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

Abstract

The present application aims to provide a slurry composition for a full solid secondary battery, which can form a solid electrolyte-containing layer that can allow a full solid secondary battery to exhibit excellent output characteristics and cycle characteristics. The slurry composition of the present application contains a solid electrolyte, a particulate polymer, and an organic solvent. The particulate polymer has a core-shell structure having a core portion and a shell portion covering at least a part of the outer surface of the core portion, the glass transition temperature of the polymer constituting the core portion is -60°C or higher and -10°C or lower, and the glass transition temperature of the polymer constituting the shell portion is 15°C or higher and 100°C or lower. Furthermore, the polymer constituting the shell portion contains a nitrogen-containing functional group monomer unit at a proportion of 10% by mass or more and 90% by mass or less.

Description

Technical Field

[0001] This invention relates to a slurry composition for all-solid-state secondary batteries, a solid electrolyte layer, and an all-solid-state secondary battery. Background Technology

[0002] In recent years, in addition to mobile terminals such as mobile information terminals and mobile electronic devices, the demand for secondary batteries, including lithium-ion batteries, has been increasing in various applications such as small household power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. Moreover, with the expansion of applications, the safety requirements for secondary batteries are further enhanced.

[0003] Therefore, as a type of secondary battery with high safety, all-solid-state secondary batteries that use solid electrolytes instead of organic solvent electrolytes, which are highly flammable and pose a high risk of fire when leaked, have attracted much attention.

[0004] Here, the all-solid-state secondary battery has a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive and negative electrodes. Furthermore, the electrodes (positive and negative electrodes) of the all-solid-state secondary battery are formed, for example, by applying a slurry composition comprising electrode active materials (positive and negative electrode active materials), a binder, and a solid electrolyte onto a current collector, drying the applied slurry composition, and then depositing electrode composite material layers (positive and negative electrode composite material layers) onto the current collector. Additionally, the solid electrolyte layer of the all-solid-state secondary battery is formed, for example, by applying a slurry composition comprising a binder and a solid electrolyte onto an electrode or a release substrate, and then drying the applied slurry composition.

[0005] Moreover, patent documents 1 and 2, for example, propose slurry compositions for all-solid-state secondary batteries that use particulate polymers with core-shell structures as binders.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2015-159067;

[0009] Patent Document 2: International Publication No. 2012 / 173089. Summary of the Invention

[0010] The problem the invention aims to solve

[0011] However, the existing slurry compositions for all-solid-state secondary batteries described above still have room for improvement in enabling all-solid-state secondary batteries to exhibit excellent output and cycle characteristics by using solid electrolyte layers, electrode composite material layers, and other layers containing solid electrolytes (hereinafter referred to as "solid electrolyte layers") formed by the slurry compositions.

[0012] Therefore, the object of the present invention is to provide a slurry composition for all-solid-state secondary batteries, which can form a solid electrolyte layer that enables all-solid-state secondary batteries to exhibit excellent output and cycle characteristics.

[0013] Furthermore, the present invention aims to provide a solid electrolyte layer that enables all-solid-state secondary batteries to exhibit excellent output and cycle characteristics.

[0014] Moreover, the purpose of this invention is to provide an all-solid-state secondary battery with excellent output characteristics and cycle characteristics.

[0015] Solution for solving the problem

[0016] The inventors conducted in-depth research with the aim of solving the above-mentioned problems. Then, the inventors made a new discovery that if a slurry composition containing a solid electrolyte, a particulate polymer having a core-shell structure, and an organic solvent is used to form a solid electrolyte layer, and the core and shell of the particulate polymer are respectively composed of a specified polymer, then the all-solid-state secondary battery can exhibit excellent output and cycle characteristics, thus completing the present invention.

[0017] That is, the object of the present invention is to advantageously solve the above-mentioned problems. The all-solid-state secondary battery slurry composition of the present invention is characterized in that it comprises a solid electrolyte, a particulate polymer and an organic solvent, wherein the particulate polymer has a core-shell structure, wherein the core-shell structure has a core and a shell covering at least a portion of the outer surface of the core, wherein the polymer constituting the core has a glass transition temperature of -60°C or more and -10°C or less, wherein the polymer constituting the shell has a glass transition temperature of 15°C or more and 100°C or less, wherein the polymer constituting the shell contains nitrogen-containing functional group monomer units, and wherein when all repeating units of the polymer constituting the shell are taken as 100% by mass, the amount of the nitrogen-containing functional group monomer units contained in the polymer constituting the shell is 10% by mass or more and 90% by mass or less. If a slurry composition containing a particulate polymer as a binder is used to form a solid electrolyte layer, the all-solid-state secondary battery can exhibit excellent output and cycle characteristics. The particulate polymer has a core-shell structure, and the glass transition temperatures of the polymer constituting the core and the polymer constituting the shell (hereinafter sometimes referred to as "core polymer" and "shell polymer," respectively) are within the aforementioned ranges, and the content ratio of nitrogen-containing functional group monomer units in the shell polymer is within the aforementioned ranges.

[0018] Furthermore, in this invention, the "glass transition temperature" of the polymer can be determined using the method described in the examples.

[0019] Furthermore, in this invention, "comprising monomer units" means "a polymer obtained using the monomer contains repeating units derived from the monomer." Moreover, in this invention, the amount of a specific repeating unit in the polymer can be determined using... 1 H-NMR and 13 The measurements were performed using nuclear magnetic resonance (NMR) methods such as C-NMR.

[0020] Here, the slurry composition for all-solid-state secondary batteries of the present invention preferably comprises a shell portion of 10% by mass or more and 25% by mass or less in the total of the core portion and the shell portion. If the shell portion comprises within the above-mentioned range, even a lower pressing pressure can achieve a sufficiently high density of the solid electrolyte layer (i.e., improve the compressibility of the solid electrolyte layer). Furthermore, it is possible to improve the peel strength of the obtained solid electrolyte layer while further enhancing the output characteristics and cycle characteristics of the all-solid-state secondary battery.

[0021] Furthermore, the slurry composition for all-solid-state secondary batteries of the present invention preferably contains crosslinked monomer units in the particulate polymer, wherein when all repeating units of the particulate polymer are taken as 100% by mass, the amount of the crosslinked monomer units contained in the particulate polymer is 0.1% by mass or more and less than 2.0% by mass. If the content ratio of crosslinked monomer units in the particulate polymer is within the above range, the output characteristics and cycle characteristics of the all-solid-state secondary battery can be further improved.

[0022] Furthermore, the all-solid-state secondary battery slurry composition of the present invention preferably also contains an electrode active material. If an all-solid-state secondary battery slurry composition containing an electrode active material is used, an electrode composite material layer can be formed well.

[0023] Here, the all-solid-state secondary battery slurry composition of the present invention preferably further comprises a conductive material. If the all-solid-state secondary battery slurry composition containing electrode active materials further comprises a conductive material, the resistance of the electrode composite material layer formed using the slurry composition can be significantly reduced, and the output characteristics and cycle characteristics can be further improved.

[0024] Furthermore, the object of the present invention is to advantageously solve the above-mentioned problems. The solid-electrolyte layer of the present invention is characterized by being formed using any of the above-described all-solid-state secondary battery slurry compositions. The solid-electrolyte layer formed using the above-described all-solid-state secondary battery slurry compositions enables the all-solid-state secondary battery to exhibit excellent output and cycle characteristics.

[0025] Furthermore, the object of the present invention is to advantageously solve the above-mentioned problems. The all-solid-state secondary battery of the present invention is characterized by having the aforementioned solid electrolyte layer. The all-solid-state secondary battery having the aforementioned solid electrolyte layer exhibits excellent cell characteristics such as output characteristics and cycle characteristics.

[0026] Invention Effects

[0027] According to the present invention, a slurry composition for all-solid-state secondary batteries can be provided, which can form a solid electrolyte layer that enables all-solid-state secondary batteries to exhibit excellent output and cycle characteristics.

[0028] Furthermore, according to the present invention, a solid electrolyte layer can be provided that enables all-solid-state secondary batteries to exhibit excellent output and cycle characteristics.

[0029] Moreover, according to the present invention, an all-solid-state secondary battery with excellent output characteristics and cycle characteristics can be provided. Attached Figure Description

[0030] Figure 1 A cross-sectional view illustrating an example structure of the particulate polymer contained in the all-solid-state secondary battery slurry composition of the present invention. Detailed Implementation

[0031] The embodiments of the present invention will now be described in detail.

[0032] Here, the slurry composition for all-solid-state secondary batteries of the present invention can be used when forming a solid electrolyte layer, such as an electrode composite material layer or a solid electrolyte layer, used in all-solid-state secondary batteries such as all-solid-state lithium-ion secondary batteries. Furthermore, in the all-solid-state secondary battery of the present invention, at least one layer selected from the positive electrode composite material layer of the positive electrode, the negative electrode composite material layer of the negative electrode, and the solid electrolyte layer is composed of the solid electrolyte layer of the present invention formed using the slurry composition for all-solid-state secondary batteries of the present invention.

[0033] (Slurry composition for all-solid-state secondary batteries)

[0034] The slurry composition of the present invention comprises a solid electrolyte, a particulate polymer, and an organic solvent, and may optionally contain at least one selected from electrode active materials, conductive materials, and other components. Here, in the slurry composition of the present invention, the particulate polymer has a core-shell structure, wherein the core-shell structure comprises a core made of a polymer with a glass transition temperature of -60°C or higher and -10°C or lower, and a shell made of a polymer with a glass transition temperature of 15°C or higher and 100°C or lower. Furthermore, when all repeating units of the polymer in the shell are taken as 100% by mass, the amount of nitrogen-containing functional group monomer units in the polymer in the shell needs to be 10% by mass or higher and 90% by mass or lower.

[0035] The slurry composition of the present invention contains a solid electrolyte and a particulate polymer as a binder, and therefore can be used when forming electrode composite layers, solid electrolyte layers, and other solid electrolyte layers.

[0036] Furthermore, the solid electrolyte layer formed using the slurry composition of the present invention enables all-solid-state secondary batteries to exhibit excellent output and cycle characteristics. The reason for this is not clear, but is speculated as follows.

[0037] First, the granular polymer contained in the slurry composition of the present invention has a core-shell structure, wherein the core is formed of a polymer with a low glass transition temperature and the shell is formed of a polymer with a high glass transition temperature. Therefore, when the solid electrolyte layer obtained by drying the slurry composition is pressed, the core softens easily, allowing the solid electrolyte layer to achieve sufficient high density even at low temperatures (i.e., ensuring the pressability of the solid electrolyte layer). On the other hand, since the shell is difficult to soften, the surfaces of the solid electrolyte and any electrode active material used are not excessively covered by the polymer components.

[0038] Furthermore, the nitrogen functional groups in the polymer of the shell exhibit excellent adhesion to the solid electrolyte. Therefore, by using a shell containing a specified amount of nitrogen-containing functional group monomer units, a solid electrolyte layer with excellent peel strength can be formed.

[0039] That is, according to the slurry composition of the present invention, thanks to the contribution of the aforementioned particulate polymer, the surface of the solid electrolyte (and electrode active material) is not excessively covered by the polymer components, and a high-density solid electrolyte-containing layer with excellent peel strength can be formed. Moreover, it is considered that the output characteristics and cycle characteristics of the all-solid-state secondary battery can be improved based on the solid electrolyte-containing layer having such properties.

[0040] Furthermore, when the slurry composition of the present invention is used to form an electrode composite material layer (i.e., a slurry composition for an all-solid-state secondary battery electrode), it typically contains a solid electrolyte, a defined particulate polymer, an organic solvent, and an electrode active material, and optionally contains at least one selected from conductive materials and other components.

[0041] Furthermore, when the slurry composition of the present invention is used to form a solid electrolyte layer (i.e., a slurry composition for a solid electrolyte layer of an all-solid-state secondary battery), it typically does not contain electrode active materials and conductive materials, but instead contains a solid electrolyte, a specified particulate polymer, and an organic solvent, and optionally other components.

[0042] <Solid Electrolyte>

[0043] As a solid electrolyte, there are no particular limitations as long as it is composed of particles of solids with ion conductivity, and inorganic solid electrolytes are preferred.

[0044] There are no particular limitations on the inorganic solid electrolyte; crystalline inorganic ionic conductors, amorphous inorganic ionic conductors, or mixtures thereof can be used. Furthermore, for example, in the case of an all-solid-state secondary battery being an all-solid-state lithium-ion secondary battery, crystalline inorganic lithium-ion conductors, amorphous inorganic lithium-ion conductors, or mixtures thereof can generally be used as the inorganic solid electrolyte. In particular, from the viewpoint of further improving the output and cycle characteristics of the all-solid-state secondary battery by forming a solid electrolyte layer with excellent ionic conductivity, the inorganic solid electrolyte preferably includes at least one of a sulfide-based inorganic solid electrolyte and an oxide-based inorganic solid electrolyte.

[0045] Furthermore, the following description is provided as an example of a slurry composition for all-solid-state secondary batteries that is a slurry composition for all-solid-state lithium-ion secondary batteries, but the present invention is not limited to the following example.

[0046] Furthermore, examples of 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), silver-steresite type (Li) 7-x PS 6-xX x (where X is Cl, Br, or I, etc.)

[0047] The aforementioned crystalline inorganic lithium-ion conductors can be used alone or in combination of two or more types.

[0048] Furthermore, as non-crystalline inorganic lithium-ion conductors, examples include substances containing sulfur atoms and having ion conductivity. More specifically, examples include glass Li-Si-SO, Li-PS, and substances formed using raw material compositions containing Li2S and sulfides of elements from Groups 13 to 15 of the periodic table.

[0049] Examples of elements from Groups 13 to 15 include Al, Si, Ge, P, As, and Sb. Specifically, examples of sulfides of these elements include Al₂S₃, SiS₂, GeS₂, P₂S₃, P₂S₅, As₂S₃, and Sb₂S₃. Furthermore, methods for synthesizing amorphous inorganic lithium-ion conductors using a raw material composition include amorphization methods such as mechanical grinding and melt quenching. Moreover, for amorphous inorganic lithium-ion conductors formed using a raw material composition containing Li₂S and sulfides of elements from Groups 13 to 15 of the periodic table, Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-GeS₂, or Li₂S-Al₂S₃ are preferred, with Li₂S-P₂S₅ being more preferred.

[0050] The aforementioned non-crystalline inorganic lithium-ion conductors can be used alone or in combination of two or more types.

[0051] In the above, from the viewpoint of further improving the output and cycle characteristics of all-solid-state secondary batteries by forming a solid electrolyte layer with better ion conductivity, inorganic solid electrolytes containing Li and P, such as Li7La3Zr2O, are preferred as inorganic solid electrolytes for all-solid-state lithium-ion secondary batteries. 12 Non-crystalline sulfides containing Li and P, as well as Li7La3Zr2O 12 Because of its high conductivity, lithium ions can be used as an inorganic solid electrolyte to reduce the internal resistance of the battery and improve its output and cycle characteristics.

[0052] Furthermore, from the viewpoint of improving the output and cycle characteristics of all-solid-state secondary batteries, amorphous sulfides containing Li and P are more preferably sulfide glasses composed of Li₂S and P₂S₅, and particularly preferably sulfide glasses manufactured from a mixture of Li₂S and P₂S₅ with a Li₂S:P₂S₅ molar ratio of 65:35 to 85:15. In addition, the amorphous sulfide containing Li and P is preferably a sulfide glass-ceramic obtained by mechanically reacting a mixture of Li₂S and P₂S₅ with a Li₂S:P₂S₅ molar ratio of 65:35 to 85:15. Furthermore, from the viewpoint of maintaining high lithium-ion conductivity, the mixed raw material is preferably a Li₂S:P₂S₅ molar ratio of 68:32 to 80:20.

[0053] Furthermore, without reducing ionic conductivity, inorganic solid electrolytes may also include at least one sulfide selected from Al2S3, B2S3, and SiS2 as starting materials, in addition to Li2S and P2S5 mentioned above. The addition of this sulfide stabilizes the glass composition of the inorganic solid electrolyte.

[0054] Similarly, inorganic solid electrolytes may also contain at least one lithium ortho-oxo acid selected from Li3PO4, Li4SiO4, Li4GeO4, Li3BO3, and Li3AlO3, in addition to Li2S and P2S5. The inclusion of this lithium ortho-oxo acid can stabilize the glass composition of the inorganic solid electrolyte.

[0055] Furthermore, the aforementioned solid electrolytes can be used alone or in combination of two or more. Additionally, the particle size of the aforementioned solid electrolytes is not particularly limited and can be the same as that of existing solid electrolytes.

[0056] <Particulate Polymers>

[0057] The particulate polymer is a component that functions as a binder in the solid electrolyte layer formed using the slurry composition of the present invention.

[0058] Core-shell structure

[0059] Here, the particulate polymer has a core-shell structure, which has a core and a shell covering the outer surface of the core. Furthermore, the shell may partially cover the outer surface of the core or cover the entire outer surface of the core.

[0060] Figure 1 A cross-sectional structure of an example of a particulate polymer is shown. Figure 1In this process, the particulate polymer 100 has a core-shell structure, which includes a core portion 110 and a shell portion 120. Here, the core portion 110 is the portion of the particulate polymer 100 that is located inside the shell portion 120. Furthermore, the shell portion 120 is the portion that covers the outer surface 110S of the core portion 110, and is typically the outermost portion of the particulate polymer 100. Moreover, in... Figure 1 In the example, the shell portion 120 covers the entire outer surface 110S of the core portion 110.

[0061] Furthermore, as long as the desired effect is not significantly impaired, the particulate polymer may have any constituent elements other than the core and shell described above. Specifically, for example, the particulate polymer may also have a portion inside the core formed of a polymer different from the core. As a specific example, in the case of manufacturing particulate polymers using seed polymerization, the seed particles used may remain inside the core.

[0062] Furthermore, in the particulate polymer with a core-shell structure, when the total mass of the core and the shell is taken as 100% by mass, the proportion of the shell in the total of the core and shell is preferably 10% by mass or more, more preferably 12% by mass or more, even more preferably 14% by mass or more, preferably 25% by mass or less, more preferably 23% by mass or less, even more preferably 21% by mass or less, and particularly preferably 20% by mass or less. If the proportion of the shell in the total of the core and shell is 10% by mass or more, the excessive covering of the solid electrolyte and any contained electrode active materials by the polymer components can be sufficiently suppressed, further improving the output characteristics of the all-solid-state secondary battery. On the other hand, if the proportion of the shell in the total of the core and shell is 25% by mass or less, the flexibility of the particulate polymer can be sufficiently ensured, thus resulting in high compressibility and peel strength of the solid electrolyte layer. Moreover, the cycle characteristics of the all-solid-state secondary battery can be further improved.

[0063] Glass transition temperature

[0064] In the particulate polymer, the glass transition temperature of the polymer constituting the core needs to be -60°C or higher and -10°C or lower, preferably -55°C or higher, more preferably -50°C or higher, even more preferably -43°C or higher, preferably -15°C or lower, more preferably -20°C or lower, and even more preferably -32°C or lower. When the glass transition temperature of the polymer in the core is less than -60°C, the strength of the particulate polymer as a binder is compromised, and the cycle characteristics of the all-solid-state secondary battery decrease. On the other hand, when the glass transition temperature of the polymer in the core is greater than -10°C, the particulate polymer as a binder becomes too rigid, and the compressive strength and peel strength of the solid electrolyte layer are compromised. Furthermore, the output characteristics and cycle characteristics of the all-solid-state secondary battery decrease.

[0065] Furthermore, in the particulate polymer, the glass transition temperature of the polymer constituting the shell needs to be 15°C or higher and 100°C or lower, preferably 30°C or higher, more preferably 39°C or higher, even more preferably 45°C or higher, preferably 95°C or lower, more preferably 90°C or lower, and even more preferably 75°C or lower. When the glass transition temperature of the polymer in the shell is less than 15°C, the output characteristics of the all-solid-state secondary battery decrease because the surfaces of the solid electrolyte and the electrode active material used are excessively covered by the polymer component. On the other hand, when the glass transition temperature of the polymer in the shell is greater than 100°C, the peel strength of the solid electrolyte layer is impaired, and the output and cycle characteristics of the all-solid-state secondary battery also decrease.

[0066] In addition, the glass transition temperature of a polymer can be controlled, for example, by changing the type and / or amount of monomers used to prepare the polymer.

[0067] "composition"

[0068] [Nuclear Section]

[0069] Here, the polymer constituting the core is not particularly limited as long as its glass transition temperature is within the above-mentioned range, and preferably includes at least one selected from conjugated diene monomer units, alkylene structural units, and (meth)acrylate monomer units.

[0070] Additionally, in this invention, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0071] —Conjugated diene monomer unit—

[0072] The conjugated diene monomer, which is a conjugated diene monomer unit capable of forming the core of a polymer, is not particularly limited, and examples include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), and 2,3-dimethyl-1,3-butadiene. Among these, 1,3-butadiene is preferred. Furthermore, a single conjugated diene monomer may be used, or two or more may be used in any ratio.

[0073] —alkylene structural unit—

[0074] The alkylene structural units contained in the core polymer are composed solely of the general formula: -C n H 2n -[where n is an integer greater than or equal to 2] represents a repeating unit consisting of an alkylene structure. The alkylene structural unit can be linear or branched, and is preferably linear, i.e., a linear alkylene structural unit. Moreover, there is no particular limitation on the method of introducing the alkylene structural unit into the polymer, and methods such as (1) or (2) below can be cited as examples:

[0075] (1) A method for preparing a polymer from a monomer composition containing a conjugated diene monomer, and hydrogenating the polymer thereby converting the conjugated diene monomer unit into an alkylene structural unit;

[0076] (2) A method for preparing a polymer from a monomer composition containing a 1-olefin monomer.

[0077] Furthermore, examples of conjugated diene monomers, such as those mentioned above, are examples of conjugated diene monomers capable of forming conjugated diene monomer units. 1,3-Butadiene is particularly preferred. That is, the alkylene structural unit obtained by the method described above (1) is preferably a structural unit obtained by hydrogenating a conjugated diene monomer unit (a conjugated diene hydride unit), and more preferably a structural unit obtained by hydrogenating a 1,3-butadiene unit (a 1,3-butadiene hydride unit). Moreover, the selective hydrogenation of the conjugated diene monomer unit can be carried out using known methods such as oil layer hydrogenation and aqueous layer hydrogenation.

[0078] In addition, examples of 1-olefin monomers include ethylene, propylene, 1-butene, and 1-hexene. Ethylene is particularly preferred.

[0079] These conjugated diene monomers and 1-olefin monomers can be used individually or in combination of two or more in any ratio.

[0080] —(meth)acrylate monomer unit—

[0081] Examples of (meth)acrylate monomers that are (meth)acrylate monomer units capable of forming the core of a polymer include: 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 other alkyl acrylates; 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, and other alkyl methacrylates. Among these, n-butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate are preferred. Additionally, (meth)acrylate monomers can be used alone or in combination of two or more in any ratio.

[0082] Here, when all repeating units of the polymer in the core are taken as 100% by mass, the total amount of conjugated diene monomer units, alkylene structural units, and (meth)acrylate monomer units contained in the polymer in the core is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, particularly preferably 95% by mass or more, and preferably 99.5% by mass or less. If the content of the repeating units in the polymer in the core is 70% by mass or more, the compressibility of the solid electrolyte layer can be ensured, and the cycle characteristics of the all-solid-state secondary battery can be further improved. On the other hand, if the content of the repeating units in the polymer in the core is 99.5% by mass or less, the strength of the particulate polymer as a binder can be ensured, and the cycle characteristics of the all-solid-state secondary battery can be further improved.

[0083] Furthermore, for example, when the polymer in the core contains (meth)acrylate monomer units, when all repeating units of the polymer in the core are taken as 100% by mass, the amount of (meth)acrylate monomer units contained in the polymer in the core is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, particularly preferably 95% by mass or more, and preferably 99.5% by mass or less. If the content of (meth)acrylate monomer units in the polymer in the core is 70% by mass or more, the compressibility of the solid electrolyte layer can be ensured, and the cycle characteristics of the all-solid-state secondary battery can be further improved. On the other hand, if the content of (meth)acrylate monomer units in the polymer in the core is 99.5% by mass or less, the strength of the particulate polymer as a binder can be ensured, and the cycle characteristics of the all-solid-state secondary battery can be further improved.

[0084] —Other repeating units—

[0085] The polymer in the core portion can contain repeating units (other repeating units) other than the conjugated diene monomer units, alkylene structural units, and (meth)acrylate monomer units mentioned above. Examples of other repeating units that can be included in the polymer in the core portion include crosslinking monomer units, aromatic monovinyl monomer units, and nitrogen-containing functional group monomer units. Furthermore, the polymer in the core portion can contain one or more other repeating units. Preferably, the polymer in the core portion contains crosslinking monomer units as other repeating units.

[0086] Crosslinking monomers, which are crosslinking monomer units capable of forming the core of a polymer, are not particularly limited and can be any monomer capable of forming a crosslinked structure through polymerization. Examples of crosslinking monomers typically include those with thermal crosslinking properties. More specifically, examples include: crosslinking monomers with thermal crosslinking groups and crosslinking monomers having one olefinic double bond per molecule; and crosslinking monomers having two or more olefinic double bonds per molecule.

[0087] Examples of thermally crosslinkable crosslinking groups include epoxy groups, oxetyl groups, and combinations thereof. Among these, epoxy groups are preferred from the viewpoint of ease of adjustment of crosslinking and crosslinking density.

[0088] Furthermore, examples of crosslinking monomers that have an epoxy group as a thermally crosslinking crosslinking group and an olefinic double bond include: unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allyl phenyl glycidyl ether; and monoepoxides of dienes or polyenes such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, and 1,2-epoxy-5,9-cyclododecadiene. Alkenyl epoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, and 1,2-epoxy-9-decene; and glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linolenic acid, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, and glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid.

[0089] Furthermore, examples of crosslinking monomers having an oxetyl group as a thermally crosslinking crosslinking group and having an olefinic double bond include 3-((meth)acryloyloxymethyl)oxetane, 3-((meth)acryloyloxymethyl)-2-trifluoromethyloxetane, 3-((meth)acryloyloxymethyl)-2-phenyloxetane, 2-((meth)acryloyloxymethyl)oxetane, and 2-((meth)acryloyloxymethyl)-4-trifluoromethyloxetane.

[0090] Additionally, in this invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0091] Furthermore, examples of crosslinkable monomers having two or more olefinic double bonds per molecule include allyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane-tri(meth)acrylate, dipropylene glycol diallyl ether, polyethylene glycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethylene, trimethylolpropane-diallyl ether, allyl or vinyl ethers of polyfunctional alcohols other than those mentioned above, and divinylbenzene.

[0092] In addition, in this invention, "(meth)acrylate" means acrylate and / or methacrylate.

[0093] The crosslinking monomer can be used alone or in combination of two or more in any ratio. Moreover, from the viewpoint of further improving the output and cycle characteristics of all-solid-state secondary batteries, allyl methacrylate, ethylene glycol dimethacrylate, allyl glycidyl ether, and divinylbenzene are more preferred, and allyl methacrylate is even more preferred.

[0094] Furthermore, when all repeating units of the polymer in the core are taken as 100% by mass, the amount of crosslinking monomer units contained in the polymer in the core is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.5% by mass or less. If the content ratio of crosslinking monomer units in the polymer in the core is within the above range, the compressibility and peel strength of the solid electrolyte layer can be sufficiently ensured, and the output characteristics and cycle characteristics of the all-solid-state secondary battery can be further improved.

[0095] Examples of aromatic monovinyl monomers that are aromatic monovinyl monomer units capable of forming the core of a polymer include styrene, styrene sulfonic acid and its salts (e.g., sodium styrene sulfonate), α-methylstyrene, vinyltoluene, and 4-tert-butoxystyrene. Furthermore, aromatic monovinyl monomers can be used alone or in combination of two or more in any ratio.

[0096] Furthermore, when the polymer in the core contains aromatic monovinyl monomer units, when all repeating units of the polymer in the core are taken as 100% by mass, the amount of aromatic monovinyl monomer units contained in the polymer in the core is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 30% by mass or less, and more preferably 25% by mass or less.

[0097] As a nitrogen-containing functional group monomer unit of a polymer capable of forming the core, the same nitrogen-containing functional group monomer described in the "shell" section can be used. Furthermore, a single nitrogen-containing functional group monomer can be used, or two or more can be used in any ratio.

[0098] Furthermore, when the polymer in the core contains nitrogen-containing functional group monomer units, when all repeating units of the polymer in the core are taken as 100% by mass, the amount of nitrogen-containing functional group monomer units contained in the polymer in the core is preferably 1% by mass or more, more preferably 2% by mass or more, preferably 10% by mass or less, and more preferably 7% by mass or less.

[0099] [Shell]

[0100] The polymer constituting the shell needs to have a glass transition temperature within the above-mentioned range and contain nitrogen-containing functional group monomer units in a specified proportion.

[0101] —Nitrogen-containing functional group monomer unit—

[0102] As a monomer capable of forming a nitrogen-functionalized monomer unit, there is no particular limitation as long as it has nitrogen-functionalized groups such as cyano, amide, or amino groups, that is, a functional group containing a nitrogen atom. Furthermore, a nitrogen-functionalized monomer may have one type of nitrogen functional group or two or more types of nitrogen functional groups. In addition, in this invention, if a monomer has a nitrogen functional group, even if it has other characteristic structures (functional groups, etc.) besides the nitrogen functional group, that monomer is still considered a nitrogen-functionalized monomer. For example, a monomer with a nitrogen functional group is considered a "nitrogen-functionalized monomer" even if it has an acidic group, an epoxy group, and / or an oxetyl group, etc., and is not considered an "acidic monomer" or a "crosslinking monomer".

[0103] Examples of nitrogen-containing functional group monomers include cyano-containing monomers, amide-containing monomers, and amino-containing monomers.

[0104] Examples of cyano-containing monomers include α,β-ene unsaturated nitrile monomers. Specifically, there are no particular limitations on α,β-ene unsaturated nitrile monomers, as long as they are α,β-ene unsaturated compounds with a nitrile group. Examples include acrylonitrile; α-haloacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile.

[0105] Examples of amide-containing monomers include olefinic unsaturated monomers with amide groups. Specifically, examples of amide-containing monomers include N-vinylacetamide, (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, hydroxyethyl (meth)acrylamide, N-methoxymethyl (meth)acrylamide, and dimethylaminopropyl (meth)acrylamide.

[0106] Examples of amino-containing monomers include olefinic unsaturated monomers containing amino groups. Specifically, examples of amino-containing monomers include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, aminoethyl vinyl ether, and dimethylaminoethyl vinyl ether.

[0107] Nitrogen-containing functional group monomers can be used alone or in combination of two or more in any ratio. Moreover, from the viewpoint of further improving the output characteristics and cycle characteristics of all-solid-state secondary batteries, acrylonitrile, acrylamide, methacrylamide, and dimethylaminoethyl methacrylate are preferred.

[0108] Furthermore, when all repeating units of the polymer in the shell portion are taken as 100% by mass, the amount of nitrogen-containing functional group monomer units contained in the polymer in the shell portion needs to be 10% by mass or more and 90% by mass or less, preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 39% by mass or more, preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less. When the content of nitrogen-containing functional group monomer units in the polymer in the shell portion is less than 10% by mass, the peel strength of the solid electrolyte layer is impaired due to the low number of nitrogen-containing functional groups. On the other hand, when the content of nitrogen-containing functional group monomer units in the polymer in the shell portion is greater than 90% by mass, it is inferred that the adhesion between the polymer in the shell portion and the electrode active material, etc., is reduced, and therefore the peel strength of the solid electrolyte layer is impaired. That is, by making the polymer in the shell portion contain nitrogen-containing functional group monomer units in the above proportions, it has been found that the solid electrolyte layer has good peel strength, which can help improve the output characteristics and cycle characteristics of the all-solid-state secondary battery.

[0109] —Other repeating units—

[0110] The polymer in the shell contains repeating units (other repeating units) other than the nitrogen-containing functional group monomer units mentioned above. Examples of other repeating units in the polymer in the shell include (meth)acrylate monomer units, crosslinking monomer units, aromatic monovinyl monomer units, and monomer units containing acid groups. In addition, the polymer in the shell may contain one or more other repeating units.

[0111] Furthermore, the polymer of the shell preferably contains (meth)acrylate monomer units as other repeating units.

[0112] As a (meth)acrylate monomer unit of a polymer capable of forming the shell, the same monomer as the (meth)acrylate monomer described in the "core" section can be used. Among these, n-butyl acrylate is preferred. Furthermore, a single (meth)acrylate monomer can be used, or two or more monomers can be used in any ratio.

[0113] Furthermore, when all repeating units of the polymer in the shell portion are taken as 100% by mass, the amount of (meth)acrylate monomer units contained in the polymer in the shell portion is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, particularly preferably 15% by mass or more, 90% by mass or less, preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. If the content of (meth)acrylate in the polymer in the shell portion is within the above range, the compressibility and peel strength of the solid electrolyte layer can be sufficiently ensured, and the output characteristics and cycle characteristics of the all-solid-state secondary battery can be further improved.

[0114] The crosslinking monomer, which is the crosslinking monomer unit of the polymer capable of forming the shell, can be the same monomer as the crosslinking monomer described in the "core" section. Furthermore, a single crosslinking monomer can be used, or two or more can be used in any ratio.

[0115] Furthermore, when the polymer in the shell contains crosslinking monomer units, when all repeating units of the polymer in the shell are taken as 100% by mass, the amount of crosslinking monomer units contained in the polymer in the shell is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, preferably 3% by mass or less, and more preferably 2% by mass or less.

[0116] As an aromatic monovinyl monomer unit of a polymer capable of forming the shell, the aromatic monovinyl monomer can be the same monomer as the aromatic monovinyl monomer described in the "core" section. Furthermore, an aromatic monovinyl monomer can be used alone, or two or more can be used in any ratio.

[0117] Furthermore, when the polymer in the shell contains aromatic monovinyl monomer units, when all repeating units of the polymer in the shell are taken as 100% by mass, the amount of aromatic monovinyl monomer units contained in the polymer in the shell is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 50% by mass or less, and more preferably 40% by mass or less.

[0118] Examples of acidic monomers that are acidic monomer units in polymers capable of forming shells include carboxylic acid monomers, sulfonic acid monomers, phosphate monomers, and hydroxyl monomers. Furthermore, an acidic monomer can be used alone or in combination of two or more in any ratio.

[0119] Examples of monomers containing carboxylic acid groups include monocarboxylic acids and their derivatives, dicarboxylic acids and their anhydrides, and their derivatives.

[0120] Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid.

[0121] Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro-β-E-methoxyacrylic acid.

[0122] Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid.

[0123] Examples of dicarboxylic acid derivatives include: methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid; nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, fluoroalkyl maleate, and other maleic acid monoesters.

[0124] Examples of anhydrides that are dicarboxylic acids include maleic anhydride, acrylic anhydride, methylmaleic anhydride, and dimethylmaleic anhydride.

[0125] Furthermore, acid anhydrides that generate carboxylic acid groups through hydrolysis can also be used as monomers containing carboxylic acid groups. Acrylic acid and methacrylic acid are particularly preferred as monomers containing carboxylic acid groups. In addition, one type of monomer containing carboxylic acid group can be used alone, or two or more can be used in any ratio.

[0126] Examples of sulfonic acid monomers include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, styrene sulfonic acid, ethyl (meth)acrylate-2-sulfonate, and 3-allyloxy-2-hydroxypropanesulfonic acid. Furthermore, a single sulfonic acid monomer can be used alone, or two or more monomers can be used in any ratio.

[0127] In this invention, "(methyl)allyl" means allyl and / or methylallyl.

[0128] Examples of phosphate-containing monomers include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. Furthermore, phosphate-containing monomers can be used alone or in combination of two or more in any ratio.

[0129] In this invention, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0130] Examples of hydroxyl-containing monomers include: (meth)allyl alcohol, 3-buten-1-ol, 5-hexen-1-ol, and other olefinic unsaturated alcohols; alkyl alcohol esters of olefinic unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconic acid; general formula: CH2=CR a -COO-(C q H 2q O) p -H(where p is an integer from 2 to 9, q is an integer from 2 to 4, R a Esters of polyalkylene glycols and (meth)acrylic acid represented by hydrogen atoms or methyl groups; mono(meth)acrylates of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, (meth)allyl- Mono(methyl)allyl ethers of alkylene glycols such as 6-hydroxyhexyl ether; polyoxyalkylene glycol mono(methyl)allyl ethers such as diethylene glycol mono(methyl)allyl ether and dipropylene glycol mono(methyl)allyl ether; halogenated and hydroxyl-substituted mono(methyl)allyl ethers of (poly)alkylene glycols such as glycerol mono(methyl)allyl ether, (methyl)allyl-2-chloro-3-hydroxypropyl ether, and (methyl)allyl-2-hydroxy-3-chloropropyl ether; mono(methyl)allyl ethers of polyphenols such as eugenol and isoeugenol and their halogenated derivatives; (methyl)allyl-2-hydroxyethyl sulfide, (methyl)allyl-2-hydroxypropyl sulfide, and (methyl)allyl-2-hydroxypropyl sulfide, etc., of alkylene glycols. Furthermore, hydroxyl-containing monomers can be used alone or in combination of two or more in any ratio.

[0131] Here, the polymer in the shell can contain the acid-containing monomer units as described above. However, on the other hand, when the polymer in the shell contains acid-containing monomer units, the acid groups may cause the solid electrolyte to deteriorate. Therefore, from the viewpoint of suppressing the deterioration of the solid electrolyte and further improving the output characteristics and cycle characteristics of the all-solid-state secondary battery, when all repeating units of the polymer in the shell are taken as 100% by mass, the amount of acid-containing monomer units contained in the polymer in the shell is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 3% by mass or less, particularly preferably 1% by mass or less, and most preferably 0% by mass (i.e., the polymer in the shell does not contain acid-containing monomer units).

[0132] [Ratio of cross-linked monomer units]

[0133] As described above, both the polymer core and the polymer shell constituting the particulate polymer can arbitrarily contain crosslinked monomer units.

[0134] Furthermore, when all repeating units of the particulate polymer are taken as 100% by mass, the amount of crosslinking monomer units contained in the particulate polymer is preferably 0.1% by mass or more, more preferably 0.15% by mass or more, even more preferably 0.2% by mass or more, particularly preferably 0.7% by mass or more, preferably less than 2.0% by mass, and more preferably less than 1.0% by mass. If the content of crosslinking monomer units in the particulate polymer is 0.1% by mass or more, the shape (particulate) of the particulate polymer can be well maintained in organic solvents. Therefore, in the formed solid electrolyte layer, the surfaces of the solid electrolyte and the electrode active material used are not excessively covered by the polymer components, and the output characteristics of the all-solid-state secondary battery are further improved. On the other hand, if the content of crosslinking monomer units in the particulate polymer is less than 2.0% by mass, the softness and strength of the particulate polymer can be sufficiently ensured. Therefore, the compressive strength and peel strength of the solid electrolyte layer are high, and the output characteristics and cycle characteristics of the all-solid-state secondary battery are further improved.

[0135] Volume average particle size

[0136] The volume average particle size of the particulate polymer is preferably 0.05 μm or more, more preferably 0.08 μm or more, even more preferably 0.1 μm or more, preferably 0.8 μm or less, more preferably 0.45 μm or less, and even more preferably 0.3 μm or less. If the volume average particle size of the particulate polymer is 0.05 μm or more, the output characteristics of the all-solid-state secondary battery are further improved; if it is 0.8 μm or less, the peel strength of the solid electrolyte layer is high, and the cycle characteristics of the all-solid-state secondary battery are further improved.

[0137] Furthermore, in this invention, the "volume average particle size" of the particulate polymer can be measured using the method described in the examples. Additionally, the volume average particle size of the particulate polymer can be adjusted, for example, by changing the type and amount of monomers used to prepare the particulate polymer, and / or by changing the polymerization conditions of the particulate polymer (e.g., the amount of emulsifier used).

[0138] Preparation Method

[0139] Furthermore, particulate polymers having the aforementioned core-shell structure can be prepared, for example, by using monomers of the polymer in the core and monomers of the polymer in the shell, and changing the ratio of these monomers over time to perform phased polymerization. Specifically, particulate polymers can be prepared by continuous multi-stage emulsion polymerization and multi-stage suspension polymerization, in which the polymer in the later stage sequentially coats the polymer in the earlier stage.

[0140] Therefore, the following is an example of obtaining the above-mentioned particulate polymer with a core-shell structure by a multi-stage emulsion polymerization method.

[0141] During polymerization, emulsifiers can typically include anionic surfactants such as sodium dodecylbenzenesulfonate and sodium dodecyl sulfate (sodium lauryl sulfate); nonionic surfactants such as polyoxyethylene nonylphenyl ether and sorbitan monolaurate; or cationic surfactants such as octadecylamine acetate. Furthermore, polymerization initiators can include peroxides such as tert-butyl peroxide-2-ethylhexanoate, ammonium persulfate, potassium persulfate, and cumene hydroperoxide; and azo compounds such as 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)-propionamide) and 2,2'-azobis(2-amidinylpropane) hydrochloride.

[0142] Furthermore, as a polymerization step, firstly, the monomers forming the core and the emulsifier are mixed and emulsion polymerization is performed in one step to obtain a particulate polymer constituting the core. Then, in the presence of this particulate polymer constituting the core, the monomers forming the shell are polymerized, thereby obtaining the aforementioned particulate polymer with a core-shell structure.

[0143] Furthermore, in the case of preparing a particulate polymer in which the outer surface of the core is partially covered by the shell, it is preferable to supply the monomers of the polymer forming the shell to the polymerization system in batches or continuously. By supplying the monomers of the polymer forming the shell to the polymerization system in batches or continuously, the polymer constituting the shell is formed into particulate form, which combines with the core, thereby forming a shell that partially covers the core.

[0144] "content"

[0145] Furthermore, the amount of the core-shell structured particulate polymer included in the slurry composition for all-solid-state secondary batteries is not particularly limited. It is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, more preferably 10 parts by mass or less, more preferably 7.5 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of solid electrolyte. If the amount of particulate polymer is 0.1 parts by mass or more relative to 100 parts by mass of solid electrolyte, a solid electrolyte layer can be well formed; if it is 10 parts by mass or less, the ion conductivity of the solid electrolyte layer can be sufficiently ensured. Moreover, by using particulate polymer amounts within the above-mentioned ranges, the output characteristics and cycle characteristics of the all-solid-state secondary battery can be further improved.

[0146] <Organic Solvents>

[0147] The organic solvent is not particularly limited, and examples include: cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene, tetrahydronaphthalene, and mesitylene; butyl butyrate; isobutyl isobutyrate; hexyl butyrate; diisobutyl ketone; n-butyl ether; and anisole. These organic solvents can be used alone or in combination of two or more. Furthermore, from the viewpoint of further improving the output and cycle characteristics of the all-solid-state secondary battery by suppressing side reactions with the solid electrolyte, xylene, butyl butyrate, isobutyl isobutyrate, hexyl butyrate, n-butyl ether, tetrahydronaphthalene, mesitylene, and diisobutyl ketone are preferred, and xylene, butyl butyrate, isobutyl isobutyrate, and diisobutyl ketone are more preferred.

[0148] <Electrode Active Materials>

[0149] Here, the electrode active material is a material that performs electron transfer in the electrodes of an all-solid-state secondary battery. Moreover, for example, in the case of an all-solid-state secondary battery that is an all-solid-state lithium-ion secondary battery, a material capable of absorbing and releasing lithium is typically used as the electrode active material.

[0150] Furthermore, the following description is provided as an example of a slurry composition for all-solid-state secondary batteries that is a slurry composition for all-solid-state lithium-ion secondary batteries, but the present invention is not limited to the following example.

[0151] Furthermore, there are no particular limitations on the positive electrode active material used in all-solid-state lithium-ion secondary batteries; examples include positive electrode active materials composed of inorganic compounds and positive electrode active materials composed of organic compounds. Additionally, the positive electrode active material can also be a mixture of inorganic and organic compounds.

[0152] Examples of positive electrode active materials composed of inorganic compounds include transition metal oxides, lithium-transition metal composite oxides (lithium-containing composite metal oxides), and transition metal sulfides. Among these transition metals, Fe, Co, Ni, and Mn can be used. Specific examples of inorganic compounds used in positive electrode active materials include: lithium-containing composite metal oxides such as LiCoO2 (lithium cobalt oxide), LiNiO2, LiMnO2, LiMn2O4, LiFePO4, and LiFeVO4; transition metal sulfides such as TiS2, TiS3, and amorphous MoS2; and Cu2V2O3, amorphous V2O-P2O5, MoO3, V2O5, and V6O3. 13 Transition metal oxides, etc. These compounds can also be compounds in which elements have undergone partial substitution.

[0153] The above-mentioned positive electrode active materials composed of inorganic compounds can be used alone or in combination of two or more.

[0154] Examples of positive electrode active materials composed of organic compounds include polyaniline, polypyrrole, polybenzoxene, disulfide compounds, polysulfide compounds, and N-fluoropyridine. Salt, etc.

[0155] The above-mentioned positive electrode active materials formed from organic compounds can be used alone or in combination of two or more.

[0156] Furthermore, examples of carbon allotropes such as graphite and coke can be used as negative electrode active materials for all-solid-state lithium-ion secondary batteries. Additionally, negative electrode active materials composed of carbon allotropes can also be utilized in the form of mixtures or coatings with metals, metal salts, oxides, etc. Furthermore, as negative electrode active materials, the following can also be used: 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; polysiloxanes, etc.

[0157] The above-mentioned negative electrode active materials can be used alone or in combination of two or more.

[0158] <Conductive Materials>

[0159] Conductive materials are materials that ensure electrical contact between active electrode materials in an electrode composite material layer formed using an all-solid-state secondary battery slurry composition (all-solid-state secondary battery electrode slurry composition). Furthermore, conductive materials can include: carbon black (e.g., acetylene black, Ketjen black (registered trademark), furnace black, etc.), single-walled or multi-walled carbon nanotubes (including stacked cup type multi-walled carbon nanotubes), carbon nanotubes, vapor-grown carbon fibers, milled carbon fibers obtained by sintering and pulverizing polymer fibers, single-layer or multi-layer graphene, conductive carbon materials such as carbon nonwoven sheets obtained by sintering nonwoven fabrics formed from polymer fibers; and fibers or foils of various metals.

[0160] These can be used individually or in combination of two or more.

[0161] Furthermore, the proportion of conductive material in the slurry composition for all-solid-state secondary batteries relative to 100 parts by mass of electrode active material is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, preferably 10 parts by mass or less, and more preferably 7 parts by mass or less. If the amount of conductive material is within the above range, sufficient electrical contact between the electrode active materials can be ensured, further improving the output characteristics and cycle characteristics of the all-solid-state secondary battery.

[0162] <Other Ingredients>

[0163] Furthermore, other components that can be arbitrarily included in the slurry composition for all-solid-state secondary batteries include dispersants, leveling agents, defoamers, and reinforcing materials. Moreover, in the case of, for example, all-solid-state secondary batteries that are all-solid-state lithium-ion secondary batteries, lithium salts can also be included as other components. There are no particular restrictions on these other components as long as they do not affect the battery reaction.

[0164] Furthermore, there are no particular limitations on other components such as lithium salts, dispersants, leveling agents, defoamers, and reinforcing materials, and components such as those described in Japanese Patent Application Publication No. 2012-243476 can be used. In addition, there are no particular limitations on their combined amounts, and they can be set to amounts such as those described in Japanese Patent Application Publication No. 2012-243476.

[0165] <Preparation of Slurry Composition>

[0166] Furthermore, the above-mentioned slurry composition for all-solid-state secondary batteries can be obtained by dispersing or dissolving the above components in an organic solvent, for example, using any mixing method, without particular limitation.

[0167] (Including a solid electrolyte layer)

[0168] The solid electrolyte layer of the present invention is a layer containing a solid electrolyte. Examples of solid electrolyte layers include electrode composite material layers (positive electrode composite material layer and negative electrode composite material layer) that transfer electrons via electrochemical reactions, and solid electrolyte layers disposed between positive electrode composite material layers and negative electrode composite material layers that face each other.

[0169] Furthermore, the solid electrolyte layer of the present invention is a layer formed using the above-described all-solid-state secondary battery slurry composition, and can be formed, for example, by applying the above-described slurry composition to the surface of a suitable substrate to form a coating film, and then drying the formed coating film. That is, the solid electrolyte layer of the present invention is formed from the dried product of the above-described slurry composition, and typically contains a solid electrolyte, a particulate polymer having a core-shell structure (and / or polymer components derived from the particulate polymer), and optionally may also contain at least one selected from electrode active materials, conductive materials, and other components. In addition, each component contained in the solid electrolyte layer is the same as that contained in the above-described slurry composition, and the content ratio of these components is generally equal to the content ratio in the above-described slurry composition.

[0170] Furthermore, since the solid electrolyte layer of the present invention is formed from the slurry composition for all-solid secondary batteries of the present invention, the all-solid secondary battery can exhibit excellent output and cycle characteristics.

[0171] <Substrate>

[0172] Here, there are no limitations on the substrate for applying the slurry composition. For example, a coating film of the slurry composition can be formed on the surface of a release substrate, and the coating film can be dried to form a solid electrolyte layer. The release substrate can then be peeled off from the solid electrolyte layer. The solid electrolyte layer peeled off from the release substrate in this way can also serve as a self-supporting film for forming battery components (e.g., electrodes, solid electrolyte layers, etc.) of an all-solid-state secondary battery.

[0173] On the other hand, from the viewpoint of improving the manufacturing efficiency of battery components by omitting the process of stripping off the solid electrolyte layer, current collectors or electrodes can also be used as substrates. For example, when preparing an electrode composite layer, it is preferable to coat a slurry composition onto the current collector, which serves as the substrate.

[0174] Release substrate

[0175] There are no particular limitations on the release substrate; known release substrates such as imide films can be used.

[0176] "Collection of Currents"

[0177] Materials with both electrical conductivity and electrochemical durability can be used as current collectors. Specifically, current collectors composed of materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum can be used. Copper foil is particularly preferred as a current collector for the negative electrode. Furthermore, aluminum foil is particularly preferred as a current collector for the positive electrode. In addition, one of the above materials can be used alone, or two or more can be used in any ratio.

[0178] "electrode"

[0179] There are no particular limitations on the electrodes (positive and negative electrodes), but an example is an electrode on which an electrode composite material layer containing an electrode active material, a solid electrolyte, and a binder is formed on the current collector.

[0180] The electrode active material, solid electrolyte, and binder included in the electrode composite material layer of the electrode are not particularly limited, and known electrode active materials, solid electrolytes, and binders can be used. Furthermore, the electrode composite material layer in the electrode may also be a solid electrolyte-containing layer according to the present invention.

[0181] <Methods for forming solid electrolyte layers>

[0182] The following methods can be cited as specific ways to form a solid electrolyte layer.

[0183] 1) A method of applying the slurry composition of the present invention to the surface of the current collector or the electrode (in the case of the electrode, the surface on the side of the electrode composite layer, the same below), and then drying it;

[0184] 2) A method for drying a current collector or electrode after immersing it in the slurry composition of the present invention; and

[0185] 3) A method of applying the slurry composition of the present invention onto a release substrate and drying it to produce a solid electrolyte layer, and transferring the obtained solid electrolyte layer onto the surface of an electrode.

[0186] Of these methods, the methods described in 1) and 3) above, which involve coating and drying, are particularly preferred because the thickness of the layer containing the solid electrolyte layer can be easily controlled.

[0187] Application

[0188] There are no particular limitations on the method of applying the slurry composition to the substrate, and examples include, for instance, doctor blade method, reverse roller method, direct roller method, gravure printing method, extrusion method, brush coating method, etc.

[0189] "dry"

[0190] There are no particular limitations on the method for drying the slurry composition on the substrate, and known methods can be used. Examples of drying methods include drying methods using warm air, hot air, low-humidity air, vacuum drying, and drying methods using infrared rays, electron beams, etc.

[0191] Furthermore, when the electrode composite layer contains a solid electrolyte layer, it can be pressed using methods such as rolling after drying. This pressing process allows for further increases in the density of the resulting electrode composite layer.

[0192] Transfer

[0193] In the method described in 3) above, there are no particular limitations on the method of transferring the solid electrolyte layer onto the surface of the electrode or the like, and known transfer methods can be used.

[0194] (electrode)

[0195] Furthermore, the electrode obtained by forming an electrode composite layer on a current collector using the slurry composition of the present invention has an electrode composite layer comprising a solid electrolyte, a core-shell structured particulate polymer (and / or polymer components derived from the particulate polymer), and an electrode active material, optionally further comprising at least one selected from conductive materials and other components. According to this electrode, an all-solid-state secondary battery can exhibit excellent output and cycle characteristics.

[0196] (Solid electrolyte layer)

[0197] Furthermore, the solid electrolyte layer formed using the all-solid-state secondary battery slurry composition of the present invention comprises a solid electrolyte and a particulate polymer having a core-shell structure (and / or polymer components derived from the particulate polymer), and optionally contains other components. Based on this solid electrolyte layer, the all-solid-state secondary battery can exhibit excellent output and cycle characteristics.

[0198] (All-solid-state rechargeable battery)

[0199] The all-solid-state secondary battery of the present invention is characterized in that it generally has a positive electrode, a solid electrolyte layer, and a negative electrode, wherein at least one of the positive electrode composite material layer of the positive electrode, the negative electrode composite material layer of the negative electrode, and the solid electrolyte layer is a solid electrolyte layer of the present invention. That is, the all-solid-state secondary battery of the present invention has at least one of the following: a positive electrode having a positive electrode composite material layer formed using an all-solid-state secondary battery positive electrode slurry composition as an all-solid-state secondary battery slurry composition of the present invention; a negative electrode having a negative electrode composite material layer formed using an all-solid-state secondary battery negative electrode slurry composition as an all-solid-state secondary battery slurry composition of the present invention; and a solid electrolyte layer formed using an all-solid-state secondary battery solid electrolyte layer slurry composition as an all-solid-state secondary battery slurry composition of the present invention.

[0200] Furthermore, the all-solid-state secondary battery of the present invention has excellent battery cell characteristics such as output characteristics and cycle characteristics due to the solid electrolyte layer of the present invention.

[0201] Here, as an electrode for an all-solid-state secondary battery that has an electrode composite material layer containing a solid electrolyte layer, which is not part of the present invention, there is no particular limitation as long as it is an electrode composite material layer containing a solid electrolyte layer, which is not part of the present invention, and any all-solid-state secondary battery electrode can be used.

[0202] Furthermore, there are no particular limitations on the solid electrolyte layer containing the solid electrolyte layer that is not part of the present invention and can be used in the all-solid-state secondary battery of the present invention. Any solid electrolyte layer, such as those described in Japanese Patent Application Publication No. 2012-243476, Japanese Patent Application Publication No. 2013-143299, and Japanese Patent Application Publication No. 2016-143614, can be used.

[0203] Furthermore, the all-solid-state secondary battery of the present invention can be obtained by stacking the positive and negative electrodes facing each other with a positive electrode composite material layer and a negative electrode composite material layer separated by a solid electrolyte layer. After arbitrarily pressurizing to obtain the laminate, it is then placed into a battery container in its original state or by winding, folding, etc., depending on the battery shape, and sealed. Additionally, if necessary, porous metal mesh, fuses, PTC elements, or other overcurrent protection components, conductive plates, etc., can be inserted into the battery container to prevent pressure rise and overcharging / discharging. The battery shape can be any of the following: coin-shaped, button-shaped, sheet-shaped, cylindrical, square, or flat.

[0204] Example

[0205] The present invention will now be described in detail based on embodiments, but the present invention is not limited to these embodiments. Furthermore, in the following description, unless otherwise specified, "%" and "parts" refer to quality standards.

[0206] Furthermore, in the examples and comparative examples, the glass transition temperature of various polymers, the volume average particle size of particulate polymers, the compressibility of the positive electrode composite layer, the peel strength of the negative electrode composite layer, and the output characteristics and cycle characteristics of the all-solid-state secondary battery were evaluated by the following methods.

[0207] <Glass transition temperature (Tg)>

[0208] For particulate polymers with a core-shell structure, aqueous dispersions containing the polymers (the polymer in the core and the polymer in the shell) were prepared as test samples under the same polymerization conditions as those for forming the core and shell, using monomers and various additives to form the core and shell. The aqueous dispersions were then dried at room temperature to prepare the test samples.

[0209] For particulate polymers that do not have a core-shell structure, the aqueous dispersion of the particulate polymer is used as the test sample.

[0210] A 10 mg sample was weighed in an aluminum pan and measured using a differential scanning calorimetry (DSC) apparatus (SII Nanotechnology Co., Ltd., "EXSTAR DSC6220") at a heating rate of 10 °C / min within the measurement temperature range of -100 °C to 500 °C, under conditions specified in JIS Z8703. The resulting differential scanning calorimetry (DSC) curve was obtained. An empty aluminum pan was used as a reference. During the heating process, the glass transition temperature (°C) was determined by intersecting the baseline of the DSC curve just before the endothermic peak appears (when the differential signal (DDSC) is 0.05 mW / min / mg or higher) with the tangent line of the DSC curve at the first bend after the endothermic peak.

[0211] <Volume average particle size>

[0212] The volume-average particle size of the particulate polymer was determined by laser diffraction. Specifically, an aqueous dispersion containing the particulate polymer (with the solid content adjusted to 0.1% by mass) was used as the sample. Then, in the particle size distribution (volume basis) measured using a laser diffraction particle size distribution measuring device (Beckman Coulter, trade name "LS-230"), the particle size D50, which represents the cumulative volume of 50% calculated from the smallest particle size side, was taken as the volume-average particle size.

[0213] <Repressive>

[0214] The fabricated positive electrode was stamped into a 10mm diameter circle to serve as a test piece. This test piece was then pressed using a uniaxial press at a specified pressure for 2 minutes to ensure the positive electrode composite layer achieved the target density of 3.0 g / cm³. 3 The minimum required compression pressure. The lower the compression pressure, the better the compressibility of the positive electrode composite layer containing the solid electrolyte layer.

[0215] A: Pressurization pressure is less than 200MPa

[0216] B: Compressed pressure is above 200MPa and below 300MPa

[0217] C: Compressed pressure is above 300MPa and below 400MPa

[0218] D: Compressed pressure above 400 MPa

[0219] <Peel strength>

[0220] The fabricated negative electrode was cut into rectangles 1.0 cm wide and 10 cm long to serve as test pieces. Cellophane tape (as specified in JIS Z1522) was adhered to the side surface of the negative electrode composite layer of the test piece. The cellophane tape was then peeled off from one end of the test piece at a speed of 50 mm / min in a 180° direction, and the stress was measured. Three measurements were performed, and the average value was taken as the peel strength (N / m), which was evaluated according to the following standards. A higher peel strength indicates better adhesion of the negative electrode composite layer containing the solid electrolyte layer and a stronger bond with the current collector.

[0221] A: Peel strength is above 3N / m

[0222] B: Peel strength is above 2N / m and less than 3N / m

[0223] C: Peel strength is above 1N / m and less than 2N / m

[0224] D: Peel strength less than 1 N / m

[0225] <Output Characteristics>

[0226] A three-cell all-solid-state secondary battery was charged to 4.2V using a constant current method at 0.1C, and then discharged to 3.0V at 0.1C. The 0.1C discharge capacity was calculated. Next, it was charged to 4.2V at 0.1C, and then discharged to 3.0V at 2C. The 2C discharge capacity was calculated. The average 0.1C discharge capacity of the three cells was taken as discharge capacity 'a', and the average 2C discharge capacity of the three cells was taken as discharge capacity 'b'. The ratio of discharge capacity 'b' to discharge capacity 'a' (capacity ratio) was calculated as: discharge capacity 'b' / discharge capacity 'a' × 100 (%). The ratio was then evaluated according to the following criteria. A higher capacity ratio indicates better output characteristics of the all-solid-state secondary battery.

[0227] A: Capacity ratio is above 80%

[0228] B: Capacity ratio is above 70% and below 80%.

[0229] C: Capacity ratio is above 60% and below 70%.

[0230] D: Capacity ratio less than 50%

[0231] <Cyclic Characteristics>

[0232] The all-solid-state secondary battery was charged at 0.2C from 3V to 4.2V at 25°C, and then discharged at 0.2C from 4.2V to 3V. This charge-discharge cycle was repeated 50 times. The percentage ratio of the 0.2C discharge capacity of the 50th cycle to the 0.2C discharge capacity of the 1st cycle was calculated. This calculated value was used as the capacity retention rate, and evaluated according to the following criteria. The higher the capacity retention rate, the less the discharge capacity decreased, indicating better cycle characteristics of the all-solid-state secondary battery.

[0233] A: Capacity retention rate is over 90%.

[0234] B: Capacity retention rate is above 80% and below 90%.

[0235] C: Capacity retention rate is above 70% and below 80%.

[0236] D: Capacity retention rate less than 70%

[0237] (Example 1)

[0238] <Preparation of particulate polymers with core-shell structure>

[0239] Add 90 parts of ion-exchanged water and 0.5 parts of sodium lauryl sulfate as an emulsifier to a 1L flask (reaction vessel) with a stirrer and a rubber stopper. Replace the gas phase with nitrogen and heat to 60°C. Dissolve 0.25 parts of ammonium persulfate (APS) as a polymerization initiator in 20.0 parts of ion-exchanged water and add it to the flask.

[0240] On the other hand, in another container (emulsion container), 30 parts of deionized water, 0.5 parts of sodium lauryl sulfate as an emulsifier, 51.3 parts of n-butyl acrylate and 28 parts of ethyl acrylate as (meth)acrylate monomers, and 0.7 parts of allyl methacrylate as a crosslinking monomer (all of the above are core monomers) were mixed to obtain a monomer composition. This monomer composition was continuously added to the 1L flask with a rubber stopper for 3 hours to carry out polymerization. The reaction was carried out at 60°C during the addition process. After the addition was completed, the mixture was further stirred at 70°C. When the monomer consumption reached 98%, 5 parts of n-butyl acrylate as a (meth)acrylate monomer and 15 parts of acrylonitrile as a nitrogen-containing functional group monomer (all of the above are shell monomers) were mixed in the emulsion container to obtain a monomer composition. This monomer composition was added to the reaction vessel for 1 hour. The reaction was carried out at 70°C during the addition process. After the addition was complete, the mixture was stirred at 80°C for 3 hours to obtain an aqueous dispersion of the particulate polymer with a core-shell structure. The volume average particle size of the particulate polymer was determined using this aqueous dispersion. The results are shown in Table 1. Furthermore, the glass transition temperatures of the polymer in the core and shell were determined. The results are shown in Table 1.

[0241] <Preparation of Adhesive Composition>

[0242] In the aqueous dispersion of the particulate polymer obtained by the above method, an appropriate amount of xylene as an organic solvent is added to obtain a mixture. Then, vacuum distillation is performed at 80°C to remove water and excess xylene from the mixture, yielding a binder composition (solids concentration: 8%).

[0243] <Preparation of Slurry Composition for Positive Electrode Composite Layer>

[0244] A slurry composition for the positive electrode composite layer was prepared by mixing 70 parts of lithium cobalt oxide (number average particle size: 11.5 μm) as the positive electrode active material, 25.5 parts of sulfide glass composed of Li₂S and P₂S₅ (Li₂S / P₂S₅ = 70 mol% / 30 mol%, number average particle size: 0.9 μm) as the solid electrolyte, 2.5 parts of acetylene black as the conductive material, and 2 parts (equivalent solid content) of the binder composition obtained by the above method. Xylene was then added as an organic solvent to adjust the solid content concentration to 80%, and the mixture was stirred using a planetary mixer for 60 minutes. Then, xylene was added again to adjust the solid content concentration to 55%, and the mixture was stirred for 10 minutes.

[0245] <Preparation of Slurry Composition for Negative Electrode Composite Layer>

[0246] A slurry composition for the negative electrode composite layer was prepared by mixing 60 parts of graphite (number average particle size: 20 μm) as the negative electrode active material, 36.5 parts of sulfide glass composed of Li₂S and P₂S₅ (Li₂S / P₂S₅ = 70 mol% / 30 mol%, number average particle size: 0.9 μm) as the solid electrolyte, 1.5 parts of acetylene black as the conductive material, and 2.5 parts (equivalent solid content) of the binder composition obtained by the above method. Xylene was then added as an organic solvent to adjust the solid content concentration to 60%, and the mixture was stirred using a planetary mixer for 60 minutes. Then, xylene was added again to adjust the solid content concentration to 40%, and the mixture was stirred using a planetary mixer.

[0247] <Preparation of slurry compositions for solid electrolyte layers>

[0248] In a glove box under argon atmosphere (moisture concentration 0.6 ppm, oxygen concentration 1.8 ppm), 100 parts of a sulfide glass composed of Li₂S and P₂S₅ (Li₂S / P₂S₅ = 70 mol% / 30 mol%, number average particle size: 0.9 μm) as solid electrolyte particles and 2 parts (equivalent amount of solid component) of the binder composition obtained by the above method were mixed. Xylene was then added as an organic solvent to adjust the solid component concentration to 60 ppm, and the mixture was stirred for 60 minutes using a planetary mixer. Then, xylene was added again to adjust the solid component concentration to 45%, and the mixture was stirred using a planetary mixer to prepare a slurry composition for a solid electrolyte layer.

[0249] <Manufacturing of All-Solid-State Secondary Batteries>

[0250] The above-mentioned slurry composition for the positive electrode composite layer was coated onto the surface of the current collector (aluminum foil, thickness: 20 μm) and dried (at 120°C for 60 minutes) to form a positive electrode composite layer (containing a solid electrolyte layer) with a thickness of 50 μm, thus obtaining the positive electrode. The compressibility of the positive electrode composite layer was evaluated using this positive electrode. The results are shown in Table 1.

[0251] In addition, the above-mentioned slurry composition for the negative electrode composite layer was coated onto the surface of another current collector (copper foil, thickness: 15 μm) and dried (at 120°C for 60 minutes) to form a negative electrode composite layer (containing a solid electrolyte layer) with a thickness of 60 μm, thus obtaining the negative electrode. The peel strength of the negative electrode composite layer was evaluated using this negative electrode. The results are shown in Table 1.

[0252] Next, the above-mentioned slurry composition for the solid electrolyte layer is coated onto the imide film (thickness: 25 μm) and dried (at 120°C for 60 minutes) to form a solid electrolyte layer (containing the solid electrolyte layer) with a thickness of 150 μm. The solid electrolyte layer on the imide film and the positive electrode are bonded together in such a way that the solid electrolyte layer is in contact with the positive electrode composite material layer, and then pressed under a pressure of 400 MPa (pressing pressure) to transfer the solid electrolyte layer from the imide film onto the positive electrode composite material layer, thereby obtaining a positive electrode with a solid electrolyte layer.

[0253] The aforementioned positive and negative electrodes with solid electrolyte layers were bonded together by bringing the solid electrolyte layer of the positive electrode into contact with the negative electrode composite material layer. The positive electrode with solid electrolyte layer was then pressed under a pressure of 400 MPa (compression pressure) to obtain an all-solid-state secondary battery. The thickness of the solid electrolyte layer in the pressed all-solid-state secondary battery was 120 μm. The output characteristics and cycle characteristics of this all-solid-state secondary battery were evaluated. The results are shown in Table 1.

[0254] (Examples 2-3, 16)

[0255] In preparing the binder composition and various slurry compositions, butyl butyrate (Example 2), diisobutyl ketone (Example 3), and isobutyl isobutyrate (Example 16) were used instead of xylene, respectively. Otherwise, particulate polymers with core-shell structures, binder compositions, various slurry compositions, and all-solid-state secondary batteries were prepared in the same manner as in Example 1.

[0256] Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Tables 1 and 3.

[0257] (Examples 4-8, 10-15)

[0258] By varying the types and amounts of the monomers used in the core and / or shell, particulate polymers with the compositions shown in Tables 1 and 2 were prepared. Using these particulate polymers, binder compositions, various slurry compositions, and all-solid-state secondary batteries were prepared in the same manner as in Example 1, except that...

[0259] Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Tables 1-3.

[0260] (Example 9)

[0261] In preparing the core-shell structured particulate polymer, the amount of sodium lauryl sulfate added to the reaction vessel was changed from 0.5 parts to 0.2 parts. Otherwise, the core-shell structured particulate polymer, binder composition, various slurry compositions, and all-solid-state secondary battery were prepared in the same manner as in Example 1.

[0262] Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0263] (Comparative Example 1)

[0264] In addition to using a particulate polymer without a core-shell structure prepared as described below, binder compositions, various slurry compositions, and all-solid-state secondary batteries were prepared in the same manner as in Example 1.

[0265] Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 4.

[0266] <Preparation of Particulate Polymers>

[0267] Add 90 parts of ion-exchanged water and 0.5 parts of sodium lauryl sulfate as an emulsifier to a 1L flask (reaction vessel) with a stirrer and a rubber stopper. Replace the gas phase with nitrogen and heat to 60°C. Dissolve 0.25 parts of ammonium persulfate (APS) as a polymerization initiator in 20.0 parts of ion-exchanged water and add it to the flask.

[0268] On the other hand, in another container (emulsion container), 30 parts of deionized water, 0.5 parts of sodium lauryl sulfate as an emulsifier, 56.3 parts of n-butyl acrylate and 28 parts of ethyl acrylate as (meth)acrylate monomers, 15 parts of acrylonitrile as a nitrogen-containing functional group monomer, and 0.7 parts of allyl methacrylate as a crosslinking monomer were mixed to obtain a monomer composition. This monomer composition was continuously added to the above-mentioned 1L flask with a rubber stopper for 3 hours to carry out polymerization. The reaction was carried out at 60°C during the addition process. After the addition was completed, the mixture was further stirred at 80°C for 3 hours to obtain an aqueous dispersion of particulate polymer without a core-shell structure. The volume average particle size of the particulate polymer was measured using this aqueous dispersion. The results are shown in Table 4. In addition, the glass transition temperature of the particulate polymer was measured. The results are shown in Table 4.

[0269] (Comparative Examples 2-5)

[0270] By varying the types and amounts of the monomers used in the core and / or shell, a particulate polymer with the composition shown in Table 4 was prepared. Using this particulate polymer, binder compositions, various slurry compositions, and all-solid-state secondary batteries were prepared in the same manner as in Example 1, except that...

[0271] Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 4.

[0272] Additionally, in Tables 1-4,

[0273] “BA” represents the n-butyl acrylate unit.

[0274] “EA” represents the ethyl acrylate unit.

[0275] “2EHA” represents the 2-ethylhexyl acrylate unit.

[0276] “AN” represents an acrylonitrile unit.

[0277] “ST” represents styrene unit.

[0278] "AMA" represents allyl methacrylate unit.

[0279] “DVB” represents the divinylbenzene unit.

[0280] “MAAm” represents the methacrylamide unit.

[0281] “DMAEM” stands for dimethylaminoethyl methacrylate unit.

[0282] "MAA" represents methacrylic acid unit.

[0283] "DIBK" stands for diisobutyl ketone.

[0284] "Sulfide" refers to sulfide glass (Li2S / P2S5).

[0285] [Table 1]

[0286]

[0287] [Table 2]

[0288]

[0289] [Table 3]

[0290]

[0291] [Table 4]

[0292]

[0293] As shown in Tables 1-3, the all-solid-state secondary batteries exhibited excellent output and cycle characteristics in Examples 1-16. Furthermore, it can be seen that the solid-state electrolyte layer in Examples 1-16 possessed excellent compressibility and peel strength.

[0294] On the other hand, according to Table 4, it can be seen that in Comparative Example 1, which uses a particulate polymer without a core-shell structure; Comparative Example 2, in which the glass transition temperature of the polymer in the core exceeds the upper limit; Comparative Example 3, in which the glass transition temperature of the polymer in the shell is lower than the lower limit; Comparative Example 4, in which the proportion of nitrogen-containing functional group monomer units in the polymer in the shell is lower than the lower limit; and Comparative Example 5, in which the proportion of nitrogen-containing functional group monomer units in the polymer in the shell is higher than the upper limit, the compressibility and peel strength of the solid electrolyte layer are reduced, and the output characteristics and cycle characteristics of the all-solid-state secondary battery are impaired.

[0295] Industrial availability

[0296] According to the present invention, a slurry composition for all-solid-state secondary batteries can be provided, which can form a solid electrolyte layer that enables all-solid-state secondary batteries to exhibit excellent output and cycle characteristics.

[0297] Furthermore, according to the present invention, a solid electrolyte layer can be provided that enables all-solid-state secondary batteries to exhibit excellent output and cycle characteristics.

[0298] Moreover, according to the present invention, an all-solid-state secondary battery with excellent output characteristics and cycle characteristics can be provided.

[0299] Explanation of reference numerals in the attached figures

[0300] 100: Particulate polymer;

[0301] 110: Core area;

[0302] 110S: The outer surface of the core;

[0303] 120: Shell.

Claims

1. A slurry composition for all-solid-state secondary batteries, comprising a solid electrolyte, particulate polymer, and an organic solvent. The particulate polymer has a core-shell structure, the core-shell structure having a core and a shell covering at least a portion of the outer surface of the core. The polymer constituting the core has a glass transition temperature above -60°C and below -10°C. The polymer constituting the shell has a glass transition temperature of 15°C or higher and 100°C or lower. The polymer constituting the shell portion comprises nitrogen-containing functional group monomer units. When all repeating units of the polymer constituting the shell portion are taken as 100% by mass, the amount of nitrogen-containing functional group monomer units contained in the polymer constituting the shell portion is 10% by mass or more and 90% by mass or less. The particulate polymer comprises crosslinking monomer units, and when all repeating units of the particulate polymer are taken as 100% by mass, the amount of the crosslinking monomer units contained in the particulate polymer is 0.7% by mass or more and less than 2.0% by mass. The shell portion accounts for 12% or more and 23% or less of the total mass of the core portion and the shell portion.

2. The slurry composition for all-solid-state secondary batteries according to claim 1, wherein, The slurry composition for all-solid-state secondary batteries also includes electrode active materials.

3. The slurry composition for all-solid-state secondary batteries according to claim 2, wherein, The slurry composition for all-solid-state secondary batteries also includes conductive materials.

4. A solid electrolyte layer formed using any one of the all-solid-state secondary battery slurry compositions according to claims 1 to 3.

5. An all-solid-state secondary battery having the solid electrolyte layer as described in claim 4.

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