Binder composition for secondary battery, slurry composition for secondary battery, functional layer for secondary battery, and secondary battery

Abstract

The purpose of the present invention is to provide a binder composition that: makes it possible to prepare a slurry composition that has excellent storage stability; and can also give a functional layer excellent adhesion. This binder composition includes a polymer and a solvent. The polymer includes 5–45 mass% of (meth)acrylate ester monomer units that have an aromatic hydrocarbon ring and 50–90 mass% of structural units that are represented by formula (I). In formula (I), R1 represents a hydrocarbon group that has at least 4 carbon atoms and does not have an aromatic hydrocarbon ring, and R2 represents a hydrogen atom, a methyl group, or -CH2-C(=O)-O-R1. When there are multiple R1s, the multiple R1s may be the same or different.

Description

[Technical Field]

[0001] The present invention relates to a binder composition for a secondary battery, a slurry composition for a secondary battery, a functional layer for a secondary battery, and a secondary battery. [Background technology]

[0002] Secondary batteries, such as nonaqueous electrolyte secondary batteries using an organic solvent electrolyte (hereinafter sometimes abbreviated as "nonaqueous secondary batteries") and all-solid-state secondary batteries using a solid electrolyte instead of an organic solvent electrolyte, are small, lightweight, have high energy density, and can be repeatedly charged and discharged, and are therefore used in a wide range of applications. Therefore, in recent years, improvements to battery components such as electrodes have been studied in order to further improve the performance of secondary batteries.

[0003] Here, when producing battery components for secondary batteries, a binder composition for secondary batteries containing a polymer as a binder and a solvent is used. Specifically, the binder composition is mixed with, for example, particles (hereinafter referred to as "functional particles") that are formulated to provide the battery component with a desired function, to prepare a slurry composition for secondary batteries. Next, the solvent is removed from the slurry composition for secondary batteries to form a functional layer for secondary batteries (such as an electrode mixture layer or a solid electrolyte layer), and this functional layer for secondary batteries can be used as a battery component or a part thereof.

[0004] In order to improve the performance of secondary batteries, improvements have been made to binders used in the production of battery components (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-88486 [Patent Document 2] International Publication No. 2016 / 136090 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the binder compositions containing the conventional binders described above have room for improvement in terms of ensuring sufficient storage stability of the slurry composition while also providing excellent adhesiveness to the functional layer.

[0007] Therefore, an object of the present invention is to provide a binder composition for a secondary battery that can prepare a slurry composition for a secondary battery having excellent storage stability and can also provide excellent adhesion to a functional layer for a secondary battery. Another object of the present invention is to provide a slurry composition for a secondary battery that is excellent in storage stability and adhesiveness and that can form a functional layer for a secondary battery. Another object of the present invention is to provide a functional layer for a secondary battery having excellent adhesiveness, and a secondary battery including the functional layer for a secondary battery. [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 polymer having a predetermined composition as a binder contained in a binder composition for a secondary battery, it is possible to ensure sufficient storage stability of the slurry composition while also allowing the functional layer to exhibit excellent adhesiveness, thereby completing the present invention.

[0009] That is, an object of the present invention is to advantageously solve the above-mentioned problems, and the binder composition for a secondary battery of the present invention is a binder composition for a secondary battery containing a polymer and a solvent, wherein the polymer contains a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring in a proportion of 5% by mass or more and 45% by mass or less, and the polymer is represented by the following formula (I): [ka] [In formula (I), R 1 represents a hydrocarbon group having 4 or more carbon atoms and not having an aromatic hydrocarbon ring, and R 2is a hydrogen atom, a methyl group, or -CH2-C(=O)-OR 1 In addition, in formula (I), R 1 If there are multiple R 1 may be the same or different. The binder composition is characterized by containing 50% by mass or more and 90% by mass or less of structural units represented by the following formula (I): (wherein the structural units (I) are the same or different). By using a binder composition containing a polymer containing a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring and a structural unit represented by the above formula (I) (hereinafter, sometimes referred to as structural unit (I)) in the above-mentioned proportions, respectively, and a solvent, a slurry composition having excellent storage stability can be prepared, and a functional layer having excellent adhesiveness can be formed from the slurry composition for secondary batteries. 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 % and mol %) of the "structural unit" (including the "monomer unit") in the polymer is expressed as follows: 1 This can be measured using a nuclear magnetic resonance (NMR) method such as H-NMR. In the present invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0010] Here, in the binder composition for secondary batteries of the present invention, the molar ratio of the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring to the structural unit represented by formula (I) in the polymer is preferably 0.08 to 0.80. If the molar ratio of the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring to the structural unit (I) (content ratio (mol%) of the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring / content ratio (mol%) of the structural unit (I)) is within the above-mentioned range, the storage stability of the slurry composition can be further improved.

[0011] In the binder composition for a secondary battery of the present invention, the polymer preferably further contains at least one selected from the group consisting of a vinyl cyanide monomer unit, a diene monomer unit, and an aromatic vinyl monomer unit. If the polymer contains at least one of the above-mentioned monomer units, the adhesiveness of the functional layer and the storage stability of the slurry composition can be further improved.

[0012] The present invention also aims to advantageously solve the above-mentioned problems, and provides a slurry composition for a secondary battery, which is characterized by containing functional particles and any of the binder compositions for a secondary battery described above. A slurry composition containing functional particles and any of the binder compositions described above has excellent storage stability, and the use of the slurry composition for a secondary battery allows the formation of a functional layer with excellent adhesiveness. In the slurry composition for a secondary battery of the present invention, the functional particles are, for example, at least one selected from the group consisting of electrode active material particles, solid electrolyte particles, and conductive material particles.

[0013] The present invention also aims to advantageously solve the above-mentioned problems, and provides a functional layer for a secondary battery of the present invention, which is formed using any of the above-mentioned slurry compositions for a secondary battery. The functional layer formed using any of the above-mentioned slurry compositions has excellent adhesiveness.

[0014] The present invention aims to advantageously solve the above-mentioned problems, and provides a secondary battery comprising the functional layer for a secondary battery described above. The secondary battery comprising the functional layer described above has excellent cell characteristics such as output characteristics and cycle characteristics. [Effects of the Invention]

[0015] According to the present invention, it is possible to prepare a slurry composition for a secondary battery having excellent storage stability, and to provide a binder composition for a secondary battery that can exert excellent adhesion to a functional layer for a secondary battery. Furthermore, according to the present invention, it is possible to provide a slurry composition for a secondary battery that is excellent in storage stability and adhesiveness and that can form a functional layer for a secondary battery. Furthermore, according to the present invention, it is possible to provide a functional layer for a secondary battery having excellent adhesiveness, and a secondary battery including the functional layer for a secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail. The binder composition for secondary batteries of the present invention is used in the production of secondary batteries such as non-aqueous secondary batteries and all-solid-state secondary batteries. For example, the binder composition for secondary batteries of the present invention can be used to form a functional layer for secondary batteries (e.g., a solid electrolyte layer containing solid electrolyte particles, an electrode mixture layer containing electrode active material particles and, optionally, solid electrolyte particles and / or conductive material particles) that constitutes a battery component of a secondary battery. Here, the slurry composition for secondary batteries of the present invention comprises the binder composition for secondary batteries of the present invention and can be used to form a functional layer for secondary batteries. Furthermore, the functional layer for secondary batteries of the present invention is formed using the slurry composition for secondary batteries of the present invention. Furthermore, the secondary battery of the present invention comprises the functional layer for secondary batteries of the present invention.

[0017] (Binder composition for secondary batteries) The binder composition of the present invention contains a polymer and a solvent, and may further contain other components as desired. Here, the binder composition of the present invention is characterized in that the polymer contains 5% by mass or more and 45% by mass or less of a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring, and the polymer is represented by the following formula (I): [ka] [In formula (I), R 1 represents a hydrocarbon group having 4 or more carbon atoms and not having an aromatic hydrocarbon ring, and R 2 is a hydrogen atom, a methyl group, or -CH2-C(=O)-OR 1 In addition, in formula (I), R 1 If there are multiple R1 may be the same or different.] in a proportion of 50% by mass or more and 90% by mass or less. The binder composition of the present invention contains a polymer containing the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring and the structural unit (I) in the above-mentioned proportions, and a solvent. Therefore, by using this binder composition, it is possible to provide a slurry composition for secondary batteries having excellent storage stability and a functional layer for secondary batteries having excellent adhesiveness.

[0018] <Polymer> Here, as described above, the polymer contains at least a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring and the structural unit (I), and optionally contains other structural units.

[0019] <<Composition>> [(Meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring] It is believed that the inclusion of (meth)acrylic acid ester monomer units having an aromatic hydrocarbon ring allows the polymer to adsorb particularly well to electrode active material particles and conductive material particles, which have a high affinity for aromatic hydrocarbon rings. This results in a good dispersion state in the slurry composition, improving the storage stability of the slurry composition. Additionally, the (meth)acrylic acid ester monomer units having an aromatic hydrocarbon ring have a (meth)acrylic acid ester skeleton, which can contribute to improving the adhesive properties and flexibility of the polymer. Therefore, the polymer containing (meth)acrylic acid ester monomer units having an aromatic hydrocarbon ring can improve the adhesiveness of the functional layer.

[0020] Here, 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 preferable. The monomer unit may have one type of aromatic hydrocarbon ring or two or more types of aromatic hydrocarbon rings. Furthermore, the aromatic hydrocarbon ring may have at least one hydrogen atom on the ring substituted with another group (such as a halogen atom), but it is preferable that the aromatic hydrocarbon ring has no substituent (is unsubstituted).

[0021] Examples of (meth)acrylic acid ester monomers having an aromatic hydrocarbon ring that can form (meth)acrylic acid ester monomer units having an aromatic hydrocarbon ring include phenoxyethyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, and phenoxy polyethylene glycol (meth)acrylate. These may be used alone or in combination of two or more. Among these, phenoxyethyl (meth)acrylate and ethoxylated o-phenylphenol (meth)acrylate are preferred from the viewpoint of further improving the adhesion of the functional layer and enhancing the cell characteristics of the secondary battery. In the present invention, the term "(meth)acrylate" means acrylate and / or methacrylate.

[0022] Here, the proportion of (meth)acrylic acid ester monomer units having an aromatic hydrocarbon ring among all structural units contained in the polymer, assuming all structural units to be 100% by mass, must be 5% by mass or more and 45% by mass or less, as described above, preferably 7% by mass or more, more preferably 10% by mass or more, preferably 43% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less. If the proportion of (meth)acrylic acid ester monomer units having an aromatic hydrocarbon ring among all structural units is less than 5% by mass, the adhesiveness of the functional layer will decrease. On the other hand, if the proportion of (meth)acrylic acid ester monomer units having an aromatic hydrocarbon ring among all structural units exceeds 45% by mass, while electrode active material particles and conductive material particles can be dispersed well, the dispersibility of solid electrolyte particles will decrease. As a result, the storage stability of a slurry composition containing solid electrolyte particles cannot be ensured.

[0023] [Structural unit represented by formula (I)] The structural unit (I) is represented by the following formula (I): [ka] It is shown as follows.

[0024] The polymer has the structural unit (I), and thus R 1 This is presumably due to the contribution of the hydrocarbon group having 4 or more carbon atoms and no aromatic hydrocarbon ring, which achieves a good dispersion state of the solid electrolyte particles in the slurry composition and further improves the storage stability of the slurry composition. In addition, since the structural unit (I) does not contain an aromatic hydrocarbon ring, it does not excessively increase the glass transition temperature of the polymer and can contribute to improving the adhesive ability and flexibility of the polymer. Therefore, the polymer having the structural unit (I) can improve the adhesiveness of the functional layer. The polymer may contain only one type of structural unit (I), or may contain two or more types of structural unit (I).

[0025] In the above formula (I), R 1 is not particularly limited as long as it is a hydrocarbon group that does not have an aromatic hydrocarbon ring in its structure and has a total of 4 or more carbon atoms, but is preferably an alkyl group having 4 or more carbon atoms, and more preferably an alkyl group having 4 to 12 carbon atoms. Preferred examples of the alkyl group having 4 to 12 carbon atoms include a butyl group (n-butyl group, sec-butyl group, isobutyl group, tert-butyl group), a 2-ethylhexyl group, and a dodecyl group (lauryl group).

[0026] In the above formula (I), R 2 is a hydrogen atom, a methyl group, or -CH2-C(=O)-OR 1 Represents R 2 R included in 1 A specific example of this is the aforementioned R 1 Among these, R 2 is preferably a hydrogen atom or a methyl group.

[0027] The structural unit (I) can be introduced into a polymer by preparing the polymer using a monomer having the corresponding structure. For example, R 1 is an alkyl group having from 4 to 12 carbon atoms, the structural unit (I) can be introduced into the polymer by using, as a monomer, an ethylenically unsaturated carboxylic acid alkyl ester monomer in which the alkyl group bonded to the non-carbonyl oxygen atom has from 4 to 12 carbon atoms. Preferred examples of the ethylenically unsaturated carboxylic acid alkyl ester monomer in which the alkyl group bonded to a non-carbonyl oxygen atom has 4 to 12 carbon atoms include butyl (meth)acrylate (n-butyl (meth)acrylate, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate), 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and dibutyl itaconate. These may be used alone or in combination of two or more.

[0028] Here, the proportion of the structural unit (I) among all structural units contained in the polymer, assuming all structural units to be 100% by mass, must be 50% by mass or more and 90% by mass or less, as described above, preferably 55% by mass or more, more preferably 60% by mass or more, preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. If the proportion of the structural unit (I) among all structural units is less than 50% by mass, the adhesiveness of the functional layer decreases. On the other hand, if the proportion of the structural unit (I) among all structural units exceeds 90% by mass, while solid electrolyte particles can be dispersed well, the dispersibility of electrode active material particles and conductive material particles decreases. Therefore, the storage stability of a slurry composition containing electrode active material particles and / or conductive material particles cannot be ensured.

[0029] Furthermore, the molar ratio of the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring to the structural unit (I) is preferably 0.08 or more, more preferably 0.09 or more, even more preferably 0.10 or more, particularly preferably 0.18 or more, and is preferably 0.80 or less, more preferably 0.65 or less, and even more preferably 0.50 or less. If the molar ratio is 0.08 or more, the dispersibility of the electrode active material particles and the conductive material particles in the slurry composition can be improved, and if it is 0.80 or less, the dispersibility of the solid electrolyte particles in the slurry composition can be improved. Therefore, if the molar ratio is within the above-mentioned range, the storage stability of the slurry composition can be further improved.

[0030] Other structural units The other structural units include, but are not limited to, vinyl cyanide monomer units, diene monomer units, aromatic vinyl monomer units, and crosslinkable monomer units. The polymer may contain only one type of other structural unit, or may contain two or more types. From the viewpoint of further improving the storage stability of the slurry composition and the adhesiveness of the functional layer, the polymer preferably contains at least one selected from the group consisting of vinyl cyanide monomer units, diene monomer units, and aromatic vinyl monomer units.

[0031] - 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.

[0032] Here, the proportion of vinyl cyanide monomer units among all structural units contained in the polymer is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, and preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 35% by mass or less, assuming that all structural units are 100% by mass. If the proportion of vinyl cyanide monomer units among all structural units is 3% by mass or more, the adhesiveness of the functional layer can be improved, and if it is 40% by mass or less, the solubility of the polymer in solvents (especially organic solvents) can be sufficiently ensured, and the storage stability of the slurry composition can be further improved. Furthermore, particularly when the binder composition for secondary batteries is a binder composition for all solid-state secondary batteries, the proportion of vinyl cyanide monomer units among all structural units contained in the polymer, where all structural units are taken as 100% by mass, is preferably 5% by mass or more, more preferably 6% by mass or more, even more preferably 7% by mass or more, and preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 35% by mass or less. If the proportion of vinyl cyanide monomer units among all structural units is 5% by mass or more, a good dispersion state of solid electrolyte particles is achieved in the slurry composition, and the storage stability of the slurry composition can be further improved. If the proportion is 40% by mass or less, the solubility of the polymer in solvents (particularly organic solvents) is sufficiently ensured, and the storage stability of the slurry composition can be further improved. In particular, when the binder composition for secondary batteries is a binder composition for non-aqueous secondary batteries such as lithium-ion secondary batteries, the proportion of vinyl cyanide monomer units among all structural units contained in the polymer is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, and preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 35% by mass or less, where the total structural units is 100% by mass. If the proportion of vinyl cyanide monomer units among all structural units is 3% by mass or more, the leveling properties of the slurry composition can be improved, and if it is 40% by mass or less, the solubility of the polymer in solvents (particularly organic solvents) can be sufficiently ensured, and the storage stability of the slurry composition can be further improved.

[0033] -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.

[0034] When the polymer contains diene monomer units, the proportion of the diene monomer units in all structural units contained in the polymer, assuming that all structural units are 100% by mass, is preferably 5% by mass or more, more preferably 6% by mass or more, even more preferably 7% by mass or more, and preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 35% by mass or less. When the proportion of diene monomer units in all structural units is 5% by mass or more, a better dispersion state of the electrode active material particles and the conductive material particles in the slurry composition can be achieved, and the storage stability of the slurry composition containing the electrode active material particles and / or the conductive material particles can be further improved. On the other hand, when the proportion of diene monomer units in all structural units is 40% by mass or less, sufficient adhesion of the functional layer can be ensured.

[0035] -Aromatic vinyl monomer unit- Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include styrene, styrene sulfonic acid and its salts, α-methylstyrene, pt-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. These may be used alone or in combination of two or more. Among these, styrene is preferred. 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).

[0036] When the polymer contains aromatic vinyl monomer units, the proportion of aromatic vinyl monomer units in all structural units contained in the polymer is preferably 5% by mass or more, more preferably 6% by mass or more, even more preferably 7% by mass or more, and preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 35% by mass or less, based on 100% by mass of all structural units. When the proportion of aromatic vinyl monomer units in all structural units is 5% by mass or more, a good dispersion state of electrode active material particles and conductive material particles is achieved in the slurry composition, and the storage stability of the slurry composition containing electrode active material particles and / or conductive material particles can be further improved. On the other hand, when the proportion of aromatic vinyl monomer units in all structural units is 40% by mass or less, sufficient adhesion of the functional layer can be ensured.

[0037] -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.

[0038] 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.

[0039] <<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.

[0040] When the binder composition is a binder composition for an all-solid-state secondary battery, the polymer is preferably readily soluble in the solvent contained in the binder composition and the slurry composition. If the polymer is readily soluble in the solvent, a good dispersion state of the solid electrolyte particles and the like can be achieved in the slurry composition, and the storage stability of the slurry composition can be further improved. In addition, the adhesion of the functional layer can be further increased, and the cell characteristics of the secondary battery can be improved.

[0041] <<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. Here, in the present invention, the content ratio of each monomer in the monomer composition can be determined in accordance with the content ratio of each monomer unit and structural unit in the polymer. The polymerization method is not particularly limited, and any of solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. In each polymerization method, known emulsifiers and polymerization initiators can be used as needed. 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.

[0042] <Solvent> The solvent is not particularly limited and can be appropriately selected depending on the application of the binder composition, and either water or an organic solvent can be used. Here, examples of the organic solvent include chain aliphatic hydrocarbons such as hexane; cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone, cyclohexanone, and diisobutyl ketone; esters such as ethyl acetate, butyl acetate, butyl butyrate, hexyl butyrate, γ-butyrolactone, and ε-caprolactone; acylonitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran, ethylene glycol diethyl ether, and n-butyl ether; alcohols such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; and amides such as N-methylpyrrolidone and N,N-dimethylformamide. The solvent may be used alone or in combination of two or more.

[0043] Here, when a slurry composition for an all-solid-state secondary battery is prepared using the binder composition, the solvent is preferably xylene, butyl butyrate, hexyl butyrate, n-butyl ether, or diisobutyl ketone, and more preferably xylene or diisobutyl ketone, from the viewpoints of increasing the dispersibility of the solid electrolyte particles while suppressing deterioration due to side reactions, further improving the storage stability of the slurry composition for an all-solid-state secondary battery, and improving the cell characteristics of the all-solid-state secondary battery. When a non-aqueous secondary battery positive electrode mixture layer slurry composition is prepared using the binder composition, the solvent is preferably N-methylpyrrolidone. When a non-aqueous secondary battery negative electrode mixture layer slurry composition is prepared using the binder composition, the solvent is preferably water.

[0044] <Other ingredients> Other components that may be optionally contained in the binder composition for secondary batteries include, but are not limited to, binders other than the above-mentioned polymers, dispersants, leveling agents, antifoaming agents, and reinforcing materials. These other components are not particularly limited as long as they do not affect the battery reaction. Furthermore, these components may be used alone or in combination of two or more in any ratio.

[0045] <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, for example, subjecting the aqueous dispersion of the polymer as the binder obtained as described above to solvent substitution as necessary and further adding other components.

[0046] (Slurry composition for secondary batteries) The slurry composition for a secondary battery of the present invention contains functional particles and the binder composition for a secondary battery of the present invention described above. In other words, the slurry composition for a secondary battery of the present invention contains functional particles, the specified polymer described above, a solvent, and optionally other components. Furthermore, since the slurry composition for a secondary battery of the present invention contains the binder composition of the present invention, it has excellent storage stability, and by using the slurry composition for a secondary battery, a functional layer with excellent adhesiveness can be formed.

[0047] <Functional particles> The functional particles contained in the slurry composition for secondary batteries can be appropriately selected depending on the application of the slurry composition (the type of functional layer prepared using the slurry composition) and the like. Preferred examples of the functional particles include electrode active material particles, solid electrolyte particles, and conductive material particles.

[0048] <<Electrode active material particles>> The electrode active material particles are particles that transfer electrons in the electrode of a secondary battery. Hereinafter, as examples, a case where the slurry composition for a secondary battery is a slurry composition for an electrode mixture layer of an all-solid-state lithium-ion secondary battery and a case where the slurry composition for a secondary battery is a slurry composition for an electrode mixture layer of a non-aqueous lithium-ion secondary battery will be described, but the present invention is not limited to the following examples.

[0049] [Electrode active material particles for all-solid-state lithium-ion secondary batteries] Positive electrode active material particles for all-solid-state lithium ion secondary batteries are not particularly limited, and examples thereof include positive electrode active material particles made of an inorganic compound and positive electrode active material particles made of an organic compound.

[0050] Examples of inorganic positive electrode active material particles include particles made of 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 the positive electrode active material 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 element-substituted.

[0051] Examples of the positive electrode active material particles made of an organic compound include polyaniline, polypyrrole, polyacene, disulfide-based compounds, polysulfide-based compounds, and N-fluoropyridinium salts.

[0052] The above-mentioned positive electrode active material particles can be used alone or in combination of two or more kinds. The particle size of the positive electrode active material particles is not particularly limited, and may be the same as that of conventionally used positive electrode active material particles.

[0053] In addition, examples of the negative electrode active material particles for all-solid-state lithium ion secondary batteries include particles composed of allotropes of carbon such as graphite and coke. Note that the negative electrode active material particles composed of allotropes of carbon can also be used in the form of a mixture or coating with a metal, metal salt, oxide, or the like. In addition, as the negative electrode active material particles, 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; silicone; and the like can also be used. The above-described negative electrode active material particles can be used alone or in combination of two or more. In addition, the particle diameter of the above-described negative electrode active material particles is not particularly limited and can be the same as that of the conventionally used negative electrode active material particles.

[0054] [Electrode Active Material Particles of Non-Aqueous Lithium Ion Secondary Battery] The positive electrode active material particles for non-aqueous lithium ion secondary batteries are not particularly limited, and include lithium-containing cobalt oxide (LiCoO2), lithium manganate (LiMn2O4), lithium-containing nickel oxide (LiNiO2), lithium-containing composite oxide of Co-Ni-Mn (Li(Co Mn Ni)O2), lithium-containing composite oxide of Ni-Mn-Al, lithium-containing composite oxide of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO4), olivine-type lithium manganese phosphate (LiMnPO4), Li 1+x Mn 2-x O4 (0 < X < 2) spinel compound with excess lithium, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4 and other known positive electrode active material particles. The above-described positive electrode active material particles can be used alone or in combination of two or more. In addition, the particle diameter of the above-described positive electrode active material particles is not particularly limited and can be the same as that of the conventionally used positive electrode active material particles.

[0055] Negative electrode active material particles for non-aqueous lithium ion secondary batteries are not particularly limited, and examples thereof include particles made of known negative electrode active materials such as carbon-based active materials, silicone-based active materials, and elemental metals and alloys that form lithium alloys. The above-mentioned negative electrode active material particles can be used alone or in combination of two or more kinds. The particle size of the negative electrode active material particles is not particularly limited, and may be the same as that of conventionally used negative electrode active material particles.

[0056] <Solid electrolyte particles> The solid electrolyte particles are particles that conduct ions in the electrodes and solid electrolyte layer of the all-solid-state secondary battery. The solid electrolyte particles used in the all-solid-state lithium ion secondary battery are not particularly limited as long as they are particles made of a solid having ion conductivity, but particles made of an inorganic solid electrolyte (inorganic solid electrolyte particles) are preferably used. The inorganic solid electrolyte is not particularly limited, and a crystalline inorganic lithium ion conductor, an amorphous inorganic lithium ion conductor, or a mixture thereof can be used.

[0057] Crystalline inorganic lithium ion conductors include Li3N and 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. Examples of amorphous inorganic lithium ion conductors include substances that contain sulfur atoms and have ion conductivity. 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. 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 excellent ion conductivity, 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.

[0058] 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.

[0059] 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.

[0060] The above-mentioned solid electrolyte particles can be used alone or in combination of two or more kinds. The particle size of the solid electrolyte particles is not particularly limited, and may be the same as that of conventionally used solid electrolyte particles.

[0061] <Conductive particles> The conductive material particles are intended to ensure electrical contact between the electrode active materials in the electrode mixture layer. The conductive material particles are not particularly limited, and particles made of known conductive materials can be used. The shape of the conductive material particles is not particularly limited, and they can have any shape, such as a substantially spherical, fibrous, or plate-like shape.

[0062] Examples of conductive particles that can be used include conductive carbon materials such as carbon black (e.g., acetylene black, Ketjen Black (registered trademark), furnace black, etc.), single-walled or multi-walled carbon nanotubes (multi-walled carbon nanotubes include cup-stacked types), carbon nanohorns, vapor-grown carbon fibers, milled carbon fibers obtained by crushing polymer fibers after firing, single-walled or multi-walled graphene, and carbon nonwoven fabric sheets obtained by firing nonwoven fabric made of polymer fibers, as well as fibers or foils of various metals. The conductive particles described above can be used alone or in combination of two or more kinds. Furthermore, the size (particle diameter, fiber diameter, fiber length, etc.) of the conductive particles described above is not particularly limited, and can be the same as that of conventionally used conductive particles.

[0063] <Binder composition> As the binder composition used in preparing the slurry composition, the above-mentioned binder composition for secondary batteries of the present invention containing a polymer and a solvent, and optionally containing other components, is used.

[0064] The blending ratio of the functional particles to the binder composition for a secondary battery containing a polymer and a solvent is not particularly limited, and can be adjusted appropriately depending on the application of the slurry composition and the type of functional particles. For example, when the slurry composition is a slurry composition for an all-solid-state secondary battery, the amount of polymer contained in the slurry composition for an all-solid-state secondary battery 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 particles as functional particles. When the content of the polymer in the slurry composition for an all-solid-state secondary battery is 0.1 parts by mass or more per 100 parts by mass of solid electrolyte particles, the polymer can fully function as a binder while favorably dispersing the solid electrolyte particles. Therefore, the storage stability of the slurry composition can be further improved, and the ionic conductivity of the functional layer (solid electrolyte layer, electrode mixture layer) can be further improved, thereby improving the cell characteristics of the all-solid-state secondary battery. On the other hand, when the content of the polymer in the slurry composition for an all-solid-state secondary battery is 10 parts by mass or less per 100 parts by mass of the solid electrolyte particles, the ionic conductivity of the functional layer (solid electrolyte layer, electrode mixture layer) can be sufficiently ensured, and the cell characteristics of the all-solid-state secondary battery are not excessively impaired. For example, when the slurry composition is a slurry composition for a non-aqueous secondary battery electrode mixture layer, the amount of polymer contained in the slurry composition for a non-aqueous secondary battery electrode mixture layer 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 electrode active material particles as functional particles. When the content of the polymer in the slurry composition for a non-aqueous secondary battery electrode mixture layer is 0.1 parts by mass or more per 100 parts by mass of electrode active material particles, the polymer can fully function as a binder while well dispersing the electrode active material particles. Therefore, the storage stability of the slurry composition can be further improved, and an electrode mixture layer in which the electrode active material particles are uniformly distributed can be obtained, thereby improving the cell characteristics of the non-aqueous secondary battery. On the other hand, if the content of the polymer in the slurry composition for a non-aqueous secondary battery electrode mixture layer is 10 parts by mass or less per 100 parts by mass of the electrode active material particles, the resistance of the electrode mixture layer will not increase excessively, and the cell characteristics of the non-aqueous secondary battery can be sufficiently ensured.

[0065] <Preparation of Slurry Composition> The method for preparing the slurry composition of the present invention is not particularly limited. For example, the slurry composition can be prepared by mixing the functional particles and the binder composition of the present invention by a known mixing method. When the slurry composition of the present invention is a slurry composition for an electrode composite layer, for example, it may be prepared by mixing electrode active material particles and conductive material particles as functional particles with the binder composition of the present invention, or it may be prepared by mixing conductive material particles as functional particles with the binder composition of the present invention to prepare a slurry composition (a conductive material paste containing conductive material particles and the binder composition), and then mixing the conductive material paste with electrode active material particles as functional particles.

[0066] (Functional layer for secondary batteries) The functional layer of the present invention is a layer containing functional particles and a polymer as a binder, and examples of the functional 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 in an all-solid-state secondary battery. The functional layer of the present invention is formed using the above-mentioned slurry composition of the present invention, and can be produced, for example, 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 functional layer of the present invention consists of a dried product of the above-mentioned slurry composition, and usually contains functional particles and a polymer, and may optionally further contain other components. Note that each component contained in the functional layer is the same as that contained in the above-mentioned slurry composition, and the content ratio of these components is usually the same as the content ratio in the above-mentioned slurry composition.

[0067] Furthermore, the functional layer of the present invention is formed using the slurry composition of the present invention, and therefore has excellent adhesiveness.

[0068] <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 functional layer, and the release substrate may be peeled off from the functional layer. In this way, the functional 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 a secondary battery. However, from the viewpoint of omitting the step of peeling off the functional 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).

[0069] <<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.

[0070] <<Electrode>> The electrodes (positive electrode and negative electrode) are not particularly limited, but examples thereof include electrodes in which an electrode mixture layer containing at least electrode active material particles and a binder (and solid electrolyte particles in the case of an electrode for an all-solid-state secondary battery) is formed on the above-mentioned current collector. The electrode active material particles, binder, and solid electrolyte particles contained in the electrode mixture layer in the electrode are not particularly limited, and known materials can be used. Note that the electrode mixture layer in the electrode may correspond to the functional layer of the present invention.

[0071] <Method for forming functional layer> The following methods can be used to form a functional 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 functional layer, and the resulting functional 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 functional 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 functional layer (functional layer formation step).

[0072] <<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.

[0073] <<Functional layer formation process>> In the functional layer forming step, the method for drying the slurry composition on the substrate is not particularly limited and any known method can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. When the functional 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.

[0074] (Secondary battery) The secondary battery of the present invention includes the above-described functional layer for a secondary battery. For example, when the secondary battery of the present invention is an all-solid-state secondary battery, the all-solid-state secondary battery of the present invention usually has a positive electrode, a negative electrode, and a solid electrolyte layer, 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 functional layer of the present invention. Furthermore, for example, when the secondary battery of the present invention is a nonaqueous secondary battery, the nonaqueous secondary battery of the present invention typically has a positive electrode, a negative electrode, an electrolyte, and a separator, and at least one of the positive electrode composite layer of the positive electrode and the negative electrode composite layer of the negative electrode is the functional layer of the present invention. Furthermore, the secondary battery of the present invention has excellent cell characteristics such as output characteristics and cycle characteristics, since it is provided with the functional layer of the present invention.

[0075] <All-solid-state secondary battery> Here, the all-solid-state secondary battery electrode having an electrode mixture layer that does not correspond to the functional layer of the present invention and that can be used in the all-solid-state secondary battery of the present invention is not particularly limited as long as it has an electrode mixture layer that does not correspond to the functional layer of the present invention, and any all-solid-state secondary battery electrode can be used.

[0076] 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 functional layer of the present invention is not particularly limited, and any solid electrolyte layer can be used, such as the solid electrolyte layers described in JP-A-2012-243476, JP-A-2013-143299, and JP-A-2016-143614.

[0077] 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.

[0078] <Non-aqueous secondary battery> Here, the non-aqueous secondary battery electrode having an electrode mixture layer that does not correspond to the functional layer of the present invention and that can be used in the non-aqueous secondary battery of the present invention is not particularly limited as long as it has an electrode mixture layer that does not correspond to the functional layer of the present invention, and any non-aqueous secondary battery electrode can be used.

[0079] As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is typically used. For example, a lithium salt is used as the supporting electrolyte in a nonaqueous lithium-ion secondary battery. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, CF4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred, with LiPF6 being particularly preferred, because they are easily soluble in solvents and exhibit a high degree of dissociation. Note that one type of electrolyte may be used alone, or two or more types may be used in combination at any ratio. Generally, the use of a supporting electrolyte with a higher degree of dissociation tends to result in higher lithium ion conductivity, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0080] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, suitable organic solvents for use in the electrolyte of nonaqueous lithium-ion secondary batteries include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and ethyl methyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. Mixtures of these solvents may also be used. Among these, carbonates are preferred because of their high dielectric constant and wide stable potential range. The concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate, and known additives can be added to the electrolytic solution.

[0081] The separator is not particularly limited, and can be, for example, one described in JP 2012-204303 A. Among these, a microporous membrane made of a polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it can reduce the overall separator thickness, thereby increasing the ratio of electrode active material particles in the nonaqueous secondary battery and increasing the capacity per volume.

[0082] A nonaqueous secondary battery can be produced, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the stack as necessary according to the battery shape, placing the stack in a battery container, injecting an electrolyte into the battery container, and sealing the container. If necessary, an expanded metal, a fuse, an overcurrent protection element such as a PTC element, a lead plate, or the like can be placed in the battery container to prevent pressure buildup within the battery and overcharging and discharging. The battery may be in any shape, such as a coin type, button type, sheet type, cylindrical type, prismatic type, or flat type. [Example]

[0083] 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 polymer composition and the amount of insoluble matter in the solvent, the dispersibility and storage stability of the slurry composition, the adhesion of the functional layer (electrode mixture layer), and the output characteristics, cycle characteristics, and cycle characteristics (after slurry storage) of the secondary battery were measured or evaluated by the following methods.

[0084] <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. 1The polymer was analyzed by H-NMR. Based on the analytical values ​​obtained, the content (mass %, mol %) of each monomer unit and structural unit contained in the polymer was calculated. In addition, the molar ratio of the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring to the structural unit (I) 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 <Dispersibility> The viscosity of the slurry composition 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 functional particles (electrode active material particles, solid electrolyte particles, and conductive material particles) 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 the slurry composition immediately after preparation was sampled, and the solvent was removed from the sampled slurry composition by drying on a hot plate at 130°C for 1 hour, 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: No decrease in solid content was observed even after 6 days of storage. 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 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 applied to the surface of the 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 speed 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 electrode composite layer as a functional layer and stronger adhesion to the current collector. A: Peel strength is 3N / m or more 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 <Output characteristics - all-solid-state secondary battery> 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 90% or more B: Capacity ratio is 80% or more but less than 90% C: Capacity ratio is 50% or more but less than 80% D: Capacity ratio is less than 50% <Output characteristics - Lithium-ion secondary battery (non-aqueous secondary battery)> Three lithium-ion secondary batteries were charged to 4.2 V at a constant current of 0.2 C and then discharged to 3.0 V at 0.2 C to determine the 0.2 C discharge capacity. They were then charged to 4.2 V at 0.2 C and then discharged to 3.0 V at 2 C to determine the 2 C discharge capacity. The average of the 0.2 C discharge capacities of the three cells was defined as discharge capacity c, and the average of the 2 C discharge capacities of the three cells was defined as discharge capacity d. The ratio of discharge capacity d to discharge capacity c (capacity ratio) = discharge capacity d / discharge capacity c × 100 (%) was calculated and evaluated according to the following criteria. A higher capacity ratio indicates a lithium-ion secondary battery with better output characteristics. A: Capacity ratio is 90% or more B: Capacity ratio is 80% or more but less than 90% C: Capacity ratio is 50% or more but less than 80% D: Capacity ratio is less than 50% <Cycle characteristics - all-solid-state secondary battery> The all-solid-state secondary battery was charged from 3 V to 4.2 V at 0.1 C in a 45°C environment, and then discharged from 4.2 V to 3 V at 0.1 C, and this charge-discharge cycle was repeated 50 times. The ratio of the 0.1 C discharge capacity at the 50th cycle to the 0.1 C discharge capacity at the 1st cycle was calculated as a percentage, which was taken as the capacity retention rate A and evaluated according to the following criteria. A larger value for the capacity retention rate A means less loss in discharge capacity and more excellent cycle characteristics for the all-solid-state secondary battery. A: Capacity retention rate A is 90% or more B: Capacity retention rate A is 80% or more but less than 90% C: Capacity retention rate A is 50% or more but less than 80% D: Capacity retention rate A is less than 50% <Cycle characteristics - Lithium-ion secondary battery (non-aqueous secondary battery)> The lithium-ion secondary battery was charged from 3 V to 4.2 V at 1.0 C in a 25°C environment, and then discharged from 4.2 V to 3 V at 1.0 C, repeating this charge-discharge cycle for 100 cycles. The ratio of the 1.0 C discharge capacity at the 100th cycle to the 1.0 C discharge capacity at the first cycle was calculated as a percentage, which was taken as capacity retention rate B and evaluated according to the following criteria. A higher capacity retention rate B indicates less loss in discharge capacity and better cycle characteristics for the lithium-ion secondary battery. A: Capacity retention rate B is 90% or more B: Capacity retention rate B is 80% or more but less than 90% C: Capacity retention rate B is 50% or more but less than 80% D: Capacity retention rate B is less than 50% <Cycle characteristics (after slurry storage) - All-solid-state secondary battery -> The slurry composition was stored in a sealed glove box (water content 10 ppm or less) for 48 hours. After storage, the slurry composition was used in a dry room (water content 127 ppm, dew point equivalent to -40°C) to prepare electrodes and solid electrolyte layers in the same manner as in each of the Examples and Comparative Examples, and an all-solid-state secondary battery was fabricated. Then, the same operation as in the above-mentioned "Cycle characteristics - all-solid-state secondary battery" was performed, and the ratio of the 0.1 C discharge capacity at the 50th cycle to the 0.1 C discharge capacity at the 1st cycle was calculated as a percentage, which was taken as the capacity retention rate A' and evaluated according to the following criteria: The larger the value of the capacity retention rate A', the smaller the decrease in discharge capacity, which means that the all-solid-state secondary battery equipped with electrodes formed from the slurry composition after storage has excellent cycle characteristics. A: Capacity retention rate A' is 90% or more B: Capacity retention rate A' is 80% or more but less than 90% C: Capacity retention rate A' is 50% or more but less than 80% D: Capacity retention rate A' is less than 50% <Cycle characteristics (after slurry storage) - Lithium-ion secondary battery (non-aqueous secondary battery)> The slurry composition was stored in a sealed glove box (water content 10 ppm or less) for 48 hours. After storage, the slurry composition was used to prepare electrodes in a dry room (water content 127 ppm, dew point equivalent to -40°C) in the same manner as in each of the Examples and Comparative Examples, and lithium ion secondary batteries were fabricated. Then, the same operation as in the above-mentioned "Cycle characteristics - Lithium ion secondary battery (nonaqueous secondary battery)" was performed, and the ratio of the 1.0 C discharge capacity at the 100th cycle to the 1.0 C discharge capacity at the first cycle was calculated as a percentage, which was taken as the capacity retention rate B' and evaluated according to the following criteria: The larger the value of the capacity retention rate B', the smaller the decrease in discharge capacity, which means that the lithium ion secondary battery equipped with an electrode formed from the slurry composition after storage has excellent cycle characteristics. A: Capacity retention rate B' is 90% or more B: Capacity retention rate B' is 80% or more but less than 90% C: Capacity retention rate B' is 50% or more but less than 80% D: Capacity retention rate B' is less than 50%

[0085] Example 1 <Preparation of binder composition for secondary battery> 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 dodecylbenzenesulfonate 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 potassium 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 parts of sodium lauryl sulfate as an emulsifier, and 25 parts of phenoxyethyl acrylate, 67 parts of n-butyl acrylate, and 8 parts of acrylonitrile 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 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 diisobutyl ketone as a solvent was added to the obtained aqueous dispersion of the polymer to obtain a mixture. Then, 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 composition of the polymer was measured using the obtained binder composition. 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 positive electrode active material particles, 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 solid electrolyte particles, 2.5 parts of acetylene black as conductive material particles, 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 in a planetary mixer for 60 minutes. Further diisobutyl ketone was added to adjust the solid content to 70% and then mixed for 10 minutes to prepare a slurry composition for a positive electrode composite layer. The resulting slurry composition for a positive electrode composite layer was evaluated for dispersibility and storage stability. The results are shown in Table 1. <Preparation of Slurry Composition for Negative Electrode Mixture Layer> 65 parts of graphite (number average particle diameter: 20 μm) as negative electrode active material particles, 31.5 parts of sulfide glass consisting of Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) as solid electrolyte particles, 1.5 parts of acetylene black as conductive material particles, 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. Then, 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. <Preparation of Slurry Composition for Solid Electrolyte Layer> In a glove box under an argon gas atmosphere (water concentration 0.6 mass ppm, oxygen concentration 1.8 mass ppm), 100 parts of sulfide glass (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) composed of Li2S and P2S5 as solid electrolyte particles were mixed with 2 parts (solid content equivalent) of the binder composition obtained as described above. Diisobutyl ketone was further added as a solvent to adjust the solid content to 60 mass%, and the mixture was mixed in a planetary mixer for 60 minutes. Diisobutyl ketone was then further added to adjust the solid content to 45%, and the mixture was mixed in a planetary mixer to prepare a slurry composition for the solid electrolyte layer. <Manufacturing of all-solid-state secondary batteries> 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. In addition, the above-mentioned slurry composition for the negative electrode composite layer was applied to the surface of another 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 cycle characteristics and rate characteristics of this all-solid-state secondary battery were evaluated. The results are shown in Table 1. In addition, the above-mentioned slurry compositions (slurry composition for the positive electrode composite layer, slurry composition for the negative electrode composite layer, and slurry composition for the solid electrolyte layer) were stored separately, and a positive electrode, a negative electrode, a solid electrolyte layer, and an all-solid-state secondary battery were fabricated in the same manner as above, except that the stored slurry compositions were used, and the cycle characteristics (after slurry storage) were evaluated. The results are shown in Table 1.

[0086] Example 2 In preparing the binder composition for secondary batteries, except that 67 parts of 2-ethylhexyl acrylate, 25 parts of phenoxyethyl acrylate, and 8 parts of acrylonitrile were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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 1.

[0087] Example 3 In preparing the binder composition for secondary batteries, except that 30 parts of n-butyl acrylate, 40 parts of lauryl acrylate, 20 parts of phenoxyethyl acrylate, and 10 parts of acrylonitrile were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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 1.

[0088] Example 4 In preparing the binder composition for secondary batteries, except that 50 parts of n-butyl acrylate, 40 parts of phenoxyethyl acrylate, and 10 parts of acrylonitrile were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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 1.

[0089] Example 5 In preparing the binder composition for secondary batteries, except that 85 parts of n-butyl acrylate, 7 parts of phenoxyethyl acrylate, and 8 parts of acrylonitrile were used as monomers, a binder composition for secondary batteries, a slurry composition for positive electrode composite layer, a slurry composition for negative electrode composite layer, a slurry composition for solid electrolyte layer, and an all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0090] (Examples 6 and 7) In preparing the binder composition for secondary batteries and various slurry compositions, except that xylene (Example 6) and butyl butyrate (Example 7) were used as the solvent instead of diisobutyl ketone, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and all-solid secondary batteries were produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

[0091] Example 8 In preparing the binder composition for secondary batteries, except that 67 parts of n-butyl acrylate, 25 parts of phenyl acrylate, and 8 parts of acrylonitrile were used as monomers, a binder composition for secondary batteries, a slurry composition for positive electrode composite layer, a slurry composition for negative electrode composite layer, a slurry composition for solid electrolyte layer, 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 1.

[0092] Example 9 In preparing the binder composition for secondary batteries, except that 67 parts of n-butyl acrylate, 25 parts of ethoxylated o-phenylphenol acrylate, and 8 parts of acrylonitrile were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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.

[0093] Example 10 In preparing the binder composition for secondary batteries, except that 67 parts of n-butyl acrylate, 25 parts of phenoxy polyethylene glycol acrylate, and 8 parts of acrylonitrile were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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.

[0094] Example 11 In preparing the binder composition for secondary batteries, except that 60 parts of n-butyl acrylate, 29.8 parts of phenoxyethyl acrylate, 10 parts of acrylonitrile, and 0.2 parts of allyl methacrylate were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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.

[0095] Example 12 Except for using the secondary battery binder composition prepared as follows, a positive electrode composite layer slurry composition, a negative electrode composite layer slurry composition, a solid electrolyte layer slurry composition, 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. <Preparation of binder composition for secondary battery> A reactor was charged with 2 parts of potassium oleate as an emulsifier, 0.1 parts of potassium phosphate as a stabilizer, and 150 parts of water, and further charged with 5 parts of acrylonitrile, 35 parts of 1,3-butadiene, 50 parts of n-butyl acrylate, and 10 parts of phenoxyethyl acrylate 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. Subsequently, an appropriate amount of diisobutyl ketone as a solvent was added to the obtained aqueous dispersion of the polymer to obtain a mixture. Then, 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 composition of the polymer was measured using the obtained binder composition. The results are shown in Table 2.

[0096] Example 13 In preparing the binder composition for secondary batteries, except that 58 parts of n-butyl acrylate, 20 parts of phenoxyethyl acrylate, 7 parts of acrylonitrile, and 15 parts of styrene were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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.

[0097] Examples 14 and 15 <Preparation of binder composition for non-aqueous secondary battery positive electrode mixture layer (Example 14)> An aqueous dispersion of a polymer (hydrogenated nitrile rubber) was obtained in the same manner as in Example 12. Using the obtained aqueous dispersion of the polymer, the amount of the polymer insoluble in N-methylpyrrolidone (solvent) was calculated, and the polymer was identified as being either readily soluble or sparingly soluble in N-methylpyrrolidone. The results are shown in Table 2. Next, an appropriate amount of N-methylpyrrolidone as a solvent was added to the obtained aqueous dispersion of the polymer to obtain a mixture. Then, water and excess N-methylpyrrolidone were removed from the mixture by vacuum distillation at 80°C to obtain a binder composition for a positive electrode composite layer (solid content: 8%). The composition of the polymer was measured using the obtained binder composition. The results are shown in Table 2. <Preparation of binder composition for non-aqueous secondary battery negative electrode mixture layer (Example 15)> 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 dodecylbenzenesulfonate 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 potassium 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 20 parts of phenoxyethyl acrylate, 58 parts of n-butyl acrylate, 5 parts of acrylonitrile, 14 parts of styrene, and 3 parts of ethylene glycol dimethacrylate 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. After the reaction was completed, the solids concentration was adjusted to 30%, and an aqueous dispersion of the polymer (binder composition for the negative electrode composite layer) was obtained. The amount of the polymer insoluble in water (solvent) was calculated using the obtained aqueous dispersion of the polymer (binder composition for the negative electrode composite layer), and the polymer was identified as being either readily soluble or sparingly soluble in water. The results are shown in Table 2. The composition of the polymer was measured using the aqueous dispersion of the polymer (binder composition for negative electrode mixture layer). The results are shown in Table 2. <Preparation of Slurry Composition for Nonaqueous Secondary Battery Positive Electrode Mixture Layer (Example 14)> The planetary mixer was fitted with Co-Ni-Mn lithium composite oxide active material particles NMC532 (LiNi 5 / 10 Co 2 / 10 Mn 3 / 10 96.5 parts of 02), 1.5 parts of acetylene black (manufactured by Denka, product name "HS-100") as conductive particles, and 2 parts (solids equivalent) of the above-mentioned binder composition for the positive electrode composite layer were added and mixed. Furthermore, N-methylpyrrolidone as a solvent was gradually added, and the mixture was stirred and mixed at a temperature of 25±3°C and a rotation speed of 40 rpm to obtain a slurry composition for the positive electrode composite layer with a viscosity of 3600 mPa·s (using a Brookfield viscometer, temperature: 25±3°C, rotor: M4, rotor rotation speed: 60 rpm). The dispersibility and storage stability of the resulting slurry composition for the positive electrode composite layer were evaluated. The results are shown in Table 2. <Preparation of Slurry Composition for Non-Aqueous Secondary Battery Negative Electrode Mixture Layer (Example 15)> A planetary mixer was charged with 97 parts of natural graphite (theoretical capacity: 360 mAh / g) as negative electrode active material particles and 1 part (solid content equivalent) of carboxymethyl cellulose (CMC) as a thickener. The mixture was then diluted with ion-exchanged water to a solid content of 65% and then kneaded for 60 minutes at a rotation speed of 45 rpm. Next, 1.5 parts (solid content equivalent) of the binder composition for the negative electrode composite layer described above was added and kneaded for 40 minutes at a rotation speed of 40 rpm. Ion-exchanged water was then added to obtain a slurry composition for the negative electrode composite layer, with a viscosity of 3000±500 mPa·s (measured using a Brookfield viscometer at 25°C and a rotor rotation speed of 60 rpm). The resulting slurry composition for the negative electrode composite layer was evaluated for dispersibility and storage stability. The results are shown in Table 2. <Preparation of Positive Electrode for Non-Aqueous Secondary Battery (Example 14)> The above-mentioned slurry composition for the positive electrode composite layer was applied to a 20 μm thick aluminum foil current collector using a comma coater in an amount of 18±0.5 mg / cm 2 The aluminum foil was then transported at a speed of 200 mm / min through an oven at 120°C for 2 minutes and then through an oven at 130°C for 2 minutes to dry the slurry composition on the aluminum foil, thereby obtaining a positive electrode substrate having a positive electrode composite layer formed on the current collector. Thereafter, the positive electrode composite layer side of the prepared positive electrode blank was roll-pressed in an environment at a temperature of 25±3°C, and the density of the positive electrode composite layer was adjusted to 3.20 g / cm 3 The positive electrode was used to evaluate the adhesiveness of the positive electrode mixture layer. The results are shown in Table 2. <Preparation of Negative Electrode for Non-Aqueous Secondary Battery (Example 15)> The above-mentioned slurry composition for the negative electrode composite layer was applied to the surface of a 15 μm thick copper foil current collector using a comma coater in an amount of 10±0.5 mg / cm 2 Thereafter, the copper foil coated with the slurry composition for a negative electrode composite layer was transported at a speed of 400 mm / min through an oven at a temperature of 120°C for 2 minutes and then through an oven at a temperature of 130°C for 2 minutes, thereby drying the slurry composition on the copper foil and obtaining a negative electrode blank in which a negative electrode composite layer was formed on a current collector. Thereafter, the negative electrode composite layer side of the prepared negative electrode blank was roll-pressed in an environment at a temperature of 25±3°C, and the density of the negative electrode composite layer was adjusted to 1.65 g / cm 3 The negative electrode was used to evaluate the adhesiveness of the negative electrode mixture layer. The results are shown in Table 2. <Preparation of Separator (Examples 14 and 15)> A single-layer polypropylene separator (manufactured by Celgard Co., Ltd., product name "Celgard 2500") was prepared as the separator. <Preparation of Lithium-Ion Secondary Batteries (Examples 14 and 15)> A single-layer laminate cell (with an initial design discharge capacity of 30 mAh) was fabricated using the negative electrode, positive electrode, and separator described above. It was then placed in an aluminum foil bag and vacuum dried at 60°C for 10 hours. A 1.0 M LiPF solution (solvent: ethylene carbonate (EC) / diethyl carbonate (DEC) = 5 / 5 (volume ratio), additive: vinylene carbonate 2 vol% (solvent ratio)) was then filled as the electrolyte. The aluminum foil was then heat-sealed at 150°C to seal the opening, completing the fabrication of a nonaqueous lithium-ion secondary battery. The cycle and rate characteristics of this lithium-ion secondary battery were evaluated. The results are shown in Table 2. The positive electrode composite layer slurry composition and the negative electrode composite layer slurry composition were separately stored, and the stored slurry compositions were used. The positive electrode, the negative electrode, the separator, and the lithium ion secondary battery were prepared or fabricated in the same manner as above, and the cycle characteristics (after slurry storage) were evaluated. The results are shown in Table 2.

[0098] Example 16 In preparing the binder composition for secondary batteries, except that 70 parts of n-butyl acrylate and 30 parts of phenoxyethyl acrylate were used as monomers, a binder composition for secondary batteries, a slurry composition for positive electrode composite layer, a slurry composition for negative electrode composite layer, a slurry composition for solid electrolyte layer, 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.

[0099] (Comparative Example 1) In preparing the binder composition for secondary batteries, except that 40 parts of n-butyl acrylate, 30 parts of phenoxyethyl acrylate, 15 parts of acrylonitrile, and 15 parts of styrene were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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 3.

[0100] (Comparative Example 2) In preparing the binder composition for secondary batteries, except that 52 parts of n-butyl acrylate, 4 parts of phenoxyethyl acrylate, 18 parts of acrylonitrile, and 26 parts of styrene were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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 3.

[0101] (Comparative Example 3) In preparing the binder composition for secondary batteries, except that 40 parts of n-butyl acrylate and 60 parts of phenoxyethyl acrylate were used as monomers, a binder composition for secondary batteries, a slurry composition for positive electrode composite layer, a slurry composition for negative electrode composite layer, a slurry composition for solid electrolyte layer, 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 3.

[0102] Comparative Example 4 In preparing the binder composition for secondary batteries, except that 91 parts of n-butyl acrylate, 4 parts of phenoxyethyl acrylate, and 5 parts of acrylonitrile were used as monomers, a binder composition for secondary batteries, a slurry composition for positive electrode composite layer, a slurry composition for negative electrode composite layer, a slurry composition for solid electrolyte layer, 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 3.

[0103] (Comparative Example 5) In preparing the binder composition for secondary batteries, except that 67 parts of n-butyl acrylate, 8 parts of acrylonitrile, and 25 parts of styrene were used as monomers, a binder composition for secondary batteries, a slurry composition for positive electrode composite layer, a slurry composition for negative electrode composite layer, a slurry composition for solid electrolyte layer, 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 3.

[0104] (Comparative Example 6) In preparing the binder composition for secondary batteries, except that 70 parts of ethyl acrylate, 25 parts of phenoxyethyl acrylate, and 5 parts of acrylonitrile were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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 3.

[0105] (Comparative Example 7) In preparing the binder composition for secondary batteries, except that 50 parts of methyl acrylate, 40 parts of methyl methacrylate, 5 parts of phenoxyethyl acrylate, and 5 parts of acrylonitrile were used as monomers, the binder composition for secondary batteries, the slurry composition for positive electrode composite layer, the slurry composition for negative electrode composite layer, the slurry composition for solid electrolyte layer, and the 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 3.

[0106] In addition, in Tables 1 to 3 shown below, "Aromatic hydrocarbon ring / formula (I) molar ratio" refers to the molar ratio of the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring to the structural unit represented by formula (I), "PEA" indicates a phenoxyethyl acrylate unit, "PA" indicates a phenyl acrylate unit; "EPA" indicates ethoxylated o-phenylphenol acrylate units; "PPA" indicates a phenoxy polyethylene glycol acrylate unit; "BA" indicates n-butyl acrylate units; "LA" indicates a lauryl acrylate unit; "EHA" indicates 2-ethylhexyl acrylate units; "EA" indicates an ethyl acrylate unit; "MA" indicates a methyl acrylate unit; "MAA" indicates a methyl methacrylate unit; "AN" indicates an acrylonitrile unit; "H-BD" indicates a 1,3-butadiene hydride unit; "ST" indicates a styrene unit; "AMA" indicates an allyl methacrylate unit; "EDMA" refers to ethylene glycol dimethacrylate units; "DIK" indicates diisobutyl ketone, "XY" indicates xylene, "HB" stands for butyl butyrate; "NMP" indicates N-methylpyrrolidone; "Easy" indicates easy solubility, "Nan" indicates poor solubility, "AS" indicates an all-solid-state secondary battery, "LIB" stands for lithium-ion secondary battery.

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] Tables 1 and 2 show that the binder compositions of Examples 1 to 16 can be used to prepare slurry compositions with excellent storage stability and to form functional layers (positive electrode composite layers or negative electrode composite layers) with excellent adhesive properties. Furthermore, in Examples 1 to 16, the slurry compositions have good dispersibility, enabling the fabrication of secondary batteries with excellent cell characteristics. On the other hand, Table 3 shows that in Comparative Examples 1 to 7, which used binder compositions containing polymers in which the content ratio of at least one of a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring and structural unit (I) was outside the specified range, the dispersibility and storage stability of the slurry composition, the adhesion of the functional layer, and the cell characteristics of the secondary battery were reduced. [Industrial Applicability]

[0111] According to the present invention, it is possible to prepare a slurry composition for a secondary battery having excellent storage stability, and to provide a binder composition for a secondary battery that can exert excellent adhesion to a functional layer for a secondary battery. Furthermore, according to the present invention, it is possible to provide a slurry composition for a secondary battery that is excellent in storage stability and adhesiveness and that can form a functional layer for a secondary battery. Furthermore, according to the present invention, it is possible to provide a functional layer for a secondary battery having excellent adhesiveness, and a secondary battery including the functional layer for a secondary battery.

Claims

1. A binder composition for a secondary battery comprising a polymer and a solvent, The polymer contains 5% by mass or more and 45% by mass or less of a (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring, and has a structure represented by the following formula (I): 【Chemical 1】 [In formula (I), R １ represents a hydrocarbon group having 4 or more carbon atoms and not having an aromatic hydrocarbon ring, and R ２ is a hydrogen atom, a methyl group, or —CH ２ -C(=O)-OR １ In addition, in formula (I), R １ If there are multiple R １ may be the same or different.] in a proportion of 50% by mass or more and 90% by mass or less, a molar ratio of the (meth)acrylic acid ester monomer unit having an aromatic hydrocarbon ring to the structural unit represented by formula (I) in the polymer is 0.18 or more and 0.39 or less; The polymer further comprises at least one selected from the group consisting of a vinyl cyanide monomer unit, a diene-based monomer unit, and an aromatic vinyl monomer unit.

2. A slurry composition for a secondary battery, comprising functional particles and the binder composition for a secondary battery according to claim 1.

3. 3. The slurry composition for a secondary battery according to claim 2, wherein the functional particles are at least one selected from the group consisting of electrode active material particles, solid electrolyte particles, and conductive material particles.

4. A functional layer for a secondary battery formed using the slurry composition for a secondary battery according to claim 2 or 3.

5. A secondary battery comprising the functional layer for a secondary battery according to claim 4 .

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