Electrode compositions, binders and polymers for solid-state batteries

Abstract

To provide an electrode composition excellent in sedimentation stability. 【Solution means】An electrode composition containing a polymer and a solvent, wherein the polymer contains trifluoroethylene units, and the content of trifluoroethylene units in the polymer is 50 mol% or more based on all monomer units, and the solvent is represented by the general formula (1): R 4 COOR 2 (In the formula, R 1 and R 2 are independently H, a linear or branched aliphatic group having 1 to C 10 , or an aromatic group having 6 to C 10 ).) and at least one selected from the group consisting of a ketone (2) represented by the general formula (2): R 3 COR 4 (In the formula, R 3 and R 4 are independently H, a linear or branched aliphatic group having 1 to C 10 , or an aromatic group having 6 to C 10 ).) to provide an electrode composition.

Description

[Technical Field]

[0001] This disclosure relates to electrode compositions, binders for solid-state batteries, and polymers. [Background technology]

[0002] Patent Document 1 describes a slurry for a positive electrode of a sulfide-based solid battery, comprising at least a fluorine-based copolymer containing vinylidene fluoride monomer units, a positive electrode active material, and a solvent or dispersion medium, characterized in that the content of the fluorine-based copolymer is 1.5 to 10% by volume when the dry volume is 100% by volume. The solvent or dispersion medium comprises an ester compound represented by the following formula (1). R 1 -CO2-R 2 Formula (1) (In the above formula (1), R 1 R is a linear or branched aliphatic group having 3 to 10 carbon atoms or an aromatic group having 6 to 10 carbon atoms, and 2 (A is a linear or branched aliphatic group with 4 to 10 carbon atoms.) [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-007138 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The purpose of this disclosure is to provide an electrode composition that exhibits excellent sedimentation stability. Furthermore, this disclosure aims to provide a binder for solid-state batteries that exhibits good solubility or dispersibility in solvents suitably used in sulfide-based solid-state batteries and is less prone to sedimentation in the resulting composition. In addition, in the present disclosure, an object is to provide a polymer that exhibits good solubility or dispersibility in a solvent suitably used for a sulfide-based solid battery, is less likely to precipitate in the resulting composition, and further exhibits good adhesion to a substrate.

Means for Solving the Problems

[0005] According to the present disclosure, there is provided an electrode composition containing a polymer and a solvent, wherein the polymer contains trifluoroethylene units, the content of the trifluoroethylene units in the polymer is 50 mol% or more based on all monomer units, and the solvent is at least one selected from the group consisting of an ester (1) represented by the general formula (1) and a ketone (2) represented by the general formula (2).

[0006] General formula (1):

Chemical formula

[0007] General formula (2):

Chemical formula

[0008] In the electrode composition of the present disclosure, it is preferable that the polymer further contains fluorinated monomer units (excluding trifluoroethylene units). In the electrode composition of the present disclosure, it is preferable that the polymer further contains monomer (3) units represented by the general formula (3).

[0009] General formula (3): [ka] (In the formula, R 5 ~R 7 R is independently H, F, CH3, or CF3, and X is an atomic group with a molecular weight of 500 or less, consisting of single bonds or a main chain with 1 to 20 atoms. OH (This is a C1-C5 hydrocarbon group containing H or at least one OH group.)

[0010] In the electrode composition of this disclosure, it is preferable that the content of monomer (3) units of the polymer is 0.001 to 3.0 mol% relative to the total monomer units. In the electrode composition of this disclosure, the content of the polymer is preferably 0.1 to 20% by mass relative to the mass of the electrode composition. The electrode composition of this disclosure preferably further contains a powder electrode material. In the electrode composition of this disclosure, it is preferable that the powder electrode material contains a solid electrolyte. In the electrode composition of this disclosure, it is preferable that the powder electrode material contains a conductive additive. In the electrode composition of this disclosure, it is preferable that the powder electrode material contains an electrode active material. In the electrode composition of this disclosure, it is preferable that the content of the powder electrode material is 20 to 75% by mass relative to the weight of the electrode composition.

[0011] Furthermore, this disclosure provides a binder for solid batteries containing a polymer that contains trifluoroethylene units, wherein the trifluoroethylene unit content is 50 mol% or more relative to the total monomer units.

[0012] The binder for solid-state batteries of this disclosure can be suitably used as a binder for sulfide-based solid-state batteries.

[0013] Furthermore, the present disclosure provides a polymer containing trifluoroethylene units and monomer (3) units represented by general formula (3), wherein the content of trifluoroethylene units is 50 mol% or more relative to the total monomer units.

[0014] General formula (3): [ka] (In the formula, R 5 ~R 7 R is independently H, F, CH3, or CF3, and X is an atomic group with a molecular weight of 500 or less, consisting of single bonds or a main chain with 1 to 20 atoms. OH (This is a C1-C5 hydrocarbon group containing H or at least one OH group.)

[0015] In the polymers of this disclosure, the content of monomer (3) units is preferably 0.001 to 3.0 mol% relative to the total monomer units. [Effects of the Invention]

[0016] According to this disclosure, it is possible to provide an electrode composition with excellent sedimentation stability. Furthermore, this disclosure provides a binder for solid-state batteries that exhibits good solubility or dispersibility in solvents suitably used in sulfide-based solid-state batteries and is less prone to sedimentation in the resulting composition. Furthermore, according to this disclosure, it is possible to provide a polymer that exhibits good solubility or dispersibility in solvents suitably used in sulfide-based solid-state batteries, is less prone to sedimentation in the resulting composition, and exhibits good adhesion to a substrate. [Modes for carrying out the invention]

[0017] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0018] The electrode composition of this disclosure contains a polymer and a solvent. The polymer functions as a binder in the electrode when an electrode is formed using the electrode composition.

[0019] As an example of a composition containing such a binder, Patent Document 1 describes a slurry for a positive electrode of a sulfide-based solid battery, which contains at least a fluorine copolymer containing vinylidene fluoride monomer units, a positive electrode active material, and a solvent or dispersion medium. In this slurry for a positive electrode of a sulfide-based solid battery, an ester compound represented by the above formula is used as the solvent or dispersion medium in order to prevent a decrease in ionic conductivity when mixed with a sulfide-based solid electrolyte.

[0020] However, the slurry for the positive electrode of a sulfide-based solid battery described in Patent Document 1 has the problem that the fluorine copolymer is not easily soluble in the ester compound (solvent or dispersion medium), and the settling stability of the resulting slurry is not sufficient.

[0021] In the electrode composition of this disclosure, a polymer containing trifluoroethylene units in a specific amount is used together with at least one solvent selected from the group consisting of esters (1) and ketones (2). By combining a polymer with a limited composition with a limited type of solvent in this way, the polymer can be easily dissolved in the solvent, making it easier to prepare the electrode composition compared to conventional electrode compositions. Furthermore, the resulting electrode composition exhibits excellent sedimentation stability.

[0022] (polymer) The polymer contained in the electrode composition of this disclosure contains trifluoroethylene units.

[0023] The polymer described above may be a homopolymer containing only trifluoroethylene units, or a copolymer containing trifluoroethylene units and other monomer units other than trifluoroethylene. The electrode composition of this disclosure may contain one or more polymers containing trifluoroethylene units.

[0024] The content of trifluoroethylene units in the above polymer is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 65 mol% or more, and particularly preferably 70 mol% or more, with an upper limit of 100 mol% relative to the total monomer units.

[0025] The content of other monomer units in the above polymer is preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 35 mol% or less, and particularly preferably 30 mol% or more, with a lower limit of 0 mol%, relative to the total number of monomer units.

[0026] If the above polymer contains other monomer units, these other monomers may be fluorinated monomers or non-fluorinated monomers.

[0027] Examples of fluorinated monomers (excluding trifluoroethylene) include vinylidene fluoride (VdF), tetrafluoroethylene (TFE), vinyl fluoride, chlorotrifluoroethylene (CTFE), fluoroalkyl vinyl ether, hexafluoropropylene (HFP), (perfluoroalkyl)ethylene, 2,3,3,3-tetrafluoropropene, and trans-1,3,3,3-tetrafluoropropene.

[0028] As the fluoroalkyl vinyl ether, a fluoroalkyl vinyl ether having a fluoroalkyl group with 1 to 5 carbon atoms is preferred, and at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), and perfluoro(propyl vinyl ether) is more preferred.

[0029] As the fluorinated monomer, at least one selected from the group consisting of VdF, TFE, CTFE, 2,3,3,3-tetrafluoropropene, HFP, and fluoroalkyl vinyl ether is preferred, and at least one selected from the group consisting of CTFE, 2,3,3,3-tetrafluoropropene, HFP, and fluoroalkyl vinyl ether is more preferred.

[0030] The fluorinated monomer may or may not have a polar group. A fluorinated monomer having a polar group may be used as the fluorinated monomer.

[0031] From the viewpoint of obtaining even better sedimentation stability, it is preferable that the content of vinylidene fluoride units in the above polymer be small. The content of vinylidene fluoride units in the above polymer is preferably less than 40 mol%, more preferably less than 30 mol%, even more preferably less than 20 mol%, particularly preferably less than 10 mol%, preferably 0 mol% or more, and more preferably 1 mol% or more, relative to the total monomer units.

[0032] Examples of non-fluorinated monomers include non-fluorinated monomers without polar groups, such as ethylene and propylene, and non-fluorinated monomers with polar groups. Hereinafter, fluorinated monomers with polar groups and non-fluorinated monomers with polar groups may be collectively referred to as polar group-containing monomers.

[0033] When a non-fluorinated monomer having a polar group is used, the polar group is introduced into the polymer, thereby providing excellent adhesion between the electrode material layer and the current collector. The polar group is preferably at least one selected from the group consisting of carbonyl group-containing groups, epoxy groups, hydroxyl groups, sulfonic acid groups, sulfate groups, phosphoric acid groups, amino groups, amide groups, and alkoxy groups; more preferably at least one selected from the group consisting of carbonyl group-containing groups, epoxy groups, and hydroxyl groups; and even more preferably a carbonyl group-containing group. The above hydroxyl group does not include hydroxyl groups that constitute part of the above carbonyl group-containing group. Furthermore, the above amino group is a monovalent functional group obtained by removing hydrogen from ammonia, a primary or secondary amine.

[0034] The carbonyl group-containing group mentioned above is a functional group having a carbonyl group (-C(=O)-). The carbonyl group-containing group is preferably a group represented by the general formula: -COOR (where R represents a hydrogen atom, an alkyl group, or a hydroxyalkyl group) or a carboxylic acid anhydride group, and more preferably a group represented by the general formula: -COOR. The number of carbon atoms in the alkyl group and hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and even more preferably 1 to 3. Specific examples of groups represented by the general formula: -COOR include -COOCH2CH2OH, -COOCH2CH(CH3)OH, -COOCH(CH3)CH2OH, -COOH, -COOCH3, -COOC2H5, etc. If the group represented by the general formula: -COOR is -COOH or contains -COOH, then -COOH may be a carboxylate salt such as a metal carboxylate salt or an ammonium carboxylate salt.

[0035] Furthermore, the carbonyl group-containing group may also be a group represented by the general formula: -X-COOR (where X is an atomic group whose main chain consists of 1 to 20 atoms and has a molecular weight of 500 or less, and R represents a hydrogen atom, an alkyl group, or a hydroxyalkyl group). The number of carbon atoms in the alkyl group and hydroxyalkyl group is preferably 1 to 16, more preferably 1 to 6, and even more preferably 1 to 3.

[0036] The amide group described above is preferably a group represented by the general formula: -CO-NRR' (where R and R' independently represent a hydrogen atom or a substituted or unsubstituted alkyl group), or a bond represented by the general formula: -CO-NR”- (where R represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted phenyl group).

[0037] The above polar group-containing monomers include hydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate and 2-hydroxypropyl acrylate; alkylidenemalonate esters such as dimethyl methylidenemalonate; vinyl carboxyalkyl ethers such as vinyl carboxymethyl ether and vinyl carboxyethyl ether; carboxyalkyl (meth)acrylates such as 2-carboxyethyl acrylate and 2-carboxyethyl methacrylate; (meth)acryloyloxyalkyl dicarboxylic acid esters such as acryloyloxyethyl succinic acid, acryloyloxypropyl succinic acid, methacryloyloxyethyl succinic acid, acryloyloxyethyl phthalic acid, and methacryloyloxyethyl phthalic acid; monoesters of unsaturated dibasic acids such as monomethyl maleate, monoethyl maleate, monomethyl citraconic acid, and monoethyl citraconic acid; general formula (4): [ka] (In the formula, R 11 ~R 13 R independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. 14 Y represents a single bond or a hydrocarbon group with 1 to 8 carbon atoms. 1 represents inorganic cations and / or organic cations. Examples include monomers represented by (4); unsaturated dibasic acids such as maleic acid, maleic anhydride, citraconic acid, and citraconic anhydride; etc.

[0038] As the polar group-containing monomer units that the polymer may contain, units based on monomer (4) represented by general formula (4) are preferred.

[0039] In general formula (4), Y 1 '' represents inorganic cations and / or organic cations. Examples of inorganic cations include H, Li, Na, K, Mg, Ca, Al, and Fe. Examples of organic cations include NH4 and NH3R. 15 NH2R 15 2. NHR 15 3. NR 15 4(R 15 Each independently represents an alkyl group having 1 to 4 carbon atoms. Examples of cations include Y. 1 Preferred cations are H, Li, Na, K, Mg, Ca, Al, and NH4; more preferred are H, Li, Na, K, Mg, Al, and NH4; even more preferred are H, Li, Al, and NH4; and particularly preferred is H. For convenience, specific examples of inorganic and organic cations are listed without symbols or valencies.

[0040] In general formula (4), R 11 ~R 13 R independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. The hydrocarbon group is a monovalent hydrocarbon group. The number of carbon atoms in the hydrocarbon group is preferably 4 or less. Examples of the hydrocarbon group include alkyl groups, alkenyl groups, alkynyl groups, etc., with methyl or ethyl groups being preferred. 11 and R 12 R is preferably independently a hydrogen atom, a methyl group, or an ethyl group. 13 It is preferable that this is a hydrogen atom or a methyl group.

[0041] In general formula (4), R 14 The symbol represents a single bond or a hydrocarbon group having 1 to 8 carbon atoms. The hydrocarbon group is a divalent hydrocarbon group. The number of carbon atoms in the hydrocarbon group is preferably 4 or less. Examples of the hydrocarbon group include alkylene groups and alkenylene groups with the above number of carbon atoms, and among these, at least one selected from the group consisting of methylene, ethylene, ethylidene, propyridene, and isopropylidene groups is preferred, with methylene being more preferred.

[0042] The monomer (4) is preferably at least one selected from the group consisting of (meth)acrylic acid and its salts, vinylacetic acid (3-butenic acid) and its salts, 3-pentenoic acid and its salts, 4-pentenoic acid and its salts, 3-hexenoic acid and its salts, 4-heptenoic acid and its salts, and 5-hexenoic acid and its salts.

[0043] Since the above polymer provides excellent adhesion between the electrode material layer and the current collector, it is preferable to further contain monomer (3) units represented by general formula (3) as other monomer units.

[0044] General formula (3): [ka] (In the formula, R 5 ~R 7 R is independently H, F, CH3, or CF3, and X is an atomic group with a molecular weight of 500 or less, consisting of single bonds or a main chain with 1 to 20 atoms. OH (This is a C1-C5 hydrocarbon group containing H or at least one OH group.)

[0045] R 5 ~R 7 R is independently H, F, CH3, or CF3. 5 ~R 7 H or CH3 are preferred as the base material.

[0046] X is an atomic group with a molecular weight of 500 or less, consisting of single bonds or a main chain with 1 to 20 atoms.

[0047] The number of atoms in the main chain of the atomic group is 1 to 20, more preferably 1 to 14, even more preferably 1 to 8, and particularly preferably 1 to 7. The number of atoms in the main chain of the atomic group refers to the number of unsaturated bonds (CR). 5 R 6 =CR 7 This refers to the number of atoms in the skeletal structure of a chain that connects a carbonyl group (-C(=O)-) with the fewest possible number of atoms.

[0048] The molecular weight of the atomic group is preferably 450 or less, more preferably 390 or less, even more preferably 340 or less, preferably 14 or more, more preferably 20 or more, and even more preferably 28 or more.

[0049] As for the atomic group, a divalent group represented by one of the following formulas is preferred because it is possible to obtain an electrode mixture that is less prone to viscosity increase and an electrode material layer with even better adhesion to the current collector. General formula (3a):*-L 1 - (In the formula, *- represents an unsaturated bond (CR) 5 R 6 =CR 7 -) is a bonding hand that connects with L 1 (This refers to an alkylene group with 1 to 20 carbon atoms.) General formula (3b):*-CO-L 2 - (In the formula, *- represents an unsaturated bond (CR) 5 R 6 =CR 7 -) is a bonding hand that connects with L 2 (This refers to an alkylene group with 1 to 19 carbon atoms.) General formula (3c):*-OL 3 - (In the formula, *- represents an unsaturated bond (CR) 5 R 6 =CR 7 -) is a bonding hand that connects with L 3 (This refers to an alkylene group with 1 to 19 carbon atoms.) General formula (3d):*-COO-L 4 - (In the formula, *- represents an unsaturated bond (CR) 5 R 6 =CR 7 -) is a bonding hand that connects with L 4 (This refers to an alkylene group with 1 to 18 carbon atoms.) General formula (3e):*-COO-L 5 -OCO-L 6 - (In the formula, *- represents an unsaturated bond (CR) 5 R 6 =CR7 -) is a bonding hand that connects with L 5 and L 6 These are independently alkylene groups, and L 5 and L 6 The total number of carbon atoms is between 2 and 16.

[0050] The atomic group is preferably at least one selected from the group consisting of a divalent group represented by general formula (3a), a divalent group represented by general formula (3c), a divalent group represented by general formula (3d), and a divalent group represented by general formula (3e), and more preferably at least one selected from the group consisting of a divalent group represented by general formula (3c), a divalent group represented by general formula (3d), and a divalent group represented by general formula (3e).

[0051] L 1 ~L 6 Independently, alkylene groups having 1 to 10 carbon atoms are preferred, alkylene groups having 1 to 4 carbon atoms are more preferred, alkylene groups having 1 to 3 carbon atoms are even more preferred, and methylene groups or ethylene groups are particularly preferred.

[0052] R OH R is a C1-C5 hydrocarbon group containing H or at least one OH. OH H is preferred. OH When H is present, the resulting carboxyl group (-COOH) may form salts with cations such as Li, Na, K, Mg, Ca, Al, and NH4.

[0053] Examples of monomers (3) include unsaturated monocarboxylic acids having 3 to 6 carbon atoms, such as (meth)acrylic acid, vinyl acetic acid (3-butenoic acid), 3-pentenoic acid, 4-pentenoic acid, 3-hexenoic acid, 4-heptenoic acid, and 5-hexenoic acid; vinyl carboxyalkyl ethers having 3 to 6 carbon atoms, such as vinyl carboxymethyl ether and vinyl carboxyethyl ether; carboxyalkyl (meth)acrylates having 5 to 12 carbon atoms, such as carboxyethyl acrylate of acryloyloxyethyl succinate and 2-carboxyethyl methacrylate; (meth)acryloyloxyalkyl dicarboxylic acid esters having 7 to 16 carbon atoms, such as acryloyloxyethyl succinate, acryloyloxypropyl succinate, methacryloyloxyethyl succinate, acryloyloxyethyl phthalate, and methacryloyloxyethyl phthalate; and salts thereof.

[0054] Among the monomers (3), at least one selected from the group consisting of (meth)acrylic acid, 3-butenoic acid, 4-pentenoic acid, 2-carboxyethyl acrylate, hydroxyethyl acrylate, 2-hydroxypropyl acrylate, acryloyloxyethyl succinic acid, and salts thereof is preferred, with (meth)acrylic acid being more preferred.

[0055] As other monomers, at least one selected from the group consisting of VdF, TFE, CTFE, monomer (3), 2,3,3,3-tetrafluoropropene, HFP, monofluoroethylene, and fluoroalkyl vinyl ether is preferred, and at least one selected from the group consisting of CTFE, monomer (3), 2,3,3,3-tetrafluoropropene, HFP, monofluoroethylene, and fluoroalkyl vinyl ether is more preferred.

[0056] The content of monomer (3) units in the above polymer is preferably 0.001 to 3.0 mol%, more preferably 2.0 mol% or less, more preferably 0.10 mol% or more, and even more preferably 0.50 mol% or more, relative to the total monomer units.

[0057] When the above polymer contains monomer (3) units, the content of trifluoroethylene units in the above polymer is preferably 97.0 to 99.999 mol%, more preferably 98.0 mol% or more, more preferably 99.9 mol% or less, and even more preferably 99.5 mol% or less, relative to the total monomer units.

[0058] As for polymers, in particular, Trifluoroethylene homopolymer, Trifluoroethylene / VdF copolymer, Trifluoroethylene / TFE copolymer, Trifluoroethylene / HFP copolymer, Trifluoroethylene / CTFE copolymer, Trifluoroethylene / fluoroalkyl vinyl ether copolymer, Trifluoroethylene / 2,3,3,3-tetrafluoropropene copolymer, Trifluoroethylene / VdF / CTFE copolymer, Trifluoroethylene / VdF / HFP copolymer, Trifluoroethylene / (meth)acrylic acid copolymer, Trifluoroethylene / 3-butenic acid copolymer, Trifluoroethylene / 3-butenic acid copolymer, Trifluoroethylene / 2-carboxyethyl acrylate copolymer, Trifluoroethylene / acryloyloxyethyl succinate copolymer, Trifluoroethylene / VdF / (meth)acrylic acid copolymer, Trifluoroethylene / TFE / (meth)acrylic acid copolymer, Trifluoroethylene / HFP / (meth)acrylic acid copolymer, Trifluoroethylene / CTFE / (meth)acrylic acid copolymer, Trifluoroethylene / fluoroalkyl vinyl ether / (meth)acrylic acid copolymer, Trifluoroethylene / 2,3,3,3-tetrafluoropropene / (meth)acrylic acid copolymer, Trifluoroethylene / VdF / CTFE / (meth)acrylic acid copolymer, Trifluoroethylene / VdF / HFP / (meth)acrylic acid copolymer These are some examples.

[0059] In this disclosure, the composition of the polymer is, for example, 19 It can be measured by 1F-NMR. Furthermore, if the polymer contains polar group-containing monomer units as other monomer units, the content of these polar group-containing monomer units can be measured, for example, by acid-base titration of the acid group if the polar group is an acidic group such as a carboxylic acid.

[0060] The weight-average molecular weight (in polystyrene equivalent) of the polymer is preferably 10,000 to 3,000,000, more preferably 30,000 or more, even more preferably 50,000 or more, particularly preferably 200,000 or more, more preferably 2,400,000 or less, even more preferably 2,200,000 or less, and particularly preferably 2,000,000 or less. The above weight-average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as the solvent.

[0061] The number-average molecular weight (in polystyrene terms) of the polymer is preferably 7,000 to 1,500,000, more preferably 21,000 or more, even more preferably 35,000 or more, more preferably 1,400,000 or less, even more preferably 1,200,000 or less, and particularly preferably 1,100,000 or less. The above number-average molecular weight can be measured by gel permeation chromatography (GPC) using dimethylformamide as the solvent.

[0062] The solution viscosity of the polymer is preferably 10 to 4000 mPa·s, more preferably 50 mPa·s or more, even more preferably 100 mPa·s or more, particularly preferably 150 mPa·s or more, more preferably 3000 mPa·s or less, even more preferably 2000 mPa·s or less, and particularly preferably 1500 mPa·s or less. The solution viscosity is the viscosity of an N-methyl-2-pyrrolidone (NMP) solution containing 5% by mass of the copolymer. The viscosity of the NMP solution can be measured at 25°C using a B-type viscometer.

[0063] The melting point of the polymer is preferably 100 to 250°C. The melting point of the polymer can be determined using a differential scanning calorimetry (DSC) device, by raising the temperature from 30°C to 300°C at a rate of 10°C / min, then lowering it to 30°C at a rate of 10°C / min, and then raising it again to 300°C at a rate of 10°C / min, and recording the temperature as the temperature at which the heat of fusion curve reaches its maximum value.

[0064] The polymer content in the electrode composition is preferably 0.1 to 20% by mass, more preferably 0.2 to 10% by mass, and even more preferably 0.5 to 3% by mass, relative to the mass of the electrode composition.

[0065] The polymer can be suitably produced by a method of polymerizing trifluoroethylene and, if necessary, other monomers in a reactor.

[0066] While polymerization methods such as suspension polymerization, emulsion polymerization, and solution polymerization can be employed, suspension polymerization and emulsion polymerization are preferred due to the ease of post-processing and other factors.

[0067] The polymerization temperature is not particularly limited, but from the viewpoint of polymerization rate and the cost required for temperature control, it is preferably 0 to 95°C, and more preferably 15 to 95°C. In particular, the polymerization temperature in suspension polymerization is preferably 15 to 45°C. In particular, the polymerization temperature in emulsion polymerization is 55 to 95°C.

[0068] The polymerization pressure is not particularly limited, but from the viewpoint of polymerization rate and reactor pressure resistance, it is preferably 0.3 to 1 MPaG, more preferably 0.4 MPaG or higher, and more preferably 0.8 MPaG or lower.

[0069] In the polymerization described above, polymerization initiators, surfactants, chain transfer agents, and solvents can be used, and conventionally known ones can be used. As the polymerization initiator, oil-soluble radical polymerization initiators or water-soluble radical polymerization initiators can be used.

[0070] The oil-soluble radical polymerization initiator may be a known oil-soluble peroxide, for example, Dialkyl peroxycarbonates such as dinormal propyl peroxydicarbonate, diisopropyl peroxydicarbonate, and disec-butyl peroxydicarbonate; Peroxy esters such as t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-hexyl peroxy 2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, and t-amyl peroxypivalate; Dialkyl peroxides such as di-t-butyl peroxide; Di[fluoro(or fluorochloro)acyl]peroxides; These are some typical examples.

[0071] Examples of di[fluoro(or fluorochloro)acyl]peroxides include diacylperoxides represented as [(RfCOO)-]2 (where Rf is a perfluoroalkyl group, an ω-hydroperfluoroalkyl group, or a fluorochloroalkyl group).

[0072] Examples of di[fluoro(or fluorochloro)acyl]peroxides include di(ω-hydro-dodecafluorohexanoyl)peroxide, di(ω-hydro-tetradecafluoroheptanoyl)peroxide, di(ω-hydro-hexadecafluorononanoyl)peroxide, di(perfluorobutyryl)peroxide, di(perfluoropareryl)peroxide, di(perfluorohexanoyl)peroxide, di(perfluoroheptanoyl)peroxide, di(perfluorooctanoyl)peroxide, di(perfluorononanoyl)peroxide, di(ω-chloro-hexafluorobutyryl)peroxide, di(ω-chloro-decafluorohexanoyl)peroxide, Examples include di(ω-chloro-tetradecafluorooctanoyl) peroxide, ω-hydro-dodecafluoroheptanoyl-ω-hydrohexadecafluorononanoyl-peroxide, ω-chloro-hexafluorobutyryl-ω-chloro-decafluorohexanoyl-peroxide, ω-hydrododecafluoroheptanoyl-perfluorobutyryl-peroxide, di(dichloropentafluorobutanoyl) peroxide, di(trichlorooctafluorohexanoyl) peroxide, di(tetrachloroundecafluorooctanoyl) peroxide, di(pentachlorotetradecafluorodecanoyl) peroxide, and di(undecachlorotriacontafluorodocosanoyl) peroxide.

[0073] The water-soluble radical polymerization initiator may be a known water-soluble peroxide, such as ammonium salts, potassium salts, and sodium salts of persulfuric acid, perboric acid, perchloric acid, superphosphate, and percarbonate; organic peroxides such as disuccinate peroxide and diglutaric acid peroxide; t-butyl permalate; and t-butyl hydroperoxide. A reducing agent such as sulfites may also be used in combination with the peroxide, and the amount used may be 0.1 to 20 times the amount of the peroxide.

[0074] Preferred polymerization methods include suspension polymerization in the presence of a peroxide polymerization initiator and emulsion polymerization in the presence of a redox polymerization initiator. Examples of peroxide polymerization initiators include the oil-soluble peroxides mentioned above. Examples of redox polymerization initiators include combinations of the peroxides mentioned above and reducing agents.

[0075] As the surfactant, known surfactants can be used, such as nonionic surfactants, anionic surfactants, and cationic surfactants. Among these, fluorine-containing anionic surfactants are preferred, and linear or branched fluorine-containing anionic surfactants having 4 to 20 carbon atoms, which may contain ether bonds (i.e., oxygen atoms may be inserted between carbon atoms), are more preferred. The amount of surfactant added (relative to the solvent) is preferably 50 to 5000 ppm.

[0076] By polymerizing in the presence of a chain transfer agent, the solution viscosity, weight-average molecular weight, and other properties of the resulting polymer can be appropriately adjusted. Examples of chain transfer agents include hydrocarbons such as ethane, isopentane, n-hexane, and cyclohexane; aromatics such as toluene and xylene; ketones such as acetone; acetic acid esters such as ethyl acetate and butyl acetate; alcohols such as methanol and ethanol; mercaptans such as methyl mercaptan; and halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride.

[0077] The amount of chain transfer agent added can vary depending on the magnitude of the chain transfer constant of the chain transfer agent, but it is usually 0.01 to 20% by mass relative to the solvent.

[0078] Examples of solvents include water, and mixed solvents of water and alcohol.

[0079] For polymerization such as suspension polymerization, a fluorine-based solvent may be used in addition to water. Examples of fluorine-based solvents include hydrochlorofluoroalkanes such as CH3CClF2, CH3CCl2F, CF3CF2CCl2H, and CF2ClCF2CFHCl; chlorofluoroalkanes such as CF2ClCFClCF2CF3 and CF3CFClCFClCF3; perfluorocyclobutanes such as CF3CF2CF2CF3, CF3CF2CF2CF2CF3, and CF3CF2CF2CF2CF2CF3; CF2HCF2CF2CF2H, CF3CFHCF2CF2CF3, CF3CFHCFHCF2CF3, CF2HCF2CF2CF2CF2H, CF2HCFHCF2CF2CF3, CF3CF2CF2CF2CF2CF2H, and CF3CH Examples include hydrofluorocarbons such as (CF3)CF3CF2CF3, CF3CF(CF3)CFHCF2CF3, CF3CF(CF3)CFHCFHCF3, CF3CH(CF3)CFHCF2CF3, CF2HCF2CF2CF2CF2CF2CF2H, CF3CF2CF2CF2CH2CH3, and CF3CH2CF2CH3; (perfluoroalkyl)alkyl ethers such as F(CF2)4OCH3, F(CF2)4OC2H5, (CF3)2CFOCH3, and F(CF2)3OCH3; and hydrofluoroalkyl ethers such as CF3CH2OCF2CHF2, CHF2CF2CH2OCF2CHF2, and CF3CF2CH2OCF2CHF2. Among these, perfluoroalkanes or hydrofluoroalkyl ethers are preferred. The amount of fluorinated solvent used is preferably 10 to 100% by mass relative to the solvent, from the viewpoint of suspension and economy.

[0080] In suspension polymerization, suspending agents such as methylcellulose, methoxylated methylcellulose, propoxylated methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, polyvinyl alcohol, polyethylene oxide, and gelatin can be used. The amount of suspending agent added (relative to the solvent) is preferably 0.005 to 1.0% by mass, more preferably 0.01 to 0.4% by mass.

[0081] Examples of polymerization initiators used in suspension polymerization include diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, di(secondary butyl)peroxycarbonate, isobutyryl peroxide, di(chlorofluoroacyl)peroxide, di(perfluoroacyl)peroxide, t-butyl peroxypivalate, and t-amyl peroxypivalate. The amount used is preferably 0.1 to 5% by mass relative to the total amount of monomers. By adjusting the amount of polymerization initiator added, the solution viscosity and weight-average molecular weight of the resulting polymer can be appropriately adjusted.

[0082] In suspension polymerization, the degree of polymerization of the resulting polymer may be adjusted by adding chain transfer agents such as ethyl acetate, methyl acetate, acetone, methanol, ethanol, n-propanol, acetaldehyde, propylaldehyde, ethyl propionate, and carbon tetrachloride. The amount used is usually 0.1 to 5% by mass, preferably 0.5 to 3% by mass, relative to the total amount of monomers. By adjusting the amount of chain transfer agent added, the solution viscosity, weight-average molecular weight, etc., of the resulting polymer can be appropriately adjusted.

[0083] The total amount of monomers used is such that the mass ratio of total monomers to water is 1:1 to 1:10, preferably 1:2 to 1:5.

[0084] If an aqueous dispersion containing the polymer is obtained after polymerization, the polymer can be recovered by coagulating, washing, and drying the dispersion. Alternatively, if the polymer is obtained as a slurry, the slurry can be removed from the reactor, washed, and dried to recover the polymer. Drying allows the polymer to be recovered in powder form.

[0085] (solvent) The electrode compositions of this disclosure contain at least one solvent selected from the group consisting of esters (1) represented by general formula (1) and ketones (2) represented by general formula (2).

[0086] General formula (1): [Chemical formula] (In the formula, R 1 and R 2 are each independently H, a linear or branched aliphatic group of C1-C 10 , or an aromatic group of C6-C 10 .)

[0087] General formula (2): [Chemical formula] (In the formula, R 3 and R 4 are each independently H, a linear or branched aliphatic group of C1-C 10 , or an aromatic group of C6-C<00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0091] R 1 As, C1 - C 10 linear or branched aliphatic groups are preferred, and linear or branched alkyl groups of C1 - C 10 or linear or branched alkenyl groups of C2 - C 10 are more preferred. A methyl group, an ethyl group, a propyl group, a vinyl group, an isopropenyl group, a butyl group or a pentyl group is preferred, and a propyl group, a butyl group or a pentyl group is more preferred. These groups may be either linear or branched, but are preferably linear.

[0092] R 2 The aliphatic group has 1 - 10 carbon atoms, preferably 3 or more, more preferably 4 or more, preferably 8 or less, and more preferably 6 or less. As the aliphatic group of R 2 an alkyl group is preferred. The alkyl group may be linear or branched.

[0093] R 2 The aromatic group has 6 - 10 carbon atoms. The hydrogen atom bonded to the carbon atom of the aromatic ring of the aromatic group may or may not be substituted. Examples of the substituent include an alkyl group such as a methyl group and a halo group such as a chlorine atom. As the aromatic group of R 2 a phenyl group or a benzyl group is preferred.

[0094] R 2 As, C1 - C 10 linear or branched aliphatic groups are preferred, and linear or branched alkyl groups of C1 - C 10 are more preferred. A methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group or a hexyl group is preferred, and a butyl group, a pentyl group or a hexyl group is more preferred. These groups may be either linear or branched, but are preferably linear.

[0095] The ester (1) represented by general formula (1) is preferably at least one selected from the group consisting of ethyl acetate, ethyl butyrate, butyl methacrylate, propyl propionate, ethyl butyrate, butyl butyrate, butyl pentanoate, butyl hexanoate, pentyl butyrate, pentyl pentanoate, pentyl hexanoate, hexyl butyrate, hexyl pentanoate, and hexyl hexanoate, with butyl butyrate being more preferred.

[0096] R in general formula (2) 3 and R 4 These are independently H, C1~C 10 A linear or branched aliphatic group, or C6~C 10 It is an aromatic group.

[0097] R 3 and R 4 The number of carbon atoms in the aliphatic group is 1 to 10, preferably 3 or less, and more preferably 2 or less. 3 An alkyl group is preferred as the aliphatic group. The alkyl group may be linear or branched.

[0098] R 3 and R 4 The aromatic group has 6 to 10 carbon atoms. The hydrogen atoms bonded to the carbon atoms of the aromatic ring of the aromatic group may or may not be substituted. Examples of substituents include alkyl groups such as methyl groups, and halo groups such as chlorine atoms. 3 and R 4 The aromatic group is preferably a phenyl group or a benzyl group.

[0099] R 3 and R 4 For example, C1~C 10 Linear or branched aliphatic groups are preferred, C1-C 10Linear or branched alkyl groups are more preferred, with methyl, ethyl, propyl, butyl, pentyl, or hexyl groups being preferred, and methyl or ethyl groups being more preferred. These groups may be linear or branched, but linear is preferred.

[0100] The ketone (2) represented by general formula (2) is preferably at least one selected from the group consisting of acetone and methyl ethyl ketone.

[0101] (powder electrode material) The electrode composition of this disclosure preferably further contains a powder electrode material. Examples of powder electrode materials include solid electrolytes, conductive additives, and electrode active materials.

[0102] The powder electrode material preferably contains a solid electrolyte. As the solid electrolyte, a solid electrolyte capable of intercalating and releasing metal ions such as lithium ions can be used. Examples of solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, and crystalline oxides / oxynitrides. Among these, the powder electrode material preferably contains a sulfide-based solid electrolyte. Since the electrode composition of this disclosure contains a polymer containing trifluoroethylene units and the solvent described above, even when the powder electrode material contains a sulfide-based solid electrolyte, an electrode composition in which the polymer and powder electrode material are sufficiently dispersed can be easily obtained. When an electrode material layer is formed using the electrode composition, an electrode material layer can be obtained in which the powder electrode material is sufficiently bound and exhibits sufficient ionic conductivity.

[0103] As a sulfide-based solid electrolyte, there are no particular limitations as long as it is a solid electrolyte containing a sulfur atom, but examples include Li2S-P2S5, Li2S-P2S3, Li2S-P2S3-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, LiI-Li2S-SiS2-P2S5, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, Li3PS4-Li4GeS4, Li 3.4 P 0.6 Si 0.4 S4, Li 3.25 P 0.25 Ge 0.76 S4, Li 4-x Ge 1-x P x Examples include S4.

[0104] Examples of oxide-based solid electrolytes include LiPON (lithium oxynitride phosphate), Li2O-B2O3-P2O5, Li2O-SiO2, and Li 1.3 Al 0.3 Ti 0.7 (PO4)3, La 0.51 Li 0.34 TiO 0.74 , Li3PO4, Li2SiO2, Li2SiO4, Li 0.5 La 0.5 TiO3, Li 1.5 Al 0.5 Ge 1.5 Examples include (PO4)3.

[0105] Examples of crystalline oxides and oxynitrides include LiI, Li3N, and Li5La3Ta2O 12 Li7La3Zr2O 12 Li6BaLa2Ta2O 12 Li3PO (4-3 / 2w) N w (w<1), Li 3.6 Si 0.6 P 0.4 Examples include O4.

[0106] The powder electrode material preferably contains a conductive additive. Examples of conductive additives include carbon black such as acetylene black and Ketjen black; carbon fibers such as multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, and vapor-grown carbon fibers (VGCF); and metal powders such as SUS powder and aluminum powder.

[0107] The powder electrode material preferably contains an electrode active material. The electrode active material may be either a positive electrode active material or a negative electrode active material.

[0108] Examples of positive electrode active materials include LiCoO2, Li(Ni,Co,Al)O2, and Li 1+x Ni 1 / 3 Mn 1 / 3 Co 1 / 3 O2 (where x is a non-negative real number), LiNiO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, Li3Fe2(PO4)3, Li3V2(PO4)3, Li 1+x Mn 2-x-y M y Heteroatomic-substituted Li-Mn spinel having a composition represented by O4 (where M is at least one metal selected from the group consisting of Al, Mg, Co, Fe, Ni, and Zn, and y is a real number of 0 or more), lithium titanate (Li x TiO y Examples include lithium metal phosphate having a composition represented by LiMPO4 (where M is Fe, Mn, Co, or Ni).

[0109] Among the positive electrode active materials, LiCoO2, Li(Ni,Co,Al)O2, and LiNi are particularly noteworthy. 1 / 3 Mn 1 / 3 Co 1 / 3 O2 is preferred. Furthermore, in this disclosure, positive electrode active materials coated on the surface of each of these materials may be used. The coating material usable in this disclosure should contain a substance that has lithium ion conductivity and can maintain the form of a coating layer on the surface of the active material. Examples of coating materials include LiNbO3 and Li4Ti5O. 12Examples include Li3PO4. The shape of the positive electrode active material is not particularly limited, but a powder form is preferred.

[0110] The average particle size of the positive electrode active material is preferably, for example, 1 to 50 μm, more preferably 1 to 20 μm, and especially 3 to 7 μm. If the average particle size of the positive electrode active material is too small, it may become difficult to handle, and if the average particle size is too large, it may be difficult to obtain a flat positive electrode material layer. The average particle size of the positive electrode active material can be determined, for example, by measuring the particle size of the active material carrier observed with a scanning electron microscope (SEM) and averaging the results.

[0111] Examples of negative electrode active materials include carbonaceous materials such as artificial graphite, graphite carbon fiber, resin-calcined carbon, pyrolysis vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-calcined carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon, as well as silicon-containing compounds such as silicon and silicon alloys, and Li4Ti5O 12 Examples include any one of the following, or a mixture of two or more. Among these, materials containing at least a portion of carbonaceous material, or silicon-containing compounds, can be used particularly suitably.

[0112] The content of the powder electrode material in the electrode composition is preferably 20 to 75% by mass, and more preferably 30 to 70% by mass, relative to the mass of the electrode composition.

[0113] The electrode composition of this disclosure may contain materials other than those described above. The content of materials other than those described above in the electrode composition is preferably 8% by mass or less, and more preferably 4% by mass or less, based on the mass of the electrode composition.

[0114] One method for preparing the electrode composition is to disperse and mix the powder electrode material in a solution or dispersion in which the polymer is dissolved or dispersed in a solvent. The resulting electrode composition is then uniformly applied to a current collector such as a metal foil or metal mesh, dried, and pressed as necessary to form an electrode material layer on the current collector, thus forming the electrode. Alternatively, the polymer and the powder electrode material may be mixed first, and then a solvent may be added to prepare the electrode composition.

[0115] The electrode compositions of this disclosure can be suitably used as materials for forming electrodes in batteries such as secondary batteries and capacitors. The battery may be a primary battery, a rechargeable battery (secondary battery), or an energy storage element. The battery may be a non-aqueous electrolyte battery or a solid-state battery. The electrode compositions of this disclosure can be suitably used as electrode compositions for solid-state batteries, such as sulfide-based solid-state batteries. As a sulfide-based solid-state battery, an all-solid-state lithium-ion secondary battery using a sulfide-based solid electrolyte is preferred.

[0116] The electrode composition disclosed herein may be a positive electrode composition used for manufacturing a positive electrode, or a negative electrode forming composition used for manufacturing a negative electrode. The electrode material layer formed from the electrode composition disclosed herein may be a positive electrode material layer or a negative electrode material layer.

[0117] (electrode) The electrode of this disclosure may comprise only an electrode material layer formed by the electrode composition described above, or it may comprise a current collector and an electrode material layer formed by the electrode composition described above. The electrode material layer is formed using the electrode composition of this disclosure and may be provided on one side of the current collector or on both sides.

[0118] The thickness of the electrode material layer varies depending on the intended application of the sulfide-based solid battery, but is preferably 10 to 250 μm, more preferably 20 to 200 μm, and even more preferably 30 to 150 μm.

[0119] Examples of materials for the current collector include aluminum, stainless steel (SUS), nickel, iron, titanium, chromium, gold, platinum, and zinc, with aluminum and stainless steel (SUS) being preferred. Examples of shapes for the current collector include foil, plate, and mesh, with foil being preferred.

[0120] Electrodes can be manufactured, for example, by coating a current collector with the above-mentioned electrode composition and drying the resulting coating film. Coating methods include spraying, screen printing, doctor blade application, bar coating, roll coating, gravure printing, and die coating. Drying methods include vacuum drying, heat drying, and vacuum heat drying. There are no specific restrictions on the conditions for vacuum drying and heat drying; they can be set as appropriate.

[0121] The amount of electrode composition applied varies depending on the composition of the electrode composition and the intended use of the electrode, but is generally 5 to 30 mg / cm³ in a dry state. 2 It is approximately as follows. Furthermore, the electrode thickness is not particularly limited, but is generally between 10 and 250 μm.

[0122] (battery) The battery of this disclosure comprises at least a positive electrode and a negative electrode, wherein one or both of the positive electrode and the negative electrode are formed by an electrode comprising only an electrode material layer formed by the electrode composition described above, or an electrode comprising a current collector and an electrode material layer formed by the electrode composition described above.

[0123] The battery of this disclosure may be a secondary battery, a capacitor, or the like. Furthermore, the battery of this disclosure may be a primary battery, a rechargeable battery (secondary battery), or an energy storage element. The battery may be a non-aqueous electrolyte battery or a solid-state battery. The battery of this disclosure is preferably a solid-state battery, such as a sulfide-based solid-state battery. As a sulfide-based solid-state battery, an all-solid-state lithium-ion secondary battery using a sulfide-based solid electrolyte is preferred.

[0124] The solid-state battery of the present disclosure is a solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, wherein one or both of the positive electrode and the negative electrode are formed by electrodes comprising only an electrode material layer formed from the electrode composition described above, or electrodes comprising a current collector and an electrode material layer formed from the electrode composition described above.

[0125] If neither the positive electrode nor the negative electrode has an electrode material layer formed from the above-mentioned electrode composition, that electrode may have the same configuration as a known electrode.

[0126] The solid electrolyte layer may contain solid electrolytes such as sulfide-based solid electrolytes, oxide-based solid electrolytes, or crystalline oxides / oxynitrides, but it is preferable that it contains a sulfide-based solid electrolyte.

[0127] The battery of this disclosure may include a separator between the positive electrode and the negative electrode. Examples of the separator include porous membranes such as polyethylene and polypropylene; and nonwoven fabrics such as resin nonwoven fabrics such as polypropylene and glass fiber nonwoven fabrics.

[0128] The battery of this disclosure may further include a battery case. The shape of the battery case is not particularly limited as long as it can accommodate the positive electrode, negative electrode, sulfide-based solid electrolyte layer, etc., as described above, but examples include cylindrical, prismatic, coin-shaped, laminated, etc.

[0129] (Bonding agent for solid-state batteries) The polymers described above can also be suitably used as binders for solid-state batteries. Next, specific embodiments of the solid-state battery binders of this disclosure will be described in detail.

[0130] The binder for solid-state batteries of this disclosure contains a polymer containing trifluoroethylene units. The polymer containing trifluoroethylene units contained in the binder for solid-state batteries of this disclosure may have the same structure as the polymer contained in the electrode composition of this disclosure, and it is preferable that it has the same structure.

[0131] The binder for solid-state batteries of this disclosure can be used in any solid-state battery using a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a crystalline oxide / oxynitride as the electrolyte, but is particularly suitable for use in sulfide-based solid-state batteries. As a sulfide-based solid-state battery, an all-solid-state lithium-ion secondary battery using a sulfide-based solid electrolyte is preferred.

[0132] Solid-state batteries typically comprise a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive and negative electrodes. The binder for solid-state batteries of this disclosure can be used for the positive electrode, the negative electrode, or the solid electrolyte layer. One preferred embodiment of the binder for solid-state batteries of this disclosure is that it is a binder for the positive electrode or a binder for the negative electrode of a solid-state battery.

[0133] The binder for solid-state batteries of this disclosure contains a polymer containing trifluoroethylene units, and therefore exhibits good solubility or dispersibility in solvents suitable for use in compositions for forming the positive electrode, negative electrode, or solid electrolyte layer of a sulfide-based solid-state battery, for example, at least one solvent selected from the group consisting of esters (1) represented by general formula (1) and ketones (2) represented by general formula (2), and is less likely to settle in the resulting composition. Furthermore, the binder for solid-state batteries of this disclosure can firmly bind powder electrode materials contained in the positive and negative electrodes of a solid-state battery, as well as solid electrolytes and conductive additives contained in the solid electrolyte layer interposed between the positive and negative electrodes.

[0134] The polymer contained in the solid-state battery binder of this disclosure preferably contains monomer (3) units in addition to trifluoroethylene units. By containing monomer (3) units, for example, when the solid-state battery binder of this disclosure is used to form a positive or negative electrode, an electrode material layer that adheres firmly to a substrate such as a current collector can be formed.

[0135] (Adhesive polymer) This disclosure also relates to polymers containing trifluoroethylene units and monomer(3) units. Specific embodiments of the polymers containing trifluoroethylene units and monomer(3) units of this disclosure will now be described in detail.

[0136] The polymer of this disclosure may have the same configuration as the polymer contained in the electrode composition of this disclosure, and it is preferable that it has the same configuration, except that it contains monomer (3) units as essential monomer units in addition to trifluoroethylene units.

[0137] The polymers of this disclosure contain trifluoroethylene units and monomer (3) units, and therefore exhibit good solubility or dispersibility in solvents suitable for use in compositions for forming the positive electrode, negative electrode, and solid electrolyte layer of sulfide-based solid batteries, for example, at least one solvent selected from the group consisting of ester (1) represented by general formula (1) and ketone (2) represented by general formula (2), and are less likely to settle in the resulting composition. Furthermore, when the polymers of this disclosure are used as a binder, they can firmly bond powder electrode materials contained in the positive and negative electrodes of the battery. In addition, the polymers of this disclosure have excellent adhesion to other materials, and for example, when the polymers of this disclosure are used as a binder for forming the positive or negative electrode, they can form an electrode material layer that adheres firmly to a substrate such as a current collector.

[0138] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims. [Examples]

[0139] Next, we will describe embodiments of the present disclosure with reference to experimental examples, but the present disclosure is not limited to such experimental examples.

[0140] <Acrylic acid unit content in polymers> The acrylic acid unit content in the polymer was measured by acid-base titration of the carboxylic acid group. Specifically, approximately 0.5 g of the polymer was dissolved in acetone at a temperature of 70-80°C. 5 ml of water was added dropwise under vigorous stirring to avoid coagulation of the polymer. Titration was performed with a 0.1 N NaOH aqueous solution until the acidity was completely neutralized at a neutralization transition of approximately -270 mV. From the measurement results, the amount of acrylic acid units contained in 1 g of polymer was determined, and the acrylic acid unit content was calculated.

[0141] <Ratio of trifluoroethylene units to fluorinated monomer units in polymers> The ratio of trifluoroethylene units to fluorinated monomer units in polymers was determined using an NMR analyzer (Agilent Technologies, VNS400MHz). 19 F-NMR measurements were performed on polymers in acetone or NMP solution.

[0142] <Weight average molecular weight> Measurements were taken using gel permeation chromatography (GPC). A Tosoh AS-8010, CO-8020, and column (three GMHHR-H columns connected in series) were used, along with a Shimadzu RID-10A. Dimethylformamide (DMF) was used as the solvent, flowing at a rate of 1.0 ml / min. The data (reference: polystyrene) was used for calculation.

[0143] <Melting point> Using a differential scanning calorimetry (DSC) system, the temperature was increased from 50°C to 300°C at a rate of 10°C / min, then decreased to 30°C at 10°C / min, and then increased again to 300°C at a rate of 10°C / min. The temperature corresponding to the maximum value in the heat of fusion curve was determined as the melting point.

[0144] <Adhesion between positive electrode material layer and current collector> A 1.2 cm × 7.0 cm test specimen was prepared by cutting the positive electrode prepared in the experimental example and comparative example. After fixing the positive electrode material layer side of the test specimen to a movable jig with double-sided tape, tape was applied to the surface of the positive electrode current collector, and the stress (N / cm) when the tape was pulled 90 degrees at a speed of 100 mm / min was measured using an autograph. A 1N load cell was used in the autograph.

[0145] <Slurry Stability Test> The slurry viscosity was measured immediately after preparation of the mixture and 5 days after preparation, and the stability of the slurry was evaluated based on the following calculation formula. Slurry viscosity was measured using a Type B viscometer (Toki Sangyo Co., Ltd., TV-10M) under the conditions of 25°C, rotor No. M4, and rotation speed of 6 rpm. The value obtained 10 minutes after the start of measurement was adopted as the slurry viscosity of the mixture. Slurry stability (%) = Viscosity 5 days after mixing preparation / Viscosity immediately after mixing preparation × 100

[0146] Furthermore, the following positive electrode active materials and conductive additives were used in the experimental and comparative examples. NMC111: LiNi 0.33 Mn 0.33 Co 0.33 O2 AB: Acetylene Black

[0147] <Synthesis Example 1> (Synthesis of trifluoroethylene homopolymer (polymer a)) 1200g of water, 800g of perfluorocyclobutane, and 1g of cyclohexane were placed in a 4.11L autoclave, and the temperature inside the chamber was raised to 20°C. Trifluoroethylene was added until the pressure reached 0.6 MPaG, and 15g of a perfluorohexane solution of 8 wt% di(ω-hydro-dodecafluorohexanoyl) peroxide (hereinafter abbreviated as "DHP") was added as an initiator to carry out the polymerization reaction. During the polymerization reaction, trifluoroethylene was added to maintain the pressure at 0.6 MPa, and the polymerization reaction continued until 80g of trifluoroethylene had been added. The monomers in the autoclave were purged, and the resulting polymer (polymer a) was recovered. Polymer a had a weight-average molecular weight of 340,000, measured by GPC, and a melting point of 196°C, measured by DSC.

[0148] <Synthesis Example 2> (Synthesis of trifluoroethylene-acrylic acid copolymer (polymer b)) In a 100 mL autoclave, 40 g of 1,1,2,2-tetrafluoro-1-(2,2,2-trifluoroethoxy)ethane (HFE-347pc-f), 15 g of trifluoroethylene, 0.05 g of acrylic acid, and 0.5 g of an 8 wt% DHP perfluorohexane solution as an initiator were charged, and the temperature was raised to 25°C to carry out the polymerization reaction. The reaction was allowed to proceed until the pressure decreased from 0.72 MPa to 0.67 MPa, the monomers in the autoclave were purged, and the resulting copolymer (polymer b) was recovered. Polymer b had a trifluoroethylene-based polymerization unit / acrylic acid-based polymerization unit ratio of 98.9 / 1.1 (molar ratio) measured by acid-base titration of the carboxylic acid group, a weight-average molecular weight of 850,000 measured by GPC, and a melting point of 199°C measured by DSC.

[0149] <Synthesis Example 3> (Synthesis of trifluoroethylene-acrylic acid copolymer (polymer c)) 40 g of HFE-347pc-f, 15 g of trifluoroethylene, 0.12 g of acrylic acid, and 0.5 g of a perfluorohexane solution of 8 wt% DHP as an initiator were charged into a 100 mL autoclave, and the temperature was raised to 25 °C to carry out the polymerization reaction. The reaction was allowed to proceed until the pressure decreased from 0.55 MPa to 0.50 MPa, the monomers in the autoclave were purged, and the resulting copolymer (polymer c) was recovered. Polymer c had a trifluoroethylene-based polymerization unit / acrylic acid-based polymerization unit ratio of 98.3 / 1.7 (molar ratio) as measured by acid-base titration of the carboxylic acid group, a weight-average molecular weight of 520,000 as measured by GPC, and a melting point of 201 °C as measured by DSC.

[0150] <Synthesis Example 4> (Synthesis of trifluoroethylene-chlorotrifluoroethylene-acrylic acid copolymer (polymer e)) 40 g of HFE-347pc-f, 0.02 g of acrylic acid, 9.0 g of trifluoroethylene, 1.4 g of chlorotrifluoroethylene, and 0.5 g of a perfluorohexane solution of 8 wt% DHP as an initiator were charged into a 100 mL autoclave, and the temperature was raised to 25°C to carry out the polymerization reaction. The reaction was allowed to proceed until the pressure was reduced from 0.60 MPa to 0.50 MPa, the monomers in the autoclave were purged, and the resulting copolymer (polymer e) was recovered. Polymer e had a molar ratio of trifluoroethylene-based polymerization units / chlorotrifluoroethylene-based polymerization units / acrylic acid-based polymerization units of 92.1 / 7.6 / 0.3, measured by NMR and acid-base titration of the carboxylic acid group. Its weight-average molecular weight, measured by GPC, was 330,000, and its melting point, measured by DSC, was 179°C.

[0151] <Synthesis Example 5> (Synthesis of trifluoroethylene-chlorotrifluoroethylene-acrylic acid copolymer (polymer f)) 40 g of HFE-347pc-f, 7.0 g of trifluoroethylene, 4.2 g of chlorotrifluoroethylene, 0.03 g of acrylic acid, and 0.5 g of a perfluorohexane solution of 8 wt% DHP as an initiator were charged into a 100 mL autoclave, and the temperature was raised to 25°C to carry out the polymerization reaction. The reaction was allowed to proceed until the pressure was reduced from 0.60 MPa to 0.50 MPa, the monomers in the autoclave were purged, and the resulting copolymer (polymer f) was recovered. Polymer f had a molar ratio of trifluoroethylene-based polymerization units / chlorotrifluoroethylene-based polymerization units / acrylic acid-based polymerization units of 59.5 / 40.0 / 0.5, as measured by NMR and acid-base titration of the carboxylic acid group. Its weight-average molecular weight, as measured by GPC, was 240,000, and its melting point, as measured by DSC, was 123°C.

[0152] <Synthesis Example 6> (Synthesis of trifluoroethylene-vinylidene fluoride copolymer (polymer g)) In a 3 L autoclave, 1000 g of water, 500 g of HFE-347pc-f, 5 g of a perfluorohexane solution of 8 wt% DHP as an initiator, 1 g of n-pentane, and a mixed gas of trifluoroethylene and vinylidene fluoride were added until the pressure reached 0.54 MPaG. The polymerization reaction was carried out at 20°C. The mixed gas of trifluoroethylene and vinylidene fluoride was added to maintain a pressure of 0.54 MPaG until the added gas mixture reached 380 g. The monomers in the autoclave were purged, and the resulting copolymer (polymer g) was recovered. NMR measurements of polymer g showed a trifluoroethylene-based polymerization unit / vinylidene fluoride-based polymerization unit ratio of 43.0 / 57.0 (molar ratio), GPC measurements showed a weight-average molecular weight of 560,000, and DSC measurements showed a melting point of 165°C.

[0153] <Synthesis Example 7> (Synthesis of trifluoroethylene-vinylidene fluoride-acrylic acid copolymer (polymer h)) 40 g of HFE-347pc-f, 12 g of trifluoroethylene, 4 g of vinylidene fluoride, 0.1 g of acrylic acid, and 0.5 g of a perfluorohexane solution of 8 wt% DHP as an initiator were charged into a 100 mL autoclave, and the temperature was raised to 25 °C to carry out the polymerization reaction. The reaction was allowed to proceed until the pressure decreased from 0.7 MPa to 0.4 MPa, the monomers in the autoclave were purged, and the resulting copolymer (polymer h) was recovered. Polymer h had a molar ratio of trifluoroethylene-based polymerization units / vinylidene fluoride-based polymerization units / acrylic acid-based polymerization units of 41.9 / 57.7 / 0.4, as measured by NMR and acid-base titration of the carboxylic acid group. Its weight-average molecular weight, as measured by GPC, was 1.31 million, and its melting point, as measured by DSC, was 170 °C.

[0154] The properties of the polymers obtained in each synthesis example were evaluated using the method described above. The results are shown in Table 1.

[0155] [Table 1]

[0156] <Experimental Example 1> (Preparation of positive electrode mixture) Polymer a was used as the binder, NMC111 as the positive electrode active material, AB as the conductive additive, and butyl butyrate as the solvent. The mixture was stirred to obtain a mixture with an active material / conductive additive / binder composition ratio of 96 / 2 / 2. The mixture was allowed to stand at room temperature, and the slurry stability of the mixture was evaluated. The results are shown in Table 2.

[0157] (Fabrication of the positive electrode) The resulting mixture was uniformly applied to one side of a positive electrode current collector (aluminum foil with a thickness of 20 μm), and after the butyl butyrate was completely evaporated, a positive electrode comprising a positive electrode material layer and a positive electrode current collector was fabricated by pressing with a pressure of 10 tons using a roll press machine. The adhesion of the positive electrode material layer to the positive electrode current collector is shown in Table 2.

[0158] <Experimental Example 2> (Preparation of positive electrode mixture and fabrication of positive electrode) Except for using polymer b as the binder, the cathode mixture was prepared and the cathode fabricated using the same method as in Experimental Example 1, and the results of the same evaluation are shown in Table 2.

[0159] <Experimental Example 3> (Preparation of positive electrode mixture and fabrication of positive electrode) Table 2 shows the results of the preparation of the cathode mixture and the fabrication of the cathode, which were performed in the same manner as in Experimental Example 1, except that polymer c was used as the binder.

[0160] <Experimental Example 4> (Preparation of positive electrode mixture and fabrication of positive electrode) Table 2 shows the results of the preparation of the cathode mixture and the fabrication of the cathode, which were performed in the same manner as in Experimental Example 1, except that polymer e was used as the binder.

[0161] <Experimental Example 5> (Preparation of positive electrode mixture and fabrication of positive electrode) Table 2 shows the results of the preparation of the cathode mixture and the fabrication of the cathode, performed in the same manner as in Experimental Example 1, except that propyl propionate was used as the solvent.

[0162] <Experimental Example 6> (Preparation of positive electrode mixture and fabrication of positive electrode) Table 2 shows the results of the preparation of the cathode mixture and the fabrication of the cathode, which were performed in the same manner as in Experimental Example 1, except that polymer f was used as the binder and propyl propionate as the solvent.

[0163] <Experimental Example 7> (Preparation of positive electrode mixture and fabrication of positive electrode) Table 2 shows the results of the preparation of the cathode mixture and the fabrication of the cathode, which were performed in the same manner as in Experimental Example 1, except that polymer b was used as the binder and acetone as the solvent.

[0164] <Experimental Example 8> (Preparation of positive electrode mixture and fabrication of positive electrode) Table 2 shows the results of the preparation of the cathode mixture and the fabrication of the cathode, which were performed in the same manner as in Experimental Example 1, except that polymer c was used as the binder and methyl ethyl ketone (MEK) was used as the solvent.

[0165] <Comparative Example 1> (Preparation of positive electrode mixture and fabrication of positive electrode) The cathode mixture was prepared using the same method as in Experimental Example 1, except that polymer g was used as the binder. However, the slurry settled, and the cathode could not be fabricated. The reason for this is thought to be that polymer g does not dissolve in butyl butyrate.

[0166] <Comparative Example 2> (Preparation of positive electrode mixture and fabrication of positive electrode) The cathode mixture was prepared using the same method as in Experimental Example 1, except that polymer h was used as the binder. However, the slurry settled, and the cathode could not be fabricated. The reason for this is thought to be that polymer h does not dissolve in butyl butyrate.

[0167] The results are shown in Table 2.

[0168] [Table 2]

Claims

1. An electrode composition containing a polymer and a solvent, The polymer contains trifluoroethylene units, and the content of trifluoroethylene units in the polymer is 50 mol% or more relative to the total monomer units. The solvent is at least one selected from the group consisting of esters (1) represented by general formula (1) and ketones (2) represented by general formula (2). Composition for electrodes. General formula (1): 【Chemistry 9】 (In the formula, R １ and R ２ H and C are independent of each other. １ ~C １０ A linear or branched aliphatic group, or C ６ ~C １０ (It is an aromatic group.) General formula (2): 【Chemistry 10】 (wherein, R ３ and R ４ are each independently H, C １ to C １０ linear or branched aliphatic group, or C ６ to C １０ aromatic group.)

2. The electrode composition according to claim 1, wherein the polymer further contains fluorinated monomer units (excluding trifluoroethylene units).

3. The electrode composition according to claim 1 or 2, wherein the polymer further contains monomer (3) units represented by general formula (3). General formula (3): 【Chemistry 11】 (In the formula, R ５ ~R ７ These are independently H, F, and CH ３ or CF ３ X is an atomic group with a molecular weight of 500 or less, where the single bond or main chain consists of 1 to 20 atoms, and R ＯＨ C contains H or at least one OH group. １ ~C ５ (It is a hydrocarbon group.)

4. The electrode composition according to claim 3, wherein the content of monomer (3) units of the polymer is 0.001 to 3.0 mol% relative to the total monomer units.

5. The electrode composition according to any one of claims 1 to 4, wherein the content of the polymer is 0.1 to 20% by mass with respect to the mass of the electrode composition.

6. Furthermore, the electrode composition according to any one of claims 1 to 5, further containing a powder electrode material.

7. The electrode composition according to claim 6, wherein the powder electrode material contains a solid electrolyte.

8. The electrode composition according to claim 6 or 7, wherein the powder electrode material contains a conductive additive.

9. The electrode composition according to any one of claims 6 to 8, wherein the powder electrode material contains an electrode active material.

10. The electrode composition according to any one of claims 6 to 9, wherein the content of the powder electrode material is 20 to 75% by mass relative to the weight of the electrode composition.

11. A binder for solid batteries containing a polymer that contains trifluoroethylene units, wherein the trifluoroethylene unit content is 50 mol% or more relative to the total monomer units.

12. A binder for solid batteries according to claim 11, which is for use in sulfide-based solid batteries.

13. A polymer containing trifluoroethylene units and monomer (3) units represented by general formula (3), wherein the content of trifluoroethylene units is 50 mol% or more relative to the total monomer units. General formula (3): 【Chemistry 12】 (In the formula, R ５ ~R ７ These are independently H, F, and CH ３ or CF ３ X is an atomic group with a molecular weight of 500 or less, where the single bond or main chain consists of 1 to 20 atoms, and R ＯＨ C contains H or at least one OH group. １ ~C ５ (It is a hydrocarbon group.)

14. The polymer according to claim 13, wherein the content of monomer (3) units is 0.001 to 3.0 mol% relative to the total monomer units.

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