unsaturated hydrocarbon groups having 2 to 20 carbon atoms include alkenyl groups such as ethenyl group (vinyl group), 1-propenyl group, 2-propenyl group (allyl group), and 1-methylethenyl group (isopropenyl group), and alkynyl groups such as ethynyl group, 1-propynyl group, and 2-propynyl group (propargyl group). The number of carbon atoms in the chain-like unsaturated hydrocarbon group is preferably 2 to 4.

[0026] Examples of cyclic unsaturated hydrocarbon groups having 3 to 20 carbon atoms include cyclic unsaturated hydrocarbon groups such as cyclopentadienyl, norbornyl, phenyl, naphthyl, indenyl, azurenyl, phenanthryl, and anthracenyl groups; groups in which the hydrogen atoms of a cyclic unsaturated hydrocarbon group are replaced by hydrocarbon groups having 1 to 15 carbon atoms, such as 3-methylphenyl (m-tolyl), 4-methylphenyl (p-tolyl), 4-ethylphenyl, 4-t-butylphenyl, 4-cyclohexylphenyl, biphenylyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl, and 2,4,6-trimethylphenyl (mesityl); and groups in which the hydrogen atoms of a linear or branched saturated hydrocarbon group are replaced by cyclic saturated or cyclic unsaturated hydrocarbon groups having 3 to 19 carbon atoms, such as benzyl and cumyl groups. The number of carbon atoms in the cyclic unsaturated hydrocarbon group is preferably 6 to 10.

[0027] Examples of alkylene groups having 1 to 20 carbon atoms include methylene group, ethylene group, dimethylmethylene group (isopropylidene group), ethylmethylene group, 1-methylethylene group, 2-methylethylene group, 1,1-dimethylethylene group, 1,2-dimethylethylene group, and n-propylene group. The number of carbon atoms in the alkylene group is preferably 1 to 6.

[0028] Examples of arylene groups having 6 to 20 carbon atoms include o-phenylene groups, m-phenylene groups, p-phenylene groups, and 4,4'-biphenylene groups. The number of carbon atoms in the arylene group is preferably 6 to 12.

[0029] Examples of aryl groups include those derived from aromatic compounds, such as phenyl, 1-naphthyl, 2-naphthyl, anthracenyl, phenantrenyl, tetracerenyl, chrysenyl, pyrenyl, indenyl, azurenyl, pyrrolyl, pyridyl, furanyl, and thiophenyl groups, although these overlap somewhat with the previously mentioned examples of cyclic unsaturated hydrocarbon groups having 3 to 20 carbon atoms.

[0030] Examples of the aforementioned aromatic compounds include aromatic hydrocarbons and heterocyclic aromatic compounds such as benzene, naphthalene, anthracene, phenanthrene, tetracene, chrysene, pyrene, indene, azulene, pyrrole, pyridine, furan, and thiophene.

[0031] Examples of substituted aryl groups include those that partially overlap with the examples of cyclic unsaturated hydrocarbon groups having 3 to 20 carbon atoms mentioned above, but also include groups in which one or more hydrogen atoms of the aryl group are substituted with substituents selected from hydrocarbon groups having 1 to 20 carbon atoms, aryl groups, silicon-containing groups, nitrogen-containing groups, oxygen-containing groups, halogen atoms, and halogen-containing groups. Specifically, these include 3-methylphenyl group (m-tolyl group), 4-methylphenyl group (p-tolyl group), 3-ethylphenyl group, 4-ethylphenyl group, 3,4-dimethylphenyl group, 3,5-dimethylphenyl group, biphenylyl group, 4-(trimethylsilyl)phenyl group, and 4-aminophenyl group. These include the 4-(dimethylamino)phenyl group, 4-(diethylamino)phenyl group, 4-morpholinylphenyl group, 4-methoxyphenyl group, 4-ethoxyphenyl group, 4-phenoxyphenyl group, 3,4-dimethoxyphenyl group, 3,5-dimethoxyphenyl group, 3-methyl-4-methoxyphenyl group, 3,5-dimethyl-4-methoxyphenyl group, 3-(trifluoromethyl)phenyl group, 4-(trifluoromethyl)phenyl group, 3-chlorophenyl group, 4-chlorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 5-methylnaphthyl group, and 2-(6-methyl)pyridyl group.

[0032] Examples of silicon-containing groups include alkylsilyl groups such as trimethylsilyl, triethylsilyl, t-butyldimethylsilyl, and triisopropylsilyl, which are hydrocarbon groups having 1 to 20 carbon atoms in which carbon atoms are replaced by silicon atoms; arylsilyl groups such as dimethylphenylsilyl, methyldiphenylsilyl, and t-butyldiphenylsilyl; pentamethyldisilanyl; and trimethylsilylmethyl. The number of carbon atoms in alkylsilyl groups is preferably 1 to 10, and the number of carbon atoms in arylsilyl groups is preferably 6 to 18.

[0033] Examples of nitrogen-containing groups include amino groups, nitro groups, N-morpholinyl groups, and, in the above-mentioned hydrocarbon groups having 1 to 20 carbon atoms or silicon-containing groups, groups in which the =CH- structural unit is replaced by a nitrogen atom, groups in which the -CH2- structural unit is replaced by a nitrogen atom to which a hydrocarbon group having 1 to 20 carbon atoms is bonded, or groups in which the -CH3 structural unit is replaced by a nitrogen atom to which a hydrocarbon group having 1 to 20 carbon atoms is bonded or a nitrile group, such as dimethylamino groups, diethylamino groups, dimethylaminomethyl groups, cyano groups, pyrrolidinyl groups, piperidinyl groups, and pyridinyl groups. Dimethylamino groups and N-morpholinyl groups are preferred as nitrogen-containing groups.

[0034] Oxygen-containing groups include hydroxyl groups, the aforementioned hydrocarbon groups having 1 to 20 carbon atoms, silicon-containing groups, or nitrogen-containing groups in which the -CH2- structural unit is replaced by an oxygen atom or a carbonyl group, or in which the -CH3 structural unit is replaced by an oxygen atom to which a hydrocarbon group having 1 to 20 carbon atoms is bonded, such as methoxy groups, ethoxy groups, t-butoxy groups, phenoxy groups, trimethylsiloxy groups, methoxyethoxy groups, hydroxymethyl groups, methoxymethyl groups, ethoxymethyl groups, t-butoxymethyl groups, 1-hydroxyethyl groups, 1 Examples of oxygen-containing groups include methoxyethyl group, 1-ethoxyethyl group, 2-hydroxyethyl group, 2-methoxyethyl group, 2-ethoxyethyl group, n-2-oxabutylene group, n-2-oxapentylene group, n-3-oxapentylene group, aldehyde group, acetyl group, propionyl group, benzoyl group, trimethylsilylcarbonyl group, carbamoyl group, methylaminocarbonyl group, carboxyl group, methoxycarbonyl group, carboxymethyl group, ethocarboxymethyl group, carbamoylmethyl group, furanyl group, and pyranyl group. Methoxyethyl group is preferred as the oxygen-containing group.

[0035] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine, which are elements of Group 17. Examples of halogen-containing groups include trifluoromethyl, tribromomethyl, pentafluoroethyl, and pentafluorophenyl groups, which are hydrocarbon groups, silicon-containing groups, nitrogen-containing groups, or oxygen-containing groups with 1 to 20 carbon atoms, in which a hydrogen atom is substituted by a halogen atom.

[0036] In the above general formula [IV], R 10 , R 11 , R 12 and R 13 If one or more of the groups are hydrocarbon groups having one or more double bonds, examples of such hydrocarbon groups include ethenyl group (vinyl group), 1-propenyl group, 2-propenyl group (allyl group), 1-methylethenyl group (isopropenyl group), 1-butenyl group, 2-butenyl group, 3-butenyl group, 1,4-hexadienyl group, etc. For example, R 10 When is an ethenyl group (vinyl group), the compound of the above general formula [IV] is represented by the following general formula [IV-I].

[0037]

[0038] In equation [IV-I], n is an integer between 0 and 2, and R 11 , R 12 and R 13 R is an atom or substituent selected from a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, a halogen atom, and a halogen-containing group, and each may be the same or different, and the hydrocarbon group may have a double bond. 11 From R 13 Any two substituents of may be bonded to each other to form a ring, and the ring may contain a double bond, R 12 and R 13 And may form an alkylidene group, R 11 and R 13 These two elements may be bonded to each other to form a double bond.

[0039] In the above general formula [IV], R 10 From R 13 If any two substituents up to are bonded to each other to form a ring, and the ring contains a double bond, then the compound of the above general formula [IV] can be represented, for example, by the following general formulas [IV-II] or [IV-III].

[0040]

[0041] In equations [IV-II] and [IV-III], n is an integer between 0 and 2, and R 11 , R 12 and R 13 R is an atom or substituent selected from a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, a halogen atom, and a halogen-containing group, and each may be the same or different. The hydrocarbon group may have a double bond, 11 From R 13 Any two substituents of may be bonded to each other to form a ring, and the ring may contain a double bond, R 12 and R 13 And may form an alkylidene group, R 11 and R 13 These two elements may be bonded to each other to form a double bond.

[0042] In the above general formula [IV], R 10 and R 11 And, or R 12 and R 13 When an alkylidene group is formed by these, the alkylidene group is usually an alkylidene group having 1 to 20 carbon atoms, specifically a methylene group (CH2=), an ethylidene group (CH3CH=), a propyridene group (CH3CH2CH=), and an isopropylidene group ((CH3)2C=), etc. For example, R 10 and R 11 When an ethylidene group is formed by these, the compound of the above general formula [IV] is represented by the following general formula [IV-IV].

[0043]

[0044] In equation [IV-IV], n is an integer between 0 and 2, and R 12 and R 13 R is an atom or substituent selected from a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, a halogen atom, and a halogen-containing group, and each may be the same or different, and the hydrocarbon group may have a double bond. 12 and R 13 These may be bonded to each other to form a ring, and the ring may contain a double bond, R12 and R 13 They may form alkylidene groups.

[0045] In the above general formula [IV], R 10 and R 12 toga, or R 11 and R 13 When these two elements are bonded to each other to form a double bond, the compound of the above general formula [IV] can be represented, for example, by the following general formula [IV-V].

[0046]

[0047] In equation [IV-V], n is an integer between 0 and 2, and R 11 and R 13 R is a substituent selected from a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing group, a nitrogen-containing group, an oxygen-containing group, a halogen atom, and a halogen-containing group, and each of these substituents may be the same or different, and the hydrocarbon group may have a double bond. 11 and R 13 These elements may be bonded to each other to form a ring, and the ring may contain a double bond.

[0048] Among the non-conjugated cyclic polyenes represented by the above general formula [IV], R 10 From R 13 Examples of compounds in which at least one of the hydrocarbon groups has one or more double bonds include 5-vinyl-2-norbornene (VNB) and the following compounds. Of these, 5-vinyl-2-norbornene (VNB) is preferred.

[0049]

[0050] Among the non-conjugated cyclic polyenes represented by the above general formula [IV], R 10 From R 13 Examples of compounds in which any two substituents up to a certain point are bonded to each other to form a ring, and the ring contains a double bond, include dicyclopentadiene (DCPD), dimethyldicyclopentadiene, and the following compounds. Of these, dicyclopentadiene (DCPD) is preferred.

[0051]

[0052] Among the non-conjugated cyclic polyenes represented by the above general formula [IV], R 10 and R 11 or R 12 and R 13 form an alkylidene group. Examples of such compounds include 5-methylene-2-norbornene, 5-ethylidene-2-norbornene (ENB), 5-isopropylidene-2-norbornene, and the following compounds. Among these, 5-ethylidene-2-norbornene (ENB) is preferred.

[0053]

[0054] Among the non-conjugated cyclic polyenes represented by the above general formula [IV], R 10 and R 12 or R 11 and R 13 are bonded to each other to form a double bond. The following compounds are preferred as such compounds.

[0055]

[0056] As the non-conjugated cyclic polyene represented by the above general formula [IV], a non-conjugated cyclic polyene with n = 0 is preferred, particularly an alkylidene group-substituted non-conjugated cyclic polyene with n = 0 in the above general formula [IV], a double bond-containing ring-substituted non-conjugated cyclic polyene with n = 0 in the above general formula [IV], and a double bond-containing hydrocarbon group-substituted non-conjugated cyclic polyene with n = 0 are preferred. Specifically, as the non-conjugated cyclic polyene represented by the above general formula [IV], 5-ethylidene-2-norbornene (ENB), dicyclopentadiene (DCPD), and 5-vinyl-2-norbornene (VNB) are more preferred. Among these, 5-ethylidene-2-norbornene (ENB) or 5-vinyl-2-norbornene (VNB) is particularly preferred.

[0057] The ratio (%) of the structural unit (a1) of the polymer (A) according to the present disclosure may be 77% by mass or more and less than 100% by mass, preferably 77 to 95% by mass, and more preferably 77 to 90% by mass.

[0058] The polymer (A) according to this disclosure preferably contains structural unit (a2) in addition to structural unit (a1). When the polymer (A) according to this disclosure is a polymer containing structural unit (a1) and structural unit (a2), when the total of structural unit (a1), structural unit (a2), and structural unit (a3) ​​is 100% by mass, the ratio (%) of structural unit (a2) is preferably greater than 0% by mass and 23% by mass or less, more preferably 5% by mass or more and 23% by mass or less, even more preferably 10% by mass or more and 20% by mass or less.

[0059] If the polymer (A) according to this disclosure is a polymer containing structural unit (a1), structural unit (a2), and structural unit (a3), then when the total of structural unit (a1), structural unit (a2), and structural unit (a3) ​​is 100% by mass, a polymer is preferred in which the ratio of structural unit (a2) (%) is 5% by mass or more and 18% by mass or less, and the ratio of structural unit (a3) ​​(%) is 5% by mass or more and 18% by mass or less, a polymer is more preferred in which the ratio of structural unit (a2) (%) is 8% by mass or more and 15% by mass or less, and the ratio of structural unit (a3) ​​(%) is 8% by mass or more and 15% by mass or less, and a polymer is even more preferred in which the ratio of structural unit (a2) (%) is 10% by mass or more and 15% by mass or less, and the ratio of structural unit (a3) ​​(%) is 8% by mass or more and 13% by mass or less. When the ratio of each structural unit of polymer (A) according to this disclosure is within the above range, an appropriate branched structure based on structural unit (a2) is formed, and as a result, molecular entanglement increases, and a polymer with excellent flexibility can be obtained.

[0060] The polymer (A) according to this disclosure may be a polymer containing structural unit (a1) and structural unit (a3). When the polymer (A) according to this disclosure is a polymer containing structural unit (a1) and structural unit (a3), when the total of structural unit (a1), structural unit (a2), and structural unit (a3) ​​is 100% by mass, the ratio (%) of structural unit (a3) ​​is preferably greater than 0% by mass and 23% by mass or less, more preferably 5% by mass or more and 23% by mass or less, even more preferably 10% by mass or more and 20% by mass or less.

[0061] The polymer (A) relating to this disclosure may be a polymer with a relatively large amount of crystalline structure, but it is preferable that it be a polymer with a relatively large amount of amorphous structure or an amorphous polymer. Polymers with a large amount of amorphous structure have excellent flexibility, so when used as a binder, the dispersion state of the binder in the electrode and solid electrolyte layer becomes more uniform, and an all-solid-state battery with better electrode strength and battery characteristics can be obtained.

[0062] As polymer (A), a polymer is mentioned in which structural unit (a2) contains either or both of structural units derived from propylene and structural units derived from 1-butene, and structural unit (a3) ​​contains one or more selected from the group consisting of structural units derived from 5-methylene-2-norbornene, structural units derived from 5-ethlylidene-2-norbornene, structural units derived from 5-isopropylidene-2-norbornene, structural units derived from 5-vinyl-2-norbornene, and structural units derived from dicyclopentadiene, and the ratio (%) of structural unit (a1) is 77% by mass or more. As polymer (A), a polymer is particularly preferred in which structural unit (a2) contains either or both of structural units derived from propylene and structural units derived from 1-butene, and structural unit (a1) is 77% by mass or more.

[0063] The weight-average molecular weight (Mw) of polymer (A) according to this disclosure is not particularly limited. From the viewpoint of more fully exhibiting the effect of improving electrode strength and battery characteristics, the weight-average molecular weight (Mw) of polymer (A) is preferably 100,000 or more, more preferably 180,000 or more, even more preferably 180,000 to 700,000, even more preferably 190,000 to 600,000, even more preferably 200,000 to 500,000, and particularly preferably 200,000 to 300,000. When the weight-average molecular weight (Mw) of polymer (A) according to this disclosure is within the above range, a polymer with excellent solubility in the solvent is obtained when preparing the binder solution, and furthermore, a binder with an excellent balance of adhesion and flexibility is obtained.

[0064] The weight-average molecular weight (Mw) of polymer (A) is determined by GPC (gel permeation chromatography). GPC measurement can be performed, for example, under the conditions described in the examples below. The weight-average molecular weight (Mw) is determined by creating a calibration curve using commercially available monodisperse standard polystyrene and determining it based on the PS conversion / general calibration method.

[0065] A commercially available polymer may be used as the polymer (A) according to this disclosure. The polymer (A) according to this disclosure is obtained by polymerizing ethylene with, optionally, one or both of a C3-C20 α-olefin and a non-conjugated polyene.

[0066] Polymerization methods include gas-phase methods, solution methods, and slurry methods. In addition to conventionally known catalysts for olefin polymerization such as vanadium-based catalysts, titanium-based catalysts, and magnesium-supported titanium catalysts, catalysts such as metallocene catalysts described in International Publication No. 2001 / 53369, International Publication No. 2001 / 27124, International Publication No. 2006 / 054613, International Publication No. 2014 / 050817, Japanese Patent Publication No. 3-193796, or Japanese Patent Publication No. 2-41303 can be used to produce the product.

[0067] Polymers containing structural units (a1) and (a2) can be synthesized, for example, by the method described in International Publication No. 2024 / 053644 or a modified thereof. Polymers containing structural units (a1), (a2), and (a3) ​​can be synthesized, for example, by the method described in International Publication No. 2015 / 122415 or a modified thereof.

[0068] The monomers contained in the polymer (A) relating to this disclosure may be monomers derived from fossil fuels, monomers derived from biomass, or a combination of monomers derived from fossil fuels and monomers derived from biomass. Monomers derived from biomass are monomers made from any natural raw materials and their residues, including fungi, yeasts, algae, and bacteria, and which are of plant or animal origin.

[0069] The binder for all-solid-state batteries according to this disclosure contains the polymer (A) described above. The binder for all-solid-state batteries according to this disclosure may be a composition consisting only of polymer (A), and may also contain other components other than polymer (A) according to this disclosure, to the extent that the objectives of the present invention are not impaired. Examples of other components include various additives such as weather stabilizers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, anti-slip agents, anti-blocking agents, anti-fogging agents, nucleating agents, lubricants, pigments, dyes, anti-aging agents, hydrochloric acid absorbers, inorganic or organic fillers, organic or inorganic foaming agents, crosslinking agents, crosslinking aids, adhesives, softeners, flame retardants, and polymers other than polymer (A). Hereinafter, polymers other than polymer (A) will also be referred to as "other polymers". When the binder for all-solid-state batteries according to this disclosure contains other polymers, the content of other polymers is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of polymer (A) according to this disclosure.

[0070] There are no particular limitations on the method for producing the binder for all-solid-state batteries according to this disclosure, and various known methods can be used. For example, the binder for all-solid-state batteries can be prepared by dry blending the polymer (A) and other components as needed using a Henschel mixer, tumbler blender, V-blender, etc., by melt-kneading the dry-blended polymer (A) using a single-screw extruder, multi-screw extruder, Banbury mixer, etc., and by stirring and mixing in the presence of a solvent.

[0071] [Electrode (Second Embodiment)] An electrode according to one embodiment of the present disclosure is characterized by containing the binder for all-solid-state batteries (first embodiment) according to the present disclosure. The binder for all-solid-state batteries according to the present disclosure may be contained in any part of the electrode according to the present disclosure, but it is preferably contained as a binder to improve the adhesion of the active material to the current collector.

[0072] The electrode according to this disclosure is constructed by forming an active material layer on a current collector. The active material layer comprises an active material and a binder for all-solid-state batteries according to this disclosure, and preferably further contains a conductive additive and a thickener as needed. The electrode according to this disclosure is preferably an electrode for an all-solid-state battery.

[0073] The electrode according to this disclosure may be a positive electrode or a negative electrode. The positive electrode can be constructed by forming a positive electrode active material layer on a current collector. The negative electrode can be constructed by forming a negative electrode active material layer on a current collector.

[0074] The positive electrode active material layer can be manufactured by dry-mixing the positive electrode active material, a binder, and, if necessary, a solid electrolyte, a conductive additive, and a thickener, forming it into a sheet, and then pressing it onto the positive electrode current collector. Alternatively, the positive electrode active material layer can also be manufactured by dissolving or dispersing the positive electrode active material, a binder, and, if necessary, a solid electrolyte, a conductive additive, and a thickener in a liquid medium to form a slurry, applying the resulting slurry to the positive electrode current collector, and drying it.

[0075] The negative electrode active material layer can be formed using a slurry containing a negative electrode active material, a binder, and, if necessary, a solid electrolyte, a conductive additive, and a thickening agent, similar to the positive electrode active material layer described above.

[0076] <Positive Electrode Active Material> Various lithium-containing composite oxides can be used as the positive electrode active material in the electrode of this disclosure. The lithium-containing composite oxide used as the positive electrode active material may be one type or two or more types.

[0077] As lithium-containing composite oxides, composite oxides containing lithium and transition metal atoms are preferred. As lithium-containing composite oxides, compounds containing at least one selected from the group consisting of Co, Ni, and Mn as the transition metal atom are preferred, and may also contain atoms other than lithium and these transition metal atoms as needed. The other atoms are, for example, at least one selected from the group consisting of P, Na, Mg, Ca, Sr, B, Al, Ge, Ti, V, Cr, Fe, Cu, Zr, Nb, Mo, W, Sn, Hf, and Ta. Hereinafter, the other atoms will also be referred to as "additive elements".

[0078] Lithium-containing composite oxides, especially those containing Al and Mg as additive elements, have the advantage of being less prone to degradation of the positive electrode structure. When Ca and Mg are included among these additive elements, the capacity retention rate during battery cycling can be improved without significantly reducing the initial discharge capacity. This is thought to be because calcium and magnesium ions, which do not contribute to the battery reaction, are dissolved in the Li site, reducing the distortion of crystal structure changes during cycling. Ca, by being dissolved in the Li site, is thought to act as a pillar-like element, contributing to the stabilization of the crystal structure. Mg is thought to contribute to further improvement of cycle characteristics and high durability. Na is thought to promote crystal growth during firing. Other additive elements are also thought to contribute to improvements in battery capacity, cycle characteristics, output characteristics, safety, and durability.

[0079] The lithium-containing composite oxide may be a compound that does not contain any of Co, Ni, or Mn. An example of such a compound is lithium iron phosphate (LiFePO4). ４ Examples include lithium transition metals such as )

[0080] As lithium-containing composite oxides, compounds having the composition represented by the following general formula (P1) are preferred. Hereinafter, compounds having the composition represented by the following general formula (P1) may be referred to as "compound (P1)".

[0081]

[0082] In general formula (P1), A is an element other than Li, Ni, Mn, and Co. For example, it is the above-described additive element. A contained in one molecule of compound (P1) may be one type of atom or two or more types of atoms.

[0083] In general formula (P1), a to f are real numbers satisfying the following relationships.

[0084] 0.8 ≤ a ≤ 1.2 0 ≤ b ≤ 0.95 0 ≤ c ≤ 0.5 0 ≤ d ≤ 1.0 0.7 ≤ b + c + d ≤ 1.1 0 ≤ e ≤ 0.1 1.8 ≤ f ≤ 2.2

[0085] Compound (P1) preferably has a laminated structure in which a Li layer composed of lithium ions and a transition metal oxide layer containing Ni, Co, and Mn are laminated. Compound (P1) having such a laminated structure has a relatively small change in lattice volume when lithium is desorbed, and also has a small amount of oxygen release during overcharge.

[0086] The superlattice structure of compound (P1) can be confirmed, for example, by crystal structure analysis by electron beam diffraction measurement (TEM).

[0087] Compound (P1) appropriately refers to known methods described in, for example, Japanese Patent No. 4995444, Japanese Patent No. 5277686, JP-A-2013-101968, JP-A-2013-175410, Japanese Patent No. 4880936, Japanese Patent No. 5271751, Japanese Patent No. 5317390, JP-A-2010-282761, JP-A-2009-158330, JP-A-2010-199077, Japanese Patent No. 5365711, JP-A-2012-252964, Japanese Patent No. 5365711, JP-A-2012-252964, JP-A-2015-176760, etc., and can be produced by the synthesis methods described therein or appropriately modified methods. For example, lithium hydroxide (LiOH·H ２ O), nickel hydroxide (Ni(OH) ２ ), cobalt hydroxide (Co(OH) ２ ) and manganese hydroxide (Mn(OH) ２ ２Compound (P1) can be produced by mixing the following in a mixing ratio such that Li:Ni:Co:Mn is in the desired molar ratio, and then calcining the resulting mixed raw material in an oxygen atmosphere at a temperature of, for example, 850 to 1000°C.

[0088] Various lithium-free compounds can also be used as the positive electrode active material for the positive electrode of the all-solid-state battery according to this disclosure. The lithium-free compound used as the positive electrode active material may be one type or two or more types. Examples of lithium-free compounds include sulfur (S) and titanium disulfide (TiS). ２ ), iron(III) fluoride (FeF ３ ) etc.

[0089] There are no particular restrictions on the content of the positive electrode active material or lithium-containing composite oxide in the positive electrode active material layer, but it is usually 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the total amount of the positive electrode active material layer. Furthermore, from the viewpoint of the ionic conductivity of the positive electrode active material layer, the content of the positive electrode active material or lithium-containing composite oxide in the positive electrode active material layer is usually 99% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less.

[0090] The positive electrode active material may be coated or have components that do not undergo oxidation-reduction reactions during charging and discharging added to it as needed. The lithium-containing composite oxide content of the positive electrode active material is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to the total positive electrode active material. The component that does not undergo oxidation-reduction reactions during charging and discharging is, for example, LiNbO ３ Examples include positive electrode coating materials and additives commonly used in non-aqueous electrolyte lithium-ion batteries, such as 1,4-butanesultone.

[0091] <Negative Electrode Active Material> As the negative electrode active material used in the electrode in this disclosure, for example, at least one selected from the group consisting of metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides that can be doped and dedoped with lithium ions, transition metal nitrides that can be doped and dedoped with lithium ions, and carbon materials that can be doped and dedoped with lithium ions can be used. These may be used individually or as a mixture containing two or more of these. Examples of oxides that can be doped and dedoped with lithium ions include silicon oxide, lithium titanate, and the lithium-containing composite oxides mentioned above for the positive electrode. Examples of metals or alloys that can be alloyed with lithium or lithium ions include silicon, silicon alloys, tin, and tin alloys. Among these, carbon materials that can be doped and dedoped with lithium ions are preferred. Examples of such carbon materials include carbon black, activated carbon, graphite materials, amorphous carbon materials, etc. The carbon material may be in the form of fibers, spheres, potatoes, or flakes.

[0092] Examples of amorphous carbon materials include hard carbon, coke, mesocarbon microbeads (MCMB), and mesophase-pitch carbon fiber (MCF). Examples of graphite materials include natural graphite and artificial graphite. Examples of artificial graphite include graphitized MCMB and graphitized MCF. Materials containing boron can also be used as graphite materials. Furthermore, graphite materials can include materials coated with metals such as gold, platinum, silver, copper, and tin, materials coated with amorphous carbon, and materials that are mixtures of amorphous carbon and graphite.

[0093] These carbon materials may be used individually or in a mixture of two or more types. Among the carbon materials, those with a (002) plane interplanar spacing d(002) of 0.340 nm or less, as measured by X-ray analysis, are particularly preferred. The carbon material has a true density of 1.70 g / cm³. ３ Highly crystalline carbon materials having properties similar to graphite are also preferred. Using such carbon materials can increase the energy density of the battery.

[0094] When the above metal or alloy is used as the negative electrode active material, the negative electrode configuration may include a negative electrode active material layer formed on a current collector by methods such as vapor deposition, sputtering, or plating. There are no particular restrictions on the content of the negative electrode active material in the negative electrode active material layer, but it is usually 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the total amount of the negative electrode active material layer. Furthermore, from the viewpoint of the ionic conductivity of the negative electrode active material layer, the content of the negative electrode active material in the negative electrode active material layer is usually 99% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less.

[0095] <Solid Electrolyte> The active material layer may contain a solid electrolyte from the viewpoint of ionic conductivity. Specifically, the solid electrolytes listed below as solid electrolytes constituting the solid electrolyte layer of the all-solid-state battery can be used. The solid electrolyte contained in the active material layer may be one of the substances listed below used alone, or two or more may be used in any combination and ratio. The solid electrolyte contained in the active material layer may be the same type of substance as the solid electrolyte constituting the solid electrolyte layer of the all-solid-state battery, or it may be a different substance.

[0096] When the active material layer contains a solid electrolyte, the proportion of the solid electrolyte in the active material layer is usually 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of further improving ionic conductivity. Furthermore, the proportion of the solid electrolyte in the active material layer is usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of containing a sufficient amount of active material.

[0097] <Conductive Additives> Conductive additives may be included in the active material layer to enhance electronic conductivity. There are no particular restrictions on the type of conductive additive, but specific examples include metallic materials such as copper and nickel; graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; carbon nanotubes; amorphous carbon such as needle coke; and so on. These substances may be used individually or in any combination and ratio of two or more.

[0098] From the viewpoint of further improving electronic conductivity, the proportion of conductive additive in the active material layer is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. Furthermore, from the viewpoint of further improving battery capacity, the proportion of conductive additive in the active material layer is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0099] <Binder> The electrode according to this disclosure contains, together with the active material, the binder for all-solid-state batteries according to this disclosure in the active material layer. The electrode according to this disclosure may contain only the binder for all-solid-state batteries according to this disclosure as the binder, or it may contain other binders in addition to the binder for all-solid-state batteries according to this disclosure. The other binder is not particularly limited, and in the case of a coating method, any material that is stable with respect to the liquid medium used during electrode manufacturing is acceptable. Specific examples of binders include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylonitrile, polyacrylamide, aromatic polyamide, cellulose, and nitrocellulose; rubbery polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers and their hydrogenated products; and EPDM (ethylene-propylene-diene) excluding the binder for all-solid-state batteries related to this disclosure. Examples include thermoplastic elastomer polymers such as the original copolymer, styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer and its hydrogenated products; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, and propylene-α-olefin copolymer, excluding the binder for all-solid-state batteries according to this disclosure; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer; and polymer compositions having ionic conductivity for alkali metal ions, particularly lithium ions. These substances may be used individually or in any combination and ratio of two or more.

[0100] From the viewpoint of the mechanical strength of the electrodes, the proportion of binder in the active material layer is usually 0.1% by mass or more, preferably 0.3% by mass or more, and more preferably 0.5% by mass or more. Furthermore, from the viewpoint of further improving battery capacity and conductivity, the proportion of binder in the active material layer is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0101] <Thickening Agents> The thickening agents are not particularly limited and include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, starch oxide, starch phosphorylated, casein, and salts thereof. These substances may be used individually or in any combination and ratio of two or more.

[0102] If the active material layer contains a thickening agent, the proportion of the thickening agent in the active material layer is usually 0.1% by mass or more, preferably 0.3% by mass or more, and more preferably 0.5% by mass or more, from the viewpoint of the stability of the slurry containing the active material. Furthermore, the proportion of the binder in the active material layer is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of further improving battery capacity and conductivity.

[0103] <Liquid Medium> The liquid medium used to form a slurry in which the active material is dispersed to form an active material layer is not particularly limited in type, as long as it is a solvent capable of dissolving or dispersing the active material, binder, and conductive additives and thickeners used as needed. Either a polar solvent or a non-polar organic solvent may be used as the above liquid medium. The polar solvent may be a protic polar solvent or an aprotic polar solvent.

[0104] Examples of protic polar solvents include relatively bulky alcohol-based polar solvents such as tert-butanol; and amine-based polar solvents such as diethylenetriamine and N,N-dimethylaminopropylamine. Examples of aprotic polar solvents include ketone-based polar solvents such as cyclohexanone, N-methylpyrrolidone (NMP), methyl ethyl ketone, and acetone; amide-based polar solvents such as hexamethylphosphoramide, dimethylacetamide, and dimethylformamide; ether-based polar solvents such as tetrahydrofuran (THF), dimethyl ether, ethylene oxide, and anisole (methoxybenzene); sulfoxide compounds such as dimethyl sulfoxide; and ester-based polar solvents such as methyl acrylate and methyl acetate. Examples of nonpolar organic solvents include aromatic nonpolar solvents such as tetralin, benzene, xylene, toluene, methylnaphthalene, quinoline, and pyridine; and aliphatic hydrocarbon-based nonpolar solvents such as hexane. These solvents may be used individually or in any combination and ratio of two or more. When using a protic polar solvent as the liquid medium, a dispersant may be added along with the thickener, and a slurry may be formed using a latex such as SBR.

[0105] As a liquid medium for forming the slurry, a low-polarity organic solvent or a non-polar organic solvent is preferred from the viewpoint of minimizing the influence on the solid electrolyte, and a non-polar solvent is more preferred from the viewpoint of the reactivity of the solid electrolyte. The binder for all-solid-state batteries according to this disclosure has high affinity for low-polarity organic solvents and non-polar organic solvents, and therefore the dispersibility of the binder in the slurry is improved, resulting in an electrode with a more uniform binder dispersion state.

[0106] <Positive Electrode Current Collector> The material used for the positive electrode current collector is usually a metal material such as aluminum, stainless steel, nickel plating, titanium, or tantalum, or a carbon material such as carbon cloth or carbon paper. Among these, metal materials are preferred, and aluminum is particularly preferred. In terms of shape, for metal materials, examples include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foamed metal, while for carbon materials, examples include carbon plate, carbon thin film, and carbon cylinder. Among these, metal thin films are preferred because they are currently used in industrialized products. The thin film may be formed in a mesh shape as appropriate.

[0107] When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but from the viewpoint of strength, it is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. From the viewpoint of the energy density of the battery and ease of handling, the thickness of the thin film positive electrode current collector is usually 100 mm or less, preferably 1 mm or less, and more preferably 50 μm or less.

[0108] The thickness of the positive electrode active material layer is typically between 10 μm and 300 μm. The positive electrode active material layer obtained by coating and drying is preferably compacted using a roller press or the like to increase the packing density of the positive electrode active material.

[0109] <Negative Electrode Current Collector> As for the material of the negative electrode current collector, there are metallic materials such as copper, nickel, stainless steel, and nickel-plated steel, but copper is particularly preferred from the viewpoint of ease of processing and cost. The shape of the current collector when the current collector is made of a metallic material is, for example, a metallic foil, a metallic cylinder, a metallic coil, a metallic plate, a metallic thin film, expanded metal, punched metal, foamed metal, etc. Among these, a metallic thin film is preferred, and copper foil is more preferred. Even more preferred are rolled copper foil produced by the rolling method and electrolytic copper foil produced by the electrolytic method. When the thickness of the copper foil is thinner than 25 μm, copper alloys with higher strength than pure copper, such as phosphor bronze, titanium copper, Corson alloy, and Cu-Cr-Zr alloy, may be used as the material of the copper foil.

[0110] The thickness of the negative electrode active material layer is typically between 10 μm and 300 μm. The negative electrode active material layer obtained by coating and drying is preferably compacted using a roller press or the like to increase the packing density of the negative electrode active material.

[0111] [Electrolyte Layer (Third Embodiment)] An electrolyte layer according to one embodiment of the present disclosure is an electrolyte layer for an all-solid-state battery, characterized in that it contains the binder for all-solid-state batteries according to the present disclosure (first embodiment). The binder for all-solid-state batteries according to the present disclosure may be contained in any part of the electrolyte layer according to the present disclosure, but it is preferably contained as a binder for forming a solid electrolyte layer in which the solid electrolyte is uniformly dispersed.

[0112] The electrolyte layer can be prepared by dry-mixing a solid electrolyte, a binder, and a thickener, etc., as needed, forming a sheet, and pressing it onto a substrate. Alternatively, the electrolyte layer can be prepared by dissolving or dispersing a solid electrolyte, a binder, and a thickener, etc., as needed, in a liquid medium to form a slurry, applying the resulting slurry to a substrate, and drying it.

[0113] As a thickening agent to be included in the electrolyte layer, the same substance as the thickening agent to be included in the active material layer of the electrode described above can be used. Furthermore, as the liquid medium used when preparing the slurry, the same substance as the liquid medium used in the slurry for manufacturing the active material layer of the electrode described above can be used.

[0114] <Solid Electrolyte> The solid electrolyte, which is the main component of the electrolyte according to this disclosure, is not particularly limited as long as it can conduct ions, and examples include sulfide-based solid electrolytes, oxide-based solid electrolytes, hydride-based solid electrolytes, etc. Of these, from the viewpoint of high ionic conductivity, it is preferable that at least a part of the solid electrolyte is a sulfide-based solid electrolyte. The solid electrolyte may be used alone, or two or more may be used in any combination and ratio.

[0115] Examples of sulfide-based solid electrolytes include crystalline, glass-based, and glass-ceramic types. From the viewpoint of high ionic conductivity, crystalline sulfide-based solid electrolytes are preferred. Among these, argyrodite-type sulfide solid electrolytes are more preferred from the viewpoint of excellent performance in all aspects, including ionic conductivity, oxidation-reduction resistance, and heat resistance. As sulfide-based solid electrolytes, various sulfide-based solid electrolytes described in literature such as Patent Document 1, Patent Document 4, and Japanese Patent Application Publication No. 2020-126760 can be appropriately selected. As sulfide-based solid electrolytes, high ionic conductivity is preferred, for example, Li ２ S-P ２ S ５ Li ２ S-P ２ S ５ -LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-P ２ S ５ -Li ３ N, Li ２ S-SiS ２ Li ２ S-SiS ２ -LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ -LiI, Li ２ S-SiS ２ -P ２ S ５ -LiI, Li ２ S-B ２ S ３ Li ２ S-P２ S ５ -Z ｍ S ２ｎ (However, m and n are positive numbers, and Z is one of Ge, Zn, or Ga.) Li ２ S-GeS ２ Li ２ S-SiS ２ -Li ３ PO ４ Li ２ S-SiS ２ -Li ｘ MO ｙ (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, or In.) Li １０ GeP ２ S １２ Li （７-ａ-２） PS （６-ａ-ｂ） X ａ (However, X is at least one of F, Cl, Br, and I, and 0.4 ≤ a ≤ 2.2, -0.9 ≤ b ≤ (-a + 2)) are some examples. Among these, Li is considered to have good ionic conductivity. ２ S-P ２ S ５ Li ２ S-P ２ S ５ -LiI, Li ２ S-P ２ S ５ -LiCl, Li （７-ａ-２） PS （６-ａ-ｂ） X ａ (wherein X is preferably at least one of F, Cl, Br, and I, and 0.4 ≤ a ≤ 2.2 and -0.9 ≤ b ≤ (-a + 2)) ｘ Li ２ S. (100- ｘ ) P ２ S ５ (70≦x≦80), Li （７-ａ-２） PS （６-ａ-ｂ） X ａ (wherein X is at least one of F, Cl, Br, and I, and 0.4 ≤ a ≤ 2.2, -0.9 ≤ b ≤ (-a + 2)) is more preferable.

[0116] When the solid electrolyte contained in the all-solid-state battery according to this disclosure is used in combination with other solid electrolytes other than sulfide-based solid electrolytes, the other solid electrolyte can be appropriately selected from among the solid electrolytes used in all-solid-state batteries. Examples of the other solid electrolytes include oxide-based solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, pseudo-solid electrolytes, and the like.

[0117] The lower limit of the average thickness of the solid electrolyte layer in an all-solid-state battery is preferably 0.1 μm, and more preferably 1 μm. The upper limit of the average thickness of the solid electrolyte layer is preferably 500 μm, and more preferably 50 μm. By setting the average thickness of the solid electrolyte layer to be above the lower limit, it becomes possible to reliably insulate the positive electrode and the negative electrode. By setting the average thickness of the solid electrolyte layer to be below the upper limit, it becomes possible to increase the energy density of the all-solid-state battery.

[0118] [All-Solid-State Battery (Fourth Embodiment)] An all-solid-state battery according to one embodiment of the present disclosure is an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer, characterized in that it contains the binder for all-solid-state batteries according to the present disclosure (first embodiment). The binder for all-solid-state batteries according to the present disclosure may be contained in any part of the all-solid-state battery according to the present disclosure.

[0119] The all-solid-state battery according to this disclosure may be an all-solid-state battery in which the binder for the all-solid-state battery according to this disclosure is contained only in the positive electrode active material layer, or in which it is contained only in the negative electrode active material layer, or in which it is contained only in the solid electrolyte layer. Furthermore, the all-solid-state battery according to this disclosure may be an all-solid-state battery in which the binder for the all-solid-state battery according to this disclosure is contained in the positive electrode active material layer and the negative electrode active material layer but not in the solid electrolyte layer, or in which it is contained in the positive electrode active material layer and the solid electrolyte layer but not in the negative electrode active material layer, or in which it is contained in the positive electrode active material layer, the negative electrode active material layer and the solid electrolyte layer. In other words, the all-solid-state battery according to the present disclosure includes a second embodiment, which is an all-solid-state battery containing the electrode according to the present disclosure and a third embodiment, which is an all-solid-state battery not containing the electrode according to the present disclosure and a third embodiment, which is an all-solid-state battery not containing the electrode according to the present disclosure and a third embodiment, which is an all-solid-state battery containing both the electrode according to the present disclosure and a third embodiment, which is an all-solid-state battery.

[0120] <Fabrication of All-Solid-State Batteries> The all-solid-state battery according to this disclosure can be manufactured by the same manufacturing method as a general all-solid-state battery, except that the binder for all-solid-state batteries according to this disclosure is used as a material for forming one of the layers. In particular, it is preferable to use the binder for all-solid-state batteries according to this disclosure as a material for forming the electrode or solid electrolyte layer.

[0121] All-solid-state batteries can be manufactured by bonding laminates, each layer stacked in an appropriate order, together by high-temperature and high-pressure processing. High-temperature and high-pressure processing can be carried out, for example, by hot pressing at a temperature of 80 to 250°C, preferably 100 to 200°C, more preferably 130 to 180°C, and a pressure of 10 to 1000 MPa, preferably 25 to 900 MPa, more preferably 50 to 800 MPa.

[0122] <Battery Structure> The all-solid-state battery according to this disclosure can take various known shapes, and can be formed into cylindrical, coin-shaped, prismatic, film-shaped, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be modified according to the purpose.

[0123] Furthermore, the all-solid-state battery according to this disclosure may be an all-solid-state battery obtained by charging and discharging an all-solid-state battery before charging and discharging, which includes a negative electrode, a positive electrode, and a solid electrolyte layer. That is, the all-solid-state battery according to this disclosure may be a charged and discharged all-solid-state battery produced by first manufacturing an all-solid-state battery before charging and discharging, which includes a negative electrode, a positive electrode, and a solid electrolyte layer, and then charging and discharging this all-solid-state battery before charging and discharging one or more times.

[0124] The applications of the all-solid-state battery relating to this disclosure are not particularly limited and can be used in a variety of known applications. For example, it can be widely used in notebook computers, mobile computers, mobile phones, headphone stereos, video cameras, LCD TVs, handheld vacuum cleaners, electronic organizers, calculators, radios, backup power supplies, motors, automobiles, electric vehicles, motorcycles, electric motorcycles, bicycles, electric bicycles, lighting fixtures, game consoles, watches, power tools, cameras, etc., regardless of whether they are small portable devices or large devices.

[0125] The present disclosure will be described in more detail by showing examples, etc., but the present disclosure is not limited to the following examples, etc., unless it exceeds the gist of the disclosure.

[0126] [Example 1] Polymer (A-1) was produced using ethylene and 1-butene as raw materials, with a structural unit (a1) ratio (%) of 80% by mass and a structural unit (a2) ratio (%) of 20% by mass. Specifically, n-hexane was supplied at a rate of 14.2 L / h to one feed port of a 300 L continuous polymerizer, and a mixed hexane solution of isopropylidene (3-tert-butyl-5-methylcyclopentadienyl-fluorenyl) zirconium dichloride (main catalyst 1), modified methylaluminoxane, and triisobutylaluminum was continuously supplied at a rate of 0.22 L / h from the other feed port. Here, the zirconium equivalent concentration was 0.5 mmol / L, the aluminum equivalent concentration of modified methylaluminoxane was 4 mmol / L, the aluminum equivalent concentration of triisobutylaluminum was 100 mmol / L, and the total amount of hexane was 10 L. Simultaneously, 1-butene was continuously supplied from another supply port of the polymerizer at a rate of 2.0 kg / h, ethylene at 8.0 kg / h, and hydrogen at 0.6 NL / h. Continuous solution polymerization was carried out under conditions of polymerization temperature of 60°C, polymerization pressure of 0.8 MPaG, and residence time of 1.5 hours to obtain 1-butene-ethylene copolymer (A-1).

[0127] [Example 2] Polymer (A-2) was produced in the same manner as in Example 1, except that the supply amounts of ethylene and 1-butene, as well as hydrogen, were changed so that the supply ratio of these substances was as shown in Table 1, and the polymer (A-2) had a structural unit (a1) ratio (%) of 90% by mass and a structural unit (a2) ratio (%) of 10% by mass.

[0128] [Example 3] Following the description in [Synthesis Example C1] of International Publication No. 2015 / 122415, an ethylene / 1-butene / 5-ethylidene-2-norbornene copolymer (polymer (A-3)) was obtained with a structural unit (a1) ratio (%) of 77% by mass, a structural unit (a2) ratio (%) of 12.6% by mass, and a structural unit (a3) ​​ratio (%) of 10.4% by mass.

[0129] [Comparative Example 1] Polymer (A-4) was produced in the same manner as in Example 1, except that the supply amounts of ethylene, propylene, and 5-vinyl-2-norbornene were changed to match the supply amounts shown in Table 1, along with the supply amounts of hydrogen, with a structural unit (a1) ratio (%) of 60% by mass, a structural unit (a2) ratio (%) of 38.5% by mass, and a structural unit (a3) ​​ratio (%) of 1.5% by mass.

[0130] [Comparative Example 2] Polymer (A-5) was produced in the same manner as in Example 1, except that the supply amounts of ethylene, propylene, and 1-butene were changed to match the supply ratios shown in Table 1, along with the supply amounts of hydrogen, with a structural unit (a1) ratio (%) of 10% by mass, a structural unit (a2) ratio (%) of 20% by mass, and a structural unit (a3) ​​ratio (%) of 70% by mass.

[0131] <Measurement of Weight-Average Molecular Weight (Mw)> For each polymer, GPC measurements were performed under the following conditions to determine the weight-average molecular weight (Mw). The weight-average molecular weight (Mw) was calculated using a calibration curve created with commercially available monodisperse standard polystyrene, based on the conversion method described below. The measurement results are shown in Table 1.

[0132] (Measurement conditions) Apparatus: Gel permeation chromatograph HLC-8321 GPC / HT type (manufactured by Tosoh Corporation) Organic solvent: o-dichlorobenzene Columns: 2 TSKgel GMH6-HT columns, 2 TSKgel GMH6-HTL columns (both manufactured by Tosoh Corporation) Flow rate: 1.0 mL / min Sample: 0.15 mg / mL o-dichlorobenzene solution temperature: 140°C Molecular weight conversion: PS conversion / general calibration method Note: The coefficients of the Mark-Houwink viscosity formula are used in the calculation of the general calibration. The Mark-Houwink coefficients for PS were the values ​​described in the literature (J. Polym. Sci., Part A-2, 8, 1803 (1970)).

[0133] <Measurement of Glass Transition Temperature (°C)> The glass transition temperature of each polymer resin film was measured using a differential scanning calorimetry system (Diamond DSC, PerkinElmer) in accordance with JIS 7121. Specifically, 5 mg of the resin film was packed into an aluminum pan, heated to 200°C, held at 200°C for 5 minutes, cooled to -40°C at 10°C / min, held at -40°C for 5 minutes, and then heated again at 10°C / min. The endothermic curve during this process was used to determine the glass transition temperature. The measurement results are shown in Table 1.

[0134] <Density of polymer (g / cm³) ３ ) > Density of each polymer (g / cm³) ３ The values ​​were measured in accordance with JIS K7112 (density gradient pipe method).

[0135] <Preparation of Binder Solution> Each polymer was dissolved in a mixed solution of tetralin and anisole in a mass ratio of 5:1 (tetralin / anisole (5:1 wt) solution) to prepare a binder solution. Specifically, the polymer was added to the tetralin / anisole (5:1 wt) solution and heated and mixed at 80°C to prepare a binder solution with a polymer concentration of 5 wt%.

[0136] <Preparation of electrode (positive electrode)> 2.48 g of LiNbO ３ LiNi coated ０．５ Co ０．２ Mn ０．３ O ２ 0.46 g of argyrodite-type sulfide solid electrolyte, 0.03 g of vapor-grown carbon fiber (VGCF), 0.36 g of the binder solution, and 0.14 g of ethylcellulose solution were weighed out, and a tetralin / anisole (5:1 wt) dispersion medium was added. The mixture was then mixed in a rotary-orbit mixer at 2000 rpm for 20 minutes to obtain a cathode composite slurry. The ethylcellulose solution used was a 5 wt% ethylcellulose solution prepared by dissolving ethylcellulose in a tetralin / anisole (5:1 wt) solution at 80°C. The obtained cathode composite slurry was then applied to aluminum foil at a basis weight of 20 mg / cm². ２ The material was coated using an applicator, and the dispersion medium was removed by vacuum drying at 100°C to obtain a positive electrode on aluminum foil.

[0137] <Preparation of Electrode (Negative Electrode)> 2.03 g of graphite, 0.92 g of argyrodite-type sulfide solid electrolyte, and 0.06 g of the aforementioned binder solution were weighed out, and a tetralin / anisole (5:1 wt) dispersion medium was added. The mixture was then mixed in a rotary-orbit mixer at 2000 rpm for 20 minutes to obtain a negative electrode mixture slurry. The obtained negative electrode mixture slurry was then applied to carbon-coated SUS foil at a basis weight of 16 mg / cm². ２ The material was coated using an applicator, and the dispersion medium was removed by vacuum drying at 100°C to obtain the negative electrode.

[0138] <Preparation of Solid Electrolyte Layer> 2.94 g of the argyrodite-type sulfide solid electrolyte, 0.85 g of the binder solution, and 0.42 g of the ethylcellulose solution obtained by the same method as in <Preparation of Electrode (Positive Electrode)> were weighed out, and a tetralin / anisole (5:1 wt) solution, which is the dispersion medium, was added and mixed in a rotary-orbit mixer to obtain a solid electrolyte layer slurry. The prepared slurry was coated onto a SUS foil with an applicator, and the dispersion medium was removed by vacuum drying at 100°C to obtain a solid electrolyte layer with a thickness of 60 μm or 200 μm on the SUS foil.

[0139] <Measurement of Ionic Conductivity of Solid Electrolyte Layer> The 60 μm thick solid electrolyte layer prepared in <Fabrication of Solid Electrolyte Layer> above was sandwiched between SUS foils and pressed at 580 MPa. After this, AC impedance measurement was performed and evaluated. The impedance was measured at a frequency of 7 MHz to 1 Hz and an amplitude of 100 mV, and the ionic conductivity (mS / cm) was obtained from the following formula.

[0140] [Ionic conductivity (mS / cm)] = [Film thickness (μm)] / [Area (cm²)] ２ )]×[Resistance (Ω)])

[0141] <Evaluation by Mandrel Test> The solid electrolyte layer with a thickness of 200 μm, prepared in <Preparation of Solid Electrolyte Layer> above, was wrapped around a mandrel with a diameter of 5 mm and evaluated for cracks or chips.

[0142] <Preparation of Solid Electrolyte Layer Transfer Negative Electrode> The negative electrode on the carbon-coated SUS foil prepared in <Preparation of Electrode (Negative Electrode)> and the solid electrolyte layer on the SUS foil prepared in <Preparation of Solid Electrolyte Layer> were placed opposite each other and pressed with 3 kN using a roll press machine at 180°C to remove the SUS foil of the solid electrolyte layer and obtain a solid electrolyte layer transfer negative electrode.

[0143] <Fabrication of All-Solid-State Battery> The positive electrode on Al foil, fabricated in <Fabrication of Electrode (Positive Electrode)>, was placed on the solid electrolyte layer side of the solid electrolyte layer transfer negative electrode fabricated in <Fabrication of Solid Electrode Transfer>, and an all-solid-state battery was fabricated by applying pressure at 180°C and 580 MPa using a warm isostatic press.

[0144] <Evaluation of Battery Performance> The all-solid-state battery fabricated in the <Fabrication of All-Solid-State Batteries> section above underwent three cycles of CC-CV charge-discharge measurements at 25°C and 0.1C. The CC cutoff voltage was set to 4.35V to 3V, and the CV termination current was set to 0.01C. The Coulomb efficiency (%) was measured after the third cycle.

[0145] The results of each measurement are shown in Table 1. In Table 1, A and B have the following meanings.

[0146] In the "Binder Solution" column: "A": The polymer dissolved and a binder solution was prepared. "B": Undissolved polymer particles were visually confirmed, and a binder solution could not be prepared.

[0147] In the sections for "Preparation of electrodes (positive electrode)", "Preparation of electrodes (negative electrode)", and "Preparation of solid electrolyte layer": "A": Slurry was prepared, and electrodes and solid electrolytes were prepared by coating with it. "B": Slurry could not be prepared, or coating could not be performed, and electrodes, etc., could not be prepared.

[0148] In the "Mandrel Test" column: "A": No cracks or chips were found. "B": Cracks, chips, or both were observed.

[0149] In the "Coulomb Efficiency" column: "A": 99.0% or higher. "B": Less than 99.0%.

[0150]

[0151] As shown in Table 1, polymer (A-5), which had a structural unit (a1) ratio of 10% by mass, did not dissolve in the tetralin / anisole (5:1 wt) solution, making it impossible to prepare a binder solution and thus impossible to fabricate electrodes or solid electrolyte layers. Polymers (A-1) to (A-4), which had a structural unit (a1) ratio of 60% by mass or more, dissolved in the tetralin / anisole (5:1 wt) solution, and electrodes, solid electrolyte layers, and all-solid-state batteries could be fabricated. In particular, the solid electrolyte layers prepared from polymers (A-1) to (A-3), which had a structural unit (a1) ratio of 77% by mass or more, showed no cracks or chips in the mandrel test and exhibited excellent electrode strength. The all-solid-state batteries prepared from polymers (A-1) to (A-3) had a Coulomb efficiency of 99.0% or more and exhibited excellent battery characteristics. In contrast, the solid electrolyte layer prepared from polymer (A-4) with a structural unit (a1) ratio of 60% by mass showed cracking and chipping in the mandrel test, and the Coulomb efficiency of the fabricated battery was less than 99.0%. These results indicate that for polymers containing structural unit (a1) and structural unit (a2), and polymers containing structural unit (a1), structural unit (a2), and structural unit (a3), a higher ratio of structural unit (a1) is superior as a binder for all-solid-state batteries, resulting in all-solid-state batteries with excellent electrode strength and battery characteristics.

Claims

1. A binder for all-solid-state batteries, comprising a polymer (A) containing two or more structural units selected from the group consisting of structural units derived from ethylene (a1), structural units derived from α-olefins having 3 to 20 carbon atoms (a2), and structural units derived from non-conjugated polyenes (a3), wherein the polymer (A) contains 77% by mass or more of the structural units derived from ethylene (a1), the structural units derived from α-olefins having 3 to 20 carbon atoms (a2), and the structural units derived from non-conjugated polyenes (a3), with the total of these being 100% by mass.

2. The binder for all-solid-state batteries according to claim 1, wherein the weight-average molecular weight (Mw) of the polymer (A) is 100,000 or more.

3. The binder for an all-solid-state battery according to claim 1, wherein the polymer (A) is a copolymer comprising a structural unit (a1) derived from ethylene and a structural unit (a2) derived from an α-olefin having 3 to 20 carbon atoms, or a copolymer comprising a structural unit (a1) derived from ethylene, a structural unit (a2) derived from an α-olefin having 3 to 20 carbon atoms, and a structural unit (a3) ​​derived from a non-conjugated polyene.

4. The binder for all-solid-state batteries according to claim 1, wherein the polymer (A) comprises structural units (a1) derived from ethylene and structural units (a2) derived from an α-olefin having 3 to 20 carbon atoms, and when the total of the structural units (a1) derived from ethylene, the structural units (a2) derived from the α-olefin having 3 to 20 carbon atoms, and the structural units (a3) ​​derived from the non-conjugated polyene is 100% by mass, the ratio of the structural units (a2) derived from the α-olefin having 3 to 20 carbon atoms is greater than 0% by mass and 23% by mass or less.

5. The binder for all-solid-state batteries according to claim 1, wherein the polymer (A) comprises structural units (a1) derived from ethylene, structural units (a2) derived from α-olefins having 3 to 20 carbon atoms, and structural units (a3) ​​derived from non-conjugated polyenes, and when the total of the structural units (a1) derived from ethylene, the structural units (a2) derived from α-olefins having 3 to 20 carbon atoms, and the structural units (a3) ​​derived from non-conjugated polyenes is 100% by mass, the ratio of structural units (a2) derived from α-olefins having 3 to 20 carbon atoms is 5% by mass or more and 18% by mass or less, and the ratio of structural units (a3) ​​derived from non-conjugated polyenes is 5% by mass or more and 18% by mass or less.

6. The binder for all-solid-state batteries according to claim 1, wherein the structural unit (a2) derived from an α-olefin having 3 to 20 carbon atoms is a structural unit derived from an α-olefin having 3 to 4 carbon atoms.

7. The binder for all-solid-state batteries according to claim 1, wherein the structural unit (a3) ​​derived from the non-conjugated polyene is a structural unit derived from 5-ethylidene-2-norbornene.

8. An electrode comprising a binder for an all-solid-state battery according to any one of claims 1 to 5.

9. An electrolyte layer comprising the binder for an all-solid-state battery according to any one of claims 1 to 5.

10. A solid-state battery comprising a binder for solid-state batteries according to any one of claims 1 to 5.

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