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

Abstract

The present invention provides a binder composition for a secondary battery, comprising a polymer, an organic solvent, and a compound formed of an organic or inorganic substance. The compound has a solubility in water at 25 °C of 10% by mass or less and contains an element (excluding carbon and germanium) belonging to Group 13 and / or Group 14 of the periodic table. The content of the element in the binder composition is 5 mass ppm or more and 5000 mass ppm or less relative to the polymer.

Description

Technical Field

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

[0002] Secondary batteries such as non-aqueous electrolyte secondary batteries using an organic solvent electrolyte (hereinafter sometimes simply referred to as "non-aqueous secondary batteries") and all-solid-state secondary batteries using a solid electrolyte instead of an organic solvent electrolyte have characteristics such as being small, lightweight, having a high energy density, and being capable of repeated charge and discharge, and have been used in a wide range of applications.

[0003] Here, when manufacturing battery components of a secondary battery, a binder composition for a secondary battery containing an organic solvent and a polymer as a binder material can be used. Specifically, a slurry composition for a secondary battery is prepared by mixing the binder composition with, for example, components that are blended to cause the battery components to exhibit desired functions. Next, by removing the organic solvent from the slurry composition for a secondary battery, an electrode composite layer for a secondary battery, a solid electrolyte layer, etc. can be formed, and they are used as battery components or parts of battery components.

[0004] Moreover, in order to improve the performance of secondary batteries, improvements to the binder composition for secondary batteries are being made.

[0005] For example, Patent Document 1 provides a binder composition for a positive electrode of a non-aqueous secondary battery, which contains an organic solvent and a specific polymer, and the solution turbidity of the binder composition for a positive electrode of the non-aqueous secondary battery is within a specified range.

[0006] In addition, Patent Document 2 provides a solid electrolyte composition containing a specified inorganic solid electrolyte (A), a dehydrating agent (B), and a dispersion medium (C).

[0007] In addition, Patent Document 3 provides an all-solid-state secondary battery having, in order, a positive electrode active material layer, an inorganic solid electrolyte layer, and a negative electrode active material layer, and at least one of the positive electrode active material layer, the inorganic solid electrolyte layer, and the negative electrode active material layer contains at least a cyclic compound having a siloxane bond and an inorganic solid electrolyte containing a metal belonging to Group 1 or Group 2 of the periodic table and having ion conductivity.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-160421;

[0011] Patent Document 2: International Publication No. WO 2017 / 199821;

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2016-33917. Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] However, there is still room for improvement in the above-described conventional binder composition in terms of improving the water resistance of the secondary battery while enabling the secondary battery to exhibit excellent battery characteristics.

[0015] Therefore, an object of the present invention is to provide a binder composition for a secondary battery that can improve the water resistance of the secondary battery and enable the secondary battery to exhibit excellent battery characteristics.

[0016] In addition, an object of the present invention is to provide a slurry composition for a secondary battery that can improve the water resistance of the secondary battery and enable the secondary battery to exhibit excellent battery characteristics.

[0017] Furthermore, an object of the present invention is to provide a solid electrolyte layer-containing product having excellent water resistance, and an all-solid-state secondary battery having excellent battery characteristics and a method for manufacturing the same.

[0018] Means for Solving the Problems

[0019] The inventors of the present invention conducted intensive studies to solve the above problems. As a result, the inventors newly found that if a binder composition containing a polymer, an organic solvent, and a compound formed of an inorganic substance or an organic substance is used, and the compound contains a specific element and has a specific property, the water resistance of the secondary battery can be improved and the secondary battery can exhibit excellent battery characteristics, thus completing the present invention.

[0020] That is, an object of the present invention is to advantageously solve the above problems. The binder composition for a secondary battery of the present invention (hereinafter also simply referred to as "binder composition") is characterized by containing a polymer, an organic solvent, and a compound formed of an organic substance or an inorganic substance. The solubility of the compound in water at 25°C is 10% by mass or less, and the compound contains an element belonging to Group 13 and / or Group 14 of the periodic table (excluding carbon and germanium). The content of the above element in the binder composition for a secondary battery is 5 mass ppm or more and 5000 mass ppm or less relative to the polymer. If the binder composition contains a polymer, an organic solvent, and a compound having a solubility in water of a specified value or less and containing a specified element, and the content of the above element in the binder composition is within a specified range, then by using this binder composition, the water resistance of the secondary battery can be improved and the secondary battery can exhibit excellent battery characteristics.

[0021] Here, in the binder composition for a secondary battery of the present invention, the above polymer preferably has at least one functional group selected from a carbonyl group, an ether group, a carboxyl group, and a hydroxyl group. By using a polymer having the above specific functional group, the adhesiveness of the polymer can be improved.

[0022] Moreover, in the binder composition for a secondary battery of the present invention, the above compound preferably has at least one structure selected from -O-Si-O-, SiO2, and -O-Al-O-. If the compound contained in the binder composition of the present invention has at least one structure selected from -O-Si-O-, SiO2, and -O-Al-O-, then by using this binder composition, the water resistance of the secondary battery can be further improved and the secondary battery can exhibit excellent battery characteristics.

[0023] Moreover, in the binder composition for a secondary battery of the present invention, it is preferable that the above polymer contains at least any one of a vinyl cyanide monomer unit, an aromatic monomer unit, or a conjugated diene monomer unit and / or an alkylene structural unit in the proportions shown in the following (i) to (iii).

[0024] (i) contains a vinyl cyanide monomer unit in a proportion of 2% by mass or more and 35% by mass or less

[0025] (ii) contains an aromatic monomer unit in a proportion of 5% by mass or more and 40% by mass or less

[0026] (iii) contains a conjugated diene monomer unit and / or an alkylene structural unit in a proportion of 20% by mass or more and 60% by mass or less

[0027] By the polymer contained in the binder composition containing at least any one of a vinyl cyanide monomer unit, an aromatic monomer unit, and a conjugated diene monomer unit and / or an alkylene structural unit in the above proportions, in the slurry composition prepared using this binder composition, the dispersibility of each component contained in this slurry composition can be improved.

[0028] In addition, in the present invention, "containing a monomer unit" means "containing a structural unit (repeating unit) derived from the monomer in a polymer obtained using the monomer". Further, in the present invention, the content ratio of the "structural unit" in the polymer can be measured using 1 nuclear magnetic resonance (NMR) methods such as 1H-NMR.

[0029] In addition, an object of the present invention is to advantageously solve the above problems. The slurry composition for a secondary battery of the present invention (hereinafter also simply referred to as "slurry composition") is characterized by containing any one of the above binder compositions for a secondary battery. If a slurry composition containing any one of the above binder compositions is used, the water resistance of the secondary battery can be improved and the secondary battery can exhibit excellent battery characteristics.

[0030] Moreover, the slurry composition for a secondary battery of the present invention preferably contains a solid electrolyte. If a slurry composition containing a solid electrolyte is used, the water resistance of the all-solid-state secondary battery can be improved and the all-solid-state secondary battery can exhibit excellent battery characteristics.

[0031] In addition, an object of the present invention is to advantageously solve the above problems. The solid electrolyte-containing layer of the present invention is characterized by being formed using the above slurry composition containing a solid electrolyte. If the slurry composition of the present invention containing a solid electrolyte is used to form the solid electrolyte-containing layer, a solid electrolyte-containing layer that can be easily densified can be formed.

[0032] Moreover, an object of the present invention is to advantageously solve the above problems. The all-solid-state secondary battery of the present invention is characterized by having the above solid electrolyte-containing layer. The all-solid-state secondary battery having the solid electrolyte-containing layer of the present invention has excellent water resistance and can exhibit excellent battery characteristics.

[0033] In addition, an object of the present invention is to advantageously solve the above problems. The manufacturing method of the all-solid-state secondary battery of the present invention is characterized by including a step of pressing the above solid electrolyte-containing layer at a pressure of less than 300 MPa. According to the manufacturing method of the present invention, an all-solid-state secondary battery having excellent water resistance and capable of exhibiting excellent battery characteristics can be manufactured.

[0034] Advantages of the Invention

[0035] According to the present invention, a binder composition for a secondary battery can be provided, which can improve the water resistance of the secondary battery and enable the secondary battery to exhibit excellent battery characteristics.

[0036] In addition, according to the present invention, a slurry composition for a secondary battery can be provided, which can improve the water resistance of the secondary battery and enable the secondary battery to exhibit excellent battery characteristics.

[0037] Furthermore, according to the present invention, a solid electrolyte-containing layer with excellent water resistance, an all-solid-state secondary battery with excellent battery characteristics, and a manufacturing method thereof can be provided. Detailed Embodiments

[0038] Hereinafter, the embodiments of the present invention will be described in detail.

[0039] The binder composition for secondary batteries and the slurry composition for secondary batteries of the present invention are used to fabricate secondary batteries such as non-aqueous secondary batteries and all-solid-state secondary batteries. Moreover, the binder composition for secondary batteries of the present invention is used when preparing the slurry composition for secondary batteries of the present invention. In addition, the slurry composition for secondary batteries of the present invention is used, for example, when forming a solid electrolyte layer-containing layer such as an electrode composite layer and a solid electrolyte layer that can be used in an all-solid-state secondary battery. Furthermore, the solid electrolyte layer-containing layer of the present invention is formed using the slurry composition for secondary batteries of the present invention. Moreover, the all-solid-state secondary battery of the present invention has the solid electrolyte layer-containing layer of the present invention. In addition, the all-solid-state secondary battery of the present invention can be manufactured by the manufacturing method of the all-solid-state secondary battery of the present invention.

[0040] (Binder composition for secondary batteries)

[0041] The binder composition of the present invention contains a polymer, an organic solvent, and a compound formed of an organic or inorganic substance, and the binder composition may optionally contain other components. Here, the binder composition of the present invention is characterized in that the solubility of the above compound in water at a temperature of 25 °C is 10% by mass or less and contains an element belonging to Group 13 and / or Group 14 of the periodic table (excluding carbon and germanium), and the content of the above element in the binder composition is 5 mass ppm or more and 5000 mass ppm or less relative to the above polymer.

[0042] (Polymer)

[0043] As the polymer contained in the binder composition of the present invention, any polymer that can be generally used as a binder material in secondary batteries can be used. Among them, as the polymer, a polymer having at least one functional group selected from a carbonyl group, an ether group, a carboxyl group, and a hydroxyl group is preferably used. If a polymer having any of the above functional groups is used, the adhesiveness of the polymer can be improved.

[0044] The polymer having the above functional group can be obtained, for example, by introducing the above functional group into the polymer. Here, the method of introducing the above functional group into the polymer is not particularly limited. For example, a polymer can be prepared using a monomer containing the above functional group, or a polymer having the above functional group at the end can be obtained by end-modifying any polymer.

[0045] (Polymer having a carbonyl group)

[0046] The polymer having a carbonyl group can be obtained by polymerizing a monomer composition containing a carbonyl group-containing monomer. Here, as the carbonyl group-containing monomer, a (meth)acrylate monomer can be mentioned. In addition, in this specification, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0047] As the (meth)acrylate monomer, examples thereof include: acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; and methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, etc.

[0048] In addition, as the carbonyl group-containing monomer, examples thereof include: polycarboxylic acid esters such as allyl methyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, fluoroalkyl maleate, monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, dibutyl itaconate. They can be used alone or in combination of two or more.

[0049] Moreover, when the total repeating units (the sum of monomer units and structural units) in the polymer is 100% by mass, the content ratio of the carbonyl group-containing monomer units derived from the carbonyl group-containing monomer in the polymer is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less. By making the content ratio of the carbonyl group-containing monomer units in the polymer 25% by mass or more, the adhesion strength between the electrode composite layer and the current collector can be improved by using the slurry composition prepared with the binder composition of the present invention. In addition, by making the content ratio of the carbonyl group-containing monomer units in the polymer 95% by mass or less, the dispersibility of the electrode active material and the conductive additive can be improved in the slurry composition prepared with the binder composition of the present invention.

[0050] [Polymer having an ether group]

[0051] The polymer having an ether group is obtained by polymerizing a monomer composition containing a monomer having an ether group. Here, examples of the monomer having an ether group include: phenoxyethyl acrylate, ethoxylated o-phenylphenol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, allyl glycidyl ether, glycerol monoallyl ether, 4-hydroxybutyl acrylate glycidyl ether, methoxypolyethylene glycol (meth)acrylate, and the like.

[0052] Moreover, when the total repeating units in the polymer are 100% by mass, the content ratio of the ether group-containing monomer units derived from the ether group-containing monomer in the polymer is preferably 5% by mass or more, more preferably 7.5% by mass or more, still more preferably 10% by mass or more, preferably 50% by mass or less, and more preferably 40% by mass or less. By making the content ratio of the ether group-containing monomer units in the polymer 5% by mass or more, the adhesion strength between the electrode composite layer and the current collector can be improved. In addition, by making the content ratio of the ether group-containing monomer units in the polymer 50% by mass or less, the dispersibility of the electrode active material and the conductive assistant can be improved in the slurry composition prepared using the binder composition of the present invention.

[0053] [Polymer having a carboxyl group]

[0054] The polymer having a carboxyl group is obtained by polymerizing a monomer composition containing a monomer having a carboxyl group. Here, examples of the monomer having a carboxyl group include: carboxylic acid monomers such as acrylic acid, methacrylic acid, ethylacrylic acid (2-ethylacrylic acid), itaconic acid, maleic acid, fumaric acid, citraconic acid; and ethylenically unsaturated carboxylic acid compounds such as monoalkyl maleate monomers such as monomethyl maleate, monoethyl maleate, monon-butyl maleate, monomethyl fumarate, monoethyl fumarate, and monon-butyl fumarate. They can be used alone or in combination of two or more.

[0055] Moreover, when the total repeating units in the polymer are 100% by mass, the content ratio of the carboxyl group-containing monomer units derived from the carboxyl group-containing monomer in the polymer is preferably 1% by mass or more, more preferably 1.5% by mass or more, still more preferably 2% by mass or more, preferably 10% by mass or less, and more preferably 8% by mass or less. By making the content ratio of the carboxyl group-containing monomer units in the polymer 1% by mass or more, the adhesion strength between the electrode composite layer and the current collector can be improved. In addition, by making the content ratio of the carboxyl group-containing monomer units in the polymer 10% by mass or less, a solid electrolyte layer-containing layer capable of exhibiting excellent ionic conductivity can be formed using the slurry composition prepared using the binder composition of the present invention.

[0056] [Polymer having a hydroxyl group]

[0057] The polymer having a hydroxyl group is obtained by polymerizing a monomer composition containing a hydroxyl group-containing monomer. Here, examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate and hydroxyethyl acrylamide.

[0058] Moreover, when the total repeating units in the polymer are 100% by mass, the content ratio of the hydroxyl group-containing monomer units derived from the hydroxyl group-containing monomer in the polymer is preferably 1% by mass or more, more preferably 1.5% by mass or more, still more preferably 2% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less. By making the content ratio of the hydroxyl group-containing monomer units in the polymer 1% by mass or more, the adhesion strength between the electrode composite layer and the current collector can be improved. In addition, by making the content ratio of the hydroxyl group-containing monomer units in the polymer 10% by mass or less, a solid electrolyte-containing layer capable of exhibiting excellent ionic conductivity can be formed by using the slurry composition prepared with the binder composition of the present invention.

[0059] In addition, the polymer contained in the binder composition of the present invention can contain monomer units such as vinyl cyanide monomer units, aromatic monomer units, conjugated diene monomer units, and / or alkylene structural units.

[0060] [Vinyl cyanide monomer units]

[0061] Examples of the vinyl cyanide monomer capable of forming vinyl cyanide monomer units include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-ethylacrylonitrile. They can be used alone or in combination of two or more. Among them, acrylonitrile is preferred.

[0062] Moreover, when the total repeating units in the polymer are 100% by mass, the content ratio of the vinyl cyanide monomer units in the polymer is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, preferably 35% by mass or less, more preferably 28% by mass or less, still more preferably 26% by mass or less. By making the content ratio of the vinyl cyanide monomer units in the polymer 2% by mass or more, a solid electrolyte-containing layer in which the solid electrolyte is well dispersed can be formed by using the slurry composition prepared with the binder composition of the present invention. In addition, by making the content ratio of the vinyl cyanide monomer units in the polymer 35% by mass or less, the solubility of the polymer in an organic solvent can be made good. Therefore, by using the slurry composition prepared with this binder composition, the dispersibility of each component contained in the slurry composition can be improved.

[0063] [Aromatic monomer units]

[0064] Examples of the aromatic monomer capable of forming an aromatic monomer unit include styrene, styrenesulfonic acid and its salts, α-methylstyrene, p-tert-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, vinylnaphthalene, phenoxyethyl acrylate, and the like. They may be used alone or in combination of two or more. Among them, styrene is preferred.

[0065] Moreover, when the total repeating units in the polymer are 100% by mass, the content ratio of the aromatic monomer unit in the polymer is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 10% by mass or more, preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less. By making the content ratio of the aromatic monomer unit in the polymer 5% by mass or more, the dispersibility of the electrode active material and the conductive auxiliary material can be improved by using the slurry composition prepared with the binder composition of the present invention. In addition, by making the content ratio of the aromatic monomer unit in the polymer 40% by mass or less, the adhesion strength between the electrode composite layer and the current collector can be improved by using the slurry composition prepared with the binder composition of the present invention. In addition, by using this slurry composition, a solid electrolyte-containing layer in which the solid electrolyte is well dispersed can be formed.

[0066] [Conjugated diene monomer unit]

[0067] Examples of the conjugated diene monomer capable of forming a conjugated diene monomer unit include 1,3-butadiene, 2-methyl-1,3-butadiene (hereinafter referred to as "isoprene"), 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, aliphatic conjugated diene monomers such as substituted and side-chain conjugated hexadienes, and the like. They may be used alone or in combination of two or more.

[0068] In addition, in the present invention, the "diene monomer unit" also includes a structural unit (hydride unit) obtained by further hydrogenating the monomer unit contained in the polymer obtained using a diene monomer.

[0069] [Alkylene structural unit]

[0070] The alkylene structural unit is a repeating unit composed only of an alkylene structure represented by the general formula: -C n H 2n -(wherein n is an integer of 2 or more).

[0071] In addition, the alkylene structural unit may be linear or branched, and the alkylene structural unit is preferably linear, that is, a linear alkylene structural unit. Further, the number of carbon atoms of the alkylene structural unit is preferably 4 or more (that is, n in the above general formula is an integer of 4 or more).

[0072] Moreover, the method for introducing the alkylene structural unit into the polymer is not particularly limited, and examples thereof include the following methods (1) or (2):

[0073] (1) A method of preparing a polymer from a monomer composition containing a conjugated diene monomer and hydrogenating the polymer to convert the conjugated diene monomer unit into an alkylene structural unit

[0074] (2) A method of preparing a polymer from a monomer composition containing a 1-alkene monomer.

[0075] Among them, the method of (1) is easy to manufacture the polymer, so this method is preferred.

[0076] That is, the alkylene structural unit is preferably a structural unit obtained by hydrogenating a conjugated diene monomer unit (conjugated diene hydride unit), and more preferably a structural unit obtained by hydrogenating a 1,3-butadiene unit (1,3-butadiene hydride unit).

[0077] In addition, examples of the 1-alkene monomer include ethylene, propylene, 1-butene, 1-hexene, etc. They can be used alone or in combination of two or more.

[0078] Moreover, when the total repeating units in the polymer are 100% by mass, the content ratio of the conjugated diene monomer unit and / or the alkylene structural unit in the polymer is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, preferably 60% by mass or less, more preferably 55% by mass or less, still more preferably 50% by mass or less. In addition, in the present invention, when both the conjugated diene monomer unit and the alkylene structural unit are contained in the polymer, the total of the conjugated diene monomer unit and the alkylene structural unit is preferably within the above range. Moreover, by making the content ratio of the conjugated diene monomer unit and / or the alkylene structural unit in the polymer 20% by mass or more, the dispersibility of the electrode active material and the conductive auxiliary material can be improved by using the slurry composition prepared with the binder composition of the present invention. In addition, by making the content ratio of the conjugated diene monomer unit and / or the alkylene structural unit in the polymer 60% by mass or less, the adhesion strength between the electrode composite layer and the current collector can be improved by using the slurry composition prepared with the binder composition of the present invention. In addition, by using this slurry composition, a solid electrolyte-containing layer in which the solid electrolyte is well dispersed can be formed.

[0079] [Other monomer units]

[0080] Moreover, the polymer contained in the binder composition of the present invention may further contain other monomer units in addition to the above-mentioned monomer units. Moreover, as other monomers capable of forming such monomer units, there is no particular limitation, and examples thereof include crosslinkable monomers (for example, allyl methacrylate, ethylene glycol dimethacrylate, etc.).

[0081] [Preparation method of polymer]

[0082] The preparation method of the polymer contained in the binder composition of the present invention is not particularly limited, and it can be prepared, for example, by polymerizing a monomer composition containing the above-mentioned monomers and optionally performing hydrogenation.

[0083] Here, in the present invention, the content ratio of each monomer in the monomer composition can be determined according to the content ratio of each monomer unit and structural unit in the polymer.

[0084] In addition, the polymerization method is not particularly limited, and any method such as solution polymerization method, suspension polymerization method, bulk polymerization method, emulsion polymerization method, etc. can be used. In each polymerization method, known emulsifiers and polymerization initiators can be used as needed.

[0085] Furthermore, the hydrogenation method is not particularly limited, and a usual method using a catalyst can be used (refer to, for example, International Publication No. 2012 / 165120, International Publication No. 2013 / 080989, and Japanese Unexamined Patent Application Publication No. 2013-8485).

[0086] [Organic solvent]

[0087] The organic solvent contained in the binder composition of the present invention is not particularly limited, and can be appropriately selected according to the use of the binder composition. Here, as the organic solvent, for example: aromatic hydrocarbons such as toluene, xylene, mesitylene; ketones such as methyl ethyl ketone, cyclohexanone, diisobutyl ketone; esters such as ethyl acetate, butyl acetate, butyl butyrate, hexyl butyrate, isobutyl isobutyrate, γ-butyrolactone, ε-caprolactone; ethers such as tetrahydrofuran, ethylene glycol diethyl ether, n-butyl ether. They can be used alone or in combination of two or more.

[0088] Moreover, in the case of preparing a slurry composition for an all-solid-state secondary battery using the binder of the present invention, from the viewpoint of improving the dispersibility of the solid electrolyte while suppressing deterioration caused by side reactions, as the organic solvent, xylene, mesitylene, diisobutyl ketone, butyl butyrate, hexyl butyrate, n-butyl ether are preferred, and xylene, mesitylene, diisobutyl ketone are more preferred.

[0089] [Compound formed of organic or inorganic substance]

[0090] The compound formed of an organic or inorganic substance contained in the binder composition of the present invention is a compound having a solubility of 10% by mass or less in water at a temperature of 25°C and containing an element belonging to Group 13 and / or Group 14 of the periodic table. Herein, in the present invention, among the elements belonging to Group 13 and / or Group 14 of the periodic table, carbon and germanium are excluded.

[0091] Moreover, the above compound contained in the binder composition of the present invention preferably has at least one structure selected from -O-Si-O-, SiO2, and -O-Al-O-, and more preferably has at least one structure selected from -O-Si-O- and -O-Al-O-. If the compound has any of the structures of -O-Si-O-, SiO2, and -O-Al-O-, a secondary battery with improved water resistance can be manufactured by using the binder composition of the present invention.

[0092] Herein, as the compound having at least one structure selected from -O-Si-O-, SiO2, and -O-Al-O-, for example, zeolite, silica gel, polydimethylsiloxane, etc. can be cited. They can be used alone, or two or more of them can be used in combination. Among them, from the viewpoint of improving the water resistance and cycle characteristics of the secondary battery, as the above compound, zeolite, silica gel, and polydimethylsiloxane are preferred.

[0093] <Other components>

[0094] There is no particular limitation on other components that can be optionally contained in the binder composition of the present invention. As other components, for example, binder materials, dispersants, leveling agents, defoaming agents, and reinforcing materials other than the above polymers can be cited. These other components are not particularly limited as long as they do not affect the battery reaction. In addition, these components can be used alone, or two or more of them can be used in combination at any ratio.

[0095] <Properties of the binder composition for secondary batteries>

[0096] The binder composition of the present invention contains at least the above polymer, organic solvent, and compound. In this binder composition, the content of the above elements needs to be 5 mass ppm or more and 5000 mass ppm or less relative to the polymer. Thus, by using the binder composition of the present invention, the water resistance of the secondary battery can be improved and the secondary battery can exhibit excellent battery characteristics.

[0097] Here, the content of the above elements in the binder composition of the present invention is preferably 10 mass ppm or more, more preferably 20 mass ppm or more, further preferably 500 mass ppm or more, preferably 4000 mass ppm or less, more preferably 3500 mass ppm or less, further preferably 3000 mass ppm or less, and particularly preferably 2000 mass ppm or less, relative to the above polymer. If the content of the above elements in the binder composition is 10 mass ppm or more relative to the above polymer, deterioration caused by side reactions can be suppressed. In addition, if the content of the above elements is 3500 mass ppm or less relative to the above polymer, coagulation of each component in the slurry composition can be suppressed by using the slurry composition prepared from the binder composition of the present invention, and the slurry characteristics can be improved. Furthermore, if the content of the above elements is 3000 mass ppm or less relative to the above polymer, an increase in the cell resistance of the secondary battery can be sufficiently suppressed.

[0098] <Method for preparing binder composition for secondary battery>

[0099] The method for preparing the binder composition of the present invention is not particularly limited. For example, the above polymer, compound, and other components used as needed can be mixed in an organic solvent for preparation. At this time, the mixing method is not particularly limited, and a commonly used mixer or disperser can be used for mixing.

[0100] (Slurry composition for secondary battery)

[0101] The slurry composition for secondary battery of the present invention at least contains the above binder composition for secondary battery of the present invention. More specifically, the slurry composition of the present invention at least contains the above polymer, organic solvent, and compound, and can optionally contain other components. Moreover, since the slurry composition of the present invention contains the above binder composition, by using this slurry composition, the water resistance of the secondary battery can be improved and the secondary battery can exhibit excellent battery characteristics.

[0102] Here, the slurry composition of the present invention can contain a solid electrolyte as the above other component. According to the slurry composition containing the solid electrolyte, by using this slurry composition, a solid electrolyte-containing layer with excellent water resistance can be formed.

[0103] <Method for preparing slurry composition for secondary battery>

[0104] The method for preparing the slurry composition of the present invention is not particularly limited. For example, any mixing device can be used to arbitrarily mix the binder composition with other components such as a solid electrolyte for preparation.

[0105] <Solid electrolyte>

[0106] The solid electrolyte that can be arbitrarily included in the paste composition of the present invention is not particularly limited as long as it is particles formed of a solid having ion conductivity, and for example, an inorganic solid electrolyte can be used.

[0107] The inorganic solid electrolyte is not particularly limited, and a crystalline inorganic ion conductor, an amorphous inorganic ion conductor, or a mixture thereof can be used. Moreover, when the solid electrolyte-containing layer formed using the paste composition of the present invention is used in an all-solid-state lithium secondary battery, as the inorganic solid electrolyte, a crystalline inorganic lithium ion conductor, an amorphous inorganic lithium ion conductor, or a mixture thereof can generally be used. Among them, from the viewpoint of forming a solid electrolyte-containing layer having further excellent ion conductivity, the inorganic solid electrolyte preferably contains at least one of a sulfide-based inorganic solid electrolyte and an oxide-based inorganic solid electrolyte.

[0108] Moreover, examples of the crystalline inorganic lithium ion conductor include: Li3N, LISICON (Li 14 Zn(GeO4)4), perovskite type (e.g., Li 0.5 La 0.5 TiO3), garnet type (e.g., Li7La3Zr2O 12 ), LIPON (Li 3+y PO 4-x N x ), Thio-LISICON (Li 3.25 Ge 0.25 P 0.75 S4), etc.

[0109] The amorphous inorganic lithium ion conductor is not particularly limited as long as it contains S (sulfur atom) and has ion conductivity (sulfide solid electrolyte material). Here, when the paste composition of the present invention is used in a solid-state lithium secondary battery, as the sulfide solid electrolyte material, a sulfide solid electrolyte material formed using a raw material composition containing Li2S and elements of Group 13 to Group 15 can be cited. As a method for synthesizing the sulfide solid electrolyte material using such a raw material composition, for example, an amorphization method can be cited. As the amorphization method, for example, a mechanical milling method and a melt quenching method can be cited, and the mechanical milling method is preferably used. This is because the mechanical milling method can be processed at room temperature, simplifying the manufacturing process.

[0110] As elements of Group 13 to Group 15 above, for example, Al, Si, Ge, P, As, Sb, etc. can be cited. In addition, as sulfides of elements of Group 13 to Group 15, specifically, Al2S3, SiS2, GeS2, P2S3, P2S5, As2S3, Sb2S3, etc. can be cited. Among them, sulfides of Group 14 or Group 15 are preferably used. In particular, as the sulfide solid electrolyte material formed from the raw material composition containing Li2S and sulfides of elements of Group 13 to Group 15, Li2S-P2S5 material, Li2S-SiS2 material, Li2S-GeS2 material or Li2S-Al2S3 material is preferred, and Li2S-P2S5 material is more preferred. This is because they have excellent Li ion conductivity.

[0111] The above-mentioned crystalline inorganic lithium ion conductor can be used alone or in combination of two or more. In addition, the particle size of the solid electrolyte is not particularly limited and can be the same as that of the solid electrolyte used in the past.

[0112] (including solid electrolyte layer)

[0113] The solid electrolyte layer-containing layer of the present invention (hereinafter also simply referred to as "solid electrolyte layer-containing layer") is a layer formed using the slurry composition of the present invention. Moreover, the slurry composition used in forming the solid electrolyte layer-containing layer of the present invention contains at least a solid electrolyte. Here, the solid electrolyte layer-containing layer of the present invention can be used as, for example, an electrode composite layer (positive electrode composite layer, negative electrode composite layer) for electron transfer via an electrochemical reaction, a solid electrolyte layer provided between the opposing positive electrode composite layer and negative electrode composite layer, and is not particularly limited.

[0114] The method for forming the solid electrolyte layer-containing layer of the present invention is not particularly limited. For example, it can be formed by coating the slurry composition of the present invention containing the above-mentioned solid electrolyte on the surface of a suitable substrate to form a coating film, and then drying the formed coating film. That is, the solid electrolyte layer-containing layer of the present invention is formed from the dried product of the slurry composition of the present invention containing the above-mentioned solid electrolyte, and generally contains at least a solid electrolyte, a polymer, and a compound containing an element belonging to Group 13 and / or Group 14 of the periodic table. In addition, each component contained in the solid electrolyte layer-containing layer is the same as each component contained in the above-mentioned slurry composition, and the content ratio of these components is generally equal to the content ratio in the above-mentioned slurry composition.

[0115] In addition, the content of the solid electrolyte in the solid electrolyte layer-containing layer can be, for example, 10% by mass or more and 100% by mass or less. In addition, the thickness of the solid electrolyte layer-containing layer can be, for example, 1 μm or more and 500 μm or less.

[0116] Since the solid electrolyte layer-containing layer of the present invention is formed from the slurry composition of the present invention, it has excellent water resistance. Further, when the solid electrolyte layer-containing layer of the present invention is used as an electrode composite layer, even when pressing treatment is performed at a pressure (pressing pressure) of, for example, less than 300 MPa, the electrode composite layer can be sufficiently densified.

[0117] (All-solid-state secondary battery)

[0118] The all-solid-state secondary battery of the present invention has the above-described solid electrolyte layer-containing layer of the present invention. Here, the all-solid-state secondary battery of the present invention has, for example, a positive electrode, a solid electrolyte layer, and a negative electrode, and at least one of the positive electrode composite layer of the positive electrode, the negative electrode composite layer of the negative electrode, and the solid electrolyte layer is the solid electrolyte layer-containing layer of the present invention.

[0119] Moreover, since the all-solid-state secondary battery of the present invention has the solid electrolyte layer-containing layer of the present invention, it has excellent water resistance and excellent battery characteristics.

[0120] Here, as the electrode for an all-solid-state secondary battery that can be used in the all-solid-state secondary battery of the present invention and has an electrode composite layer that does not belong to the solid electrolyte layer-containing layer of the present invention, as long as it is an electrode for an all-solid-state secondary battery having an electrode composite layer that does not belong to the solid electrolyte layer-containing layer of the present invention, there is no particular limitation, and any electrode for an all-solid-state secondary battery can be used.

[0121] In addition, as the solid electrolyte layer that can be used in the all-solid-state secondary battery of the present invention and does not belong to the solid electrolyte layer-containing layer of the present invention, there is no particular limitation, and any solid electrolyte layer such as the solid electrolyte layers described in Japanese Unexamined Patent Application Publication No. 2012-243476, Japanese Unexamined Patent Application Publication No. 2013-143299, and Japanese Unexamined Patent Application Publication No. 2016-143614 can be used.

[0122] Moreover, the all-solid-state secondary battery of the present invention can be obtained as follows: The positive electrode and the negative electrode are laminated in such a manner that the positive electrode composite layer of the positive electrode and the negative electrode composite layer of the negative electrode face each other with the solid electrolyte layer interposed therebetween, and the laminate is optionally pressurized. Then, depending on the battery shape, it is directly inserted into a battery container or wound, folded, etc. and inserted into a battery container, and sealed to obtain the battery. Further, if necessary, an overcurrent prevention element such as a porous metal mesh, a fuse, a PTC element, a guide plate, etc. is placed in the battery container, and the pressure rise and overcharge / discharge inside the battery can be prevented. The shape of the battery can be any of coin shape, button shape, sheet shape, cylindrical shape, square shape, flat shape, etc.

[0123] (Method for manufacturing an all-solid-state secondary battery)

[0124] The manufacturing method of the all-solid-state secondary battery of the present invention includes a step of pressing the solid electrolyte layer-containing material of the present invention under a pressure of less than 300 MPa (pressing step), and can optionally include a step of coating the slurry composition of the present invention on a substrate (coating step) and a step of drying the slurry composition coated on the substrate to form a solid electrolyte layer-containing layer (solid electrolyte layer-containing layer forming step) before the pressing step. In addition, hereinafter, the manufacturing method of the all-solid-state secondary battery in the case where the solid electrolyte layer-containing layer of the present invention is used as an electrode composite layer of the secondary battery will be described. The manufacturing method of the all-solid-state secondary battery of the present invention is not particularly limited as long as it includes at least the above-mentioned pressing step.

[0125] <Coating step>

[0126] In the coating step, the slurry composition is coated on the substrate. Here, as the method of coating the slurry composition on the substrate, there is no particular limitation, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, and the like.

[0127] <Solid electrolyte layer-containing layer forming step>

[0128] In the solid electrolyte layer-containing layer forming step, the slurry composition on the substrate is dried. Here, as the method of drying the slurry composition on the substrate, there is no particular limitation, and known methods can be used. As the drying method, for example, drying methods using warm air, hot air, low-humidity air; vacuum drying methods; drying methods using irradiation of infrared rays, electron beams, etc. can be cited.

[0129] <Pressing step>

[0130] In the pressing step, the solid electrolyte layer-containing layer is pressed under a pressing pressure of less than 300 MPa. Here, as the method of performing the pressing treatment, there is no particular limitation, and roll pressing or the like can be used for the pressing treatment. Moreover, in the manufacturing method of the all-solid-state secondary battery of the present invention, in the case of forming a solid electrolyte layer that functions as an electrode composite layer, even when the solid electrolyte layer-containing layer is pressed under a pressing pressure as low as less than 300 MPa, the electrode composite layer can be sufficiently densified.

[0131] Examples

[0132] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In addition, in the following description, unless otherwise specified, "%" and "parts" indicating amounts are based on mass.

[0133] In addition, unless otherwise specified, in a polymer produced by copolymerizing a plurality of monomers, the proportion of monomer units formed by polymerizing a certain monomer in the above polymer generally coincides with the ratio (feed ratio) of the certain monomer in all the monomers used for the polymerization of the polymer.

[0134] Moreover, in the examples and comparative examples, the content, dispersibility, ionic conductivity, peel strength of the positive electrode, cell resistance, pressibility, and cell characteristics (cycle characteristics) of the elements belonging to Group 13 and / or Group 14 of the periodic table with respect to the polymer in the binder composition were measured or evaluated by the following methods. In addition, the solubility in water of the compounds used in the examples and comparative examples was measured by the following method.

[0135] <Content of elements belonging to Group 13 and / or Group 14 of the periodic table>

[0136] About 1 g of the binder composition was heated in an electric furnace at 550 °C for about 3 hours for ashing. Then, about 5 mL of concentrated sulfuric acid was added to the ashed binder composition to dissolve it, and about 5 mL of concentrated nitric acid was slowly added for wet decomposition. After decomposition, the acid was concentrated, and the volume was made up to 10 mL with ultrapure water. The metal ion concentration in the binder composition was measured using an ICP-AES device (manufactured by Nippon Seimitsu Electronics Co., Ltd., model "SPS-5100"). Based on the obtained value of the metal ion concentration, the content of the elements belonging to Group 13 and / or Group 14 of the periodic table (except for carbon and germanium) with respect to the polymer contained in the binder composition was calculated.

[0137] <Dispersibility>

[0138] The viscosity of the slurry composition for the solid electrolyte layer was measured with a Brookfield B-type viscometer at 60 rpm (temperature 25 °C), and evaluation was carried out according to the following criteria. The smaller the viscosity of the slurry composition for the solid electrolyte layer, the better the dispersion of the solid electrolyte contained in the slurry composition for the solid electrolyte layer.

[0139] A: Viscosity less than 3000 mPa·s

[0140] B: Viscosity of 3000 mPa·s or more and less than 5000 mPa·s

[0141] C: Viscosity of 5000 mPa·s or more and less than 8000 mPa·s

[0142] D: Viscosity of 8000 mPa·s or more or non-dispersion (no fluidity)

[0143] <Ionic conductivity>

[0144] Inside a glove box (with a moisture content of 1 ppm or less), the slurry composition for the solid electrolyte layer was dried using a hot plate at a temperature of 130°C. The resulting powder was formed into a cylindrical shape with a diameter of 10 mm and a thickness of 1 mm as a measurement sample. The lithium-ion conductivity (at a temperature of 25°C) of this measurement sample was measured using the alternating current impedance method. Additionally, during the measurement, a frequency response analyzer (manufactured by Solartron Analytical, UK, product name "Solartron (registered trademark) 1260") was used, and the measurement conditions were an applied voltage of 10 mV and a measurement frequency range of 0.01 MHz to 1 MHz. The obtained lithium-ion conductivity was designated as S0.

[0145] Separately, inside a drying chamber (with a moisture content of 127 ppm or less, corresponding to a dew point of -40°C), the slurry composition for the solid electrolyte layer was dried using a hot plate at a temperature of 130°C. The resulting powder was formed into a cylindrical shape with a diameter of 10 mm and a thickness of 0.5 mm as a measurement sample. The lithium-ion conductivity (at a temperature of 25°C) of this measurement sample was measured in the same manner as S0 above. The obtained lithium-ion conductivity was designated as S1.

[0146] Then, the conductivity retention rate = S1 / S0 × 100 (%) was calculated and evaluated according to the following criteria. It is considered that the larger the conductivity retention rate, the more effectively the deterioration of the solid electrolyte caused by moisture can be suppressed, and the better the water resistance. In addition, the larger the conductivity retention rate, the more excellent the ion conductivity of the solid electrolyte layer (including the solid electrolyte layer) formed using this slurry composition for the solid electrolyte layer can be.

[0147] A: The conductivity retention rate is 95% or more

[0148] B: The conductivity retention rate is 85% or more and less than 95%

[0149] C: The conductivity retention rate is 60% or more and less than 85%

[0150] D: The conductivity retention rate is less than 60%

[0151] <Peeling strength of the positive electrode>

[0152] A rectangular test piece with a width of 1.0 cm and a length of 10 cm was cut out from the positive electrode. After pasting a transparent tape (transparent tape specified in JIS Z1522) on the side surface of the positive electrode composite layer of this test piece, the transparent tape was peeled off from one end of the test piece along the 180° direction at a speed of 50 mm / min, and the stress during peeling was measured. The measurement was carried out 3 times in total, and the average value was calculated. This average value was used as the peeling strength (N / m) of the positive electrode and evaluated according to the following criteria. The larger the peeling strength of the positive electrode, the better the adhesiveness of the positive electrode composite layer and the stronger the close fit with the current collector.

[0153] A+: The peel strength is 4 N / m or more.

[0154] A: The peel strength is 3 N / m or more and less than 4 N / m.

[0155] B: The peel strength is 2 N / m or more and less than 3 N / m.

[0156] C: The peel strength is 1 N / m or more and less than 2 N / m.

[0157] D: The peel strength is less than 1 N / m.

[0158] <Battery cell resistance>

[0159] Charge the all-solid-state secondary battery of three battery cells to 4.2 V by the constant current method of 0.1 C, then discharge it to 3.0 V at 0.1 C, and obtain the 0.1 C discharge capacity. Next, charge it to 4.2 V at 0.1 C, and then discharge it to 3.0 V at 2 C, and obtain the 2 C discharge capacity. Take the average value of the 0.1 C discharge capacities of the three battery cells as the discharge capacity a, take the average value of the 2 C discharge capacities of the three battery cells as the discharge capacity b, and calculate the ratio of the discharge capacity b to the discharge capacity a (capacity ratio) = discharge capacity b / discharge capacity a × 100 (%). Evaluate according to the following criteria. The larger the value of the capacity ratio, the lower the battery cell resistance.

[0160] A: The capacity ratio is 90% or more.

[0161] B: The capacity ratio is 80% or more and less than 90%.

[0162] C: The capacity ratio is 60% or more and less than 80%.

[0163] D: The capacity ratio is less than 60%.

[0164] <Pressibility>

[0165] Cut the fabricated positive electrode into a diameter of 10 mm, and use a uniaxial press to press it at a specified pressure for 2 minutes to measure the pressing pressure (MPa) when the target density reaches 3.3 g / cm 3 Evaluate according to the following criteria. The lower the pressing pressure, the more excellent the pressibility.

[0166] A: Less than 200 MPa

[0167] B: 200 MPa or more and less than 300 MPa

[0168] C: 300 MPa or more and less than 400 MPa

[0169] D: 400 MPa or more

[0170] <Battery cell characteristics (cycle characteristics)>

[0171] The obtained all-solid-state secondary battery was repeatedly charged and discharged 50 cycles as follows: charged from 3 V to 4.2 V at 0.1C at 45 °C, and then discharged from 4.2 V to 3 V at 0.1C. The ratio of the 0.1C discharge capacity of the 50th cycle to the 0.1C discharge capacity of the 1st cycle was calculated as a percentage, and this value was used as the capacity retention rate and evaluated according to the following criteria. The larger the value of the capacity retention rate, the less the discharge capacity decreases, and the more excellent the cell characteristics (cycle characteristics).

[0172] A: The capacity retention rate is 90% or more

[0173] B: The capacity retention rate is 80% or more and less than 90%

[0174] C: The capacity retention rate is 70% or more and less than 80%

[0175] D: The capacity retention rate is less than 70%

[0176] <Solubility of the compound in water>

[0177] The solubility of the compounds used in the examples and comparative examples in water at a temperature of 25 °C was measured by the EPA method (EPA Chemical Fate testing Guideline CG-1500 Water Solubility).

[0178] (Example 1)

[0179] <Preparation of the binder composition>

[0180] 100 parts of ion-exchanged water and 0.2 part of sodium dodecylbenzenesulfonate as an emulsifier were added to a 1 L flask with a rubber stopper equipped with a stirrer. The gas phase part was replaced with nitrogen, and the temperature was raised to 60 °C. Then, 0.25 part of ammonium persulfate (APS) as a polymerization initiator was dissolved in 20.0 parts of ion-exchanged water and added to the flask.

[0181] On the other hand, 40 parts of ion-exchanged water, 1.0 part of sodium lauryl sulfate as an emulsifier, 69 parts of n-butyl acrylate as a carbonyl-containing monomer, 6 parts of acrylonitrile as a cyanated vinyl monomer, and 25 parts of styrene as an aromatic monomer were mixed in another container to obtain a monomer composition. This monomer composition was continuously added to the above-mentioned 1 L flask with a rubber stopper over 3 hours for polymerization. During the addition, the reaction was carried out at a temperature of 60 °C. After the addition was completed, the mixture was further stirred at 80 °C for 3 hours to terminate the reaction.

[0182] Next, an appropriate amount of diisobutyl ketone as an organic solvent was added to obtain a mixture. Then, vacuum distillation was carried out at a temperature of 80 °C to remove water and excess diisobutyl ketone from the mixture, and a binder precursor composition (solid component concentration: 8%) was obtained.

[0183] Furthermore, 5 parts of a first synthetic zeolite (manufactured by Shin-Etsu Chemical Co., Ltd., product name “Molecular Sieve 4A”, shape: powder, particle size: 325 mesh, solubility in water at a temperature of 25 °C: less than 0.1%) as a compound containing an element belonging to Group 13 and / or Group 14 of the periodic table was added to the obtained binder precursor composition, and after 24 hours, filtration was carried out using a 10-μm filter, whereby a binder composition was obtained.

[0184] <Preparation of Slurry Composition for Positive Electrode Composite Material Layer>

[0185] 70 parts of lithium cobaltate as a positive electrode active material (number average particle size: 11.5 μm), 25.5 parts of a sulfide glass formed from Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle size: 0.9 μm) as a solid electrolyte, 2.5 parts of acetylene black as a conductive material, and 2 parts (equivalent amount of solid component) of the binder composition obtained as described above were mixed, and then diisobutyl ketone as an organic solvent was added to adjust the solid component concentration to 80%, and then mixed for 60 minutes using a planetary mixer. Then, diisobutyl ketone was added again to adjust the solid component concentration to 70%, and then mixed for 10 minutes to prepare a slurry composition for a positive electrode composite material layer.

[0186] <Preparation of Slurry Composition for Negative Electrode Composite Material Layer>

[0187] 60 parts of graphite as negative electrode active material particles (number average particle size: 20 μm), 36.5 parts of a sulfide glass formed from Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle size: 0.9 μm) as solid electrolyte particles, 1.5 parts of acetylene black as conductive material particles, and 2 parts (equivalent amount of solid component) of the binder composition obtained as described above were mixed, and then diisobutyl ketone as an organic solvent was added to adjust the solid component concentration to 65%, and then mixed for 60 minutes using a planetary mixer. Then, diisobutyl ketone was added again to adjust the solid component concentration to 60%, and then mixed using a planetary mixer to prepare a slurry composition for a negative electrode composite material layer.

[0188] <Preparation of Slurry Composition for Solid Electrolyte Layer>

[0189] In a glove box under an argon atmosphere (moisture concentration: 0.6 mass ppm, oxygen concentration: 1.8 mass ppm), 100 parts of a sulfide glass formed from Li2S and P2S5 (Li2S / P2S5 = 70 mol% / 30 mol%, number average particle diameter: 0.9 μm) as solid electrolyte particles, 2 parts (equivalent amount of solid component) of the binder composition obtained as described above were mixed, and then diisobutyl ketone as an organic solvent was added. The solid component concentration was adjusted to 60 mass%, and then mixed for 60 minutes using a planetary mixer. Then, diisobutyl ketone was added again, the solid component concentration was adjusted to 45%, and then mixed using a planetary mixer to prepare a slurry composition for a solid electrolyte layer. Various measurements were performed using the obtained slurry composition for a solid electrolyte layer. The results are shown in Table 1.

[0190] <Manufacture of All-Solid-State Secondary Battery>

[0191] The above slurry composition for a positive electrode composite layer was coated on the surface of a current collector (aluminum foil, thickness: 20 μm) and dried (temperature: 120°C, 60 minutes) to form a positive electrode composite layer (including a solid electrolyte layer) with a thickness of 50 μm, thereby obtaining a positive electrode. The peel strength and pressability of the positive electrode were measured using this positive electrode. The results are shown in Table 1.

[0192] In addition, the above slurry composition for a negative electrode composite layer was coated on the surface of another current collector (copper foil, thickness: 15 μm) and dried (temperature: 120°C, 60 minutes) to form a negative electrode composite layer (including a solid electrolyte layer) with a thickness of 60 μm, thereby obtaining a negative electrode.

[0193] Next, the above slurry composition for a solid electrolyte layer was coated on an imide film (thickness: 25 μm) and dried (temperature: 120°C, 60 minutes) to form a solid electrolyte layer (including a solid electrolyte layer) with a thickness of 150 μm. Lamination was performed in such a manner that the positive electrode composite layer was in contact with the solid electrolyte layer, and pressing treatment was performed by applying a pressure of 400 MPa (pressing pressure), thereby transferring the solid electrolyte layer from the imide film to the positive electrode composite layer, and thus obtaining a positive electrode with a solid electrolyte layer.

[0194] The positive electrode with a solid electrolyte layer and the negative electrode were laminated in such a manner that the solid electrolyte layer of the positive electrode with a solid electrolyte layer was in contact with the negative electrode composite layer of the negative electrode, and pressing treatment was performed by applying a pressure of 400 MPa (pressing pressure) to the solid electrolyte layer (including a solid electrolyte layer) of the positive electrode with a solid electrolyte layer, thereby obtaining an all-solid-state secondary battery. The thickness of the solid electrolyte layer of the all-solid-state secondary battery after pressing was 120 μm. The cell resistance and cell characteristics (cycle characteristics) of the all-solid-state secondary battery were measured using this all-solid-state secondary battery. The results are shown in Table 1.

[0195] (Example 2)

[0196] When preparing the binder composition, as the monomer, 25 parts of phenoxyethyl acrylate as an ether group-containing monomer was used instead of styrene as an aromatic monomer. Except for this, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1.

[0197] (Examples 3 and 4)

[0198] When preparing the binder composition, the content of the elements belonging to Group 13 and / or Group 14 of the periodic table contained in the binder composition relative to the polymer was adjusted to 4300 mass ppm (Example 3) and 12 mass ppm (Example 4). Except for this, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1.

[0199] (Example 5)

[0200] When preparing the binder composition, as the compound containing the elements belonging to Group 13 and / or Group 14 of the periodic table, the second synthetic zeolite (manufactured by Shin-Etsu Chemical Co., Ltd., product name “Molecular Sieve 13X”, shape: powder, particle size: 325 mesh, solubility in water at 25 °C: 0.1%) was used instead of the first synthetic zeolite. Except for this, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1.

[0201] (Example 6)

[0202] When preparing the binder composition, as the compound containing the elements belonging to Group 13 and / or Group 14 of the periodic table, the third synthetic zeolite (manufactured by Shin-Etsu Chemical Co., Ltd., product name “Molecular Sieve 3A”, shape: powder, particle size: 325 mesh, solubility in water at 25 °C: 0.2%) was used instead of the first synthetic zeolite. Except for this, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1.

[0203] (Example 7)

[0204] When preparing the binder composition, as a compound containing an element belonging to Group 13 and / or Group 14 of the periodic table, the 4th synthetic zeolite (manufactured by Zeochem, product name "ZEOflair 110", shape: powder, particle size: 325 mesh, solubility in water at 25 °C: 0.1%) was used instead of the 1st synthetic zeolite. Except for this, the binder composition, the slurry composition for the positive composite material layer, the slurry composition for the negative composite material layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1.

[0205] (Example 8)

[0206] When preparing the binder composition, as a compound containing an element belonging to Group 13 and / or Group 14 of the periodic table, silica gel (manufactured by Toyota Chemical Industry Co., Ltd., product name "Silica Gel A Type", solubility in water at 25 °C: 0.3%) was used instead of the 1st synthetic zeolite. Except for this, the binder composition, the slurry composition for the positive composite material layer, the slurry composition for the negative composite material layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 2.

[0207] (Example 9)

[0208] When preparing the binder composition, 71 parts of n-butyl acrylate as a carbonyl group-containing monomer, 3 parts of methacrylic acid as a carboxyl group-containing monomer, 6 parts of acrylonitrile as a cyanovinyl monomer, and 20 parts of styrene as an aromatic monomer were used. Except for this, the binder composition, the slurry composition for the positive composite material layer, the slurry composition for the negative composite material layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 2.

[0209] (Example 10)

[0210] When preparing the binder composition, 2-hydroxyethyl acrylate as a hydroxyl group-containing monomer was used instead of the carboxyl group-containing monomer. Except for this, the binder composition, the slurry composition for the positive composite material layer, the slurry composition for the negative composite material layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery were produced in the same manner as in Example 9, and various evaluations were carried out. The results are shown in Table 2.

[0211] (Examples 11, 12, 16, 17)

[0212] When preparing the binder composition, butyl butyrate (Example 11), mesitylene (Example 12), xylene (Example 16), and isobutyl isobutyrate (Example 17) were used as organic solvents instead of diisobutyl ketone. Otherwise, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the 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 Tables 2 and 3.

[0213] (Example 13)

[0214] The binder composition prepared as described below was used. Otherwise, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the 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 2.

[0215] <Preparation of Binder Composition>

[0216] In a reactor, 2 parts of potassium oleate as an emulsifier, 0.1 part of potassium phosphate as a stabilizer, and 150 parts of water were added. Then, 35 parts of n-butyl acrylate as a carbonyl-containing monomer, 19 parts of acrylonitrile as a cyanated vinyl monomer, 31 parts of 1,3-butadiene as a conjugated diene monomer, 15 parts of styrene as an aromatic monomer, and 0.31 part of tert-dodecyl mercaptan as a molecular weight regulator were added. In the presence of 0.015 part of ferrous sulfate as an activator and 0.05 part of terpin hydroperoxide as a polymerization initiator, emulsion polymerization was initiated at a temperature of 10°C. At the moment when the polymerization conversion rate reached 85%, 0.2 part of hydroxylamine sulfate was added per 100 parts of the monomer to terminate the polymerization.

[0217] After the polymerization was terminated, heating was continued, and steam distillation was performed under reduced pressure at a temperature of 70°C to recover the unreacted monomer. Then, 2 parts of alkylated phenol as an anti-aging agent were added to obtain a polymer (copolymer latex).

[0218] <<Hydrogenation Reaction>>

[0219] 400 mL (total solid content: 48 g) of the aqueous dispersion of the obtained polymer was put into a 1-liter autoclave equipped with a stirrer, and nitrogen was circulated for 10 minutes to remove the dissolved oxygen in the polymer solution. Then, 50 mg of palladium acetate was dissolved in 180 mL of water in which 4 times the molar amount of nitric acid was added relative to Pd, and it was added as a hydrogenation reaction catalyst. After replacing the system with hydrogen twice, the contents of the autoclave were heated to a temperature of 50°C under a state of being pressurized with hydrogen to a pressure of 3 MPa, and the hydrogenation reaction was carried out for 6 hours.

[0220] Restore the content to room temperature, create a nitrogen environment within the system, and then use an evaporator to concentrate until the solid component concentration reaches 40% to obtain a polymer (hydrogenated nitrile rubber).

[0221] After solidifying 100 g of the obtained polymer (hydrogenated nitrile rubber) with 1 L of methanol, vacuum dry it at 60 °C for 12 hours. Use 1 1H-NMR to analyze the dried polymer. Calculate the content ratios (%) of each monomer unit and structural unit contained in the polymer based on the obtained analytical values. The results are shown in Table 2.

[0222] Next, add an appropriate amount of diisobutyl ketone to the aqueous dispersion of the obtained polymer to obtain a mixture. Then, perform vacuum distillation at 80 °C to remove water and excess diisobutyl ketone from the mixture to obtain a binder precursor composition (solid component concentration: 8%).

[0223] Furthermore, add 5 parts of the first synthetic zeolite (manufactured by Shin-Etsu Chemical Co., Ltd., product name "Molecular Sieve 4A, shape: powder, particle size: 325 mesh", solubility in water at 25 °C: less than 0.1%) as a compound containing elements belonging to Group 13 and / or Group 14 of the periodic table to the binder precursor composition, and filter it through a 10-μm filter after 24 hours to obtain a binder composition.

[0224] (Example 14)

[0225] As the polymer, use two polymers, Polymer A and Polymer B (mass ratio of Polymer A to Polymer B is 1:1). Except for this, prepare the slurry compositions for the positive electrode composite layer, the negative electrode composite layer, the solid electrolyte layer, and the all-solid-state secondary battery in the same manner as in Example 1, and conduct various evaluations. The results are shown in Table 3. In addition, Polymer A and Polymer B are prepared as follows.

[0226] <Preparation of the diisobutyl ketone dispersion of Polymer A>

[0227] Add 100 parts of ion-exchanged water to a 1-L flask with a rubber stopper equipped with a stirrer, displace the gas phase with nitrogen, and after heating to 70 °C, add a solution prepared by dissolving 0.5 part of ammonium persulfate (APS) as a polymerization initiator in 20.0 parts of ion-exchanged water.

[0228] On the other hand, in another container, mix 40 parts of ion-exchanged water, 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier, 50 parts of n-butyl acrylate as a carbonyl-containing monomer, 20 parts of ethyl acrylate, 10 parts of acrylonitrile as a cyanovinyl monomer, and 20 parts of styrene as an aromatic vinyl monomer to obtain a monomer composition.

[0229] The obtained monomer composition was continuously added to the above-mentioned 1-L flask with a rubber stopper over 2 hours for polymerization. Additionally, during the addition of the monomer composition, the reaction temperature was set at 70°C. After adding the monomer composition, it was stirred at 80°C for 3 hours, and then the polymerization was terminated.

[0230] Then, an appropriate amount of diisobutyl ketone as an organic solvent was added to the aqueous dispersion of the obtained Polymer A to obtain a mixture.

[0231] Then, vacuum distillation was carried out at 80°C to remove water and excess diisobutyl ketone from the mixture, obtaining a diisobutyl ketone dispersion of Polymer A (solid content concentration: 8%).

[0232] <Preparation of Diisobutyl Ketone Dispersion of Polymer B>

[0233] 100 parts of ion-exchanged water was added to a 1-L flask with a rubber stopper equipped with a stirrer, and the gas phase was replaced with nitrogen. After heating to 70°C, a solution prepared by dissolving 0.5 part of ammonium persulfate (APS) as a polymerization initiator in 20.0 parts of ion-exchanged water was added.

[0234] On the other hand, in another container, 40 parts of ion-exchanged water, 1.0 part of sodium dodecylbenzenesulfonate as an emulsifier, 54.5 parts of n-butyl acrylate as a carbonyl-containing monomer, 25 parts of ethyl acrylate, 10 parts of acrylonitrile as a cyano vinyl monomer, 10 parts of styrene as an aromatic monomer, and 0.5 part of allyl methacrylate as another monomer were mixed to obtain a monomer composition.

[0235] The obtained monomer composition was continuously added to the above-mentioned 1-L flask with a rubber stopper over 2 hours for polymerization. Additionally, during the addition of the monomer composition, the reaction temperature was set at 70°C. After adding the monomer composition, it was stirred at 80°C for 3 hours, and then the polymerization was terminated.

[0236] Then, an appropriate amount of diisobutyl ketone as an organic solvent was added to the aqueous dispersion of the obtained Polymer B to obtain a mixture.

[0237] Then, vacuum distillation was carried out at 80°C to remove water and excess diisobutyl ketone from the mixture, obtaining a diisobutyl ketone dispersion of Polymer B (solid content concentration: 8%).

[0238] <Preparation of Binder Composition Containing Polymer A and Polymer B>

[0239] The polymer A diisobutyl ketone dispersion and the polymer B diisobutyl ketone solution obtained as described above are mixed in such a way that their quantitative ratio (equivalent amount of solid content) is polymer A: polymer B = 1:1 to prepare a binder composition.

[0240] (Example 15)

[0241] When preparing the binder composition, 52 parts of n-butyl acrylate as a carbonyl group-containing monomer, 42 parts of ethyl acrylate, 3 parts of methacrylic acid as a carboxyl group-containing monomer, and 3 parts of 2-hydroxyethyl acrylate as a hydroxyl group-containing monomer are used. Otherwise, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery are produced in the same manner as in Example 1, and various evaluations are carried out. The results are shown in Table 3.

[0242] (Example 18)

[0243] When preparing the binder composition, 65 parts of n-butyl acrylate as a carbonyl group-containing monomer, 25 parts of ethyl acrylate, and 10 parts of acrylonitrile as a cyanated vinyl monomer are used. Otherwise, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery are produced in the same manner as in Example 16, and various evaluations are carried out. The results are shown in Table 3.

[0244] (Comparative Example 1)

[0245] When preparing the binder composition, a compound containing an element belonging to Group 13 and / or Group 14 of the periodic table is not used. Otherwise, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery are produced in the same manner as in Example 1, and various evaluations are carried out. The results are shown in Table 4.

[0246] (Comparative Example 2)

[0247] When preparing the binder composition, the content of the element belonging to Group 13 and / or Group 14 of the periodic table in the binder composition is adjusted to 10,000 mass ppm. Otherwise, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery are produced in the same manner as in Example 1, and various evaluations are carried out. The results are shown in Table 4.

[0248] (Comparative Example 3)

[0249] When preparing the polymer, by using sodium hydroxide, it is adjusted to contain Na in the binder composition instead of containing elements belonging to Group 13 and / or Group 14 of the periodic table. Except for this, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery are produced in the same manner as in Example 1, and various evaluations are carried out. The results are shown in Table 4.

[0250] (Comparative Example 4)

[0251] When preparing the polymer, by using sodium hydroxide and calcium hydroxide, it is adjusted to contain Na and Ca in the binder composition instead of containing elements belonging to Group 13 and / or Group 14 of the periodic table. Except for this, the binder composition, the slurry composition for the positive composite layer, the slurry composition for the negative composite layer, the slurry composition for the solid electrolyte layer, and the all-solid-state secondary battery are produced in the same manner as in Example 1, and various evaluations are carried out. The results are shown in Table 4.

[0252] In addition, in Tables 1 to 4 shown below,

[0253] "BA" represents n-butyl acrylate units,

[0254] "PEA" represents phenoxyethyl acrylate units,

[0255] "EA" represents ethyl acrylate units,

[0256] "MAA" represents methacrylic acid units,

[0257] "B-HEA" represents 2-hydroxyethyl acrylate units,

[0258] "AN" represents acrylonitrile units,

[0259] "ST" represents styrene units,

[0260] "H-BD" represents 1,3-butadiene hydride units,

[0261] "AMA" represents allyl methacrylate units,

[0262] "DIK" represents diisobutyl ketone,

[0263] "HB" represents butyl butyrate,

[0264] "MES" represents mesitylene.

[0265] [Table 1]

[0266]

[0267] [Table 2]

[0268]

[0269] [Table 3]

[0270]

[0271] [Table 4]

[0272]

[0273] As can be seen from Tables 1 to 3, by using a binder composition containing a polymer, an organic solvent, and a compound having a solubility of 10% by mass or less in water at 25°C and containing an element belonging to Group 13 and / or Group 14 of the periodic table (excluding carbon and germanium), and the content of the above element in the binder composition is 5 mass ppm or more and 5000 mass ppm or less relative to the polymer (Examples 1 to 18), an all-solid-state secondary battery having excellent water resistance and excellent battery characteristics can be manufactured.

[0274] In contrast, it is known that when using a binder composition not containing the above compound (Comparative Example 1), a binder composition in which the content of the element belonging to Group 13 and / or Group 14 of the periodic table relative to the polymer is outside the above range (Comparative Example 2), or a binder composition not containing an element belonging to Group 13 and / or Group 14 of the periodic table (Comparative Examples 3 and 4), the all-solid-state secondary battery obtained has poor water resistance and battery characteristics compared to the all-solid-state secondary batteries obtained in each example.

[0275] Industrial Applicability

[0276] According to the present invention, a binder composition for a secondary battery can be provided, which can improve the water resistance of the secondary battery and enable the secondary battery to exhibit excellent battery characteristics.

[0277] Furthermore, according to the present invention, a slurry composition for a secondary battery can be provided, which can improve the water resistance of the secondary battery and enable the secondary battery to exhibit excellent battery characteristics.

[0278] Furthermore, according to the present invention, an all-solid-state electrolyte layer having excellent water resistance, an all-solid-state secondary battery having excellent battery characteristics, and a manufacturing method thereof can be provided.

Claims

1. A binder composition for a secondary battery, comprising a polymer, an organic solvent, and a compound formed of an organic or inorganic substance, wherein the solubility of the compound in water at 25 °C is 10% by mass or less, and the compound contains an element belonging to Group 13 and / or Group 14 of the periodic table other than carbon and germanium, the compound is silica gel or zeolite, the content of the element in the binder composition for a secondary battery is 20 mass ppm or more and 4000 mass ppm or less relative to the polymer.

2. The binder composition for a secondary battery according to claim 1, wherein, The polymer has at least one functional group selected from a carbonyl group, an ether group, a carboxyl group, and a hydroxyl group.

3. The binder composition for a secondary battery according to claim 1, wherein, The polymer contains a vinyl cyanide monomer unit in a proportion of 2% by mass or more and 35% by mass or less.

4. The binder composition for a secondary battery according to claim 1, wherein, The polymer contains an aromatic monomer unit in a proportion of 5% by mass or more and 40% by mass or less.

5. The binder composition for a secondary battery according to any one of claims 1 to 4, wherein The polymer contains a conjugated diene monomer unit and / or an alkylene structural unit in a proportion of 20% by mass or more and 60% by mass or less.

6. A slurry composition for a secondary battery, comprising the binder composition for a secondary battery according to any one of claims 1 to 5.

7. The slurry composition for a secondary battery according to claim 6, which contains a solid electrolyte.

8. A solid electrolyte-containing layer formed by using the slurry composition for a secondary battery according to claim 7.

9. A all-solid-state secondary battery having the solid electrolyte-containing layer according to claim 8.

10. A method for manufacturing an all-solid-state secondary battery, comprising a step of pressing the solid electrolyte-containing layer according to claim 8 at a pressure of less than 300 MPa.

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