Binder composition for all-solid-state secondary battery, slurry composition for all-solid-state secondary battery, solid electrolyte-containing layer and all-solid-state secondary battery

Abstract

The purpose of the present invention is to provide a binder composition for all-solid-state secondary batteries, said binder composition being capable of preparing a slurry composition for all-solid-state secondary batteries exhibiting excellent dispersibility and storage stability, while enabling a solid electrolyte-containing layer to exhibit excellent ion conductivity. A binder composition for all-solid-state secondary batteries according to the present invention contains a polymer, ions of a metal in group 1 or group 2 of the periodic table, and a solvent. The solvent contains an organic solvent having 8 or more carbon atoms; and the content of the metal ions relative to the polymer is from 5 ppm by mass to 5,000 ppm by mass.

Description

[Technical Field]

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

[0002] In recent years, demand for secondary batteries such as lithium-ion secondary batteries has been increasing for a variety of applications, including not only portable terminals such as personal digital assistants and portable electronic devices, but also small-sized home power storage devices, motorcycles, electric vehicles, hybrid electric vehicles, etc. As the range of applications expands, further improvements in the safety of secondary batteries are being demanded.

[0003] Therefore, as a highly safe secondary battery, all-solid-state secondary batteries using solid electrolytes instead of organic solvent electrolytes, which are highly flammable and have a high risk of catching fire when leaking, have attracted attention. The solid electrolyte is contained in the all-solid-state secondary battery as a solid electrolyte-containing layer (electrode mixture layer, solid electrolyte layer) in which components such as the solid electrolyte are bound to each other by a binder, for example. Here, to form the solid electrolyte-containing layer, a slurry composition for the solid electrolyte-containing layer is used, which is prepared using a binder composition containing a polymer as a binder and a solvent. For example, an electrode mixture layer can be formed by removing the solvent from a slurry composition for an electrode mixture layer containing a binder composition, a solid electrolyte, and an electrode active material. Also, for example, a solid electrolyte layer can be formed by removing the solvent from a slurry composition for a solid electrolyte layer containing a binder composition and a solid electrolyte.

[0004] In order to improve the performance of all-solid-state secondary batteries, improvements have been made to binder compositions and methods for forming solid electrolyte-containing layers using binder compositions (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-205449 [Patent Document 2] Japanese Patent Application Publication No. 2019-91632 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional binder compositions described above have room for improvement in terms of improving the dispersibility and storage stability of the slurry composition, as well as increasing the ionic conductivity of the solid electrolyte-containing layer formed using the slurry composition.

[0007] Therefore, an object of the present invention is to provide a binder composition for an all-solid-state secondary battery that can prepare a slurry composition for an all-solid-state secondary battery having excellent dispersibility and storage stability, and that can cause a solid electrolyte-containing layer to exhibit excellent ion conductivity. Another object of the present invention is to provide a slurry composition for an all-solid-state secondary battery that is excellent in dispersibility and storage stability and is capable of forming a solid electrolyte-containing layer that is excellent in ion conductivity. Another object of the present invention is to provide a solid electrolyte-containing layer having excellent ion conductivity, and an all-solid-state secondary battery including the solid electrolyte-containing layer. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems, and have newly discovered that by using a binder composition containing a polymer, ions of a predetermined metal, and a predetermined organic solvent, in which the content of the metal ions relative to the polymer is within a predetermined range, it is possible to ensure sufficient dispersibility and storage stability of the slurry composition while allowing the solid electrolyte-containing layer to exhibit excellent ion conductivity, thereby completing the present invention.

[0009] That is, the present invention has an object to advantageously solve the above-mentioned problems, and provides a binder composition for an all-solid-state secondary battery comprising a polymer, ions of a metal belonging to Group 1 or Group 2 of the periodic table, and a solvent, wherein the solvent comprises an organic solvent having 8 or more carbon atoms, and the content of the metal ions is 5 ppm by mass or more and 5,000 ppm by mass or less relative to the polymer. By using a binder composition comprising a polymer, ions of a metal belonging to Group 1 or Group 2 of the periodic table (hereinafter sometimes abbreviated as "Group 1-2 metal ions"), and a solvent, wherein the amount of Group 1-2 metal ions relative to the polymer is within the above-mentioned range, and the solvent contains an organic solvent having 8 or more carbon atoms, a slurry composition with excellent dispersibility and storage stability can be prepared, and a solid electrolyte-containing layer with excellent ion conductivity can be formed from the slurry composition for a secondary battery. In the present invention, the content of ions of metals belonging to Group 1 or 2 of the periodic table in the polymer can be measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Specifically, the content can be measured by the method described in the examples.

[0010] In the binder composition for an all-solid-state secondary battery of the present invention, the organic solvent having 8 or more carbon atoms preferably has at least one selected from the group consisting of an aromatic hydrocarbon ring, a non-aromatic hydrocarbon group, and a carbonyl group. If the organic solvent having 8 or more carbon atoms has at least one of the above-mentioned structures, the dispersibility and storage stability of the slurry composition can be further improved, while the ionic conductivity of the solid electrolyte-containing layer can be further increased.

[0011] In the binder composition for an all-solid-state secondary battery of the present invention, the polymer preferably has at least one of a nitrogen-containing functional group and a carbonyl group. If the polymer has at least one of the above groups, it is possible to obtain effects such as further improving the dispersibility and storage stability of the slurry composition and / or improving the adhesiveness of the solid electrolyte-containing layer.

[0012] In the binder composition for an all-solid-state secondary battery of the present invention, the polymer preferably contains vinyl cyanide monomer units in a proportion of 2% by mass to 35% by mass, and the dispersibility and storage stability of the slurry composition can be further improved if the polymer contains vinyl cyanide monomer units in the above proportion. In the present invention, "containing a monomer unit" means that "a polymer obtained using the monomer contains a structural unit derived from the monomer." In addition, in the present invention, the content (mass %) of the "structural unit" (including the "monomer unit") in the polymer is expressed as follows: 1 It can be measured using nuclear magnetic resonance (NMR) techniques such as H-NMR.

[0013] In the binder composition for an all-solid-state secondary battery of the present invention, the polymer preferably contains 25% by mass or more and 95% by mass or less of (meth)acrylic acid ester monomer units having no aromatic hydrocarbon ring. If the polymer contains the (meth)acrylic acid ester monomer units having no aromatic hydrocarbon ring in the above-mentioned proportion, the dispersibility and storage stability of the slurry composition can be further improved, while the adhesiveness of the solid electrolyte-containing layer can be increased. In the present invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0014] In the binder composition for an all-solid-state secondary battery of the present invention, the polymer preferably contains aromatic monomer units in a proportion of 3% by mass to 40% by mass, and the dispersibility and storage stability of the slurry composition can be further improved if the polymer contains aromatic monomer units in the above proportion.

[0015] Furthermore, in the binder composition for an all-solid-state secondary battery of the present invention, the aromatic monomer unit preferably includes a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring. When the polymer includes a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring as the aromatic monomer unit, the adhesion of the solid electrolyte-containing layer can be improved.

[0016] The present invention also aims to advantageously solve the above-mentioned problems, and provides a slurry composition for an all-solid-state secondary battery, characterized by containing a solid electrolyte and any of the binder compositions for an all-solid-state secondary battery described above. A slurry composition containing a solid electrolyte and any of the binder compositions described above has excellent dispersibility and storage stability, and the use of this slurry composition makes it possible to form a solid electrolyte-containing layer having excellent ion conductivity.

[0017] In the slurry composition for an all-solid-state secondary battery of the present invention, the solid electrolyte preferably contains at least one of a sulfide-based inorganic solid electrolyte and an oxide-based inorganic solid electrolyte. By using a sulfide-based inorganic solid electrolyte and / or an oxide-based inorganic solid electrolyte as the solid electrolyte, the ionic conductivity of the solid electrolyte-containing layer can be further improved.

[0018] The present invention also aims to advantageously solve the above-mentioned problems, and provides a solid electrolyte-containing layer formed using any of the above-mentioned slurry compositions for an all-solid-state secondary battery. The solid electrolyte-containing layer formed using any of the above-mentioned slurry compositions has excellent ion conductivity.

[0019] The present invention has an object to advantageously solve the above-mentioned problems, and provides an all-solid-state secondary battery comprising the above-mentioned solid electrolyte-containing layer. The all-solid-state secondary battery comprising the above-mentioned solid electrolyte-containing layer has excellent cell characteristics such as output characteristics and cycle characteristics. [Effects of the Invention]

[0020] According to the present invention, it is possible to prepare a slurry composition for an all-solid-state secondary battery having excellent dispersibility and storage stability, and to provide a binder composition for an all-solid-state secondary battery that can cause a solid electrolyte-containing layer to exhibit excellent ion conductivity. Furthermore, according to the present invention, it is possible to provide a slurry composition for an all-solid-state secondary battery that is excellent in dispersibility and storage stability and is capable of forming a solid electrolyte-containing layer that is excellent in ion conductivity. Furthermore, according to the present invention, it is possible to provide a solid electrolyte-containing layer having excellent ion conductivity, and an all-solid-state secondary battery including the solid electrolyte-containing layer. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail. The binder composition for an all-solid-state secondary battery of the present invention is used to prepare a slurry composition for an all-solid-state secondary battery. Here, the slurry composition for an all-solid-state secondary battery of the present invention is used to form a solid electrolyte-containing layer such as an electrode mixture layer or a solid electrolyte layer used in an all-solid-state secondary battery such as an all-solid-state lithium-ion secondary battery. Furthermore, the solid electrolyte-containing layer of the present invention is formed using the slurry composition for an all-solid-state secondary battery of the present invention. Furthermore, the all-solid-state secondary battery of the present invention comprises the solid electrolyte-containing layer of the present invention.

[0022] (Binder composition for all-solid-state secondary battery) The binder composition of the present invention contains a polymer, a Group 1-2 metal ion, and a solvent, and may further contain other components. The binder composition of the present invention is characterized in that the content of the Group 1-2 metal ion relative to the polymer is 5 ppm by mass or more and 5,000 ppm by mass or less, and the solvent contains an organic solvent having 8 or more carbon atoms. The binder composition of the present invention contains a polymer, Group 1-2 metal ions, and a solvent, in which the Group 1-2 metal ion content is within the above-mentioned range, and contains an organic solvent having 8 or more carbon atoms as the solvent. Therefore, by using this binder composition, it is possible to provide a slurry composition for an all-solid-state secondary battery having excellent dispersibility and storage stability, and a solid electrolyte-containing layer having excellent ion conductivity.

[0023] <Polymer> The polymer is not particularly limited as long as it is a component that can bind components such as the solid electrolyte to each other (i.e., a component that can function as a binder) in the solid electrolyte-containing layer formed from the slurry composition prepared using the binder composition, and any polymer can be used.

[0024] <<Composition>> Here, the polymer preferably contains at least one of a nitrogen-containing functional group and a carbonyl group (-C(=O)-), and more preferably contains both a nitrogen-containing functional group and a carbonyl group. If the polymer has a nitrogen-containing functional group, the polymer can adsorb well with the solid electrolyte, further improving the dispersibility and storage stability of the slurry composition. Furthermore, if the polymer has a carbonyl group, the flexibility of the polymer is ensured, and the adhesiveness of the solid electrolyte-containing layer can be improved. Examples of the nitrogen-containing functional group include a nitrile group, an amino group, an imidazole group, a pyridine group, a carbazole group, and an amide group. The polymer may have one type of nitrogen-containing functional group or two or more types of nitrogen-containing functional groups.

[0025] The structural units contained in the polymer are not particularly limited. The polymer preferably contains at least one selected from the group consisting of vinyl cyanide monomer units, (meth)acrylic acid ester monomer units having no aromatic hydrocarbon ring, and aromatic monomer units. The polymer may contain structural units (other structural units) other than vinyl cyanide monomer units, (meth)acrylic acid ester monomer units having no aromatic hydrocarbon ring, and aromatic monomer units.

[0026] [Vinyl cyanide monomer unit] Examples of vinyl cyanide monomers that can form vinyl cyanide monomer units include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-ethylacrylonitrile. These may be used alone or in combination of two or more. Among these, acrylonitrile is preferred.

[0027] Here, the proportion of vinyl cyanide monomer units among all structural units contained in the polymer is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, particularly preferably 6% by mass or more, and preferably 35% by mass or less, more preferably 28% by mass or less, even more preferably 26% by mass or less, and particularly preferably 20% by mass or less, assuming that all structural units are 100% by mass. When the proportion of vinyl cyanide monomer units among all structural units is 2% by mass or more, the polymer can be well adsorbed to the solid electrolyte, thereby further improving the dispersibility and storage stability of the slurry composition. On the other hand, when the proportion of vinyl cyanide monomer units among all structural units is 35% by mass or more, the polymer can be well dissolved in a solvent (especially an organic solvent having 8 or more carbon atoms), thereby further improving the dispersibility and storage stability of the slurry composition.

[0028] [(Meth)acrylic acid ester monomer unit not having an aromatic hydrocarbon ring] The (meth)acrylic acid ester monomer capable of forming the (meth)acrylic acid ester monomer unit having no aromatic hydrocarbon ring is not particularly limited as long as it does not have an aromatic hydrocarbon ring. Examples of the (meth)acrylic acid ester monomer having no aromatic hydrocarbon ring include acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, and 2-ethylhexyl acrylate; acrylic acid alkoxy esters such as 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate; 2-(perfluoroalkyl)ethyl acrylates such as 2-(perfluorobutyl)ethyl acrylate and 2-(perfluoropentyl)ethyl acrylate; methyl Examples of the (meth)acrylic acid ester monomer include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, tridecyl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, and 2-ethylhexyl methacrylate; alkoxy methacrylates such as 2-methoxyethyl methacrylate and 2-ethoxyethyl methacrylate; and 2-(perfluoroalkyl)ethyl methacrylates such as 2-(perfluorobutyl)ethyl methacrylate and 2-(perfluoropentyl)ethyl methacrylate. The (meth)acrylic acid ester monomer also includes diesters of α,β-ethylenically unsaturated dicarboxylic acids, such as lower alkyl diesters of itaconic acid, such as diethyl itaconate and dibutyl itaconate. These may be used alone or in combination of two or more. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, butyl acrylate (n-butyl acrylate, t-butyl acrylate, etc.), and dibutyl itaconate are preferred.

[0029] Here, the proportion of (meth)acrylic acid ester monomer units not having an aromatic hydrocarbon ring among all structural units contained in the polymer is preferably 25% by mass or more, more preferably 30% by mass or more, and even more preferably 35% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 73% by mass or less, assuming that all structural units are 100% by mass. If the proportion of (meth)acrylic acid ester monomer units not having an aromatic hydrocarbon ring among all structural units is 25% by mass or more, the flexibility of the polymer can be ensured and the adhesiveness of the solid electrolyte-containing layer can be improved. If it is 95% by mass or less, the polymer can be well adsorbed to the electrode active material and the conductive material, and the dispersibility and storage stability of the slurry composition can be further improved.

[0030] [Aromatic monomer unit] The aromatic monomer capable of forming the aromatic monomer unit is not particularly limited as long as it has an aromatic ring, and examples of the aromatic monomer include an aromatic vinyl monomer and a (meth)acrylic acid ester monomer having an aromatic hydrocarbon ring. In the present invention, the aromatic vinyl monomer does not include a monomer corresponding to a (meth)acrylic acid ester monomer having an aromatic hydrocarbon ring (in other words, the aromatic vinyl monomer unit does not include a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring).

[0031] Examples of aromatic vinyl monomers include styrene, styrene sulfonic acid and its salts, α-methylstyrene, pt-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene.

[0032] The aromatic hydrocarbon ring contained in the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring is not particularly limited, but examples thereof include a benzene ring, a naphthalene ring, and an anthracene ring. Among these, a benzene ring is preferred. The monomer unit may have one type of aromatic hydrocarbon ring or two or more types of aromatic hydrocarbon rings.

[0033] Examples of the (meth)acrylic acid ester monomer having an aromatic hydrocarbon ring include phenoxyethyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, and phenoxypolyethylene glycol (meth)acrylate. In the present invention, the term "(meth)acrylate" means acrylate and / or methacrylate.

[0034] The aromatic monomers described above may be used alone or in combination of two or more. Among these, styrene and phenoxyethyl acrylate are preferred from the viewpoint of allowing the polymer to adsorb well with the solid electrolyte and further improving the dispersibility and storage stability of the slurry composition. Furthermore, from the viewpoint of ensuring the flexibility of the polymer and improving the adhesiveness of the solid electrolyte-containing layer, (meth)acrylic acid ester monomers having an aromatic hydrocarbon ring are preferred, and phenoxyethyl acrylate is more preferred.

[0035] Here, the proportion of aromatic monomer units among all structural units contained in the polymer is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, particularly preferably 10% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less, assuming that all structural units are 100% by mass. When the proportion of aromatic monomer units among all structural units is 3% by mass or more, the polymer can be well adsorbed to the solid electrolyte, further improving the dispersibility and storage stability of the slurry composition. On the other hand, when the proportion of aromatic monomer units among all structural units is 40% by mass or less, the polymer can be well adsorbed to the solid electrolyte, further improving the dispersibility and storage stability of the slurry composition, while also increasing the adhesion of the solid electrolyte-containing layer.

[0036] Other structural units The other structural units are not particularly limited, but include diene monomer units and crosslinkable monomer units. The polymer may contain only one type of other structural unit, or may contain two or more types of other structural units.

[0037] -Diene monomer units- Examples of the diene monomer capable of forming the diene monomer unit include aliphatic conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc. These may be used alone or in combination of two or more. In the present invention, the term "diene monomer unit" also includes a structural unit (hydride unit) obtained by further hydrogenating a monomer unit contained in a polymer obtained using a diene monomer. Among the diene monomers described above, 1,3-butadiene and isoprene are preferred. In other words, the diene monomer units are preferably 1,3-butadiene units, isoprene units, 1,3-butadiene hydride units, and isoprene hydride units.

[0038] When the polymer contains diene monomer units, the proportion of the diene monomer units among all structural units contained in the polymer is preferably 5% by mass or more, more preferably 6% by mass or more, and even more preferably 7% by mass or more, and preferably 50% by mass or less, and more preferably 40% by mass or less, with the total structural units being 100% by mass. If the proportion of the diene monomer units among all structural units is 5% by mass or more, the polymer can be well adsorbed to the electrode active material and the conductive material, thereby further improving the dispersibility and storage stability of the slurry composition. On the other hand, if the proportion of the diene monomer units among all structural units is 50% by mass or less, the adhesion of the solid electrolyte-containing layer can be sufficiently ensured.

[0039] -Cross-linking monomer unit- A crosslinkable monomer capable of forming a crosslinkable monomer unit is a monomer having two or more polymerizable structures (olefinic double bonds, epoxy groups, etc.) per molecule. Examples of the crosslinkable monomer include allyl (meth)acrylate, allyl glycidyl ether, and ethylene glycol di(meth)acrylate. These may be used alone or in combination of two or more.

[0040] Here, when the polymer contains crosslinkable monomer units, the proportion of the crosslinkable monomer units in all structural units contained in the polymer can be 0.1% by mass or more, preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, where all structural units are taken as 100% by mass.

[0041] <<Properties>> The polymer may be either easily soluble or poorly soluble in the solvent contained in the binder composition and the slurry composition. That is, the polymer may be in a state of being dissolved in the solvent in the binder composition and the slurry composition, or in a state of being dispersed in the solvent in the form of particles. In the present invention, a polymer being "easily soluble in a solvent" means that the amount of insoluble matter in the solvent is less than 50% by mass, and a polymer being "poorly soluble in a solvent" means that the amount of insoluble matter in the solvent is 50% by mass or more. In the present invention, the "solvent insoluble content" can be measured using the method described in the Examples. The "solvent insoluble content" of a polymer can be adjusted by changing the type of monomer used in preparing the polymer, the weight-average molecular weight of the polymer, etc. For example, the solvent insoluble content can be reduced by reducing the amount of vinyl cyanide monomer and / or crosslinkable monomer used in preparing the polymer.

[0042] Here, the polymer is preferably easily soluble in the solvent contained in the binder composition and the slurry composition. If the polymer is easily soluble in the solvent, a better dispersion state of the solid electrolyte and the like in the slurry composition can be realized, and the dispersibility and storage stability of the slurry composition can be further improved. In addition, the adhesiveness of the solid electrolyte-containing layer can be improved.

[0043] <<Preparation method>> The method for preparing the polymer is not particularly limited. For example, the polymer can be prepared by polymerizing a monomer composition containing the above-mentioned monomers and optionally hydrogenating the polymer. In the present invention, the content of each monomer in the monomer composition can be determined in accordance with the content of each monomer unit in the polymer. The polymerization method is not particularly limited, and any of solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and the like can be used. In each polymerization method, known emulsifiers and polymerization initiators can be used as needed. Here, as the emulsifier, a nonionic emulsifier such as polyoxyethylene lauryl ether can be used, but an emulsifier containing a metal ion of Groups 1 or 2, such as sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, sodium dodecyldiphenylethersulfonate, or sodium polyoxyethylene alkyl ether sulfate, can also be used. By using an emulsifier containing a metal ion of Groups 1 or 2, the metal ion of Groups 1 or 2 can be incorporated into the resulting binder composition. The hydrogenation method is not particularly limited, and a general method using a catalyst (see, for example, WO 2012 / 165120, WO 2013 / 080989, and JP 2013-8485 A) can be used.

[0044] <Ions of metals belonging to Group 1 or 2 of the periodic table> The binder composition of the present invention contains Group 1 or 2 metal ions. By including Group 1 or 2 metal ions in the binder composition, the ionic conductivity of the solid electrolyte-containing layer can be improved. Although the reason for this is unclear, it is presumed that the Group 1 or 2 metal ions in the slurry composition and the solid electrolyte-containing layer are adsorbed to the surface of the solid electrolyte by electrostatic interaction or the like, coating the surface, thereby suppressing the reaction between water and the solid electrolyte and inhibiting deterioration of the solid electrolyte due to the reaction.

[0045] Here, examples of metal ions in Groups 1 and 2 include sodium ions (Na + ), potassium ions (K + ), lithium ion (Li + ), magnesium ions (Mg 2+ ), calcium ions (Ca 2+) can be mentioned. These may be used alone or in combination of two or more. Among these, sodium ions and lithium ions are more preferred from the viewpoint of increasing the adhesion of the solid electrolyte-containing layer and further improving the ion conductivity.

[0046] The content of Group 1-2 metal ions in the binder composition must be 5 ppm by mass or more and 5,000 ppm by mass or less relative to the polymer, preferably 10 ppm by mass or more, more preferably 300 ppm by mass or more, and preferably 4,500 ppm by mass or less, and more preferably 3,000 ppm by mass or less. If the content of Group 1-2 metal ions is less than 5 ppm by mass relative to the polymer, the effect of improving the ionic conductivity of the solid electrolyte-containing layer described above cannot be fully achieved, and if it exceeds 5,000 ppm by mass, there is a risk that the metal ions will cause the solid electrolyte and polymer to aggregate, impairing the dispersibility and storage stability of the slurry composition.

[0047] The method for incorporating Group 1-2 metal ions into the binder composition is not particularly limited. For example, a binder composition containing Group 1-2 metal ions can be prepared by using an emulsifier containing the above-mentioned Group 1-2 metal ions in preparing the polymer, or by adding a substance capable of supplying Group 1-2 metal ions (such as a hydroxide of Group 1-2 metal) after preparing the polymer. Furthermore, the amount of Group 1-2 metal ions contained in the resulting binder composition can be reduced by passing the polymer through an ion exchange resin.

[0048] <Solvent> The binder composition of the present invention contains an organic solvent having 8 or more carbon atoms as a solvent. It is presumed that the inclusion of an organic solvent having 8 or more carbon atoms in the binder composition suppresses aggregation of the polymer, solid electrolyte, etc. in a slurry composition prepared using the binder composition, and the dispersibility and storage stability of the slurry composition can be improved. Moreover, organic solvents having 8 or more carbon atoms are less likely to react with the solid electrolyte, and in addition, have a high boiling point, making them easy to handle. Therefore, by using an organic solvent having 8 or more carbon atoms as the solvent, the solid electrolyte and the like can be uniformly arranged, and a solid electrolyte-containing layer with excellent ion conductivity can be formed.

[0049] <<Organic solvents with 8 or more carbon atoms>> Here, the organic solvent having 8 or more carbon atoms preferably has at least one selected from the group consisting of an aromatic hydrocarbon ring, a non-aromatic hydrocarbon group, and a carbonyl group, from the viewpoint of further improving the dispersibility and storage stability of the slurry composition while further increasing the ionic conductivity of the solid electrolyte-containing layer.

[0050] Examples of aromatic hydrocarbon rings include a benzene ring, a naphthalene ring, and an anthracene ring. The organic solvent having 8 or more carbon atoms may contain only one type of aromatic hydrocarbon ring, or may contain two or more types. Examples of non-aromatic hydrocarbon groups include alkyl groups such as methyl, propyl (n-propyl, isopropyl), and butyl (n-butyl, sec-butyl, isobutyl, and tert-butyl). The organic solvent having 8 or more carbon atoms may contain only one type of non-aromatic hydrocarbon group, or may contain two or more types.

[0051] Furthermore, the number of carbon atoms in the organic solvent must be 8 or more as described above, and from the viewpoint of further improving the dispersibility and storage stability of the slurry composition while further increasing the ionic conductivity of the solid electrolyte-containing layer, the number of carbon atoms is preferably 12 or less, more preferably 10 or less, and most preferably 9.

[0052] Specific examples of organic solvents having 8 or more carbon atoms include xylene (8 carbon atoms), butyl butyrate (8 carbon atoms), n-butyl ether (8 carbon atoms), diisobutyl ketone (9 carbon atoms), and hexyl butyrate (10 carbon atoms). These may be used alone or in combination of two or more. Among these, diisobutyl ketone is preferred from the viewpoint of further improving the dispersibility of the slurry composition and the ionic conductivity of the solid electrolyte-containing layer.

[0053] <<Other solvents>> The binder composition of the present invention may contain, as a solvent, a solvent (other solvent) other than the above-mentioned organic solvents having 8 or more carbon atoms. As such other solvents, organic solvents having 7 or less carbon atoms can be used. Specific examples of organic solvents having 7 or less carbon atoms include hexane, cyclopentane, cyclohexane, ethyl methyl ketone, cyclohexanone, ethyl acetate, butyl acetate, γ-butyrolactone, ε-caprolactone, acetonitrile, propionitrile, tetrahydrofuran, methanol, ethanol, isopropanol, ethylene glycol, ethylene glycol monomethyl ether, N-methylpyrrolidone, and N,N-dimethylformamide. These may be used alone or in combination of two or more.

[0054] However, from the viewpoint of sufficiently increasing the dispersibility and storage stability of the slurry composition and the ionic conductivity of the solid electrolyte-containing layer, the proportion of the organic solvent having 8 or more carbon atoms in the solvent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass (i.e., substantially no other solvents are contained), with the entire solvent being 100% by mass.

[0055] <Other ingredients> Other components that may be optionally contained in the binder composition are not particularly limited, but include binders other than the above-mentioned polymers, dispersants, leveling agents, antifoaming agents, conductive materials, reinforcing materials, etc. These other components are not particularly limited as long as they do not affect the battery reaction. The binder composition may also contain other metal components (other metal components) other than the metal ions of Groups 1 and 2 described above. Examples of other metal components include metals belonging to the fifth period of the periodic table (palladium, ruthenium, rhodium, etc.) One type of other metal component may be used alone, or two or more types may be used in combination. When the binder composition contains at least one of palladium, ruthenium, and rhodium, the total amount thereof is preferably 0.5 ppm by mass or more and 200 ppm by mass or less relative to the polymer. When the total amount of palladium, ruthenium, and rhodium is within the above-mentioned range, the electronic conductivity of the all-solid-state secondary battery is improved, and the output characteristics are improved. Furthermore, when the total amount of palladium, ruthenium, and rhodium is 200 ppm by mass or less, the cycle characteristics of the all-solid-state secondary battery can be sufficiently improved. Here, palladium, ruthenium, and rhodium can be contained in the binder composition by being derived from compounds such as a catalyst used in preparing the polymer. Palladium, ruthenium, and rhodium can also be contained in the binder composition by adding, to the binder composition, palladium-based compounds such as organic complexes and organic salts of palladium, ruthenium-based compounds such as organic complexes and organic salts of ruthenium, and rhodium-based compounds such as organic complexes and organic salts of rhodium, respectively. The other components described above may be used singly or in combination of two or more kinds in any ratio. In the present invention, the contents of the other metal components described above can be measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Specifically, the contents can be measured using the method described in the examples.

[0056] <Method for preparing binder composition> The method for preparing the binder composition of the present invention is not particularly limited. For example, the binder composition can be prepared by adding a substance capable of supplying metal ions of Groups 1 and 2 to the aqueous dispersion of the polymer as the binder obtained as described above, if necessary, and then performing solvent substitution with an organic solvent having 8 or more carbon atoms. Note that, if necessary, other components can also be added, for example, after solvent substitution.

[0057] (Slurry composition for all-solid-state secondary battery) The slurry composition for an all-solid-state secondary battery of the present invention contains at least a solid electrolyte and the binder composition for an all-solid-state secondary battery of the present invention described above. More specifically, the slurry composition of the present invention contains a solid electrolyte, the polymer described above, a metal ion of Group 1 or 2, a solvent containing an organic solvent having 8 or more carbon atoms, and, optionally, an electrode active material and other components. Furthermore, since the slurry composition of the present invention contains the binder composition of the present invention, it has excellent dispersibility and storage stability, and when used, it is possible to form a solid electrolyte-containing layer having excellent ion conductivity.

[0058] <Solid electrolyte> The solid electrolyte is not particularly limited as long as it is made of particles made of a solid having ion conductivity, but inorganic solid electrolytes can be preferably used. The inorganic solid electrolyte is not particularly limited, and a crystalline inorganic ion conductor, an amorphous inorganic ion conductor, or a mixture thereof can be used. For example, when the all-solid-state secondary battery is an all-solid-state lithium ion secondary battery, the inorganic solid electrolyte can usually be a crystalline inorganic lithium ion conductor, an amorphous inorganic lithium ion conductor, or a mixture thereof. In particular, from the viewpoint of forming a solid electrolyte-containing layer having even better ion conductivity, it is preferable that the inorganic solid electrolyte contains at least one of a sulfide-based inorganic solid electrolyte and an oxide-based inorganic solid electrolyte. In the following, a case where the slurry composition for an all-solid-state secondary battery is a slurry composition for an all-solid-state lithium-ion secondary battery will be described as an example, but the present invention is not limited to the following example.

[0059] As crystalline inorganic lithium ion conductors, Li3N, LISICON (Li 14 Zn(GeO4)4), perovskite type (e.g., Li 0.5 La 0.5 TiO3), garnet type (e.g. Li7La3Zr2O 12 ), LIPON(Li 3+y PO 4-x N x ), Thio-LISICON(Li 3.25 Ge 0.25 P 0.75 S4) and others. The above-mentioned crystalline inorganic lithium ion conductors can be used alone or in combination of two or more.

[0060] Furthermore, examples of amorphous inorganic lithium ion conductors include substances that contain sulfur atoms and have ion conductivity, and more specifically, examples include glass Li-Si-SO, Li-PS, and those made using a raw material composition containing LiS and a sulfide of an element of Groups 13 to 15 of the periodic table. Examples of the elements of Groups 13 to 15 include Al, Si, Ge, P, As, and Sb. Specific examples of sulfides of elements of Groups 13 to 15 include Al2S3, SiS2, GeS2, P2S3, P2S5, As2S3, and Sb2S3. Examples of methods for synthesizing amorphous inorganic lithium ion conductors using raw material compositions include amorphization methods such as mechanical milling and melt quenching. Examples of amorphous inorganic lithium ion conductors obtained using raw material compositions containing Li2S and sulfides of elements of Groups 13 to 15 of the periodic table include Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, and Li2S-Al2S3, with Li2S-P2S5 being more preferred. The amorphous inorganic lithium ion conductors described above can be used alone or in combination of two or more.

[0061] Among the above, as the inorganic solid electrolyte for the all-solid-state lithium ion secondary battery, from the viewpoint of forming a solid electrolyte-containing layer having even more excellent ion conductivity, an amorphous sulfide containing Li and P, Li7La3Zr2O 12 Amorphous sulfides containing Li and P, and Li7La3Zr2O 12 Since lithium ion conductivity is high, when used as an inorganic solid electrolyte, the internal resistance of the battery can be reduced and the output characteristics can be improved.

[0062] From the viewpoint of reducing the internal resistance of the battery and improving its output characteristics, the amorphous sulfide containing Li and P is preferably a sulfide glass composed of Li2S and P2S5, and particularly preferably a sulfide glass produced from a mixed raw material of Li2S and P2S5 in a Li2S:P2S5 molar ratio of 65:35 to 85:15. The amorphous sulfide containing Li and P is preferably a sulfide glass ceramic obtained by mechanochemically reacting a mixed raw material of Li2S and P2S5 in a Li2S:P2S5 molar ratio of 65:35 to 85:15. From the viewpoint of maintaining high lithium ion conductivity, the mixed raw material preferably has a Li2S:P2S5 molar ratio of 68:32 to 80:20.

[0063] In addition to the Li2S and P2S5, the inorganic solid electrolyte may contain at least one sulfide selected from the group consisting of Al2S3, B2S3, and SiS2 as a starting material, to the extent that the ionic conductivity is not reduced. Addition of such a sulfide can stabilize the glass component in the inorganic solid electrolyte. Similarly, the inorganic solid electrolyte may contain, in addition to Li2S and P2S5, at least one lithium ortho-oxo-oxide selected from the group consisting of Li3PO4, Li4SiO4, Li4GeO4, Li3BO3, and Li3AlO3. The inclusion of such a lithium ortho-oxo-oxide can stabilize the glass component in the inorganic solid electrolyte.

[0064] The above-mentioned solid electrolytes can be used alone or in combination of two or more. The particle size of the above-mentioned solid electrolyte is not particularly limited and can be the same as that of conventionally used solid electrolytes.

[0065] <Binder composition> The binder composition used in preparing the slurry composition is the binder composition of the present invention described above, which contains a polymer, a metal ion of Group 1 or 2, a solvent containing an organic solvent having 8 or more carbon atoms, and optionally contains other components.

[0066] The blend ratio of the solid electrolyte and the binder composition is not particularly limited. For example, the amount of the polymer derived from the binder composition contained in the slurry composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of solid electrolyte. When the content of the polymer in the slurry composition is 0.1 parts by mass or more per 100 parts by mass of solid electrolyte, the polymer can fully function as a binder while further improving the dispersibility and storage stability of the slurry composition. In addition, the ionic conductivity of the solid electrolyte-containing layer can be further improved, thereby improving the cell characteristics of the all-solid-state battery. On the other hand, when the content of the polymer in the slurry composition is 10 parts by mass or less per 100 parts by mass of solid electrolyte, the ionic conductivity of the solid electrolyte-containing layer can be sufficiently ensured, and the cell characteristics of the all-solid-state secondary battery will not be excessively impaired.

[0067] <Electrode active material> The electrode active material is a material that transfers electrons at the electrode of the all-solid-state secondary battery. For example, when the all-solid-state secondary battery is an all-solid-state lithium ion secondary battery, the electrode active material is usually a material that can absorb and release lithium. In the following, a case where the slurry composition for an all-solid-state secondary battery is a slurry composition for an all-solid-state lithium-ion secondary battery will be described as an example, but the present invention is not limited to the following example.

[0068] The positive electrode active material for the all-solid-state lithium ion secondary battery is not particularly limited, and examples thereof include a positive electrode active material made of an inorganic compound and a positive electrode active material made of an organic compound. The positive electrode active material may be a mixture of an inorganic compound and an organic compound. Examples of inorganic cathode active materials include transition metal oxides, composite oxides of lithium and transition metals (lithium-containing composite metal oxides), and transition metal sulfides. Examples of the transition metals include Fe, Co, Ni, and Mn. Specific examples of inorganic compounds used in cathode active materials include lithium-containing composite metal oxides such as LiCoO2 (lithium cobalt oxide), LiNiO2, LiMnO2, LiMn2O4, LiFePO4, and LiFeVO4; transition metal sulfides such as TiS2, TiS3, and amorphous MoS2; Cu2VO3, amorphous VO-PO5, MoO3, VO5, and VO. 13 These compounds may be partially substituted with elements. The positive electrode active materials made of the inorganic compounds described above can be used alone or in combination of two or more. Examples of the positive electrode active material made of an organic compound include polyaniline, polypyrrole, polyacene, disulfide-based compounds, polysulfide-based compounds, and N-fluoropyridinium salts. The positive electrode active materials made of the organic compounds described above can be used alone or in combination of two or more.

[0069] Examples of negative electrode active materials for all-solid-state lithium-ion secondary batteries include carbon allotropes such as graphite and coke. Negative electrode active materials made of carbon allotropes can also be used in the form of mixtures or coatings with metals, metal salts, oxides, etc. Other examples of negative electrode active materials that can be used include oxides or sulfates of silicon, tin, zinc, manganese, iron, nickel, etc.; metallic lithium; lithium alloys such as Li-Al, Li-Bi-Cd, and Li-Sn-Cd; lithium transition metal nitrides; and silicone. The above-mentioned negative electrode active materials can be used alone or in combination of two or more.

[0070] The particle size of the electrode active material (positive electrode active material, negative electrode active material) is not particularly limited and may be the same as that of a conventionally used electrode active material. The amount of the electrode active material in the slurry composition is not particularly limited and may be the same as that of a conventionally used electrode active material.

[0071] <Preparation of Slurry Composition> The above-mentioned slurry composition for an all-solid-state secondary battery is not particularly limited, and can be obtained, for example, by mixing the above-mentioned components using any mixing method.

[0072] (Solid electrolyte containing layer) The solid electrolyte-containing layer of the present invention is a layer containing a solid electrolyte, and examples of the solid electrolyte-containing layer include an electrode mixture layer (positive electrode mixture layer, negative electrode mixture layer) that transfers electrons via an electrochemical reaction, and a solid electrolyte layer provided between a positive electrode mixture layer and a negative electrode mixture layer that face each other. The solid electrolyte-containing layer of the present invention is formed using the above-mentioned slurry composition for an all-solid-state secondary battery. For example, it can be formed by applying the above-mentioned slurry composition to the surface of a suitable substrate to form a coating film, and then drying the formed coating film. That is, the solid electrolyte-containing layer of the present invention is made of a dried product of the above-mentioned slurry composition, and typically contains a solid electrolyte, a polymer, and an ion of a metal belonging to Group 1 or Group 2 of the periodic table (and / or an ion-bonding compound consisting of an ion (cation) of the metal and an anion) and may optionally further contain at least one selected from the group consisting of an electrode active material and other components. Note that the components contained in the solid electrolyte-containing layer are those contained in the above-mentioned slurry composition, and the content ratio of these components is typically the same as the content ratio in the above-mentioned slurry composition.

[0073] Furthermore, the solid electrolyte-containing layer of the present invention is formed from the slurry composition for an all-solid-state secondary battery of the present invention, and therefore can exhibit excellent ion conductivity.

[0074] <Base material> Here, there is no limitation on the substrate to which the slurry composition is applied, and for example, a coating film of the slurry composition may be formed on the surface of a release substrate, the coating film may be dried to form a solid electrolyte-containing layer, and the release substrate may be peeled off from the solid electrolyte-containing layer. In this way, the solid electrolyte-containing layer peeled off from the release substrate may be used as a free-standing film to form battery components (e.g., electrodes, solid electrolyte layers, etc.) of an all-solid-state secondary battery. However, from the viewpoint of omitting the step of peeling off the solid electrolyte-containing layer and improving the manufacturing efficiency of the battery component, it is preferable to use a current collector or an electrode as the substrate. Specifically, when preparing the electrode mixture layer, it is preferable to apply the slurry composition onto a current collector as the substrate. Furthermore, when preparing the solid electrolyte layer, it is preferable to apply the slurry composition onto an electrode (positive electrode or negative electrode).

[0075] <<Current collector>> As the current collector, a material that is electrically conductive and electrochemically durable is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. can be used. Among them, copper foil is particularly preferred as the current collector used for the negative electrode. Furthermore, aluminum foil is particularly preferred as the current collector used for the positive electrode. Note that the above materials may be used alone or in combination of two or more types in any ratio.

[0076] <<Electrode>> The electrodes (positive and negative electrodes) are not particularly limited, but examples thereof include electrodes in which an electrode mixture layer containing an electrode active material, a solid electrolyte, and a binder is formed on the above-mentioned current collector. The electrode active material, solid electrolyte, and binder contained in the electrode mixture layer in the electrode are not particularly limited, and known materials can be used. The electrode mixture layer in the electrode may correspond to the solid electrolyte-containing layer of the present invention.

[0077] <Method for forming a solid electrolyte-containing layer> The following methods can be used to form a solid electrolyte-containing layer on a substrate such as the current collector or electrode. 1) A method in which the slurry composition of the present invention is applied to the surface of a substrate (in the case of an electrode, the surface on the electrode mixture layer side; the same applies hereinafter) and then dried; 2) a method of immersing a substrate in the slurry composition of the present invention and then drying the same; and 3) A method in which the slurry composition of the present invention is applied to a release substrate, dried to produce a solid electrolyte-containing layer, and the obtained solid electrolyte-containing layer is transferred to the surface of an electrode or the like. Among these, the method 1) is particularly preferred because it allows for easy control of the thickness of the solid electrolyte-containing layer. Specifically, the method 1) includes a step of applying a slurry composition onto a substrate (application step) and a step of drying the slurry composition applied onto the substrate to form a solid electrolyte-containing layer (solid electrolyte-containing layer formation step).

[0078] <<Coating process>> In the coating step, the method for coating the slurry composition onto the substrate is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.

[0079] <<Solid electrolyte-containing layer formation process>> In the solid electrolyte-containing layer forming step, the method for drying the slurry composition on the substrate is not particularly limited and any known method can be used. Examples of the drying method include drying with warm air, hot air, or low-humidity air, vacuum drying, and drying with irradiation of infrared rays or electron beams. When the solid electrolyte-containing layer is an electrode mixture layer, it is preferable to perform a pressing treatment using a roll press or the like after drying. By performing the pressing treatment, the resulting electrode mixture layer can be further densified.

[0080] (electrode) An electrode obtained by forming an electrode mixture layer on a current collector using the slurry composition for an all-solid-state secondary battery of the present invention comprises an electrode mixture layer that contains a solid electrolyte, a polymer, and an ion of a metal belonging to Group 1 or Group 2 of the periodic table (and / or an ion-bonding compound composed of an ion (cation) of the metal and an anion), and may optionally further contain at least one selected from the group consisting of an electrode active material and other components, and can exhibit excellent ionic conductivity.

[0081] (solid electrolyte layer) Furthermore, the solid electrolyte layer formed using the slurry composition for an all-solid-state secondary battery of the present invention contains a solid electrolyte, a polymer, and an ion of a metal belonging to Group 1 or Group 2 of the periodic table (and / or an ion-bonding compound consisting of an ion (cation) of the metal and an anion), and optionally further contains other components, and can exhibit excellent ion conductivity.

[0082] (All-solid-state secondary battery) The all-solid-state secondary battery of the present invention includes the above-described solid electrolyte-containing layer of the present invention. Here, the all-solid-state secondary battery of the present invention has, for example, a positive electrode, a solid electrolyte layer, and a negative electrode, and at least one of the positive electrode composite layer of the positive electrode, the negative electrode composite layer of the negative electrode, and the solid electrolyte layer is the solid electrolyte-containing layer of the present invention. That is, the all-solid-state secondary battery of the present invention includes at least one of a positive electrode including a positive electrode composite layer formed using a slurry composition for an all-solid-state secondary battery positive electrode as a slurry composition for an all-solid-state secondary battery of the present invention, a negative electrode including a negative electrode composite layer formed using a slurry composition for an all-solid-state secondary battery negative electrode as a slurry composition for an all-solid-state secondary battery of the present invention, and a solid electrolyte layer formed using a slurry composition for an all-solid-state secondary battery electrolyte layer as a slurry composition for an all-solid-state secondary battery of the present invention. Furthermore, the all-solid-state secondary battery of the present invention is provided with the solid electrolyte-containing layer of the present invention, and therefore has excellent cell characteristics such as output characteristics and cycle characteristics.

[0083] Here, the all-solid-state secondary battery electrode that can be used in the all-solid-state secondary battery of the present invention and that has an electrode mixture layer that does not correspond to the solid electrolyte-containing layer of the present invention is not particularly limited as long as it has an electrode mixture layer that does not correspond to the solid electrolyte-containing layer of the present invention, and any all-solid-state secondary battery electrode can be used.

[0084] Furthermore, the solid electrolyte layer that can be used in the all-solid-state secondary battery of the present invention and does not fall under the category of the solid electrolyte-containing layer of the present invention is not particularly limited, and any solid electrolyte layer can be used, for example, the solid electrolyte layers described in JP-A-2012-243476, JP-A-2013-143299, JP-A-2016-143614, and the like.

[0085] The all-solid-state secondary battery of the present invention can be obtained by stacking a positive electrode and a negative electrode so that the positive electrode composite layer of the positive electrode and the negative electrode composite layer of the negative electrode face each other via a solid electrolyte layer, optionally applying pressure to obtain a laminate, and then placing the laminate in a battery container as is, or after rolling or folding, depending on the battery shape, and sealing it. If necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, etc. can be placed in the battery container to prevent pressure buildup inside the battery and overcharging and discharging. The battery shape may be any shape, such as a coin type, button type, sheet type, cylindrical type, prismatic type, or flat type. [Example]

[0086] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. In the examples and comparative examples, the composition of the polymer and the amount of insoluble matter in the solvent, the content of metal components (group 1 to 2 metal ions and other metal components) in the binder composition, the dispersibility and storage stability of the slurry composition, the adhesiveness of the positive electrode mixture layer, the ionic conductivity of the solid electrolyte layer, and the output characteristics of the all-solid-state secondary battery were measured or evaluated by the following methods.

[0087] <Composition> 100 g of the binder composition containing the polymer was solidified with 1 L of methanol, and then vacuum dried at a temperature of 60° C. for 12 hours. 1 The polymer was analyzed by H-NMR. Based on the analytical values ​​obtained, the content (mass %) of each monomer unit and structural unit contained in the polymer was calculated. <Amount of insoluble matter in solvent> The aqueous dispersion of the polymer was dried under an environment of 50% humidity and 23 to 25°C to prepare a film with a thickness of 3±0.3 mm. The prepared film was then cut into 5 mm squares to prepare film pieces. Approximately 1 g of these film pieces was precisely weighed, and the weight of the precisely weighed film piece was designated as W0. The precisely weighed film piece was then immersed in 100 g of a binder composition solvent (temperature: 25°C) for 24 hours. After immersion for 24 hours, the film piece was removed from the solvent and vacuum-dried at 105°C for 3 hours, and its weight (weight of the insoluble content) W1 was precisely weighed. The amount of insoluble content in the solvent (%) was then calculated according to the following formula: Amount insoluble in solvent (%) = W1 / W0 x 100 <Metal component content> Approximately 1 g of the binder composition was heated in an electric furnace at 550°C for approximately 3 hours and incinerated. Approximately 5 mL of concentrated sulfuric acid was then added to the incinerated binder composition to dissolve it, and approximately 5 mL of concentrated nitric acid was gradually added to perform wet decomposition. After decomposition, the acid was concentrated and the volume was adjusted to 10 mL with ultrapure water. The metal ion concentration in the binder composition was measured using an ICP-AES device (manufactured by SII Nano Technology, model number "SPS-5100"). Based on the obtained metal ion concentration value, the content of metal ions from Groups 1 and 2 in the polymer, as well as the content of palladium, ruthenium, and rhodium, were calculated. <Dispersibility> The viscosity of the slurry composition for the solid electrolyte layer was measured using a Brookfield B-type viscometer at 60 rpm (25°C) and evaluated according to the following criteria: The lower the viscosity of the slurry composition, the better the dispersion of the solid electrolyte contained in the slurry composition. A: Viscosity less than 4000 mPa·s B: Viscosity is 4000 mPa·s or more but less than 5500 mPa·s C: Viscosity is 5500 mPa·s or more but less than 8000 mPa·s D: Viscosity is 8000 mPa·s or more or the material does not disperse (no fluidity) <Storage stability> A portion of each of the slurry compositions (slurry composition for solid electrolyte layer and slurry composition for positive electrode composite layer) was sampled immediately after preparation. The sampled slurry composition was dried on a hot plate at 130°C for 1 hour to remove the solvent, and the initial solid content of the slurry composition was measured. The slurry composition was then stored in a sealed state at 25°C. The upper part of the stored slurry composition was sampled every day (24 hours) until 6 days had passed, and the solid content concentration was measured in the same manner as above. The number of days of storage at which the solid content concentration decreased by 1.0% or more from the initial solid content concentration was recorded and evaluated according to the following criteria. The longer the number of days, the more difficult it is for the solid content in the slurry composition to settle, indicating that the slurry composition has excellent storage stability. A: Even after 6 days of storage, no decrease in solid content was observed. B: A decrease in solid concentration was confirmed after 4 or 5 days of storage. C: A decrease in solid concentration was confirmed after 2 or 3 days of storage. D: A decrease in solid concentration was confirmed after one day of storage. <Adhesiveness> The positive electrode was cut into a rectangle measuring 1.0 cm wide x 10 cm long to prepare a test specimen. Cellophane tape (as specified in JIS Z1522) was attached to the surface of the positive electrode composite layer of this test specimen, and the stress was measured when the cellophane tape was peeled off from one end of the specimen in a 180° direction at a rate of 50 mm / min. The measurement was performed three times, and the average value was calculated as the peel strength (N / m) and evaluated according to the following criteria. A higher peel strength indicates better adhesion of the positive electrode composite layer and stronger adhesion to the current collector. A+: Peel strength is 4N / m or more A: Peel strength is 3N / m or more and less than 4N / m B: Peel strength is 2N / m or more and less than 3N / m C: Peel strength is 1N / m or more and less than 2N / m D: Peel strength is less than 1N / m <Ionic conductivity> First, the solid electrolyte layer slurry composition was dried on a hot plate at 130°C in a glove box (water content 1 ppm or less), and the resulting powder was formed into a cylindrical shape with a diameter of 10 mm and a thickness of 1 mm to prepare a measurement sample. The lithium ion conductivity (25°C) of this measurement sample was measured using an AC impedance method. The measurement was performed using a frequency response analyzer (manufactured by Solartron Analytical, product name "Solatron (registered trademark) 1260") under the measurement conditions of an applied voltage of 10 mV and a measurement frequency range of 0.01 MHz to 1 MHz. The obtained lithium ion conductivity was designated as S0. Separately, the slurry composition was dried on a hot plate at 130°C in a dry room (water content 127 ppm or less, equivalent to a dew point of -40°C), and the resulting powder was formed into a cylindrical shape with a diameter of 10 mm and a thickness of 0.5 mm to prepare a measurement sample. The lithium ion conductivity (25°C) of this measurement sample was measured in the same manner as in S0 above. The obtained lithium ion conductivity was designated S1. The conductivity retention rate (S1 / S0×100%) was then calculated and evaluated according to the following criteria: The greater the conductivity retention rate, the more the solid electrolyte is inhibited from deteriorating due to moisture, and the greater the ability of the solid electrolyte layer prepared using the slurry composition to exhibit excellent ionic conductivity. A: Conductivity retention rate is 90% or more B: Conductivity retention rate is 80% or more but less than 90% C: Conductivity retention rate is 50% or more but less than 80% D: Conductivity retention rate is 30% or more but less than 50% E: Conductivity retention rate is less than 30% <Output characteristics> Three all-solid-state secondary batteries were charged to 4.2 V at a constant current of 0.1 C and then discharged to 3.0 V at 0.1 C to determine the 0.1 C discharge capacity. They were then charged to 4.2 V at 0.1 C and then discharged to 3.0 V at 2 C to determine the 2 C discharge capacity. The average of the 0.1 C discharge capacities of the three cells was designated as discharge capacity a, and the average of the 2 C discharge capacities of the three cells was designated as discharge capacity b. The ratio of discharge capacity b to discharge capacity a (capacity ratio) = discharge capacity b / discharge capacity a × 100 (%) was calculated and evaluated according to the following criteria. A higher capacity ratio indicates better output characteristics for the all-solid-state secondary battery. A+: Capacity ratio is 85% or more A: Capacity ratio is 80% or more but less than 85% B: Capacity ratio is 70% or more but less than 80% C: Capacity ratio is 60% or more but less than 70% D: Capacity ratio is less than 60%

[0088] Example 1 <Preparation of Binder Composition> A 1 L flask equipped with a stirrer and a septum was charged with 100 parts of ion-exchanged water and 0.2 parts of sodium lauryl sulfate as an emulsifier, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. After that, 0.25 parts of ammonium persulfate as a polymerization initiator was dissolved in 20.0 parts of ion-exchanged water and added. Separately, a monomer composition was obtained by mixing 40 parts of ion-exchanged water, 1.0 part of sodium lauryl sulfate as an emulsifier, and 6 parts of acrylonitrile, 69 parts of butyl acrylate, and 25 parts of styrene as monomers in a separate container. This monomer composition was continuously added to the 1-L flask equipped with a septum over a period of 3 hours to carry out polymerization. The reaction was carried out at 60°C during the addition. After the addition was completed, the reaction was terminated by stirring at 80°C for an additional 3 hours. The amount of the polymer insoluble in diisobutyl ketone (solvent) was measured using the resulting aqueous dispersion of the polymer, and the polymer was determined to be either readily soluble or sparingly soluble in diisobutyl ketone. The results are shown in Table 1. Next, an appropriate amount of sodium hydroxide was added to the obtained aqueous dispersion of the polymer, and then an appropriate amount of diisobutyl ketone was added as a solvent to obtain a mixture. After that, water and excess diisobutyl ketone were removed from the mixture by vacuum distillation at 80°C, obtaining a binder composition (solid content: 8%). The obtained binder composition was used to measure the polymer composition. Furthermore, the content of metal components in the binder composition was measured. The results are shown in Table 1. <Preparation of Slurry Composition for Positive Electrode Composite Layer> 70 parts of lithium cobalt oxide (number average particle diameter: 11.5 μm) as the positive electrode active material, 25.5 parts of sulfide glass composed of Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) as the solid electrolyte, 2.5 parts of acetylene black as the conductive material, and 2 parts (solid content equivalent) of the binder composition obtained above were mixed, and diisobutyl ketone was added as a solvent to adjust the solid content to 80% and then mixed with a planetary mixer for 60 minutes. Subsequently, diisobutyl ketone was further added to adjust the solid content to 70% and then mixed for 10 minutes to prepare a slurry composition for the positive electrode composite layer. The storage stability of the resulting slurry composition for the positive electrode composite layer was evaluated. The results are shown in Table 1. <Preparation of Slurry Composition for Solid Electrolyte Layer> 100 parts of sulfide glass (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) composed of Li2S and P2S5 as a solid electrolyte was mixed with 2 parts (solid content equivalent) of the binder composition obtained above. Diisobutyl ketone was added to the resulting mixture to prepare a composition with a solid content of 80%. This composition was mixed at 2000 rpm for 2 minutes using a planetary centrifugal mixer (product name: Awatori Rentaro (registered trademark) ARE310; the same applies hereinafter). Diisobutyl ketone was added to the resulting mixture to prepare a composition with a solid content of 70%. This composition was mixed at 2000 rpm for 2 minutes using a planetary centrifugal mixer. Diisobutyl ketone was added to the resulting mixture to prepare a composition with a solid content of 65%. This composition was mixed at 2000 rpm for 2 minutes using a planetary centrifugal mixer. Diisobutyl ketone was added to the resulting mixture to prepare a composition with a solids concentration of 60%. This composition was mixed using a planetary centrifugal mixer at 2000 rpm for 2 minutes. Diisobutyl ketone was added to the resulting mixture to prepare a composition with a solids concentration of 55%. This composition was mixed using a planetary centrifugal mixer at 2000 rpm for 2 minutes. Diisobutyl ketone was added to the resulting mixture to prepare a composition with a solids concentration of 50%. This composition was mixed using a planetary centrifugal mixer at 2000 rpm for 2 minutes to prepare a slurry composition for a solid electrolyte layer. The dispersibility and storage stability of the resulting slurry composition for a solid electrolyte layer were evaluated. The ionic conductivity of the solid electrolyte layer was also evaluated using the resulting slurry composition for a solid electrolyte layer. All results are shown in Table 1. <Preparation of positive electrode> The positive electrode composite layer slurry composition was applied to the surface of a current collector (aluminum foil, thickness: 20 μm) and dried (120°C, 60 minutes) to form a positive electrode composite layer with a thickness of 50 μm, thereby obtaining a positive electrode. Using this positive electrode, the adhesiveness of the positive electrode composite layer was evaluated. The results are shown in Table 1. <Manufacturing of all-solid-state secondary batteries> 65 parts of graphite (number average particle diameter: 20 μm) as the negative electrode active material, 31.5 parts of sulfide glass composed of Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) as solid electrolyte particles, 1.5 parts of acetylene black as a conductive material, and 2 parts (solid content equivalent) of the binder composition obtained as described above were mixed, and diisobutyl ketone was added as a solvent to adjust the solid content to 65% and then mixed in a planetary mixer for 60 minutes. Subsequently, diisobutyl ketone was further added to adjust the solid content to 60% and then mixed in a planetary mixer to prepare a slurry composition for the negative electrode composite layer. The slurry composition for the negative electrode composite layer was then applied to the surface of a current collector (copper foil, thickness: 15 μm) and dried (120 ° C, 60 minutes) to form a negative electrode composite layer with a thickness of 60 μm, thereby obtaining a negative electrode. Next, the slurry composition for the solid electrolyte layer was applied to the surface of the positive electrode composite layer of the positive electrode and dried (120°C, 60 minutes) to form a solid electrolyte layer with a thickness of 150 μm, thereby obtaining a positive electrode with a solid electrolyte layer. The positive electrode with the solid electrolyte layer and the negative electrode were bonded together so that the solid electrolyte layer of the positive electrode with the solid electrolyte layer was in contact with the negative electrode composite layer of the negative electrode, and then pressed to obtain an all-solid-state secondary battery. The thickness of the solid electrolyte layer of the all-solid-state secondary battery after pressing was 100 μm. The output characteristics of this all-solid-state secondary battery were evaluated. The results are shown in Table 1.

[0089] Example 2 Except for using the binder composition prepared as follows, a slurry composition for a positive electrode composite layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. <Preparation of Binder Composition> A 1 L flask equipped with a stirrer and a septum was charged with 100 parts of ion-exchanged water and 0.2 parts of sodium lauryl sulfate as an emulsifier, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. After that, 0.25 parts of ammonium persulfate as a polymerization initiator was dissolved in 20.0 parts of ion-exchanged water and added. Separately, in a separate container, 40 parts of ion-exchanged water, 1.0 part of sodium lauryl sulfate as an emulsifier, and 7 parts of acrylonitrile, 50 parts of butyl acrylate, 23 parts of ethyl acrylate, and 20 parts of phenoxyethyl acrylate were mixed to obtain a monomer composition. This monomer composition was continuously added to the septum-equipped 1-L flask over a period of 3 hours to allow polymerization. The reaction was carried out at 60°C during the addition. After the addition was completed, the mixture was stirred at 80°C for an additional 3 hours to terminate the reaction. The amount of the polymer insoluble in diisobutyl ketone (solvent) was measured using the resulting aqueous dispersion of the polymer, and the polymer was determined to be either readily soluble or sparingly soluble in diisobutyl ketone. The results are shown in Table 1. Next, an appropriate amount of sodium hydroxide was added to the obtained aqueous dispersion of the polymer, and then an appropriate amount of diisobutyl ketone was added as a solvent to obtain a mixture. After that, water and excess diisobutyl ketone were removed from the mixture by vacuum distillation at 80°C, obtaining a binder composition (solid content: 8%). The obtained binder composition was used to measure the polymer composition. Furthermore, the content of metal components in the binder composition was measured. The results are shown in Table 1.

[0090] (Examples 3 and 4) In preparing the binder composition and the slurry composition, xylene (Example 3) and butyl butyrate (Example 4) were used as the solvent instead of diisobutyl ketone, respectively. Except for this, the binder composition, the slurry composition for the positive electrode composite layer, the slurry composition for the solid electrolyte layer, the positive electrode, and the all-solid-state secondary battery were prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0091] Example 5 Except for increasing the amount of sodium hydroxide added to the aqueous dispersion of the polymer when preparing the binder composition, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0092] Example 6 In preparing the binder composition, polyoxyethylene lauryl ether was used instead of sodium lauryl sulfate as the emulsifier, and the amount of sodium hydroxide added to the aqueous dispersion of the polymer was reduced. Except for this, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0093] (Examples 7 and 8) In preparing the binder composition, 7 parts of acrylonitrile, 50 parts of butyl acrylate, 23 parts of ethyl acrylate, and 20 parts of phenoxyethyl acrylate were used as monomers, and lithium hydroxide (Example 7) and magnesium hydroxide (Example 8) were added in appropriate amounts to the aqueous dispersion of the polymer instead of sodium hydroxide. Except for this, a binder composition, a slurry composition for a positive electrode composite layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared in the same manner as in Example 6, and various evaluations were performed. The results are shown in Table 1.

[0094] Example 9 In preparing the binder composition, except that 32 parts of acrylonitrile, 58 parts of butyl acrylate, and 10 parts of styrene were used as monomers, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0095] Example 10 In preparing the binder composition, except that 2 parts of acrylonitrile, 80 parts of butyl acrylate, and 18 parts of styrene were used as monomers, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0096] Example 11 In preparing the binder composition, except that 6 parts of acrylonitrile, 88 parts of butyl acrylate, and 6 parts of styrene were used as monomers, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0097] Example 12 In preparing the binder composition, except that 35 parts of acrylonitrile, 25 parts of butyl acrylate, and 40 parts of styrene were used as monomers, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0098] Example 13 In preparing the binder composition, except that 15 parts of acrylonitrile, 80 parts of butyl acrylate, and 5 parts of styrene were used as monomers, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0099] Example 14 In preparing the binder composition, except that 6 parts of acrylonitrile, 54 parts of butyl acrylate, and 40 parts of styrene were used as monomers, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0100] Example 15 Except for using the binder composition prepared as follows, a slurry composition for a positive electrode composite layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2. <Preparation of Binder Composition> A reactor was charged with 2 parts of potassium oleate as an emulsifier, 0.1 part of potassium phosphate as a stabilizer, and 150 parts of water, and further charged with 20 parts of acrylonitrile, 43 parts of 1,3-butadiene, 33 parts of butyl acrylate, and 14 parts of styrene as monomers, and 0.31 parts of t-dodecyl mercaptan as a molecular weight modifier. Emulsion polymerization was initiated at 10° C. in the presence of 0.015 parts of ferrous sulfate as an activator and 0.05 parts of paramenthane hydroperoxide as a polymerization initiator. When the polymerization conversion rate reached 85%, 0.2 parts of hydroxylamine sulfate per 100 parts of monomer was added to terminate the polymerization. Following termination of the polymerization, the mixture was heated and subjected to steam distillation under reduced pressure at 70°C to recover unreacted monomers, and then 2 parts of alkylated phenol was added as an antioxidant to obtain a copolymer latex. 400 mL of the resulting copolymer latex (total solids: 48 g) was placed in a 1-liter autoclave equipped with a stirrer, and nitrogen gas was passed through for 10 minutes to remove dissolved oxygen from the copolymer solution. Subsequently, 50 mg of palladium acetate was dissolved in 180 mL of water containing 4 times the molar amount of nitric acid relative to Pd as a hydrogenation catalyst and added. After the system was purged with hydrogen gas twice, the contents of the autoclave were heated to 50°C while pressurized with hydrogen gas to 3 MPa, and the hydrogenation reaction was carried out for 6 hours. The contents were returned to room temperature, and the system was emptied into a nitrogen atmosphere. The mixture was then concentrated using an evaporator to a solids concentration of 40% to obtain an aqueous dispersion of a polymer (hydrogenated nitrile rubber). The amount of insoluble matter in diisobutyl ketone (solvent) was measured using the resulting aqueous dispersion of the polymer, and the polymer was determined to be either readily soluble or sparingly soluble in diisobutyl ketone. The results are shown in Table 2. Next, an appropriate amount of potassium hydroxide was added to the obtained aqueous dispersion of the polymer, and then an appropriate amount of diisobutyl ketone was added as a solvent to obtain a mixture. After that, water and excess diisobutyl ketone were removed from the mixture by vacuum distillation at 80°C, obtaining a binder composition (solid content: 8%). The obtained binder composition was used to measure the polymer composition. Furthermore, the content of metal components in the binder composition was measured. The results are shown in Table 2.

[0101] Example 16 Except for using the binder composition prepared as follows, a slurry composition for a positive electrode composite layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2. <Preparation of Binder Composition> <<Preparation of First Binder Composition Comprising First Polymer>> A first binder composition containing a first polymer was prepared in the same manner as the binder composition of Example 1, except that 7 parts of acrylonitrile, 50 parts of butyl acrylate, 23 parts of ethyl acrylate, and 20 parts of phenoxyethyl acrylate were used as monomers. Furthermore, in the same manner as in Example 1, the first polymer was determined to be either readily soluble or sparingly soluble, the composition of the first polymer was identified, and the content of the metal component in the binder composition was measured. The results are shown in Table 2. <<Preparation of Second Binder Composition Containing Second Polymer>> A second binder composition containing a second polymer was prepared in the same manner as the binder composition of Example 1, except that 10 parts of acrylonitrile, 69.5 parts of butyl acrylate, 20 parts of styrene, and 0.5 parts of allyl methacrylate were used as monomers. Furthermore, in the same manner as in Example 1, the second polymer was determined to be either readily soluble or sparingly soluble, the composition of the second polymer was identified, and the content of the metal component in the binder composition was measured. The results are shown in Table 2. <<Mixing of first binder composition and second binder composition>> The above-mentioned first binder composition and the above-mentioned second binder composition were mixed so that the solid content equivalent ratio of the first polymer to the second polymer was 1:1 (mass ratio) to prepare a binder composition.

[0102] Example 17 In preparing the binder composition, 7 parts of acrylonitrile, 50 parts of butyl acrylate, 23 parts of ethyl acrylate, and 20 parts of phenoxyethyl acrylate were used as monomers, and in preparing the slurry compositions (slurry composition for solid electrolyte layer, slurry composition for positive electrode composite layer), an oxide-based inorganic solid electrolyte (Li7La3Zr2O 12 Except for using a slurry composition for a positive electrode composite layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery (aluminum, number average particle diameter: 1.2 μm), a binder composition, a slurry composition for a positive electrode composite layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 2.

[0103] Example 18 A slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and evaluated in the same manner as in Example 1, except that a second binder composition containing a second polymer prepared in the same manner as in Example 16 was used as the binder composition. The results are shown in Table 2.

[0104] Example 19 Except for using the binder composition prepared as follows, a slurry composition for a positive electrode composite layer, a slurry composition for a solid electrolyte layer, a positive electrode, and an all-solid-state secondary battery were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 3. <Preparation of Binder Composition> A reactor was charged with 180 parts of ion-exchanged water, 25 parts of an aqueous solution of sodium dodecylbenzenesulfonate (10% concentration) as an emulsifier, 20 parts of acrylonitrile as a monomer, 25 parts of butyl acrylate, and 0.3 parts of t-dodecyl mercaptan as a molecular weight modifier, in this order. The gas inside the reactor was then purged with nitrogen three times, after which 55 parts of 1,3-butadiene as a monomer was charged. The reactor was maintained at 10°C, and 0.1 parts of cumene hydroperoxide and 0.1 parts of ferrous sulfate as polymerization initiators were charged to initiate the polymerization reaction, which was then allowed to proceed with stirring. When the polymerization conversion reached 90%, 0.2 parts of hydroxylamine sulfate per 100 parts of monomer was added to terminate the polymerization. Residual monomer was then removed under reduced pressure at a water temperature of 80°C, yielding a particulate aqueous dispersion of a polymer precursor (copolymer latex). 400 mL of the resulting copolymer latex (total solids: 48 g) was placed in a 1-liter autoclave equipped with a stirrer, and nitrogen gas was passed through for 10 minutes to remove dissolved oxygen from the copolymer latex. Subsequently, 50 mg of palladium acetate was dissolved in 180 mL of water containing 4 times the molar amount of nitric acid relative to Pd and added as a hydrogenation catalyst. After the system was purged with hydrogen gas twice, the contents of the autoclave were heated to 50°C while pressurized with hydrogen gas to 3 MPa, and the hydrogenation reaction was carried out for 6 hours. Furthermore, 50 g of the obtained polymer was placed in a cellulose dialysis tube with a pore size of 5 nm, which was then sealed. The tube was then immersed in a container containing ion-exchanged water and dialyzed for 48 hours while allowing the surrounding ion-exchanged water to flow through, thereby removing residual palladium. Next, appropriate amounts of sodium hydroxide, a ruthenium organic complex, and a rhodium organic complex were added to the resulting aqueous dispersion of the polymer, and an appropriate amount of diisobutyl ketone was further added as a solvent to obtain a mixture. Subsequently, water and excess diisobutyl ketone were removed from the mixture by vacuum distillation at 80°C to obtain a binder composition (solid content: 8%). The resulting binder composition was used to measure the polymer composition. The content of metal components in the binder composition was also measured. The results are shown in Table 3.

[0105] (Comparative Example 1) In preparing the binder composition, polyoxyethylene lauryl ether was used instead of sodium lauryl sulfate as the emulsifier, and sodium hydroxide was not added to the aqueous dispersion of the polymer. The binder composition, slurry composition for the positive electrode mixture layer, slurry composition for the solid electrolyte layer, and positive electrode were prepared in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 3. The binder composition did not contain any metal ions of Groups 1 and 2 (less than 5 ppm by mass relative to the polymer).

[0106] (Comparative Example 2) Except for further increasing the amount of sodium hydroxide added when preparing the binder composition, a binder composition, a slurry composition for a positive electrode mixture layer, a slurry composition for a solid electrolyte layer, and a positive electrode were prepared in the same manner as in Example 5, and various evaluations were performed. The results are shown in Table 3.

[0107] (Comparative Examples 3 to 5) In preparing the binder composition and the slurry composition, except that 4-heptane (Comparative Example 3), methyl isobutyl ketone (Comparative Example 4), or ethyl acetate (Comparative Example 5) was used as the solvent instead of diisobutyl ketone, the binder composition, the slurry composition for the positive electrode composite layer, the slurry composition for the solid electrolyte layer, and the positive electrode were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0108] In addition, in Tables 1 to 3 shown below, "Vinyl cyanide" refers to a vinyl cyanide monomer unit; "(Meth)acrylic acid ester (ring-free)" does not have an aromatic hydrocarbon ring. represents a (meth)acrylic acid ester monomer unit, "Aromatic" refers to an aromatic monomeric unit; "AN" indicates an acrylonitrile unit; "BA" indicates a butyl acrylate unit; "EA" indicates an ethyl acrylate unit; "ST" indicates a styrene unit; "PEA" indicates a phenoxyethyl acrylate unit, "H-BD" indicates a 1,3-butadiene hydride unit; "AMA" indicates an allyl methacrylate unit; "Easy" indicates easy solubility, "Nan" indicates poor solubility, "DIK" indicates diisobutyl ketone, "XY" indicates xylene, "HB" stands for butyl butyrate; "HE" indicates 4-heptanone; "MBK" indicates methyl isobutyl ketone, "EAc" indicates ethyl acetate, "Sulfide" refers to a sulfide-based solid electrolyte; "Oxide" refers to an oxide-based solid electrolyte; "Na" indicates sodium ions, "Li" indicates lithium ion, "Mg" indicates magnesium ions, "K" indicates potassium ion, "Pd" indicates palladium; "Ru" indicates ruthenium; "Rh" indicates rhodium, "Number of C" indicates the number of carbon atoms.

[0109] [Table 1]

[0110] [Table 2]

[0111] [Table 3]

[0112] Tables 1 to 3 show that the binder compositions of Examples 1 to 19 can be used to prepare slurry compositions with excellent dispersibility and storage stability, and can also form solid electrolyte layers with excellent ion conductivity. Furthermore, Examples 1 to 19 also show good adhesion of the positive electrode mixture layer, enabling the all-solid-state secondary batteries to exhibit excellent output characteristics. On the other hand, Table 3 shows that in Comparative Examples 1 and 2, which used binder compositions with a content of Group 1-2 metal ions outside the specified range, the dispersibility and storage stability of the slurry composition, the ionic conductivity of the solid electrolyte layer, the adhesiveness of the positive electrode mixture layer, and the output characteristics of the all-solid-state secondary battery were reduced. Furthermore, Table 3 shows that in Comparative Examples 3 to 5, which used binder compositions containing only an organic solvent having a carbon number of 7 or less as the solvent, the dispersibility and storage stability of the slurry composition, the ionic conductivity of the solid electrolyte layer, the adhesiveness of the positive electrode composite layer, and the output characteristics of the all-solid-state secondary battery were reduced. [Industrial Applicability]

[0113] According to the present invention, it is possible to prepare a slurry composition for an all-solid-state secondary battery having excellent dispersibility and storage stability, and to provide a binder composition for an all-solid-state secondary battery that can cause a solid electrolyte-containing layer to exhibit excellent ion conductivity. Furthermore, according to the present invention, it is possible to provide a slurry composition for an all-solid-state secondary battery that is excellent in dispersibility and storage stability and is capable of forming a solid electrolyte-containing layer that is excellent in ion conductivity. Furthermore, according to the present invention, it is possible to provide a solid electrolyte-containing layer having excellent ion conductivity, and an all-solid-state secondary battery including the solid electrolyte-containing layer.

Claims

1. A binder composition for an all-solid-state secondary battery, comprising: a polymer having at least one of a nitrogen-containing functional group and a carbonyl group; ions of a metal belonging to Group 1 or Group 2 of the periodic table; and a solvent, the polymer contains vinyl cyanide monomer units in a proportion of 2% by mass or more and 35% by mass or less, and contains (meth)acrylic acid ester monomer units having no aromatic hydrocarbon ring in a proportion of 25% by mass or more and 95% by mass or less, the solvent includes an organic solvent having 8 to 12 carbon atoms, The organic solvent having 8 to 12 carbon atoms has at least one selected from the group consisting of an aromatic hydrocarbon ring and a carbonyl group. the content of the metal ions is 5 ppm by mass or more and 3,000 ppm by mass or less relative to the polymer.

2. The binder composition for an all-solid-state secondary battery according to claim 1 , wherein the polymer contains aromatic monomer units in a proportion of 3% by mass or more and 40% by mass or less.

3. The binder composition for an all-solid-state secondary battery according to claim 2 , wherein the aromatic monomer unit includes a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring.

4. A slurry composition for an all-solid-state secondary battery, comprising a solid electrolyte and the binder composition for an all-solid-state secondary battery according to any one of claims 1 to 3.

5. 5. The slurry composition for an all-solid-state secondary battery according to claim 4, wherein the solid electrolyte comprises at least one of a sulfide-based inorganic solid electrolyte and an oxide-based inorganic solid electrolyte.

6. A solid electrolyte-containing layer formed using the slurry composition for an all-solid-state secondary battery according to claim 4 or 5.

7. An all-solid-state secondary battery comprising the solid electrolyte-containing layer according to claim 6.

Images