Coated particles and method for producing same, electrode mix, solid electrolyte layer, and solid-state secondary battery

Abstract

The present invention relates to coated particles each comprising a sulfide-based particle having a surface coated with a fluorine-containing organic compound. The fluorine-containing organic compound contains a structural unit (1) that is based on a specific monomer (1) and a structural unit (2) that is based on a specific monomer (2). The average particle diameter of the coated particles is 10 nm to 10 μm.

Description

Coated particles and their manufacturing method, as well as electrode mixture, solid electrolyte layer, and all-solid-state secondary battery

[0001] The present invention relates to coated particles and a method for producing the same, as well as an electrode mixture, a solid electrolyte layer, and an all-solid-state secondary battery.

[0002] Lithium-ion secondary batteries are widely used in portable electronic devices such as mobile phones and laptop computers. Conventionally, liquid electrolytes have been used in lithium-ion secondary batteries. Meanwhile, all-solid-state lithium-ion secondary batteries (hereinafter also referred to as all-solid-state secondary batteries), which use solid electrolytes as the electrolyte for lithium-ion secondary batteries, have been attracting attention due to their potential for improved safety, high-speed charging and discharging, and compact casing.

[0003] An example of a solid electrolyte used in an all-solid-state secondary battery is a sulfide solid electrolyte. For example, Patent Document 1 describes an all-solid-state secondary battery using a sulfide solid electrolyte in a solid electrolyte layer or a positive electrode layer.

[0004] Japanese Patent Application Publication No. 2023-137378

[0005] In contrast to liquid-based batteries, in which an electrolyte solution responsible for ionic conduction penetrates between active materials to form electrodes, all-solid-state batteries generally have electrodes designed using a mixture of active materials and solid electrolytes. From the perspective of improving battery characteristics, it is desirable for solid-state batteries to have the active materials and solid electrolyte uniformly dispersed so that electronic and ionic conduction occurs at more solid interfaces, i.e., at a larger reaction area. From the perspective of such battery characteristics, the technology described in Patent Document 1 leaves room for improvement.

[0006] Furthermore, when a voltage is applied during battery operation, the potential can cause an oxidation reaction at the interface between the active material and the solid electrolyte, increasing resistance, and the oxidation resistance of the solid electrolyte is also a factor affecting battery characteristics.

[0007] The present invention aims to provide a sulfide-based material that improves the battery characteristics of all-solid-state secondary batteries and has excellent oxidation resistance, and a method for producing the same. The present invention also aims to provide an electrode mixture, a solid electrolyte layer, and an all-solid-state secondary battery that include such a sulfide-based material.

[0008] The present invention relates to the following items [1] to

[16] : [1] Coated particles in which the surfaces of sulfide-based particles are coated with a fluorine-containing organic compound, the fluorine-containing organic compound containing a structural unit (1) based on a monomer (1) represented by the following formula (1) and a structural unit (2) based on a monomer (2) represented by the following formula (2), and the average particle size of the coated particles is 10 nm or more and 10 μm or less.

[0009]

[0010] (In formula (1), X represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or CFX １ X ２ group (wherein X １ and X ２ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; Y is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent hydrocarbon group having 1 to 10 carbon atoms and an oxygen atom, -CH ２ CH ２ N(Ra)SO ２ - group (wherein Ra is an alkyl group having 1 to 4 carbon atoms), -CH ２ CH (OY １ ) CH ２ - group (where Y １ is a hydrogen atom or an acetyl group, or —(CH ２ ) ｎ SO ２ - group (n is 1 to 10), and Rf is a linear or branched fluoroalkyl group having 1 to 10 carbon atoms.

[0011]

[0012] (In formula (2), R １ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, CFX ３ X ４ group (wherein X ３ and X ４are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; R ２ is a monovalent hydrocarbon group having one or more carbon atoms, or a monovalent hydrocarbon group having one or more carbon atoms and containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms in its structure. １ is H or CH ３ If R ２is a monovalent hydrocarbon group having 3 or more carbon atoms or a monovalent hydrocarbon group having a ring structure and containing at least one atom of at least one kind selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms.) [2] The coated particle according to [1], wherein the mass ratio of the structural unit (1) to the structural unit (2) is 100:70 to 100:500. [3] The coated particle according to [1] or [2], wherein the surface fluorine concentration is 1 atomic% or more. [4] The coated particle according to any one of [1] to [3], wherein the surface fluorine concentration is 0.1 atomic% or more after the coated particle is immersed in butyl butyrate, recovered by filtration, and dried. [5] The coated particle according to any one of [1] to [4], wherein the average particle diameter is 100 nm or more and 1.0 μm or less. [6] The coated particle according to any one of [1] to [5], wherein the weight-average molecular weight of the fluorine-containing organic compound is 3,000 to 100,000. [7] The coated particle according to any one of [1] to [6], wherein the SP value of the fluorine-containing organic compound is 6.0 to 9.0. [8] The coated particle according to any one of [1] to [7], wherein the SP value of the fluorine-containing organic compound is 6.0 to 7.0. [9] The coated particle according to any one of [1] to [8], wherein the sulfide-based particle has an argyrodite-type crystal structure.

[10] An electrode mixture containing a sulfide solid electrolyte and an active material, wherein the sulfide solid electrolyte is the coated particle according to any one of [1] to [9].

[11] A solid electrolyte layer containing a sulfide solid electrolyte, wherein the sulfide solid electrolyte is the coated particle according to any one of [1] to

[10] .

[12] An all-solid-state secondary battery containing a sulfide solid electrolyte, wherein the sulfide solid electrolyte is the coated particle according to any one of [1] to

[11] .

[13] A method for producing coated particles in which the surfaces of sulfide-based particles are coated with a fluorine-containing organic compound, the method comprising wet-pulverizing the sulfide-based particles using a medium containing a fluorine-containing organic compound, wherein the wet-pulverization not only pulverizes the sulfide-based particles but also coats the sulfide-based particles with the fluorine-containing organic compound.

[14] The method for producing coated particles according to

[13] , wherein the fluorine-containing organic compound comprises a structural unit (1) based on a monomer (1) represented by the following formula (1) and a structural unit (2) based on a monomer (2) represented by the following formula (2):

[0013]

[0014] (In formula (1), X represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or CFX １ X ２ group (wherein X １ and X ２ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; Y is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent hydrocarbon group having 1 to 10 carbon atoms and an oxygen atom, -CH ２ CH ２ N(Ra)SO ２ - group (wherein Ra is an alkyl group having 1 to 4 carbon atoms), -CH ２ CH (OY １ ) CH ２ - group (where Y １ is a hydrogen atom or an acetyl group, or —(CH ２ ) ｎ SO ２ - group (n is 1 to 10), and Rf is a linear or branched fluoroalkyl group having 1 to 10 carbon atoms.

[0015]

[0016] (In formula (2), R １ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, CFX ３ X ４ group (wherein X ３ and X ４are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; R ２ is a monovalent hydrocarbon group having one or more carbon atoms, or a monovalent hydrocarbon group having one or more carbon atoms and containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms in its structure. １ is H or CH ３ If R ２ is a monovalent hydrocarbon group having 3 or more carbon atoms or a monovalent hydrocarbon group having a ring structure and containing at least one atom of at least one kind selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms.)

[15] The method for producing coated particles according to

[14] , wherein the mass ratio of the structural unit (1) to the structural unit (2) is 100:70 to 100:500.

[16] The method for producing coated particles according to any one of

[13] to

[15] , wherein the weight average molecular weight of the fluorine-containing organic compound is 3,000 to 100,000.

[0017] According to the present invention, a sulfide-based material that improves the battery characteristics of an all-solid-state secondary battery and has excellent oxidation resistance can be obtained. Furthermore, an electrode mixture, a solid electrolyte layer, and an all-solid-state secondary battery that contain such a sulfide-based material can achieve excellent battery characteristics.

[0018] FIG. 1 is a flow diagram showing a method for producing coated particles according to this embodiment.

[0019] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented with any modifications within the scope of the present invention. The term "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0020] The average particle size of the particles in this specification is the particle size D50 in the volume-based cumulative particle size distribution. The particle size D50 can be measured using a laser diffraction particle size distribution analyzer.

[0021] <Coated Particles> The coated particles according to this embodiment are sulfide-based particles whose surfaces are coated with a fluorine-containing organic compound. The fluorine-containing organic compound contains a structural unit (1) based on a monomer (1) represented by the following formula (1) and a structural unit (2) based on a monomer (2) represented by the following formula (2). The average particle size of the coated particles is 10 nm or more and 10 μm or less.

[0022] The above-described configuration improves the battery characteristics of solid secondary batteries. The reason for this is that the hydrophilic sulfide-based particles become hydrophobic when the particle surfaces are coated with a specific fluorine-containing organic compound, improving their dispersibility in solvents (e.g., solvents used in electrode coating compositions) during battery production. This is thought to be because, as a result, an electrode mixture is obtained in which the solid electrolyte is uniformly dispersed between the active material particles, ensuring high electronic and ionic conductivity. Furthermore, it is thought that the specific range of the average particle diameter of the coated particles results in a highly dense electrode mixture in which the solid electrolyte is uniformly dispersed to fill the spaces between the active material particles, contributing to high electronic and ionic conductivity.

[0023] Furthermore, the above-mentioned configuration improves the oxidation resistance of the solid secondary battery. The reason for this is presumably that the particle surfaces are coated with a specific fluorine-containing organic compound, and the coating of the fluorine-containing organic compound functions as a protective film for the sulfide-based particles, thereby suppressing the oxidation reaction at the interface between the active material and the solid electrolyte when a voltage is applied.

[0024] (Sulfide-based particles) The sulfide-based particles in the present disclosure are not limited as long as they are solid particles containing a sulfur component. The sulfide-based particles preferably function as a solid electrolyte, and more preferably function as a sulfide solid electrolyte of an all-solid-state secondary battery.

[0025] Examples of sulfide-based particles in the present disclosure include sulfide-based particles having a crystalline structure containing Li, P, and S elements, called LPS-based particles; sulfide-based particles having a crystalline structure containing Li, Ge, P, and S elements, called LGPS-based particles; sulfide-based particles having an argyrodite-type crystalline structure containing Li, P, S, and Ha; sulfide-based particles made of Li-P-S-Ha-based crystallized glass; sulfide-based particles having a thiolisicon-type crystalline structure; and crystalline phases containing oxides. Furthermore, sulfide-based particles may include a crystalline phase having the above-mentioned crystalline structure and an amorphous phase. The sulfide-based particles according to this embodiment are not limited to the above-mentioned crystalline structure, and some elements may be substituted with other elements.

[0026] Among the above crystal structures, from the viewpoint of lithium ion conductivity and battery characteristics, it is preferable that the sulfide-based particles have a crystalline phase, and that the crystalline phase has an LPS-based crystal structure or an argyrodite-type crystal structure.

[0027] When the crystalline structure of the crystalline phase of the sulfide-based particles is an LPS-based structure, the sulfide-based particles contain Li α P.S. β It is preferable that the composition be expressed by (5.5≦α≦5.6, 4.3≦β≦4.4). This ensures high lithium ion conductivity. The LPS-based crystal structure may contain at least one of Cl and Br in addition to Li, P, and S.

[0028] When the crystal structure of the crystalline phase of the sulfide-based particles is an argyrodite type, the argyrodite type crystal structure is a crystal structure having the composition formula Ag ８ GeS ６ This is the crystal structure of a group of compounds derived from minerals represented by the formula:

[0029] When the sulfide-based particles have an argyrodite-type crystal structure, the Ha element preferably contains at least one element, and more preferably contains two or more elements, selected from the group consisting of Cl, Br, and I. Furthermore, in the above, the Ha element preferably contains at least one of Cl and Br, and even more preferably contains Cl and Br.

[0030] The composition formula of the argyrodite type is Li α’ P.S. β’ Ha γ’ It is preferable that the element ratio satisfies the relationships 5≦α'≦7, 4≦β'≦6, and 1.3≦γ'≦2. It is more preferable that the element ratio satisfies the relationships 5.1<α'<6.3, 4<β'<5.3, and 1.4≦γ'≦1.9, and even more preferable that the element ratio satisfies the relationships 5.2<α'<6.2, 4.1<β'<5.2, and 1.5≦γ'≦1.8. That is, α' is preferably 5 or more, more preferably greater than 5.1, and even more preferably greater than 5.2, and is preferably 7 or less, more preferably less than 6.3, and even more preferably less than 6.2. β' is preferably 4 or more, more preferably greater than 4, and even more preferably greater than 4.1, and is preferably 6 or less, more preferably less than 5.3, and even more preferably less than 5.2. The γ' is preferably 1.3 or more, more preferably 1.4 or more, and even more preferably 1.5 or more, and is preferably 2 or less, more preferably 1.9 or less, and even more preferably 1.8 or less.

[0031] In the argyrodite-type crystal structure, some of the S element is replaced by Ha element, O element, Se element, Te element, BH element, etc. ４ , CN, etc. Also, a portion of the P element may be substituted with Si element, Al element, Sn element, In element, Cu element, Sb element, Ge element, etc.

[0032] In this specification, when the sulfide-based particles have an LPS-based crystal structure or an argyrodite-type crystal structure, it means that the sulfide-based particles have at least these crystal phases.

[0033] The sulfide-based particles in this embodiment may be sulfide-based particles containing a crystalline phase and an amorphous phase, but the crystallinity is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, and even more preferably 90 to 100% by mass. From the viewpoint of ensuring lithium ion conductivity, the crystallinity is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. Furthermore, from the viewpoint of ensuring lithium ion conductivity, the crystallinity is preferably high, and may be 100% by mass. In this specification, the crystallinity is the ratio of the crystalline phase to the total of the crystalline phase and the amorphous phase, and can be measured by X-ray diffraction measurement.

[0034] The average particle diameter of the sulfide-based particles in this embodiment is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less, from the viewpoint of obtaining good ionic conductivity when used in an all-solid-state secondary battery. The lower limit of the average particle diameter is not particularly limited, but is usually 0.01 μm or more. The average particle diameter of the sulfide-based particles can be determined by measuring the particle diameter D50 after removing the fluorine-containing organic compound on the surface of the coated particles using a solvent such as a solution obtained by adding 6% of dehydrated tertiary butyl alcohol as a dispersant to 110 ml of toluene.

[0035] (Fluorine-containing organic compound) The coated particles of the present disclosure are obtained by coating the surfaces of the sulfide-based particles with a fluorine-containing organic compound. The surfaces of the sulfide-based particles may be partially or entirely coated. Furthermore, the coated particles of the present disclosure may be obtained by coating aggregates of the sulfide-based particles with a fluorine-containing organic compound.

[0036] The fact that the surfaces of the sulfide-based particles are coated with a fluorine-containing organic compound can be confirmed by, for example, X-ray photoelectron spectroscopy (XPS), which will be described later, or by energy dispersive X-ray spectroscopy (EDX), time-of-flight secondary ion mass spectrometry (TOF-SIMS), electron probe microanalyzer (EPMA), or the like.

[0037] The fluorine-containing organic compound contains a structural unit (1) based on a monomer (1) represented by the following formula (1) and a structural unit (2) based on a monomer (2) represented by the formula (2) described below.

[0038]

[0039] In formula (1), X is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or CFX １ X ２ group (wherein X １ and X ２ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; Y is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent hydrocarbon group having 1 to 10 carbon atoms and an oxygen atom, -CH ２ CH ２ N(Ra)SO ２ - group (wherein Ra is an alkyl group having 1 to 4 carbon atoms), -CH ２ CH (OY １ ) CH ２ - group (where Y １ is a hydrogen atom or an acetyl group, or —(CH ２ ) ｎ SO ２ - group (n is 1 to 10), and Rf is a linear or branched fluoroalkyl group having 1 to 10 carbon atoms.

[0040] The monomer (1) is an acrylic acid which may have a substituent at the α-position, to which a fluoroalkyl group is ester-bonded directly or via a specific divalent organic group.

[0041] In formula (1), the hydrocarbon group may be either cyclic or acyclic, and may be either linear or branched.

[0042] In formula (1), the fluoroalkyl group is an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and also includes a perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms.

[0043] From the viewpoint of improving the oxidation resistance of the coated particles, X is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, CFX １ X ２ group (wherein X １ and X ２ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom), a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms, and among these, X is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, CF ３ group, a cyano group, an unsubstituted benzyl group, an unsubstituted phenyl group, a linear or branched fluoroalkyl group having 1 to 10 carbon atoms, or a linear or branched alkyl group having 1 to 10 carbon atoms is preferred, and a hydrogen atom, a fluorine atom, or a CF ３ group or a methyl group is more preferred, and a fluorine atom, CF ３ group or a methyl group is more preferred.

[0044] In formula (1), from the viewpoint of improving the oxidation resistance of the coated particles, Rf is preferably a linear or branched fluoroalkyl group having 4 to 6 carbon atoms, and particularly preferably a linear or branched perfluoroalkyl group having 4 to 6 carbon atoms. When Rf is a linear or branched fluoroalkyl group having 4 to 6 carbon atoms, in order to improve the dispersibility of the coated particles, it is preferable that the α-position substituted acrylic ester in which the substituent at the α-position represented by X in formula (1) is a group or atom other than a hydrogen atom is used. In particular, it is preferable that the substituent at the α-position X is a methyl group (CH ３ ), when it is a fluorine atom, a coating film can be formed that does not impair the ionic conductivity and dispersibility of the solid electrolyte. In particular, it is preferable that the substituent X at the α-position is a methyl group. It is also preferable that Rf does not have a ring structure.

[0045] Furthermore, in formula (1), from the viewpoint of improving the oxidation resistance of the coated particle, Y is preferably a divalent hydrocarbon group having 1 to 10 carbon atoms which may have an oxygen atom, more preferably an alkylene group having 1 to 10 carbon atoms, even more preferably an alkylene group having 1 to 5 carbon atoms, and even more preferably an alkylene group having 1 to 3 carbon atoms. Furthermore, it is also preferable that Y does not have a ring structure.

[0046] Specific examples of the monomer (1) include the following compounds: CH ２ =C(CH ３ )-C(=O)-O-(CH ２ ) ｎ -C ｍ F ２ｍ＋１ (n=1-10, m=1-10)

[0047] The monomer (1) may be produced by a known method, or a commercially available product may be used. The monomer (1) may be used alone or in combination of two or more.

[0048] Next, the monomer (2) will be described. The monomer (2) is represented by the following formula (2): The structural unit (2) based on the monomer (2) is thought to contribute to the adsorption of the fluorine-containing organic compound to the sulfide-based particles.

[0049]

[0050] In formula (2), R １ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, CFX ３ X ４ group (wherein X ３ and X ４ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; R ２is a monovalent hydrocarbon group having one or more carbon atoms, or a monovalent hydrocarbon group having one or more carbon atoms and containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms in its structure.

[0051] R １ From the viewpoint of improving the dispersibility of the coated particles, is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 20 carbon atoms, and more preferably a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms.

[0052] In formula (2), R ２ The hydrocarbon group as R may contain one or more atoms of at least one kind selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms in its structure, from the viewpoint of improving the dispersibility and oxidation resistance of the coated particles, and has one or more carbon atoms. The number of carbon atoms is preferably three or more, and may be five or more. The number of carbon atoms is preferably 30 or less, and more preferably 15 or less. In addition, R ２ The atom that may be contained in the hydrocarbon group as the above is preferably at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, and a silicon atom, and more preferably at least one of an oxygen atom and a silicon atom.

[0053] R ２Examples of the monovalent hydrocarbon group as R include groups having a hydrocarbon ring, such as groups having an aliphatic hydrocarbon ring or groups having an aromatic hydrocarbon ring, and aliphatic hydrocarbon groups without a ring. Examples of the group having an aliphatic hydrocarbon ring include cycloalkyl groups, groups having a heterocycle such as a glycidyl group, and groups having a bridged hydrocarbon ring such as isobornyl, bornyl, fensil, adamantyl, and norbornyl. Examples of the group having an aromatic hydrocarbon ring include a phenyl group and a benzyl group. Examples of the group having a hydrocarbon ring include a cycloalkyl group, a group having a bridged hydrocarbon ring, and a benzyl group, and more preferably a group having a bridged hydrocarbon ring. The hydrocarbon ring may be directly bonded to a carboxyl group or may be bonded to a carboxyl group via a linear or branched alkylene group having 1 to 5 carbon atoms. The hydrocarbon ring may be further substituted with a hydroxyl group or an alkyl group (having, for example, 1 to 5 carbon atoms). Examples of the aliphatic hydrocarbon group without a ring include linear or branched alkyl groups which may have an ether bond. R ２ Among these, the hydrocarbon group as R is preferably a group having an aliphatic hydrocarbon ring or a group having an aromatic hydrocarbon ring. ２ The hydrocarbon group as R may or may not contain a fluorine atom. ２ When the hydrocarbon group as R ２ is a structure different from —Y—Rf in the monomer (1).

[0054] R ２ The monovalent hydrocarbon group containing at least one of an oxygen atom and a silicon atom as the group represented by the formula (I) includes a monovalent hydrocarbon group containing a siloxane bond (Si—O), and preferably —[Si(CH ３ ) (CH ３ )—O]—, and more preferably, a monovalent hydrocarbon group containing a repeating unit represented by —[Si(CH ３ ) (CH ３ )-O]- and a monovalent hydrocarbon group containing an alkylene group and an alkyl group.

[0055] Specific examples of the monomer (2) include the following compounds: CH ２ = C(R １ )-C(=O)-O-(CH ２ ) ｐ CH ３ (p=1~20) CH ２ = C(R １ )-C(=O)-O-(CH ２ ) ｓ —O—[Si(CH ３ ) (CH ３ )-O] ｔ -Si(CH ３ ) (CH ３ ) —R (s=1 to 10, t=1 to 10, R: alkyl group)

[0056] Examples of monomer (2) include (meth)acrylates having a cyclohexyl group, (meth)acrylates having a benzyl group, (meth)acrylates having an isobornyl group, (meth)acrylates having a norbornyl group, and (meth)acrylates having an adamantyl group. Examples of (meth)acrylates having a cyclohexyl group include cyclohexyl methacrylate. Examples of (meth)acrylates having a benzyl group include benzyl methacrylate. Examples of (meth)acrylates having an isobornyl group include isobornyl (meth)acrylate and isobornylmethyl (meth)acrylate. Examples of (meth)acrylates having a norbornyl group include 3-methyl-norbornylmethyl (meth)acrylate, norbornylmethyl (meth)acrylate, norbornyl (meth)acrylate, 1,3,3-trimethyl-norbornyl (meth)acrylate, myrtanylmethyl (meth)acrylate, isopinocamphanyl (meth)acrylate, 2-{[5-(1',1',1'-trifluoro-2'-trifluoromethyl-2'-hydroxy)propyl]norbornyl} (meth)acrylate, etc. Examples of (meth)acrylates having an adamantyl group include 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, 3-hydroxy-1-adamantyl (meth)acrylate, 1-adamantyl-α-trifluoromethyl (meth)acrylate, etc.

[0057] The monomer (2) may be produced by a known method, or a commercially available product may be used. The monomer (2) may be used alone or in combination of two or more.

[0058] The mass ratio of the structural unit (1) to the structural unit (2) is preferably 100:70 to 100:500. It is believed that the structural unit (2) is mainly adsorbed onto the surface of the sulfide-based particles, and the sulfide particles can be sufficiently coated when the mass ratio of the structural unit (2) is 70 or more. The mass ratio of the structural unit (2) is more preferably 90 or more, and even more preferably 140 or more.

[0059] Although there is no particular limitation on the method for polymerizing the monomers (1) and (2), it is preferable to carry out solution polymerization in a fluorine-containing solvent. According to this method, the fluorine-containing organic compound formed has good solubility in the fluorine-containing solvent, so that the radical polymerization reaction can proceed smoothly without forming any precipitate.

[0060] The fluorine-containing organic compound in this embodiment preferably has a weight-average molecular weight of 3,000 to 100,000, more preferably 5,000 to 30,000. When the weight-average molecular weight is in this range, the steric hindrance of the fluorine-containing organic compound is small, and the sulfide-based particles can be uniformly coated, which is preferable. The weight-average molecular weight of the fluorine-containing organic compound can be calculated by GPC (gel permeation chromatography).

[0061] The fluorine-containing organic compound in this embodiment preferably has an SP value (solubility parameter) of 6.0 or more from the viewpoint of improving the coating ability on sulfide-based particles. Furthermore, from the viewpoint of compatibility with the solvent used in battery fabrication, the SP value is preferably 9.0 or less, and from the viewpoint of improving the oxidation resistance when the coated particles are used in a solid secondary battery, the SP value is more preferably 7.0 or less. The SP value of the fluorine-containing organic compound is calculated by the Fedors calculation method using the cohesive energy density E (cal / mol) and the molar molecular volume (molar volume) V (cm ３ / mol), the SP value σ=(ΣE / ΣV) １／２ In the case of polymers, when m<3, the number of atoms constituting the main chain of the minimum repeating unit is 4m (cm ３ / mol) is 2m (cm when m≧3 ３ / mol) is added as a correction coefficient.

[0062] <Method for producing coated particles> The coated particles according to this embodiment can be produced by a method of immersing sulfide-based particles of the present disclosure in a solution obtained by dissolving the fluorine-containing organic compound of the present disclosure in a solvent or a dispersion obtained by dispersing the compound in a dispersion medium, followed by drying (immersion method), a method of spraying the solution or dispersion onto sulfide-based particles, followed by drying (spray drying method), a method of wet-pulverizing sulfide-based particles using a medium containing a fluorine-containing organic compound (wet-pulverization method), a PVD method, a CVD method, or the like. Among the above methods, the immersion method or wet-pulverization method is preferred.

[0063] In the immersion method and spray-drying method, the sulfide-based particles are preferably pulverized using a bead mill or the like to a predetermined average particle size, preferably an average particle size of 100 nm to 10 μm. The solvent or dispersion medium for the fluorine-containing organic compound is preferably an organic solvent, such as a fluorine-based solvent, toluene, xylene, dibutyl ether, heptane, or n-butyl butyrate. One type can be used alone, or two or more types can be mixed. The organic solvent is preferably one that has been dehydrated to reduce its water content. Regarding the mixing ratio of the sulfide-based particles and the fluorine-containing organic compound, from the viewpoint of suppressing an increase in resistance while exerting the effect of a coating, the amount of the fluorine-containing organic compound relative to the sulfide-based particles is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass.

[0064] When the coated particles according to this embodiment are produced by a wet milling method, the sulfide-based particles are wet-milled using a medium containing a fluorine-containing organic compound. This reduces the number of manufacturing steps, as the sulfide-based particles are pulverized and coated with the fluorine-containing organic compound at the same time. The sulfide-based particles before wet milling may be in a coarsely pulverized state with an average particle size of approximately 1 to 500 μm. The medium is preferably an organic solvent similar to that used in the immersion method and spray-drying method. For wet milling, a bead mill or the like is preferably used to mill the particles to a desired particle size, preferably an average particle size of 10 nm or more and 10 μm or less. The mixing ratio of the sulfide-based particles and the fluorine-containing organic compound is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass, from the viewpoint of suppressing an increase in resistance while exerting the effect of the coating.

[0065] <Physical Properties of Coated Particles> The coated particles according to this embodiment have an average particle diameter of 10 nm or more and 10 μm or less. This range is preferable because good dispersibility can be obtained when used as a solid electrolyte. The average particle diameter is preferably 100 nm or more and 5 μm or less, and particularly preferably 100 nm or more and 1.0 μm or less.

[0066] The coated particles according to this embodiment preferably have a surface fluorine concentration of 1 atomic % or more. A surface fluorine concentration within this range is preferred because a sufficient amount of fluorine-containing organic compound is present on the particle surface. The upper limit of the surface fluorine concentration is not particularly limited, but is preferably 15 atomic % or less. In this embodiment, the surface fluorine concentration can be calculated from the height of the F1s peak in the spectrum measured by XPS. For XPS, for example, monochromatic Al Kα radiation can be used.

[0067] Furthermore, the coated particles according to this embodiment preferably have a surface fluorine concentration of 0.1 atomic % or more after the coated particles are immersed in butyl butyrate, recovered by filtration, and dried (hereinafter also referred to as "surface fluorine concentration after immersion in butyl acetate"). Butyl butyrate is a solvent used in the actual production of battery components such as electrode mixtures. The coated particles according to this embodiment do not experience a decrease in surface fluorine concentration even under conditions simulating those during battery production, and a sufficient amount of fluorine-containing organic compound is present on the particle surface. There is no particular upper limit to the surface fluorine concentration after immersion in butyl acetate, but it is preferably 15 atomic % or less.

[0068] <Sulfide solid electrolyte, solid electrolyte layer, electrode mixture, all-solid-state secondary battery> The coated particles according to this embodiment can be suitably used as a sulfide solid electrolyte. The coated particles according to this embodiment can also be suitably used as a constituent material of an all-solid-state secondary battery, specifically, for an electrode mixture or a solid electrolyte layer, and are particularly suitable for all-solid-state secondary batteries, and are even more suitable for all-solid-state lithium-ion secondary batteries. That is, the electrode mixture is used in an all-solid-state secondary battery and contains an active material and the coated particles as a sulfide solid electrolyte. The solid electrolyte layer is also used in an all-solid-state secondary battery and contains the coated particles as a sulfide solid electrolyte.

[0069] The electrode mixture, solid electrolyte layer, and all-solid-state secondary battery may further contain other solid electrolytes in addition to the coated particles according to this embodiment.

[0070] The active material contained in the electrode mixture may be a conventionally known material. The positive electrode active material is not particularly limited as long as it can reversibly absorb and release alkali metal ions, detach and insert (intercalate) alkali metal ions, or reversibly dope and dedope counter anions of the alkali metal ions. Here, the alkali metal ion is preferably a lithium ion. Specific examples of the positive electrode active material include lithium cobaltate, lithium nickelate, lithium manganate, lithium titanate, lithium metal phosphate, composite metal oxides, heteroelement-substituted Li—Mn spinel, lithium metal phosphate, LiCoN, Li ２ SiO ３ , Li ４ SiO ４ , transition metal oxide, TiS ２ , Si, SiO ２ , Si alloys, lithium storage intermetallic compounds, lithium alloys, polyanion olivine type positive electrodes, etc. Examples of composite metal oxides include LiNi ｘ M １－ｘ O ２ (wherein x satisfies 0.5≦x<1, and M is at least one element selected from the group consisting of Co, Mn, and Al). The heteroelement-substituted Li—Mn spinel is, for example, LiMn １．５ Ni ０．５ O４ , LiMn １．５ Al ０．５ O ４ , LiMn １．５ Mg ０．５ O ４ , LiMn １．５ Co ０．５ O ４ , LiMn １．５ Fe ０．５ O ４ , and LiMn １．５ Zn ０．５ O ４ Examples of lithium metal phosphate include LiFePO ４ , LiMnPO ４ , LiCoPO ４ , and LiNiPO ４ The transition metal oxides include, for example, V ２ O ５ , and MoO ３ The lithium storage intermetallic compound is, for example, Mg ２ Sn, Mg ２ Ge, Mg ２ Sb and Cu ３ Examples of lithium alloys include Li—Au, Li—Mg, Li—Sn, Li—Si, Li—Al, Li—B, Li—C, Li—Ca, Li—Ga, Li—Ge, Li—As, Li—Se, Li—Ru, Li—Rh, Li—Pd, Li—Ag, Li—Cd, Li—In, Li—Sb, Li—Ir, Li—Pt, Li—Hg, Li—Pb, Li—Bi, Li—Zn, Li—Tl, Li—Te, and Li—At. Examples of Si alloys include alloys with metals such as Li, and may also be alloys with at least one metal selected from the group consisting of Sn, Ge, and Al.

[0071] The shape of the positive electrode active material is not particularly limited, and may be particulate. When the positive electrode active material is particulate, the positive electrode active material may be primary particles or secondary particles.

[0072] A coating layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material. The formation of the coating layer is preferable because it can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of the Li ion conductive oxide include LiNbO. ３ , Li ４ Ti ５ O １２ , and Li ３ P.O. ４ The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coating layer may cover, for example, 70% or more, or may cover 90% or more of the surface of the positive electrode active material.

[0073] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release alkali metal ions, detach and insert (intercalate) alkali metal ions, or reversibly dope and dedope counter anions of the alkali metal ions. Here, the alkali metal ions are preferably lithium ions. Specific examples of the negative electrode active material include lithium metal, carbon-based materials such as graphite, hard carbon, and soft carbon, metals that can form alloys with lithium such as aluminum, silicon, and tin, amorphous oxides such as silicon oxide and tin oxide, and lithium titanate.

[0074] The solid electrolyte layer may contain the coated particles according to the present embodiment, but may also contain other solid electrolytes and additives such as a binder. Conventionally known binders can be used, such as butadiene rubber, acrylate butadiene rubber, styrene butadiene rubber, polyvinylidene fluoride, and polytetrafluoroethylene. The binder content in the solid electrolyte layer may also be within a conventionally known range.

[0075] The all-solid-state secondary battery is not particularly limited as long as it includes a positive electrode and a negative electrode in addition to the coated particles according to this embodiment as the sulfide solid electrolyte. The positive electrode and the negative electrode may be an electrode mixture containing the coated particles according to this embodiment. The positive electrode active material may be the same as the positive electrode active material described in the electrode mixture, and the positive electrode may further include a positive electrode current collector, a binder, a conductive additive, etc., as needed. The positive electrode current collector may be made of aluminum, an alloy thereof, a thin metal plate such as stainless steel, or the like.

[0076] The negative electrode active material can be the same as the negative electrode active material described in the electrode mixture, and the negative electrode may further contain, as necessary, a negative electrode current collector, a binder, a conductive additive, etc. The negative electrode current collector can be a thin metal plate such as copper or aluminum.

[0077] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Examples 1-1, 1-2, 2-1, and 2-2 are working examples, and Examples 2-3 and 2-4 are comparative examples.

[0078] <Production of sulfide solid electrolyte> Li ５．４ P.S. ４．４ Cl ０．８ Br ０．８ Lithium sulfide powder (manufactured by Sigma, purity 99.98%), diphosphorus pentasulfide powder (manufactured by Sigma, purity 99%), lithium chloride powder (manufactured by Sigma, purity 99.99%), and lithium bromide powder (manufactured by Sigma, purity 99.995%) were weighed out so as to give a composition (argyrodite crystal structure) of 1000 kJ / cm2, and then placed in a quartz test tube and vacuum sealed. The mixture was dissolved at 750°C for 1 hour and then cooled to obtain a sulfide solid electrolyte.

[0079] The sulfide solid electrolyte was pulverized using a cutter mill and then further pulverized using a hand mortar to obtain a coarsely pulverized sulfide solid electrolyte. The coarsely pulverized sulfide solid electrolyte was then screened using a 100 μm mesh sieve to select particles of 100 μm or less. The average particle size of the coarsely pulverized sulfide solid electrolyte, as determined by the method described below, was 14 μm. Next, a mixed solvent (253 g) of 158.1 g of heptane (Kanto Chemical Co., Ltd., special grade (dehydrated - Super-)) and 94.9 g of dibutyl ether (Tokyo Chemical Industry Co., Ltd., stabilized with BHT) was prepared as the solvent for obtaining the finely pulverized product. Molecular sieves 4A 1 / 16 (Fujifilm Wako Pure Chemical Industries, Ltd.) were added to the mixed solvent and left to stand for 10 hours or more to dehydrate it in advance. The selected coarsely pulverized sulfide solid electrolyte (48.2 g) was added to the mixed solvent (253 g) to obtain a slurry (solid content concentration 16 mass %). 288 g of high-purity alumina balls (AL9 series, AS ONE Corporation) with a diameter of 0.5 mm were added to the slurry, and wet pulverization was carried out using a bead mill type pulverizer (LMZ015, Ashizawa Finetech Co., Ltd.) under the following conditions. (Conditions) Bead filling rate in the sample container: 80% by volume; Circumferential speed: 8 m / s; Slurry flow rate: 300 mL / min; Milling time: 10 min. Next, the wet-milled mixture was passed through a stainless steel sieve with 150 μm openings, and high-purity alumina balls with a diameter of 0.5 mm were collected. The mixture was left to stand for 3 to 5 hours, and the supernatant liquid was removed. The resulting slurry was placed in a bottle and then placed in a separable flask inserted into a mantle heater in a glove box. The mixture was then heated above the boiling point of the solvent under a nitrogen atmosphere, dried, crushed in a mortar, and passed through a 150 μm opening sieve to obtain a sulfide solid electrolyte powder. The average particle size, as determined by the method described below, was 0.7 μm.

[0080] <Average particle size> The particle size D50 in the volume-based cumulative particle size distribution was determined as the average particle size. The particle size D50 was measured using a laser diffraction particle size distribution analyzer (Microtrac MT3300EX II manufactured by Microtrac-Bell).

[0081] <Production of Coated Particles> The sulfide solid electrolyte powder (average particle diameter: 0.7 μm) produced above was used as the sulfide-based particles. The following compound was used as the fluorine-containing organic compound that coats the sulfide-based particles. Fluorine-containing organic compound A: A copolymer of the following monomer (1)-1: the following monomer (2)-1 = 100:150 (mass ratio) (weight average molecular weight: 80,400) Monomer (1)-1: perfluorohexylethyl methacrylate Monomer (2)-1: isobornyl methacrylate Fluorine-containing organic compound B: A copolymer of the following monomer (1)-2: the following monomer (2)-2 = 100:194 (mass ratio) (weight average molecular weight: 14,500) Monomer (1)-2: 2,2,2-trifluoroethyl methacrylate Monomer (2)-2: tridecyl-modified methacrylate / silicone oil = 35 / 159 (X-22-2445, Shin-Etsu Chemical) Unless otherwise noted below, all operations were carried out in a glove box controlled to a dew point of -60°C or below, and all solvents used were dehydrated beforehand.

[0082] <SP Value (Solubility Parameter)> The SP value of the fluorine-containing organic compound was measured using the above-mentioned Fedors calculation method.

[0083] [Example 1-1] A coating liquid was prepared by mixing fluorine-containing organic compound A with a mixed solvent of butane:dibutyl ether = 5:3 (mass ratio). The coating liquid was added to sulfide-based particles (sulfide solid electrolyte powder, average particle size 0.7 μm) so that the fluorine-containing organic compound A was 1.3 mass %. After stirring, the mixture was vacuum dried at 70°C for 4 hours to remove the solvent, and coated particles were obtained.

[0084] Example 1-2 Coated particles were obtained in the same manner as in Example 1-1, except that fluorine-containing organic compound B was used instead of fluorine-containing organic compound A as the fluorine-containing organic compound.

[0085] <Fluorine Concentration on the Surface of Coated Particles> To measure the surface fluorine concentration, the coated particles produced in Examples 1-1 and 1-2 above were used, and the coated particles were prepared under conditions simulating those used in battery production by immersing the coated particles in butyl butyrate, a solvent used in battery production, recovering them by filtration, and vacuum drying them for 4 hours at 70° C. The surface fluorine concentration was calculated from the height of the F1s peak in a spectrum measured by XPS analysis under the following conditions. Equipment used: ULVAC PHI PHI5000 VersaProbeIII X-ray settings: 100 μm, 25 W, 15 kV Detection area: 100 μmφ Detection angle: 45° to the sample surface Wide spectrum measurement conditions (Pass Energy: 224.0 eV, eV Step: 0.4 eV / step, Time Per Step: 20 ms, Measurement energy range: 0-750 eV, Number of cycles: 8) Note that the XPS measurement was performed on the powder to avoid changes in composition due to deterioration or deformation of the sample. The results are shown in Table 1 below.

[0086] <Production of all-solid-state secondary battery> [Example 2-1] (1) Production of positive electrode mixture LiNbO ３ The positive electrode active material (LiNi) coated with ０．６ Co ０．２ Mn ０．２ O ２ ), the coated particles produced in Example 1-1, and a conductive additive (VGCF-H) were mixed, and a 10% binder solution (a commercially available SBS-based binder using butyl butyrate as a solvent) was added. The mixture was mixed for 2 minutes at 2000 rpm using a planetary centrifugal mixer (Awatori Rentaro AR-100), and then diluted with butyl butyrate to a solids concentration of about 80% to obtain a slurry. The ratio of positive electrode active material: coated particles (solid electrolyte): conductive additive: binder in the slurry was 90:7.5:1.5:1 (mass%). The obtained slurry was applied to a carbon-coated aluminum foil using an applicator with an automatic coater, and then vacuum dried at 70 degrees for 4 hours to obtain a positive electrode mixture.

[0087] (2) Production of an all-solid-state secondary battery An all-solid-state secondary battery was produced using the positive electrode mixture obtained above in an inert gas atmosphere. ６ P.S.５ 120 mg of the Li—In alloy was placed in a die for an evaluation cell and press-molded to form a solid electrolyte layer. Using the obtained solid electrolyte layer as a base, the positive electrode mixture described in (1) above was laminated on one side, and Li—In was laminated on the other side, followed by uniaxial pressing to obtain an all-solid-state secondary battery.

[0088] Example 2-2 An all-solid-state secondary battery was obtained in the same manner as in Example 2-1, except that a positive electrode produced using the covered particles of Example 1-2 was used instead of the covered particles of Example 1-1.

[0089] Example 2-3 An all-solid-state secondary battery was obtained in the same manner as in Example 2-1, except that a positive electrode was used that was manufactured using sulfide-based particles (sulfide solid electrolyte powder having an average particle size of 0.7 μm) that were not coated with a fluorine-containing organic compound, instead of the coated particles of Example 1-1.

[0090] Example 2-4 An all-solid-state secondary battery was obtained in the same manner as in Example 2-1, except that a positive electrode was used that was manufactured using sulfide-based particles (coarsely pulverized sulfide solid electrolyte having an average particle size of 14 μm) that were not coated with a fluorine-containing organic compound, instead of the coated particles of Example 1-1.

[0091] <Evaluation of Output Characteristics of All-Solid-State Secondary Battery> In order to examine the capacity due to the charge-discharge cycle of the all-solid-state secondary batteries of Examples 2-1 to 2-3, measurements were performed under the following conditions. Among these, a comparison of the discharge capacity retention rate at 1 C was performed to evaluate the output characteristics. First, as a break-in, charge and discharge measurements were performed under CC-CV charge conditions (current 0.05 C, cutoff voltage 3.7 V vs. In-Li) and CC discharge conditions (current 0.05 C, cutoff voltage 1.9 V vs. In-Li). Next, to evaluate the output characteristics, measurements were performed under CC-CV charge conditions (current 0.1 C, cutoff voltage 3.7 V vs. In-Li) and CC discharge conditions (current 1 C, cutoff voltage 1.9 V vs. In-Li). The measurement temperature was 25°C. The discharge capacity retention rate W1 / W0×100(%) was calculated from the discharge capacity W0 during the break-in and the discharge capacity W1 at 1 C.

[0092] <Evaluation of Deterioration Rate (Oxidation Resistance) of All-Solid-State Secondary Battery> The deterioration rates of the all-solid-state secondary batteries of Examples 2-1 to 2-3 were calculated under the following conditions. First, the DC resistance was measured when a voltage of 3.35 V was applied during charging (0.1 C), and this was designated as the initial resistance R0. Next, as a deterioration test, a voltage of 3.95 V and a temperature of 60°C were maintained for two days, and then the DC resistance was measured when a voltage of 3.35 V was applied during charging (0.1 C) in the same manner as in the initial resistance measurement, and this was designated as the resistance after deterioration R1. The measurement temperature was 25°C. The deterioration rate R1 / R0 × 100 (%) was calculated from the initial resistance R0 and the resistance after deterioration R1.

[0093] The evaluation results are shown in Table 1 below.

[0094]

[0095] From the above results, comparing Examples 2-1 and 2-2 with Example 2-3, the batteries of Examples 2-1 and 2-2, which used sulfide-based particles coated with a fluorine-containing organic compound as a solid electrolyte, had improved discharge capacity retention rates (output characteristics) compared to the battery of Example 2-3, which used uncoated sulfide particles. Regarding the deterioration rate, Examples 2-1 and 2-2 had lower deterioration rates than Example 2-3, resulting in improved battery characteristics. Furthermore, comparing Examples 2-1 and 2-2, it is believed that the battery of Example 2-2 had a greater reduction in deterioration rate because the SP value of the fluorine-containing organic compound was less than 7.

[0096] <Differences in Battery Characteristics Due to Particle Size of Solid Electrolyte> The initial discharge capacity was measured for the all-solid-state secondary batteries of Examples 2-3 and 2-4. The charge conditions were CC-CV (current: 0.05 C, cutoff voltage 3.7 V vs. In-Li), and the discharge conditions were CC (current: 0.05 C, cutoff voltage 1.9 V vs. In-Li). The results are shown in Table 2 below.

[0097]

[0098] The above results indicate that the battery of Example 2-3, which used sulfide-based particles with an average particle size of 10 μm or less as a solid electrolyte, had a significantly higher discharge capacity than the battery of Example 2-4, which used sulfide-based particles with an average particle size of more than 10 μm as a solid electrolyte. This is thought to be because a smaller average particle size allows powders such as positive electrode active material to be dispersed more uniformly, resulting in excellent battery characteristics. Furthermore, the battery of Example 2-3 is thought to have a particularly large discharge capacity because it uses a solid electrolyte with an average particle size of 1.0 μm or less.

[0099] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-031551) filed on March 1, 2024, the contents of which are incorporated herein by reference.

Claims

1. Coated particles in which the surfaces of sulfide-based particles are coated with a fluorine-containing organic compound, the fluorine-containing organic compound comprising a structural unit (1) based on a monomer (1) represented by the following formula (1) and a structural unit (2) based on a monomer (2) represented by the following formula (2), and the average particle size of the coated particles is 10 nm or more and 10 μm or less. (In formula (1), X represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or CFX １ X ２ group (wherein X １ and X ２ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; Y is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent hydrocarbon group having 1 to 10 carbon atoms and an oxygen atom, -CH ２ CH ２ N(Ra)SO ２ - group (wherein Ra is an alkyl group having 1 to 4 carbon atoms), -CH ２ CH (OY １ ) CH ２ - group (where Y １ is a hydrogen atom or an acetyl group, or —(CH ２ ) ｎ SO ２ - group (n is 1 to 10), and Rf is a linear or branched fluoroalkyl group having 1 to 10 carbon atoms. (In formula (2), R １ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, CFX ３ X ４ group (wherein X ３ and X ４ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; R ２ is a monovalent hydrocarbon group having one or more carbon atoms, or a monovalent hydrocarbon group having one or more carbon atoms and containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms in its structure. １ is H or CH ３ If R ２ is a monovalent hydrocarbon group having 3 or more carbon atoms and containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms in its structure, or a monovalent hydrocarbon group having 6 or more carbon atoms and a ring structure.

2. The coated particle according to claim 1, wherein the mass ratio of the structural unit (1) to the structural unit (2) is 100:70 to 100:

500.

3. The coated particles according to claim 1, wherein the surface fluorine concentration is 1 atomic % or more.

4. The coated particles according to claim 1, wherein the fluorine concentration on the surface of the coated particles is 0.1 atomic % or more after the coated particles are immersed in butyl butyrate, recovered by filtration, and dried.

5. The coated particles according to claim 1, having an average particle size of 100 nm or more and 1.0 μm or less.

6. The coated particles according to claim 1, wherein the weight average molecular weight of the fluorine-containing organic compound is 3,000 to 100,000.

7. The coated particles according to claim 1, wherein the SP value of the fluorine-containing organic compound is 6.0 or more and 9.0 or less.

8. The coated particles according to claim 1, wherein the SP value of the fluorine-containing organic compound is 6.0 or more and 7.0 or less.

9. The coated particle according to claim 1, wherein the sulfide-based particle has an argyrodite-type crystal structure.

10. An electrode mixture containing a sulfide solid electrolyte and an active material, wherein the sulfide solid electrolyte is the coated particles according to any one of claims 1 to 9.

11. A solid electrolyte layer containing a sulfide solid electrolyte, wherein the sulfide solid electrolyte is the coated particle according to any one of claims 1 to 9.

12. An all-solid-state secondary battery containing a sulfide solid electrolyte, wherein the sulfide solid electrolyte is the coated particles according to any one of claims 1 to 9.

13. A method for producing coated particles in which the surfaces of sulfide-based particles are coated with a fluorine-containing organic compound, the method comprising wet-pulverizing the sulfide-based particles using a medium containing a fluorine-containing organic compound, wherein the wet-pulverization not only pulverizes the sulfide-based particles but also coats the sulfide-based particles with the fluorine-containing organic compound.

14. The method for producing coated particles described in claim 13, wherein the fluorine-containing organic compound comprises a structural unit (1) based on a monomer (1) represented by the following formula (1) and a structural unit (2) based on a monomer (2) represented by the following formula (2): (In formula (1), X represents a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or CFX １ X ２ group (wherein X １ and X ２ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; Y is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent hydrocarbon group having 1 to 10 carbon atoms and an oxygen atom, -CH ２ CH ２ N(Ra)SO ２ - group (wherein Ra is an alkyl group having 1 to 4 carbon atoms), -CH ２ CH (OY １ ) CH ２ - group (where Y １ is a hydrogen atom or an acetyl group, or —(CH ２ ) ｎ SO ２ - group (n is 1 to 10), and Rf is a linear or branched fluoroalkyl group having 1 to 10 carbon atoms. (In formula (2), R １ is a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, CFX ３ X ４ group (wherein X ３ and X ４ are the same or different and are a hydrogen atom, a fluorine atom, or a chlorine atom; a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms; R ２ is an oxygen atom, a monovalent hydrocarbon group having one or more carbon atoms, or a monovalent hydrocarbon group having one or more carbon atoms and containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, sulfur atoms, and silicon atoms in its structure. １ is H or CH ３ If R ２ is a monovalent hydrocarbon group having 3 or more carbon atoms and containing at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms in its structure, or a monovalent hydrocarbon group having 6 or more carbon atoms and a ring structure.

15. The method for producing coated particles according to claim 14, wherein the mass ratio of the structural unit (1) to the structural unit (2) is 100:70 to 100:

500.

16. The method for producing coated particles according to claim 13, wherein the weight-average molecular weight of the fluorine-containing organic compound is 3,000 to 100,000.

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