Electrode slurry additive and solid-state battery

Abstract

To provide an electrode slurry additive that enhances the dispersion stability of a component in slurry, and a solid-state battery including the same.SOLUTION: An electrode slurry additive which is an acrylic resin including a structural unit having a linear alkyl group having 14 or more carbon atoms and a structural unit having a basic functional group, has a weight average molecular weight of more than 50,000 and less than 200,000, and has an amine value of 5 mgKOH / g or more and 33 mgKOH / g or less, and there is also provided a solid-state battery containing the same.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to electrode slurry additives and solid state batteries. [Background technology]

[0002] When producing an electrode having an electrode layer containing an active material, the electrode having the electrode layer may be produced by applying and drying a slurry containing the active material, etc. (hereinafter also referred to as "electrode slurry") Additives (electrode slurry additives) may be used in the electrode slurry to improve the dispersion stability of components in the slurry, such as the active material.

[0003] Patent Document 1 proposes an all-solid-state secondary battery having a positive electrode, a solid electrolyte layer, and a negative electrode, characterized in that at least one of the positive electrode, the solid electrolyte layer, and the negative electrode contains a graft polymer. Patent Document 2 proposes an inorganic solid electrolyte-containing composition containing an inorganic solid electrolyte having ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, a polymer binder, and a dispersion medium, in which the polymer binder has a constituent component (X) having a polymer chain and a constituent component (A) having at least one functional group selected from the following functional group group (a), and the inorganic solid electrolyte-containing composition contains a polymer having a nitrogen atom-containing constituent component (N) in a content of less than 10 mol% of all constituent components, and is soluble in the dispersion medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-014387 [Patent Document 2] International Publication No. 2022 / 085637 Summary of the Invention [Problem to be solved by the invention]

[0005] The graft polymer, which is an electrode slurry additive described in Patent Document 1, does not have an adsorptive group (e.g., a basic functional group) for the active material, and therefore tends to have poor dispersibility for the active material. In addition, the polymer binder, which is an electrode slurry additive described in Patent Document 2, has an acidic functional group, and therefore tends to easily cause deterioration of the solid electrolyte when the electrode slurry contains a solid electrolyte, and may lack versatility. In the present disclosure, an additive that is added to an electrode slurry to enhance the dispersion stability of components (such as active materials) used in preparing the electrode slurry is also referred to as an "electrode slurry additive."

[0006] A problem to be solved by one embodiment of the present disclosure is to provide an electrode slurry additive that improves the dispersion stability of components in a slurry. Another problem to be solved by another embodiment of the present disclosure is to provide a solid-state battery including an electrode slurry additive that enhances the dispersion stability of components in the slurry. [Means for solving the problem]

[0007] The means for solving the above problems include the following means. <1> An acrylic resin containing a structural unit having a linear alkyl group having 14 or more carbon atoms and a structural unit having a basic functional group, The weight average molecular weight is more than 50,000 and less than 200,000, An electrode slurry additive having an amine value of 5 mgKOH / g or more and 33 mgKOH / g or less. <2> The structural units having a linear alkyl group having 14 or more carbon atoms account for 30% by mass or more and 65% by mass or less of all structural units contained in the acrylic resin. <1> 10. The electrode slurry additive according to claim 9. <3> The content of the structural unit having a basic functional group is 0.5% by mass or more and 10% by mass or less of all structural units contained in the acrylic resin. <1> or <2> 10. The electrode slurry additive according to claim 9. <4> It is a random polymer <1> ~ <3> 10. An electrode slurry additive according to any one of the preceding claims. <5> <1> ~ <4> 10. An electrode slurry comprising the electrode slurry additive according to any one of 1 to 9, an active material, a conductive additive, a solid electrolyte, and a solvent. <6> The solvent is selected from the group consisting of butyl butyrate, dibutyl ether, anisole, mesitylene, diisobutyl ketone, methyl isobutyl ketone, cyclopentyl methyl ether, toluene, and heptane. <5> 2. A slurry for an electrode according to claim 1. <7> <1> ~ <4> 10. An electrode comprising the electrode slurry additive according to any one of claims 1 to 9. <8> <1> ~ <4> 10. A solid-state battery comprising the electrode slurry additive according to any one of claims 1 to 9. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, an electrode slurry additive is provided that enhances the dispersion stability of components in a slurry. According to another embodiment of the present disclosure, there is provided a solid-state battery including an electrode slurry additive that enhances dispersion stability of components in the slurry. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention.

[0010] The term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0011] In the present disclosure, the term "acrylic resin" includes both a resin having an acrylic monomer unit having an acryloyl group and a resin having a methacrylic monomer unit having a methacryloyl group.

[0012] <Electrode slurry additives> The electrode slurry additive according to the present disclosure is an acrylic resin containing a structural unit having a linear alkyl group having 14 or more carbon atoms and a structural unit having a basic functional group, and has a weight-average molecular weight of more than 50,000 and less than 200,000, and an amine value of 5 mgKOH / g or more and 33 mgKOH / g or less.

[0013] The electrode slurry additive according to the present disclosure can improve the dispersion stability of the components in the slurry due to the above-described configuration. The reason for this is presumed to be as follows.

[0014] By including a structural unit having a basic functional group and setting the amine value to 5 mgKOH / g or more and 33 mgKOH / g or less, it efficiently adsorbs components (such as active materials) in the slurry. Furthermore, by setting the weight-average molecular weight to be in the range of more than 50,000 and less than 200,000, adsorption stability is improved. Furthermore, by including a structural unit having a linear alkyl group with 14 or more carbon atoms, dispersion stability of the components in the slurry is improved. From the above, the electrode slurry additive according to the present disclosure can improve the dispersion stability of components in the slurry.

[0015] (structure) The electrode slurry additive according to the present disclosure is an acrylic resin containing a structural unit having a linear alkyl group having 14 or more carbon atoms and a structural unit having a basic functional group. The structural unit having a linear alkyl group having 14 or more carbon atoms is preferably a structural unit derived from a polymerizable unsaturated monomer having a linear alkyl group having 14 or more carbon atoms. Furthermore, the structural unit having a basic functional group is preferably a structural unit derived from a polymerizable unsaturated monomer having a basic functional group. The electrode slurry additive according to the present disclosure, which is an acrylic resin, is preferably a copolymer, and may be either a random copolymer or a block copolymer, with a random copolymer being preferred. Among acrylic resins, poly(meth)acrylic acid ester is preferred from the viewpoint of dispersibility in the electrode slurry.

[0016] -Structural unit having a linear alkyl group having 14 or more carbon atoms- The electrode slurry additive according to the present disclosure has a structural unit having a linear alkyl group having 14 or more carbon atoms. From the viewpoint of dispersibility of the conductive additive, the number of carbon atoms in the linear alkyl group is preferably 16 or more, and more preferably 18 or more. Furthermore, it is preferably 16 to 24, and more preferably 18 to 22. The structural unit having a linear alkyl group having 14 or more carbon atoms can be used alone or in combination of two or more types.

[0017] Specific examples of the linear alkyl group having 14 or more carbon atoms include a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl (stearyl) group, a nonadecyl group, an eicosyl group, and a behenyl group, with an octadecyl (stearyl) group or a behenyl group being more preferred.

[0018] Examples of structural units having a linear alkyl group having 14 or more carbon atoms include structural units represented by the following formula (1).

[0019] [ka]

[0020] In the above formula (1), R1 is a hydrogen atom or a methyl group, and R2 is a linear alkyl group having 14 or more carbon atoms. R1 is preferably a methyl group. Specific examples of the linear alkyl group having 14 or more carbon atoms in R2 are as described above, and the preferred embodiments are also the same.

[0021] From the viewpoint of dispersibility of components in the slurry, the content of structural units having a linear alkyl group having 14 or more carbon atoms is preferably 30% by mass to 65% by mass, more preferably 35% by mass to 60% by mass, and even more preferably 40% by mass to 55% by mass, of all structural units contained in the acrylic resin. When the content of structural units having a linear alkyl group having 14 or more carbon atoms is 30% by mass or more, the dispersibility of the conductive additive is improved. When the content of structural units having a linear alkyl group having 14 or more carbon atoms is 65 parts by mass or less, the dispersibility of the active material and solid electrolyte is further improved.

[0022] Examples of the structural unit having a linear alkyl group having 14 or more carbon atoms include structural units derived from polymerizable unsaturated monomers having a linear alkyl group having 14 or more carbon atoms. Specific examples of polymerizable unsaturated monomers having a linear alkyl group having 14 or more carbon atoms include tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, stearyl(meth)acrylate, nonadecyl(meth)acrylate, eicosa(meth)acrylate, heneicosa(meth)acrylate, behenyl(meth)acrylate, tricosa(meth)acrylate, tetracosa(meth)acrylate, etc. These may be used alone or in combination of two or more.

[0023] -Structural unit having a basic functional group- The electrode slurry additive according to the present disclosure includes a constitutional unit having a basic functional group. The basic functional group means a functional group that exhibits Bronsted basicity in an aqueous solution.

[0024] Examples of basic functional groups include primary amino groups, secondary amino groups, tertiary amino groups, quaternary ammonium bases, imino groups, hydrazino groups, pyridyl groups, pyrimidyl groups, pyrazyl groups, imidazole groups, triazole groups, and amide groups. These basic functional groups may be present in one type or in combination of two or more types. Among these, from the viewpoint of dispersibility of the electrode slurry, at least one basic functional group selected from the group consisting of secondary amino groups, tertiary amino groups, imino groups, and amide groups is preferred.

[0025] Examples of the constitutional unit having a basic functional group include a constitutional unit represented by the following formula (2).

[0026] [ka]

[0027] In the above formula (2), R1 has the same meaning as R1 in the above formula (1), and R3 and R4 are a hydrogen atom or an alkyl group having one or more carbon atoms. R1 is preferably a methyl group. R3 and R4 are preferably alkyl groups having 1 to 6 carbon atoms, more preferably alkyl groups having 1 to 3 carbon atoms, and even more preferably methyl groups.

[0028] From the viewpoint of adsorption to components in the slurry, the content of the basic functional group-containing structural unit is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 8% by mass, and even more preferably 1.5% by mass to 6% by mass, based on the total amount of structural units contained in the acrylic resin. When the content of the basic functional group-containing structural unit is 0.5% by mass or more, the dispersibility of the conductive additive and active material is improved. When the content of the basic functional group-containing structural unit is 10% by mass or less, the dispersibility of the solid electrolyte is excellent.

[0029] Examples of the basic functional group-containing structural unit include a structural unit derived from a polymerizable unsaturated monomer having a basic functional group. The basic functional group-containing polymerizable unsaturated monomer can be used without any particular limitation as long as it has a basic functional group. Specific examples of polymerizable unsaturated monomers having a basic functional group include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylamide, and adducts of glycidyl(meth)acrylate and amines. These may be used alone or in combination of two or more.

[0030] -Other structural units- The electrode slurry additive according to the present disclosure may contain other structural units in addition to the structural unit having a linear alkyl group having 14 or more carbon atoms and the structural unit having a basic functional group.

[0031] Specific examples of other structural units include structural units derived from the following other polymerizable unsaturated monomers. Other polymerizable unsaturated monomers include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, isostearyl acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and tridecyl (meth)acrylate. (Meth)acrylates containing a linear, branched or cyclic alkyl group such as vinyl acrylate; polymerizable unsaturated monomers having a monocyclic aromatic hydrocarbon such as styrene, phenyl (meth)acrylate, phenyl alkyl (meth)acrylate, vinyl toluene, etc.; vinyl naphthalene, naphthyl (meth)acrylate, naphthyl alkyl (meth)acrylate, vinyl anthracene, anthracenyl (meth)acrylate, anthracenyl alkyl (meth)acrylate, vinyl pyrene, pyrenyl (meth)acrylate, pyrenyl alkyl (meth)acrylate, vinyl chrysene, vinyl naphthalene Polymerizable unsaturated monomers having polycyclic aromatic hydrocarbons, such as phthacene, vinylpentacene, and derivatives thereof; monoesters of (meth)acrylic acid with dihydric alcohols having 2 to 8 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; ε-caprolactone-modified monoesters of (meth)acrylic acid with dihydric alcohols having 2 to 8 carbon atoms; N-hydroxymethyl (meth)acrylamide; N,N-bis( hydroxyl group-containing polymerizable unsaturated monomers such as (2-hydroxymethyl)acrylamide, N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propenamide, N-hydroxyethyl(meth)acrylamide, N,N-bis(2-hydroxyethyl)acrylamide, N-hydroxypropyl(meth)acrylamide, N,N-bis(2-hydroxypropyl)acrylamide, N-(1,1-dimethyl-3-hydroxybutyl)acrylamide, allyl alcohol, and (meth)acrylates having a polyoxyalkylene chain with a hydroxyl group at the molecular terminal;Carboxyl group-containing polymerizable unsaturated monomers such as (meth)acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate; polymerizable unsaturated monomers having a urethane bond such as reaction products of isocyanate group-containing polymerizable unsaturated monomers and hydroxyl group-containing compounds or reaction products of hydroxyl group-containing polymerizable unsaturated monomers and isocyanate group-containing compounds; epoxy group-containing polymerizable unsaturated monomers such as glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, and allyl glycidyl ether; (meth)acrylates having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, and sodium salts of these sulfonic acids; Polymerizable unsaturated monomers having a sulfonic acid group such as ammonium salts; polymerizable unsaturated monomers having a phosphoric acid group such as 2-(meth)acryloyloxyethyl acid phosphate and 2-(meth)acryloyloxypropyl acid phosphate; polymerizable unsaturated monomers having an alkoxysilyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane and γ-(meth)acryloyloxypropyltriethoxysilane; perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; polymerizable unsaturated monomers having a fluorinated alkyl group such as fluoroolefins; polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group; alkoxy (meth)acrylates such as methoxy (meth)acrylate, ethoxy (meth)acrylate and butoxy (meth)acrylate;Examples of the polymerizable unsaturated monomer include allyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, 1,1,1-trishydroxymethylethane di(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate, 1,1,1-trishydroxymethylpropane tri(meth)acrylate, triallyl isocyanurate, diallyl terephthalate, and divinylbenzene. ; Among other polymerizable unsaturated monomers, it is particularly preferable to use a polymerizable unsaturated monomer having an alkyl group having 4 or more and less than 8 carbon atoms, from the viewpoint of dispersibility of the conductive assistant.

[0032] -Specific structure of electrode slurry additive- The electrode slurry additive according to the present disclosure may be a random polymer or a block polymer, but is preferably a random polymer from the viewpoint of dispersion stability. Moreover, the electrode slurry additive according to the present disclosure is preferably a poly(meth)acrylic acid ester from the viewpoint of dispersion stability.

[0033] Specific examples of acrylic resins that are electrode slurry additives according to the present disclosure are shown below. However, the electrode slurry additives according to the present disclosure are not limited to these. All of the acrylic resins in Table 1 are random polymers. The "mass %" value for each structural unit in Table 1 refers to the mass ratio of each structural unit to all structural units contained in the acrylic resin.

[0034] [Table 1]

[0035] (Weight average molecular weight) The electrode slurry additive according to the present disclosure has a weight-average molecular weight of more than 50,000 but less than 200,000, and from the viewpoint of dispersion stability, it is preferably 60,000 or more and 180,000 or less, more preferably 70,000 or more and 170,000 or less, even more preferably 80,000 or more and 160,000 or less, and also preferably 100,000 or more and 160,000 or less.

[0036] ~Measurement of weight average molecular weight~ The weight-average molecular weight of the electrode slurry additive according to the present disclosure is determined by converting the retention time (retention volume) measured using a gel permeation chromatograph (GPC) into the molecular weight of polystyrene using the retention time (retention volume) of a standard polystyrene of known molecular weight measured under the same conditions. For example, a GPC "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) can be used, and four columns, "TSKgel G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL" (trade names, all manufactured by Tosoh Corporation), can be used. The measurement can be performed under the following conditions: a mobile phase of tetrahydrofuran, a measurement temperature of 40°C, a flow rate of 1 mL / min, and a detector RI.

[0037] (amine value) The amine value of the electrode slurry additive according to the present disclosure is 5 mgKOH / g or more and 33 mgKOH / g or less, and from the viewpoint of dispersibility and conductivity of the electrode slurry, it is preferably 6 mgKOH / g or more and 30 mgKOH / g or less, more preferably 6 mgKOH / g or more and 25 mgKOH / g or less, and also preferably 6 mgKOH / g or more and 15 mgKOH / g or less.

[0038] ~Amine value measurement~ The amine value of the electrode slurry additive is measured in accordance with JIS K 7237 (1995).

[0039] (Method for synthesizing electrode slurry additives) The electrode slurry additive according to the present disclosure can be synthesized by copolymerizing a polymerizable unsaturated monomer having a linear alkyl group containing 14 or more carbon atoms, a polymerizable unsaturated monomer having a basic functional group, and, if necessary, other polymerizable unsaturated monomers. Conventional methods can be used for synthesis. For example, the additive can be produced by solution polymerization of the polymerizable unsaturated monomer in an organic solvent. However, this is not limiting. For example, bulk polymerization, emulsion polymerization, suspension polymerization, etc. may also be used. When solution polymerization is performed, continuous polymerization or batch polymerization may be used. The polymerizable unsaturated monomer may be charged all at once, charged in portions, or added continuously or intermittently.

[0040] -Polymerizable unsaturated monomers- The details of the polymerizable unsaturated monomer having a linear alkyl group having 14 or more carbon atoms, the polymerizable unsaturated monomer having a basic functional group, and other polymerizable unsaturated monomers used in the synthesis of the electrode slurry additive according to the present disclosure are as described above, and therefore will not be described here.

[0041] -Radical polymerization initiator- The radical polymerization initiator used in the polymerization may be a conventionally known one. Examples of the radical polymerization initiator include cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,3-bis(tert-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, diisopropylbenzene peroxide, tert-butylcumyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and 2,4-dichlorobenzoyl. peroxide-based polymerization initiators such as bis(tert-butylcyclohexyl)peroxide, di-tert-amyl peroxide, bis(tert-butylcyclohexyl)peroxydicarbonate, tert-butylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and tert-butylperoxy-2-ethylhexanoate; 2,2'-azobis(isobutyronitrile), 1,1-azobis(cyclohexane-1-carbonitrile), Examples of the radical polymerization initiator include azo-based polymerization initiators such as 2,2'-azobis(2-methylbutyronitrile), azocumene, 2,2'-azobisdimethylvaleronitrile, 4,4'-azobis(4-cyanovaleric acid), 2-(t-butylazo)-2-cyanopropane, 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), and dimethyl 2,2'-azobis(2-methylpropionate). One type of radical polymerization initiator may be used alone, or two or more types may be used in combination.

[0042] -solvent- The solvent used for the polymerization and / or dilution is not particularly limited, and examples thereof include water, organic solvents, and mixtures thereof. Examples of the organic solvent include hydrocarbon solvents such as n-butane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane, and cyclobutane; aromatic solvents such as toluene, xylene, mesitylene, and tetralin; ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and diethylene glycol; ethyl acetate, n-butyl acetate, isobutyl acetate, butyl butyrate, and ethylene glycol monomethyl ether; Examples of suitable solvents include ester-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; alcohol-based solvents such as ethanol, isopropanol, n-butanol, sec-butanol, and isobutanol; and amide-based solvents such as Equamide (trade name, manufactured by Idemitsu Kosan Co., Ltd.), N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropioamide, and N-methyl-2-pyrrolidone.

[0043] The solvent may be used alone or in combination of two or more kinds. In addition, if the solvent used for polymerization and / or dilution is not removed by a solvent removal step, it will be mixed into the electrode slurry additive. Therefore, it is preferable to carry out polymerization and / or dilution using the solvent used in preparing the electrode slurry, which will be described later.

[0044] When solution polymerization is carried out in an organic solvent, methods that can be used include mixing a radical polymerization initiator, a polymerizable unsaturated monomer, and an organic solvent and heating the mixture while stirring, or charging the organic solvent into a reaction vessel to suppress a temperature rise in the system due to the heat of reaction, and stirring at a temperature of 60°C to 200°C while blowing in an inert gas such as nitrogen or argon as necessary, and then adding the polymerizable unsaturated monomer and the radical polymerization initiator dropwise or mixed together over a predetermined period of time. The polymerization can generally be carried out for about 1 to 10 hours. After each stage of polymerization, an additional catalyst step may be performed, in which the reaction vessel is heated while a radical polymerization initiator is added dropwise, as necessary.

[0045] <Battery> The battery according to the present disclosure includes the electrode slurry additive according to the present disclosure described above. The battery according to the present disclosure preferably includes a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode, and a solid battery having a solid electrolyte layer as the electrolyte is preferred. The positive electrode preferably includes a positive electrode layer and a positive electrode current collector, and the negative electrode preferably includes a negative electrode layer and a negative electrode current collector. The solid battery according to the present disclosure may have a stacked structure such as a positive electrode current collector / positive electrode layer / electrolyte layer / negative electrode layer / negative electrode current collector, for example. The solid battery according to the present disclosure may be configured such that the electrode slurry additive according to the present disclosure is contained in at least one layer selected from the group consisting of a positive electrode layer, an electrolyte layer, and a negative electrode layer. The solid-state battery includes a so-called all-solid-state battery that uses a solid electrolyte as an electrolyte, and the solid electrolyte may contain an electrolytic solution in an amount of less than 10 mass % based on the total amount of the electrolyte. The solid electrolyte may also be a composite solid electrolyte containing an inorganic solid electrolyte and a polymer electrolyte.

[0046] (positive electrode) The positive electrode preferably has a positive electrode layer and a positive electrode current collector. The positive electrode layer contains a positive electrode active material and a solid electrolyte, and may contain an electrode slurry additive according to the present disclosure, a conductive aid, a binder, and other components as necessary.

[0047] -Positive electrode layer- The positive electrode active material preferably contains a lithium composite oxide. The lithium composite oxide may contain at least one element selected from the group consisting of F, Cl, N, S, Br, and I.

[0048] The solid electrolyte preferably contains at least one solid electrolyte species selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes, and more preferably contains a sulfide solid electrolyte. The sulfide solid electrolyte preferably contains sulfur (S) as a main anion element, and more preferably contains, for example, Li, A, and S. The A element is at least one element selected from the group consisting of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In. The sulfide solid electrolyte may further contain at least one of O and a halogen element.

[0049] Examples of the conductive additive include carbon materials, metal materials, and conductive polymer materials. Examples of binders include vinyl halide resins, rubbers, and polyolefin resins. Examples of other components include oxide solid electrolytes, halide solid electrolytes, thickeners, surfactants, dispersants, wetting agents, antifoaming agents, and solvents.

[0050] Examples of the solvent include the same organic solvents that can be used in synthesizing the electrode slurry additive of the present disclosure. In the present disclosure, ester-based, ether-based, ketone-based, and hydrocarbon-based solvents are preferred. Among these, solvents selected from the group consisting of butyl butyrate, dibutyl ether, anisole, mesitylene, diisobutyl ketone, methyl isobutyl ketone, cyclopentyl methyl ether, toluene, and heptane are more preferred, and solvents selected from the group consisting of anisole, mesitylene, diisobutyl ketone, and methyl isobutyl ketone are even more preferred. When preparing a slurry for an electrode or electrolyte layer, it is difficult to simultaneously and stably disperse the three components: the conductive additive, the electrolyte (particularly, a solid electrolyte), and the active material. In the present disclosure, the electrode slurry additive is included, so that a mixed system containing the three components: the conductive additive, the electrolyte (particularly, a solid electrolyte), and the active material can be stably dispersed while maintaining low reactivity with the electrolyte (particularly, a solid electrolyte).

[0051] -Positive electrode current collector- The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, iron, titanium, or carbon, and is preferably an aluminum alloy foil or aluminum foil. The positive electrode current collector may be in the form of, for example, a foil or a mesh.

[0052] (Negative electrode) The negative electrode preferably has a negative electrode layer and a negative electrode current collector, and the negative electrode layer contains a negative electrode active material and a solid electrolyte, and may contain an electrode slurry additive according to the present disclosure, a conductive aid, a binder, and other components as necessary.

[0053] -Anode layer- Examples of the negative electrode active material include Li-based active materials such as metallic lithium, carbon-based active materials such as graphite, oxide-based active materials such as lithium titanate, and Si-based active materials such as elemental Si. The solid electrolyte, conductive additive, binder and other components are the same as those described above.

[0054] -Negative electrode current collector- The negative electrode current collector collects current from the negative electrode layer. Examples of the negative electrode current collector include stainless steel, aluminum, copper, nickel, iron, titanium, and carbon, with copper being preferred. The negative electrode current collector may be in the form of, for example, a foil or a mesh.

[0055] (electrolyte layer) The electrolyte layer may be a layer containing a solid electrolyte. In the case of a layer containing a solid electrolyte (solid electrolyte layer), the solid electrolyte layer preferably contains one selected from the group consisting of a sulfide solid electrolyte, an oxide solid electrolyte, and a halide solid electrolyte. The solid electrolyte layer may contain an electrode slurry additive and a binder according to the present disclosure, or may not contain a binder. The binder that can be contained in the solid electrolyte layer may be the same as the binder described above.

[0056] <Solid-state battery manufacturing method> The method for manufacturing a solid state battery according to the present disclosure includes a step of preparing a positive electrode, a negative electrode, and an electrolyte layer or a separator (preparation step), and a step of stacking the positive electrode, the electrolyte layer or the separator, and the negative electrode in this order (stacking step).

[0057] (preparation process) The preparation step is a step of preparing a positive electrode, a negative electrode, and an electrolyte layer or a separator.

[0058] The method for producing the positive electrode, negative electrode, and electrolyte layer is not particularly limited, and a method including kneading components and a solvent that can be contained in the positive electrode layer, negative electrode layer, and electrolyte layer to obtain a slurry, applying the obtained slurry to a substrate, and pressing the dried film obtained by drying the slurry is preferred.

[0059] Suitable electrode slurries for producing positive and negative electrodes include, for example, slurries containing the electrode slurry additive according to the present disclosure, an active material, a conductive additive, a solid electrolyte, and a solvent (and preferably a binder). The solvent is effective in stabilizing dispersion when it contains at least one solvent selected from the group consisting of ester, ether, ketone, and hydrocarbon solvents. Furthermore, it is even more effective in stabilizing dispersion when it contains a solvent selected from the group consisting of butyl butyrate, dibutyl ether, anisole, mesitylene, diisobutyl ketone, methyl isobutyl ketone, cyclopentyl methyl ether, toluene, and heptane. It is even more effective in stabilizing dispersion when it contains a solvent selected from the group consisting of anisole, mesitylene, diisobutyl ketone, and methyl isobutyl ketone. That is, when a slurry containing an active material, a conductive additive, and a solid electrolyte is prepared using the above solvent, the active material, the conductive additive, and the solid electrolyte can be dispersed simultaneously and stably, resulting in improved battery performance.

[0060] Methods for pressing the dried film include roll pressing and cold isostatic pressing (CIP).

[0061] (Lamination process) The lamination step is a step of laminating a positive electrode and an electrolyte layer or a separator and a negative electrode in this order. In the lamination step, the positive electrode prepared in the preparation step, the electrolyte layer or separator, and the negative electrode are preferably laminated in this order, and pressed as necessary to obtain a laminate (electrode body).

[0062] It is preferable to fabricate the solid state battery according to the present disclosure through the above steps. [Example]

[0063] Hereinafter, examples of the electrode slurry additive and the like according to the present disclosure will be described. However, the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are all based on mass.

[0064] The synthesis procedures for the electrode slurry additives and the preparation procedures for the all-solid-state battery are described below. The structures of polymers 1 to 8 (electrode slurry additives according to the present disclosure) are the same as those of polymers 1 to 8 shown in Table 1 above.

[0065] Example 1 (Synthesis of electrode slurry additives) A reaction vessel equipped with a stirring heater and a condenser was charged with 40 parts of diisobutyl ketone, and after replacing the atmosphere with nitrogen, the temperature was maintained at 80° C. The following monomer mixture was added dropwise to the reaction vessel over a period of 6 hours. <Monomer mixture> 40 parts stearyl methacrylate (Polymerizable unsaturated monomers that form structural units having a linear alkyl group having 14 or more carbon atoms) N,N-Dimethylaminoethyl methacrylate 2 parts (Polymerizable unsaturated monomers that form structural units having basic functional groups) Isobutyl acrylate (or other polymerizable unsaturated monomer) 40 parts Isobutyl methacrylate (other polymerizable unsaturated monomer) 18 parts 2,2'-Azobis(isobutyronitrile) 0.3 parts (Radical polymerization initiator)

[0066] One hour after the end of the dropwise addition, a solution of 0.5 parts of 2,2'-azobis(isobutyronitrile) (not included in the amount in Table 1) dissolved in 10 parts of propylene glycol monomethyl ether was added dropwise to the mixture over one hour. The mixture was then maintained at 80°C for another hour. Diisobutyl ketone was then added to the mixture so that the solid content was 5%, yielding a solution of acrylic resin (a-1; electrode slurry additive). The acrylic resin (a-1) was a random copolymer and had a weight average molecular weight of 110,000.

[0067] (Fabrication of all-solid-state batteries) -Preparation process- Preparation of the positive electrode The solution of the above acrylic resin (a-1; electrode slurry additive) and the positive electrode active material (LiNi 0.33 Co 0.33 Mn 0.33 A mixture of 2 g of Li2S-P2S5, 0.03 g of a carbon material (VGCF-H, manufactured by Showa Denko K.K., VGCF is a registered trademark) serving as a conductive additive, 0.3 g of a sulfide solid electrolyte (Li2S-P2S5), and 0.3 g of a diisobutyl ketone solution containing 5 mass% of poly(vinylidene fluoride-co-hexafluoropropylene) as a binder was added and dispersed for 10 minutes using ultrasonic waves with an amplitude of 40 μm and a frequency of 20 kHz to obtain a positive electrode slurry. The slurry was then blade coated onto an aluminum foil substrate (positive electrode current collector) with a gap of 100 μm. The mixture was dried at 100°C for 30 minutes to produce a positive electrode having a positive electrode layer on the positive electrode current collector.

[0068] Preparation of the negative electrode A solution of the above acrylic resin (a-1; electrode slurry additive), 1 g of anode active material (Si simple substance), 0.13 g of a carbon material (VGCF-H, manufactured by Showa Denko K.K., VGCF is a registered trademark) serving as a conductive additive, 1.2 g of a sulfide solid electrolyte (Li2S-P2S5), and 0.8 g of a diisobutyl ketone solution containing 5% by mass of poly(vinylidene fluoride-co-hexafluoropropylene) serving as a binder were added to 2.7 g of diisobutyl ketone solvent, and the mixture was dispersed for 10 minutes using ultrasonic waves with an amplitude of 40 μm and a frequency of 20 kHz to obtain anode slurry. The slurry was then blade coated onto a nickel foil substrate (anode current collector) with a gap of 100 μm. The mixture was dried at 100 °C for 30 minutes to produce a cathode having a cathode layer on the anode current collector.

[0069] Preparation of the electrolyte layer 0.4 g of Li2S-P2S5 (sulfide solid electrolyte) and 0.05 g of a heptane solution containing 5% by mass of acrylonitrile butadiene rubber (ABR) as a binder were added to 0.8 g of heptane solvent, and the mixture was dispersed for 10 minutes using ultrasonic waves with an amplitude of 40 μm and a frequency of 20 kHz to obtain an electrolyte slurry. The resulting slurry was then blade coated onto a stainless steel foil substrate with a gap of 50 μm. The coating was dried at 100°C for 30 minutes to form an electrolyte layer on the substrate.

[0070] (Lamination process) The electrolyte layer was placed on the negative electrode current collector of the negative electrode, the stainless steel foil substrate on the electrolyte layer side was removed, and the laminate of the negative electrode and electrolyte layer was roll-pressed at room temperature with a linear pressure of 3 t / cm. The electrolyte layer was placed on the positive electrode current collector of the positive electrode, the stainless steel foil substrate on the electrolyte layer side was removed, and the laminate of the positive electrode and electrolyte layer was roll-pressed at a linear pressure of 4 t / cm and 170°C. The roll-pressed laminate of the negative electrode and electrolyte layer and the laminate of the positive electrode and electrolyte layer were each cut into 1 cm pieces. 2 The punched laminate of the negative electrode and the electrolyte layer and the punched laminate of the positive electrode and the electrolyte layer were overlapped and bonded so that the electrolyte layers were in contact with each other, thereby producing an all-solid-state battery.

[0071] <Examples 2 to 8 and Comparative Examples 1 to 8> An electrolyte slurry was prepared and an all-solid-state battery was fabricated in the same manner as in Example 1, except that the electrode slurry additives and the like in Example 1 were changed as shown in Table 2 or Table 3 below.

[0072] (Synthesis of electrode slurry additives) -Synthesis of polymers (a-2) to (a-6) and polymer (a-8)- A solution of acrylic resin (electrode slurry additive) was prepared in the same manner as in the synthesis of acrylic resin (a-1), except that the blending ratio of the polymerizable unsaturated monomers was changed to the content ratios shown in Table 2.

[0073] -Synthesis of polymer (a-7)- A solution of acrylic resin (a-7; electrode slurry additive) was prepared in the same manner as in the synthesis of acrylic resin (a-1), except that the amount of initiator was changed from 0.3 parts to 0.6 parts.

[0074] -Synthesis of comparative polymer (a-11)- A solution of acrylic resin (a-11; electrode slurry additive) was prepared in the same manner as in the synthesis of acrylic resin (a-1), except that the type and amount of initiator in the synthesis of acrylic resin (a-1) was changed as shown in Table 3.

[0075] -Synthesis of comparative polymers (a-12) to (a-18)- A solution of acrylic resin (electrode slurry additive) was prepared in the same manner as in the synthesis of acrylic resin (a-1), except that the blending ratio of the polymerizable unsaturated monomer was changed to the content ratio shown in Table 3.

[0076] <Measurement and Evaluation> -Weight-average molecular weight and amine value of electrode slurry additives- The weight average molecular weight and σ of the polymer obtained in each example were measured as described above in the sections "Measurement of weight average molecular weight of electrode slurry additive" and "Measurement of amine value of electrode slurry additive." -Evaluation of slurry particle size- The particle size of the obtained electrolyte slurry was measured in accordance with JIS K5600-2-5 (1999). The smaller the particle size value, the higher the dispersion stability of the components in the slurry. -Evaluation of resistance value- The obtained all-solid-state battery was CCCV charged at a rate of 1 / 3 C to 4.35 V, and then discharged at 1 / 3 C to 3.35 V. After that, it was further discharged at 7 C and the resistance was calculated from the change in voltage over 10 seconds.

[0077] [Table 2]

[0078] [Table 3]

[0079] In Tables 2 and 3, "-" in the column for each component of the electrode slurry indicates that the component was not used. Also, "-" in the column for "resistance value" indicates that "battery formation was not possible." In the column for slurry particle size, ">100" indicates that the slurry particle size exceeds 100 μm.

[0080] As is clear from the results shown in Tables 2 and 3, in the Examples, the electrode slurry additives improved the dispersion stability of the electrolyte slurry components. In contrast, in Comparative Examples 1 to 3 and Comparative Examples 6 to 8, the dispersibility of the components contained in the electrolyte slurry was insufficient, and the generation of agglomerates was observed. As a result, the electrolyte slurry could not be applied to the substrate, and an all-solid-state battery could not be fabricated. Furthermore, in Comparative Examples 4 and 5, although dispersion was achieved to a certain extent, the slurry particle size was high, resulting in poor dispersion stability and the resistance value could not be kept low.

Claims

1. The acrylic resin includes a structural unit having a linear alkyl group having 14 or more carbon atoms and a structural unit having a basic functional group, The weight average molecular weight is more than 50,000 and less than 200,000, An electrode slurry additive having an amine value of 5 mgKOH / g or more and 33 mgKOH / g or less.

2. 2. The electrode slurry additive according to claim 1, wherein the structural units having a linear alkyl group having 14 or more carbon atoms account for 30% by mass or more and 65% by mass or less of all structural units contained in the acrylic resin.

3. 2. The electrode slurry additive according to claim 1, wherein the constituent unit having a basic functional group is present in an amount of 0.5% by mass or more and 10% by mass or less based on the total amount of constituent units contained in the acrylic resin.

4. 2. The electrode slurry additive of claim 1 which is a random polymer.

5. A solid-state battery comprising the electrode slurry additive according to any one of claims 1 to 4.

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