JP5652322B2 - Manufacturing method of all-solid-state secondary battery - Google Patents

Description

  The present invention relates to a method for manufacturing an all-solid secondary battery.

  In recent years, secondary batteries such as lithium batteries have been used in various applications such as portable power terminals such as personal digital assistants and portable electronic devices, as well as small household power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. Has increased.

  As the use expands, further improvements in the safety of secondary batteries are required. In order to ensure safety, a method of preventing liquid leakage and a method of using an inorganic solid electrolyte instead of an organic solvent electrolyte having high flammability and extremely high ignition risk at the time of leakage are effective.

  Patent Document 1 describes an all-solid secondary battery using an organic polymer such as a styrene-butadiene-styrene block copolymer as a binder for the solid electrolyte layer.

  Patent Document 2 describes an all-solid-state secondary battery having a solid electrolyte layer formed by applying and drying a slurry composition containing a solid electrolyte and a binder.

JP 2009-80999 A JP-A-7-161346

However, in Patent Document 1, the peel strength of the obtained solid electrolyte layer may be reduced, and as a result, the internal resistance of the all-solid-state secondary battery may be increased, and output characteristics and cycle characteristics may be deteriorated.
Moreover, in patent document 2, in the process of drying a slurry composition, solid electrolyte may be unevenly distributed, As a result, the internal resistance of an all-solid-state secondary battery becomes high, and an output characteristic and cycling characteristics may deteriorate. there were.
Therefore, the present invention seeks to solve the problems associated with the prior art as described above. That is, an object of the present invention is to provide a method for producing an all-solid-state secondary battery having a solid electrolyte layer with good adhesion and excellent output characteristics and cycle characteristics.

The gist of the present invention aimed at solving such problems is as follows.
[1] In a method for producing an all-solid secondary battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer,
(1) forming a positive electrode active material layer including a positive electrode active material, a binder a and a solid electrolyte on the current collector a;
(2) forming a negative electrode active material layer including a negative electrode active material, a binder b and a solid electrolyte on the current collector b; and (3) on the positive electrode active material layer and / or the negative electrode active material layer. All-solid secondary including a step of press-molding composite particles containing solid electrolyte particles and a binder c comprising a polymer having an iodine value of 0 to 30 mg / 100 mg to form a solid electrolyte layer Battery manufacturing method.

[2] The binder a contains 10 to 28% by mass of a monomer unit having a nitrile group,
And the manufacturing method of the all-solid-state secondary battery as described in [1] which consists of a polymer whose iodine value is 0-30 mg / 100 mg.

[3] The method for producing an all solid state secondary battery according to [1] or [2], wherein the binder c is made of a polymer containing 10 to 28% by mass of a monomer unit having a nitrile group.

[4] The method for producing an all solid state secondary battery according to any one of [1] to [3], wherein the step (3) includes a step of charging the composite particles.

[5] The method for producing an all solid state secondary battery according to [4], wherein the composite particles further contain a charge control resin.

[6] The all-solid-state composite material according to any one of [1] to [5], wherein the composite particles are obtained by granulating a slurry composition containing a solid electrolyte, a binder c, and an organic solvent. A method for manufacturing a secondary battery.

[7] The method for producing an all solid state secondary battery according to any one of [1] to [6], wherein the solid electrolyte is a sulfide containing Li and P.

[8] The method for producing an all solid state secondary battery according to any one of [1] to [7], wherein the solid electrolyte is a sulfide glass composed of Li ₂ S and P ₂ S ₅ .

[9] The method for producing an all-solid-state secondary battery according to any one of [1] to [8], wherein a conductive adhesive layer is formed on at least one surface of the current collector a and / or current collector b.

  According to the present invention, it is possible to obtain a solid electrolyte layer having high peel strength by making a specific binder and solid electrolyte particles into composite particles and forming the solid electrolyte layer by pressure molding. Moreover, by forming the solid electrolyte layer by pressure forming the composite particles, it is possible to manufacture an all-solid secondary battery excellent in output characteristics and cycle characteristics by suppressing the uneven distribution of the solid electrolyte.

  The method for producing an all-solid-state secondary battery according to the present invention includes: (1) a step of forming a positive electrode active material layer including a positive electrode active material, a binder a and a solid electrolyte on a current collector a; A step of forming a negative electrode active material layer including a negative electrode active material, a binder b and a solid electrolyte on the electric body b; and (3) a solid on the positive electrode active material layer and / or the negative electrode active material layer. Forming a solid electrolyte layer by press-molding composite particles containing electrolyte particles and a binder c made of a polymer having an iodine value of 0 to 30 mg / 100 mg.

Hereinafter, the positive electrode active material layer, the negative electrode active material layer, the solid electrolyte layer, the current collector, and the method for producing the all solid secondary battery according to the present invention will be described in this order.
<Positive electrode active material layer>
The positive electrode active material layer includes a positive electrode active material, a binder a, and a solid electrolyte. Further, the positive electrode active material layer may contain other components added as necessary.

(Positive electrode active material)
The positive electrode active material is a compound that can occlude and release lithium ions. The positive electrode active material is roughly classified into those made of inorganic compounds and those made of organic compounds.

Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, composite oxides of lithium and transition metals, and transition metal sulfides. As the transition metal, Fe, Co, Ni, Mn and the like are used. Specific examples of the inorganic compound used for the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO ₄ and other lithium-containing composite metal oxides; TiS ₂ , TiS ₃ , non- Transition metal sulfides such as crystalline MoS ₂ ; transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ It is done. These compounds may be partially element-substituted.

  Examples of the positive electrode active material made of an organic compound include polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds, and N-fluoropyridinium salts. The positive electrode active material may be a mixture of the above inorganic compound and organic compound.

  The average particle diameter of the positive electrode active material is usually 0.1 to 50 μm, preferably 1 to 20 μm, from the viewpoint of improving battery characteristics such as load characteristics and cycle characteristics. When the average particle diameter is in the above range, an all-solid secondary battery having a large charge / discharge capacity can be obtained. Moreover, the handling of the slurry composition for positive electrode active material layers mentioned later and the handling at the time of manufacturing a positive electrode are easy. The average particle size can be determined by measuring the particle size distribution by laser diffraction.

(Binder A)
Examples of the binder a include polymer compounds such as a fluorine polymer, a diene polymer, a nitrile polymer, a diene polymer or a nitrile polymer is preferable, and a nitrile polymer is This is more preferable because the withstand voltage can be increased and the energy density of the all-solid-state secondary battery can be increased.

  Examples of the fluoropolymer include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP).

  The diene polymer is a polymer containing a monomer unit derived from a conjugated diene (conjugated diene monomer unit) and a monomer unit derived from an aromatic vinyl (aromatic vinyl monomer unit), or Their hydrides. The diene polymer preferably contains 30 to 70% by mass, more preferably 35 to 65% by mass of a conjugated diene monomer unit, and more preferably 30 to 70% by mass of an aromatic vinyl monomer unit. Preferably it contains 35-65 mass%. By making the content ratio of the conjugated diene monomer unit and the content ratio of the aromatic vinyl monomer unit contained in the diene polymer within the above ranges, the positive electrode active materials, the solid electrolytes, the positive electrode active material and the solid electrolyte A positive electrode having high adhesion between the particles and between the active material layer and the current collector can be obtained.

  Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene and the like. Among these, 1,3-butadiene is preferable. These can be used individually by 1 type or in combination of multiple types.

  Examples of aromatic vinyl monomers include styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, divinyl benzene, etc. Is mentioned. Of these, styrene, α-methylstyrene, and divinylbenzene are preferable. These can be used individually by 1 type or in combination of multiple types.

  The diene polymer may be a copolymer of a conjugated diene monomer, an aromatic vinyl monomer, and a monomer copolymerizable therewith. Examples of the copolymerizable monomer include α, β-unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; α, β-ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid. Olefins such as ethylene and propylene, halogen atom-containing monomers such as vinyl chloride and vinylidene chloride, vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, etc. Vinyl ethers; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; and heterocyclic-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine, and vinyl imidazole. It is. These can be used individually by 1 type or in combination of multiple types. The content ratio of the copolymerizable monomer unit in the diene polymer is preferably 40% by mass or less, more preferably 20 to 40% by mass. Specific examples of the diene polymer include a styrene-butadiene copolymer (SBR) and a styrene-butadiene-styrene block copolymer as a polymer containing a conjugated diene monomer unit and an aromatic vinyl monomer unit. (SBS) and the like, and examples of the hydride of a polymer containing a conjugated diene monomer unit and an aromatic vinyl monomer unit include a styrene-ethylene-butylene-styrene block copolymer (SEBS).

  The nitrile polymer is a polymer including a monomer unit having a nitrile group, and includes, for example, an acrylic polymer and a highly saturated nitrile polymer. The nitrile polymer preferably contains a monomer unit having a nitrile group in an amount of 10 to 28% by mass, more preferably 10 to 25% by mass, and particularly preferably 15 to 20% by mass with respect to all monomer units. To do. When the content ratio of the monomer unit having a nitrile group is in the above range, the solubility of the nitrile polymer in an organic solvent becomes good, and a slurry composition with good dispersibility can be produced. A high electrode can be obtained and the output characteristics of the battery can be improved.

  The acrylic polymer is a polymer containing a monomer unit derived from an α, β-ethylenically unsaturated nitrile monomer and an alkyl ester of an α, β-ethylenically unsaturated monocarboxylic acid, specifically Are copolymers of α, β-ethylenically unsaturated nitrile monomer and alkyl ester of α, β-ethylenically unsaturated monocarboxylic acid, and α, β-ethylenically unsaturated nitrile monomer and α , Β-ethylenically unsaturated monocarboxylic acid alkyl ester and other copolymerizable copolymer.

  The α, β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. For example, acrylonitrile; α-chloroacrylonitrile, α-bromoacrylonitrile Α-halogenoacrylonitrile such as; α-alkylacrylonitrile such as methacrylonitrile; and the like. Among these, acrylonitrile and methacrylonitrile are preferable. These can be used individually by 1 type or in combination of multiple types.

  Examples of alkyl esters of α, β-ethylenically unsaturated monocarboxylic acids include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and t-butyl acrylate, acrylic acid 2-Ethylhexyl, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, benzyl acrylate, and other acrylic acid alkyl esters; 2- (perfluorobutyl) ethyl acrylate, 2- (perfluoropentyl) acrylate 2- (perfluoroalkyl) ethyl acrylates such as ethyl; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and t-butyl methacrylate, methacrylate-2- Ethylhexyl Methacrylic acid alkyl esters such as lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate and benzyl methacrylate; 2- (methacrylic acid 2- (perfluorobutyl) ethyl methacrylate and 2- (perfluoropentyl) ethyl methacrylate 2- ( Perfluoroalkyl) ethyl; Among these, alkyl acrylate is preferable, and n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable.

  The acrylic polymer usually contains 40% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more of monomer units derived from an alkyl ester of an α, β-ethylenically unsaturated monocarboxylic acid. . In addition, the upper limit of the content ratio of the monomer unit derived from the alkyl ester of α, β-ethylenically unsaturated monocarboxylic acid in the acrylic polymer is usually 100% by mass or less, preferably 95% by mass or less.

  Other monomers copolymerizable with α, β-ethylenically unsaturated nitrile monomers and monomers derived from alkyl esters of α, β-ethylenically unsaturated monocarboxylic acids include acrylic acid. , [Alpha], [beta] -ethylenically unsaturated carboxylic acids such as methacrylic acid, itaconic acid and fumaric acid; having two or more carbon-carbon double bonds such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate and trimethylolpropane triacrylate Carboxylic acid esters: Styrene, such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, α-methylstyrene, divinylbenzene, etc. MER; Acrylamide, METAKU Amide monomers such as amide, N-methylolacrylamide, acrylamide-2-methylpropanesulfonic acid; olefins such as ethylene and propylene; diene monomers such as butadiene and isoprene; halogens such as vinyl chloride and vinylidene chloride Atom-containing monomers; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone And vinyl ketones such as hexyl vinyl ketone and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole. These can be used individually by 1 type or in combination of multiple types. Among these, α, β-ethylenically unsaturated carboxylic acids are preferable in that the peel strength of the electrode can be increased. The content of the copolymerizable monomer unit in the acrylic polymer is usually 50% by mass or less, preferably 30% by mass or less, and more preferably 1 to 10% by mass.

  The highly saturated nitrile polymer is a hydride of a copolymer of an α, β-ethylenically unsaturated nitrile monomer and a conjugated diene monomer. In the highly saturated nitrile polymer, the conjugated diene monomer is preferably 10 to 95% by mass, more preferably 34.3 to 90% by mass, and still more preferably 39 to 85% by mass with respect to all monomer units. contains. When the content ratio of the conjugated diene monomer unit is in the above range, the positive electrode active material layer can be made flexible, and further, the dispersibility of the solid electrolyte during the production of the slurry composition is good and excellent. A battery having output characteristics and high-temperature cycle characteristics can be obtained.

  Examples of the conjugated diene monomer used in the highly saturated nitrile polymer include those exemplified as the conjugated diene monomer used in the diene polymer, 2,3-dimethyl-1,3-butadiene, 1, 3-pentadiene or the like can be used. These can be used individually by 1 type or in combination of multiple types.

  In addition to the α, β-ethylenically unsaturated nitrile monomer unit and the conjugated diene monomer unit described above, the highly saturated nitrile polymer may be another unit copolymerizable with these monomer units. It may contain a monomer unit. The content ratio of such other monomer units is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less with respect to the total monomer units.

  Examples of such other copolymerizable monomers include aromatic vinyl compounds such as styrene, α-methylstyrene and vinyltoluene; fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethyl styrene, pentafluoro Fluorine-containing vinyl compounds such as vinyl benzoate, difluoroethylene, and tetrafluoroethylene; Non-conjugated diene compounds such as 1,4-pentadiene, 1,4-hexadiene, vinylnorbornene, and dicyclopentadiene; ethylene, propylene, 1-butene, Α-olefin compounds such as 4-methyl-1-pentene, 1-hexene, 1-octene; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, fumaric anhydride, etc. α, β-ethylene Unsaturated carboxylic acids and their anhydrides; α, β-ethylenically unsaturated monocarboxylic acids such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate Alkyl esters of acids; monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, Monoesters and diesters of α, β-ethylenically unsaturated polyvalent carboxylic acids such as diethyl itaconate, monobutyl itaconate, dibutyl itaconate; methoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, (meth) Acry Alkoxyalkyl esters of α, β-ethylenically unsaturated carboxylic acids such as butoxyethyl acid; α, β-ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate Hydroxyalkyl esters of acids; divinyl compounds such as divinylbenzene; di (meth) acrylic esters such as ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, and ethylene glycol di (meth) acrylate; trimethylolpropane tri (meth) ) Trimethacrylic acid esters such as acrylates; Self-crosslinkable compounds such as N-methylol (meth) acrylamide and N, N′-dimethylol (meth) acrylamide; Mentioned It is. Among these, α, β-ethylenically unsaturated carboxylic acids and alkyl esters of α, β-ethylenically unsaturated monocarboxylic acids are preferable, and acrylic acid and methyl acrylate are particularly preferable.

  The iodine value of the highly saturated nitrile polymer is preferably 0 to 30 mg / 100 mg, more preferably 5 to 20 mg / 100 mg, and particularly preferably 7 to 10 mg / 100 mg. When the iodine value of the highly saturated nitrile polymer is included in the above range, a battery having high positive electrode active material layer strength and excellent high temperature cycle characteristics can be obtained. The iodine value is determined according to JIS K 0070; 1992.

  The weight average molecular weight in terms of polystyrene by gel permeation chromatography of the highly saturated nitrile polymer is preferably 10,000 to 700,000, more preferably 50,000 to 500,000, particularly preferably 100,000. ~ 300,000. By setting the weight average molecular weight of the nitrile group-containing polymer in the above range, the positive electrode active material layer can be made flexible, and the viscosity of the slurry composition can be easily adjusted.

  The highly saturated nitrile polymer comprises a monomer unit having a nitrile group by polymerizing the above monomers by a polymerization method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, or an emulsion polymerization method. An unsaturated polymer (hereinafter sometimes referred to as a “nitrile group-containing unsaturated polymer”) is obtained, and hydrogenated to the nitrile group-containing unsaturated polymer in the presence of a hydrogenation catalyst, thereby obtaining a nitrile group. It is produced by selectively hydrogenating carbon-carbon double bonds in the unsaturated polymer containing. As the polymerization reaction, any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used. Examples of the polymerization initiator used for polymerization include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Organic peroxides, azo compounds such as α, α′-azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and the like.

  The method for hydrogenation is not particularly limited, and a normal method can be used. For example, an organic solvent solution of a nitrile group-containing unsaturated polymer may be reacted with hydrogen gas in the presence of a hydrogenation catalyst such as Raney nickel, a titanocene compound, or an aluminum-supported nickel catalyst. Further, when the nitrile group-containing unsaturated polymer is prepared by emulsion polymerization, a hydrogenation catalyst such as palladium acetate can be added to the polymerization reaction solution to bring it into contact with hydrogen gas in an aqueous emulsion state. By the hydrogenation reaction, the iodine value of the highly saturated nitrile polymer can be set within the above-described range. The highly saturated nitrile polymer used in the present invention is preferably a hydrogenated acrylonitrile / butadiene copolymer (hereinafter sometimes referred to as “hydrogenated NBR”).

  The content of the binder a is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 7 parts by mass with respect to 100 parts by mass of the positive electrode active material. When the content of the binder a is in the above range, it is possible to prevent the positive electrode active material from dropping from the electrode without inhibiting the battery reaction.

  The iodine value of the binder a is preferably 0 to 30 mg / 100 mg, more preferably 0 to 20 mg / 100 mg, and particularly preferably 0 to 10 mg / 100 mg. When the iodine value of the binder a is within the above range, the binding force is high, the film strength of the positive electrode active material layer is increased, and the high-temperature cycle characteristics of the battery are improved.

  The glass transition temperature of the binder a is preferably -80 to 25 ° C, more preferably -60 to 10 ° C, and particularly preferably -50 to -10 ° C. When the glass transition temperature is in the above range, the resulting positive electrode active material layer can have excellent strength and flexibility, and the all-solid-state secondary battery can have high output characteristics.

(Solid electrolyte)
The solid electrolyte used in the present invention is a lithium ion conductive inorganic solid electrolyte, and is not particularly limited as long as it has lithium ion conductivity. However, a crystalline inorganic lithium ion conductor or amorphous inorganic lithium is not particularly limited. It is preferable that an ionic conductor is included.

Crystalline inorganic lithium ion conductors include Li ₃ N, LISICON (Li ₁₄ Zn (GeO ₄ ) ₄ ), perovskite type Li _0.5 La _0.5 TiO ₃ , garnet type Li ₇ La ₃ Zr ₂ O ₁₀ , _{LIPON (Li 3 + y PO 4} -x N x), Thio-LISICON (Li 3.75 Ge 0.25 P 0.75 S 4) , and the like, inorganic lithium ion conductor of the amorphous, the glass Li- Si-S-O, Li-PS, etc. are mentioned. Among these, from the viewpoint of conductivity, an amorphous inorganic lithium ion conductor is preferable, and a sulfide containing Li and P is more preferable. Since sulfide containing Li and P has high lithium ion conductivity, the internal resistance of the battery can be lowered and output characteristics can be improved by using it as a solid electrolyte.

Further, the sulfide containing Li and P is more preferably a sulfide glass composed of Li ₂ S and P ₂ S ₅ from the viewpoint of lowering the internal resistance of the battery and improving the output characteristics, and Li ₂ S: P Particularly preferred is a sulfide glass produced from a mixed raw material of Li ₂ S and P ₂ S ₅ having a molar ratio of ₂ S ₅ of 65:35 to 85:15. Moreover, the sulfide containing Li and P was synthesized by a mechanochemical method by mixing a mixed material of Li ₂ S and P ₂ S ₅ having a molar ratio of Li ₂ S: P ₂ S ₅ of 65:35 to 85:15. It is preferable that it is a sulfide glass ceramic obtained.

When the solid electrolyte is produced with a mixed raw material of Li ₂ S and P ₂ S _{5 of} Li ₂ S: P ₂ S ₅ = 65: 35 to 85:15 (molar ratio), the lithium ion conductivity is high. Can be maintained. From the above viewpoint, it is more preferable that Li ₂ S: P ₂ S ₅ = 68: 32 to 80:20 (molar ratio).
Specifically, the lithium ion conductivity is preferably 1 × 10 ⁻⁴ S / cm or more, and more preferably 1 × 10 ⁻³ S / cm or more.

  The solid electrolyte used in the present invention is not limited to sulfide glass composed only of Li and P, and sulfide glass ceramic composed only of Li and P, but may contain other than Li and P as will be described later. .

  The average particle size of the solid electrolyte is preferably in the range of 0.1 to 50 μm. By setting the average particle size of the solid electrolyte within the above range, the solid electrolyte can be easily handled. In addition, since the dispersibility of the solid electrolyte is improved in the slurry composition used when the positive electrode active material layer is manufactured, the positive electrode active material layer can be easily formed. From the above viewpoint, the average particle diameter of the solid electrolyte is more preferably in the range of 0.1 to 20 μm. The average particle size can be determined by measuring the particle size distribution by laser diffraction.

The solid electrolyte used in the present invention is selected from the group consisting of Al ₂ S ₃ , B ₂ S ₃ and SiS ₂ as a starting material in addition to the Li ₂ S and P ₂ S _{5 to} the extent that ion conductivity is not lowered. It is preferable to include at least one kind of sulfide. When such a sulfide is added, the glass component in the solid electrolyte can be stabilized.
Similarly, at least one orthooxo acid selected from the group consisting of Li ₃ PO ₄ , Li ₄ SiO ₄ , Li ₄ GeO ₄ , Li ₃ BO ₃ and Li ₃ AlO ₃ in addition to Li ₂ S and P ₂ S _5. It is preferable to include lithium. When such a lithium orthooxo acid is included, the glass component in the solid electrolyte can be stabilized.

  The weight ratio of the positive electrode active material to the solid electrolyte is positive electrode active material: solid electrolyte = 90: 10 to 30:70, preferably 80:20 to 40:60. When the weight ratio of the positive electrode active material is less than the above range, the amount of the positive electrode active material in the battery is reduced, leading to a decrease in capacity as a battery. In addition, when the weight ratio of the solid electrolyte is less than the above range, sufficient conductivity cannot be obtained, and the positive electrode active material cannot be used effectively, leading to a decrease in capacity as a battery.

(Other ingredients)
In addition to the above components, the positive electrode active material layer includes components having various functions such as a lithium salt, a dispersant, a leveling agent, an antifoaming agent, a conductive agent, and a reinforcing material as other components added as necessary. May be included. These components are not particularly limited as long as they do not affect the battery reaction.

Lithium salt is composed of Li ⁺ cation and anions such as Cl ⁻ , Br ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , SCN ^{− and the} like, for example, lithium perchlorate Examples include lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoroacetate, lithium trifluoromethanesulfonate, and the like. The content of the lithium salt is preferably 0.5 to 30 parts by mass, more preferably 3 to 25 parts by mass with respect to 100 parts by mass of the binder a. By setting the content of the lithium salt in the above range, the ionic conductivity can be improved. The method for containing the lithium salt in the positive electrode active material layer is not particularly limited, and examples thereof include a method in which the binder a and the lithium salt are dissolved or dispersed in a solvent such as xylene to obtain a uniform solution.

  Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound. A dispersing agent is selected according to the solid electrolyte to be used. The content of the dispersing agent is preferably in a range that does not affect the battery characteristics, and specifically, it is 10 parts by mass or less with respect to 100 parts by mass of the solid electrolyte.

  Examples of the leveling agent include surfactants such as alkyl surfactants, silicone surfactants, fluorine surfactants, and metal surfactants. By mixing the above-mentioned surfactant, it is possible to prevent the repelling that occurs when the slurry composition used in manufacturing the positive electrode active material layer is applied to the surface of the current collector, which will be described later, and to improve the smoothness of the positive electrode Can be made. The content of the leveling agent is preferably in a range that does not affect the battery characteristics. Specifically, it is 10 parts by mass or less with respect to 100 parts by mass of the solid electrolyte.

  Examples of the antifoaming agent include mineral oil antifoaming agents, silicone antifoaming agents, and polymer antifoaming agents. The antifoaming agent is selected according to the solid electrolyte used. The content of the antifoaming agent is preferably within a range that does not affect the battery characteristics, and specifically, it is 10 parts by mass or less with respect to 100 parts by mass of the solid electrolyte.

  The conductive agent is not particularly limited as long as it can impart conductivity, and usually includes carbon powders such as acetylene black, carbon black and graphite, and fibers and foils of various metals. The addition amount of the conductive agent is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 5 parts by mass, and particularly preferably 1 to 3 parts by mass with respect to 100 parts by mass of the positive electrode active material. By setting the content of the conductive agent in the above range, it is possible to impart sufficient electron conductivity to the positive electrode active material layer while keeping the battery capacity high.

  As the reinforcing material, various inorganic and organic spherical, plate-like, rod-like or fibrous fillers can be used. The amount of the reinforcing material added is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 5 parts by mass, and particularly preferably 1 to 3 parts by mass with respect to 100 parts by mass of the positive electrode active material. By setting the content of the reinforcing material in the above range, it is possible to impart sufficient strength to the positive electrode active material layer while keeping the battery capacity high.

<Negative electrode active material layer>
The negative electrode active material layer includes a negative electrode active material, a binder b, and a solid electrolyte. Moreover, the negative electrode active material layer may contain other components (lithium salt, dispersant, leveling agent, antifoaming agent, conductive agent and reinforcing material) added as necessary. As the solid electrolyte contained in the negative electrode active material layer and other components added as necessary, the same materials as those exemplified in the positive electrode active material layer can be used.

(Negative electrode active material)
Examples of the negative electrode active material include carbon allotropes such as graphite and coke. The negative electrode active material composed of the allotrope of carbon can also be used in the form of a mixture with a metal, a metal salt, an oxide, or the like or a cover. Moreover, as a negative electrode active material, lithium alloys, such as oxides and sulfates, such as silicon, tin, zinc, manganese, iron, nickel, lithium metal, Li-Al, Li-Bi-Cd, Li-Sn-Cd, Lithium transition metal nitride, silicone, etc. can be used.

  The average particle diameter of the negative electrode active material is usually 1 to 50 μm, preferably 15 to 30 μm, from the viewpoint of improving battery characteristics such as load characteristics and cycle characteristics. When the average particle diameter is in the above range, an all-solid secondary battery having a large charge / discharge capacity can be obtained. Moreover, the handling of the slurry composition used when manufacturing a negative electrode active material layer and the manufacturing at the time of manufacturing a negative electrode are easy. The average particle size can be determined by measuring the particle size distribution by laser diffraction.

  The weight ratio of the negative electrode active material to the solid electrolyte is negative electrode active material: solid electrolyte = 90: 10 to 30:70, preferably 80:20 to 40:60. When the weight ratio of the negative electrode active material is less than the above range, the amount of the negative electrode active material in the battery is reduced, leading to a decrease in capacity as a battery. In addition, when the weight ratio of the solid electrolyte is less than the above range, sufficient conductivity cannot be obtained, and the negative electrode active material cannot be used effectively, leading to a decrease in capacity as a battery.

(Binder b)
Examples of the binder b include polymer compounds such as a fluorine polymer, a diene polymer, a nitrile polymer, a diene polymer or a nitrile polymer is preferable, and a nitrile polymer is This is more preferable because the withstand voltage can be increased and the energy density of the all-solid-state secondary battery can be increased. In addition, by using a nitrile polymer as the binder b, by including a monomer unit having a nitrile group in the polymer, the lithium ion conductivity is improved, so that the internal resistance in the battery is reduced. The output characteristics of the battery can be improved by reducing the size. Moreover, a negative electrode with high peel strength can be obtained. As the fluorine-based polymer, diene-based polymer and nitrile-based polymer, those similar to those exemplified for the binder a can be used. In addition, the binder b used in the present invention may be a mixture of the above-described fluorine polymer, diene polymer, and nitrile polymer.

  The content of the binder b is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 7 parts by mass with respect to 100 parts by mass of the negative electrode active material. When the content of the binder b is in the above range, it is possible to prevent the negative electrode active material from dropping from the electrode without inhibiting the battery reaction.

  The iodine value of the binder b is preferably 0 to 30 mg / 100 mg, more preferably 0 to 20 mg / 100 mg, and particularly preferably 0 to 10 mg / 100 mg. When the iodine value of the binder b is within the above range, the binding force is high, the film strength of the negative electrode active material layer is increased, and the high-temperature cycle characteristics of the battery are improved.

  The glass transition temperature of the binder b is preferably −50 to 25 ° C., more preferably −40 to 10 ° C., and particularly preferably −35 to 0 ° C. When the glass transition temperature is in the above range, the obtained negative electrode active material layer can have excellent strength and flexibility, and the obtained all-solid-state secondary battery can have high output characteristics.

<Solid electrolyte layer>
The solid electrolyte layer includes composite particles containing solid electrolyte particles and a binder c having an iodine value of 0 to 30 mg / 100 mg (hereinafter, sometimes referred to as “composite particles for a solid electrolyte layer”). It is formed by pressure forming. The composite particles preferably further contain a charge control resin. The composite particles may contain other components (lithium salt, dispersant, leveling agent, and antifoaming agent) that are added as necessary. As the solid electrolyte contained in the composite particles and other components added as necessary, the same materials as those exemplified in the positive electrode active material layer can be used.

(Binder c)
The iodine value of the binder c is 0 to 30 mg / 100 mg, preferably 0 to 20 mg / 100 mg, more preferably 0 to 10 mg / 100 mg. When the iodine value of the binder c exceeds 30 mg / 100 mg, the film strength of the solid electrolyte layer is lowered, and the high-temperature cycle characteristics of the battery are deteriorated.

  Examples of such a binder c include polymer compounds such as a fluorine polymer, a diene polymer, and a nitrile polymer, and a diene polymer or a nitrile polymer is preferable, and a nitrile polymer is preferable. The combination is more preferable in that the withstand voltage can be increased and the energy density of the all-solid-state secondary battery can be increased. Also, by using a nitrile polymer as the binder c, the lithium ion conductivity is improved by including a monomer unit having a nitrile group in the polymer, so that the internal resistance in the battery is reduced. The output characteristics of the battery can be improved by reducing the size. Moreover, a solid electrolyte layer having high peel strength can be obtained. As the fluorine-based polymer, diene-based polymer and nitrile-based polymer, those similar to those exemplified for the binder a can be used. In addition, the binder c used in the present invention may be a mixture of the above-described fluoropolymer, diene polymer, and nitrile polymer.

  The content of the binder c is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and particularly preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the solid electrolyte. is there. By setting the content of the binder c in the above range, it is possible to inhibit the movement of lithium and increase the resistance of the solid electrolyte layer while maintaining the binding property between the solid electrolytes.

  The glass transition temperature of the binder c is preferably −50 to 25 ° C., more preferably −40 to 10 ° C., and particularly preferably −35 to 0 ° C. When the glass transition temperature is in the above range, the obtained solid electrolyte layer can have excellent strength and flexibility, and the obtained all-solid-state secondary battery can have high output characteristics.

(Charge control resin)
The charge control resin used in the present invention refers to a resin having a function of imparting chargeability to the composite particles used in the present invention. Examples of the charge control resin used in the present invention include a negative charge control resin and a positive charge control resin. It is preferable to use different charge control resins depending on whether the composite particles forming the solid electrolyte layer are negatively charged or positively charged. Hereinafter, the negative charge control resin and the positive charge control resin will be described.

  The negative charge control resin has a substituent selected from a carboxyl group or a salt thereof, a phenol group or a salt thereof, a thiophenol group or a salt thereof, and a sulfonic acid group or a salt thereof in the side chain of the polymer. Examples thereof include resins. Examples of the salt of the substituent contained in the side chain of the polymer include salts with metals such as zinc, magnesium, aluminum, sodium, calcium, chromium, iron, manganese, cobalt; ammonium ion, pyridinium ion, imidazolium ion And salts with organic bases such as

  Among these, a resin having a sulfonic acid group or a salt thereof in the side chain of the polymer is preferable in that the charge amount can be improved. Specific examples include a resin obtained by copolymerizing a monovinyl monomer containing a sulfonic acid group or a salt thereof and another monovinyl monomer copolymerizable with the monovinyl monomer. Examples of other monovinyl monomers that can be copolymerized include ethylenically unsaturated carboxylic acid ester monomers, aromatic vinyl monomers, ethylenically unsaturated nitrile monomers, and vinyl esters.

  Examples of the monovinyl monomer containing a sulfonic acid group or a salt thereof include styrene sulfonic acid, sodium styrene sulfonate, potassium styrene sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, sodium vinyl sulfonate, and methacryl sulfonic acid. Ammonium etc. are mentioned.

  Examples of the ethylenically unsaturated carboxylic acid ester monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid-2- And ethyl hexyl. Examples of the aromatic vinyl monomer include styrene, methyl styrene, vinyl toluene, chlorostyrene, and hydroxymethyl styrene. Examples of the ethylenically unsaturated nitrile monomer include (meth) acrylonitrile, fumaronitrile, α-chloroacrylonitrile, α-cyanoethylacrylonitrile and the like. Examples of the vinyl esters include vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl pivalate, vinyl benzoate, vinyl p-t-butylbenzoate, and vinyl salicylate.

  In the case of using a resin having a sulfonic acid group or a salt thereof in the side chain of the polymer as the negative charge control resin, the content ratio of the monomer unit of the monovinyl monomer containing a sulfonic acid group or a salt thereof is preferably Is 0.5 to 15% by mass, more preferably 1 to 10% by mass. When the content ratio of the monomer unit of the monovinyl monomer containing a sulfonic acid group or a salt thereof in the negative charge control resin is in the above range, the charge amount of the negative charge control resin can be sufficiently improved. .

The positive charge control resin has an amino group such as NH ₂ , —NHCH ₃ , —N (CH ₃ ) ₂ , —NHC ₂ H ₅ , —N (C ₂ H ₅ ) ₂ , —NHC ₂ H ₄ OH. Resins, and resins having functional groups in which they are ammonium chlorided. Such a resin is obtained by copolymerizing a monovinyl monomer containing an amino group and another monovinyl monomer copolymerizable therewith. Further, the copolymer obtained as described above can be obtained by ammonium chloride. Furthermore, although obtained by copolymerizing a monovinyl monomer containing an ammonium base and a monovinyl monomer copolymerizable therewith, it is not limited to these methods. As a monovinyl monomer copolymerizable with a monovinyl monomer containing an amino group or another monovinyl monomer copolymerizable with a monovinyl monomer containing an ammonium base, a negatively chargeable control resin is obtained. For that purpose.

  Examples of the monovinyl monomer containing an amino group include N, N-dimethylaminomethyl (meth) acrylate, N, N-diethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N , N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminobutyl (meth) acrylate, pN, N-dimethylaminophenyl (meth) acrylate, p- N, N-diethylaminophenyl (meth) acrylate, pN, N-dipropylaminophenyl (meth) acrylate, pN, N-dibutylaminophenyl (meth) acrylate, pN-laurylaminophenyl (meth) Acrylate, pN-stearylaminophenyl ( ) Acrylate, pN, N-dimethylaminobenzyl (meth) acrylate, pN, N-diethylaminobenzyl (meth) acrylate, pN, N-dipropylaminobenzyl (meth) acrylate, pN, Examples include N-dibutylaminobenzyl (meth) acrylate, pN-laurylaminobenzyl (meth) acrylate, pN-stearylaminobenzyl (meth) acrylate, acryloyloxymethylmorpholine, acryloyloxyethylmorpholine, and the like. .

  Furthermore, (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylamino Ethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminopropyl (meth) acrylamide, pN, N-dimethylaminophenyl (meth) acrylamide, pN, N-diethylamino Phenyl (meth) acrylamide, pN, N-dipropylaminophenyl (meth) acrylamide, pN, N-dibutylaminophenyl (meth) acrylamide, pN-laurylaminophenyl (meth) acrylamide, pN -Stearylaminopheny (Meth) acrylamide, pN, N-dimethylaminobenzyl (meth) acrylamide, pN, N-diethylaminobenzyl (meth) acrylamide, pN, N-dipropylaminobenzyl (meth) acrylamide, pN , N-dibutylaminobenzyl (meth) acrylamide, pN-laurylaminobenzyl (meth) acrylamide, pN-stearylaminobenzyl (meth) acrylamide, 3- (dimethylamino) propyl (meth) acrylate, 2- Examples include aminostyrene, 4-aminostyrene, allylamine and the like.

  Examples of the ammonium-containing agent used for ammonium-salting the copolymer include those commonly used. Examples thereof include alkyl halides such as methyl iodide, ethyl iodide, methyl bromide, and ethyl bromide; Examples include paratoluenesulfonic acid alkyl esters such as methyl sulfonate, ethyl paratoluenesulfonate, and propyl paratoluenesulfonate.

  The glass transition temperature of the charge control resin used in the present invention is preferably −50 to 150 ° C., more preferably 20 to 120 ° C., and most preferably 40 to 100 ° C. When the glass transition temperature of the charge control resin is in the above range, the binding property is excellent with a small amount of use, the strength of the solid electrolyte layer is strong, and the flexibility is high. The density of the solid electrolyte layer can be easily increased.

  The surface charge amount C (μ · coulomb / g) of the charge control resin used in the present invention is preferably 10 ≦ | C | ≦ 600, more preferably 50 ≦ | C | ≦ 600, and particularly preferably 300 ≦ | C |. ≦ 600. The surface charge amount in the present invention is a charge amount with respect to an iron powder carrier measured by a blow-off charge amount measuring device (manufactured by Kyocera Chemical, equipment name “TB-200” or “TB-203”). When the surface charge amount C of the charge control resin is within the above range, the charge amount of the composite particles can be further sufficiently improved.

  The content of the charge control resin used in the present invention is not particularly limited, but is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, particularly preferably 100 parts by mass of the solid electrolyte. 0.3 to 5 parts by mass. When the content of the charge control resin is in the above range, the charge amount of the composite particles can be improved, and the application efficiency of the composite particles can be further improved, so that the strength of the solid electrolyte layer is improved.

(Manufacture of composite particles for solid electrolyte layer)
The composite particles for a solid electrolyte layer can be obtained by granulating a slurry composition for a solid electrolyte layer containing the above components (solid electrolyte, binder c, preferably charge control resin, and other components). Further, the composite particles for the solid electrolyte layer are preferably externally added particles obtained by externally adding a charge control resin to the surface. When the composite particles are externally added particles, it is preferable in that the difference in chargeability between different materials (each component) can be eliminated. The slurry composition for the solid electrolyte layer is produced by kneading the solid electrolyte, the binder c, an organic solvent, preferably a charge control resin, and other components added as necessary. The solid electrolyte contained in the slurry composition for the solid electrolyte layer and other components (lithium salt, dispersant, leveling agent and antifoaming agent) added as necessary are exemplified in the positive electrode active material layer. The thing similar to a thing can be used.

  The production method of the composite particles for the solid electrolyte layer is not particularly limited, and is spray drying granulation method, rolling layer granulation method, compression granulation method, stirring granulation method, extrusion granulation method, crushing granulation method In addition, it can be produced by a known granulation method such as a fluidized bed granulation method, a fluidized bed multifunctional granulation method, a pulse combustion drying method, or a melt granulation method. Among them, the spray-drying granulation method is preferable because composite particles in which the binder is unevenly distributed near the surface can be easily obtained.

  The spray drying granulation method includes a step of dispersing or dissolving a solid electrolyte, a binder c, and other components added as necessary in an organic solvent to form a slurry composition, and the slurry composition Spray drying the product to form composite particles. Specifically, in the composite particle forming step, the slurry composition is sprayed from an atomizer using a spray dryer, and the sprayed slurry composition is dried inside a drying tower, thereby forming a slurry composition. Spherical composite particles comprising solid electrolyte particles, binder c and other components are formed. When the composite particles obtained by the spray drying granulation method are used, the solid electrolyte layer used in the present invention can be obtained with high productivity. Moreover, the internal resistance of the solid electrolyte layer can be further reduced.

  In the case of producing composite particles by spray drying granulation, the organic solvent used to obtain the slurry composition includes cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic carbonization such as toluene and xylene. Hydrogen is mentioned. These solvents can be used singly or in combination of two or more, and can be appropriately selected from the viewpoint of drying speed and environment. In particular, in the present invention, aromatic carbonization is performed from the viewpoint of reactivity with the solid electrolyte. It is preferable to use a nonpolar solvent selected from hydrogens.

  The amount of the organic solvent is such that the solid content concentration of the slurry composition is usually in the range of 1 to 50% by mass, preferably 5 to 50% by mass, more preferably 15 to 35% by mass. When the solid content concentration is within this range, the solid electrolyte and the binder c are preferably dispersed uniformly.

  The method or procedure for dispersing or dissolving the solid electrolyte, binder c, and other components in an organic solvent is not particularly limited. For example, the solid electrolyte, binder c, and other components are added to the organic solvent and mixed. A method of dissolving other components such as a dispersant in an organic solvent, and then adding and mixing the binder c dispersed or dissolved in the organic solvent, and finally adding and mixing a solid electrolyte; Examples thereof include a method in which a solid electrolyte is added to and mixed with the binder c dispersed or dissolved in a solvent, and another component such as a dispersant dispersed or dissolved in an organic solvent is added thereto and mixed. Examples of the mixing means include mixing equipment such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, and a planetary mixer. Mixing is usually performed in the range of room temperature to 80 ° C. for 10 minutes to several hours.

  The viscosity of the slurry composition is usually in the range of 5 to 3000 mPa · s, preferably 10 to 1000 mPa · s, more preferably 15 to 500 mPa · s at room temperature. When the viscosity of the slurry composition is within this range, the productivity of the composite particles can be increased. Further, the lower the viscosity of the slurry composition, the smaller the spray droplets, and the smaller the weight average particle diameter of the resulting composite particles.

  Next, the slurry composition obtained above is spray-dried and granulated to obtain composite particles. Spray drying is performed by spraying and drying the slurry composition in hot air. An atomizer is mentioned as an apparatus used for spraying the slurry composition. There are two types of atomizers: a rotating disk method and a pressure method. The rotating disk system is a system in which a slurry composition is introduced almost at the center of a disk rotating at high speed, and the slurry composition is released from the disk by the centrifugal force of the disk, and the slurry composition is atomized at that time. . The rotational speed of the disk depends on the size of the disk, but is usually 5,000 to 50,000 rpm, preferably 20,000 to 45,000 rpm. The higher the rotational speed of the disk, the smaller the spray droplets and the smaller the weight average particle diameter of the resulting composite particles. Examples of the rotating disk type atomizer include a pin type and a vane type, and a pin type atomizer is preferable. A pin-type atomizer is a type of centrifugal spraying device that uses a spraying plate, and the spraying plate has a plurality of spraying rollers removably mounted on a concentric circle along its periphery between upper and lower mounting disks. It consists of The slurry composition is introduced from the center of the spray disc, adheres to the spraying roller by centrifugal force, moves outward on the roller surface, and finally sprays away from the roller surface. On the other hand, the pressurization method is a method in which the slurry composition is pressurized and sprayed from a nozzle to be dried.

  The temperature of the sprayed slurry composition is usually room temperature, but it may be heated to room temperature or higher. Moreover, the hot air temperature at the time of spray-drying is 80-250 degreeC normally, Preferably it is 100-200 degreeC. In spray drying, the method of blowing hot air is not particularly limited, for example, a method in which the hot air and the spray direction flow in the horizontal direction, a method in which the hot air is sprayed at the top of the drying tower and descends with the hot air, and the sprayed droplet and the hot air are in countercurrent contact And a system in which sprayed droplets first flow in parallel with hot air and then drop by gravity to make countercurrent contact.

  The weight average particle diameter of the composite particles suitably used in the present invention is usually in the range of 0.1 to 1,000 μm, preferably 1 to 80 μm, more preferably 10 to 40 μm. When the weight average particle diameter of the composite particles is within this range, the composite particles are less prone to agglomerate, and electrostatic force against gravity is increased, which is preferable. Moreover, it is excellent in the film thickness precision of a solid electrolyte layer, and can improve battery productivity. The weight average particle diameter can be measured using a laser diffraction particle size distribution analyzer.

  The composite particles are preferably spherical. Evaluation of whether the composite particles are spherical or not is a value calculated by (Ll−Ls) / {(Ls + Ll) / 2} where Ls is the short axis diameter of the composite particles and Ll is the long axis diameter. (Hereinafter referred to as “sphericity”). Here, the minor axis diameter Ls and the major axis diameter Ll are average values for 100 arbitrary composite particles measured from a photographic image obtained by observing the composite particles using a reflection electron microscope. The smaller this value, the closer the spherical composite particle is to a true sphere.

  For example, the particle observed as a square in the photographic image has a sphericity of 34.4%, so that the composite particle having a sphericity exceeding 34.4% is not at least spherical. The sphericity of the composite particles is preferably 20% or less, and more preferably 15% or less. When the sphericity of the composite particles is in the above range, the internal resistance of the all-solid-state secondary battery including the solid electrolyte layer made of the composite particles can be reduced, and the output characteristics can be improved.

  The composite particles obtained by the above production method can be subjected to post-treatment after the production of the particles, if necessary. As a specific example, the surface of the composite particle is modified to improve the fluidity of the composite particle by mixing the composite particle and other components such as the solid electrolyte, the binder c, and the dispersing agent. It can be reduced, the continuous pressure moldability can be improved, or the electrical conductivity of the composite particles can be improved. Also, by mixing the composite particles and the charge control resin, composite particles (externally added particles) whose surfaces are coated with the charge control resin can be obtained, and the average charge amount of the composite particles can be adjusted. .

<Current collector>
The current collector is not particularly limited as long as it is an electrically conductive and electrochemically durable material. From the viewpoint of having heat resistance, for example, iron, copper, aluminum, nickel, stainless steel, etc. Metal materials such as titanium, tantalum, gold, and platinum are preferable. Among them, the positive electrode current collector (sometimes referred to as “current collector a”) is particularly preferably aluminum, and the negative electrode current collector (sometimes referred to as “current collector b”). Is particularly preferably copper. The shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 to 0.5 mm is preferable. The current collector is used after roughening in advance in order to increase the adhesive strength with the above-described positive electrode active material layer or negative electrode active material layer (hereinafter sometimes referred to as “electrode active material layer”). Is preferred. Examples of the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing method, an abrasive cloth paper with a fixed abrasive particle, a grindstone, an emery buff, a wire brush provided with a steel wire or the like is used.

(Conductive adhesive layer)
In order to increase the adhesive strength and conductivity between the current collector and the electrode active material layer, a conductive adhesive layer is preferably formed on at least one surface of the current collector. That is, the electrode active material layer is formed on the current collector surface via the conductive adhesive layer.

  The conductive adhesive layer contains a conductive substance, preferably carbon particles, and optionally contains a resin component. By including a resin component in the conductive adhesive layer, the adhesion between the current collector and the electrode active material layer can be increased, the internal resistance of the battery can be reduced, and the output density can be increased.

  The resin component used as necessary for the conductive adhesive layer is the same as the binder a described above. Examples of the resin component include polymer compounds such as fluorine-based polymers, diene-based polymers, acrylic polymers, polyimides, polyamides, polyurethanes, and fluorine-based polymers, diene-based polymers, or acrylic polymers. Preferably, a diene polymer or an acrylic polymer is more preferable in that the withstand voltage can be increased and the energy density of the battery can be increased.

  The content of the resin component in the conductive adhesive layer is preferably 0.5 to 20 parts by weight, more preferably 1 to 15 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the conductive substance. Part.

  The conductive adhesive layer contains a conductive substance and a resin component used as necessary, and may contain a dispersant for uniformly dispersing them. Specific examples of the dispersant include cellulosic polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose and hydroxypropylcellulose, and ammonium salts or alkali metal salts thereof; poly (meth) acrylates such as sodium poly (meth) acrylate; Examples include polyvinyl alcohol, modified polyvinyl alcohol, polyethylene oxide; polyvinyl pyrrolidone, polycarboxylic acid, oxidized starch, phosphate starch, casein, various modified starches, chitin, and chitosan derivatives. These dispersants can be used alone or in combination of two or more. Among these, a cellulose polymer is preferable, and carboxymethyl cellulose or an ammonium salt or an alkali metal salt thereof is particularly preferable.

  The amount of these dispersants can be used within a range that does not impair the effects of the present invention, and is not particularly limited, but is usually 0.1 to 15 parts by mass with respect to 100 parts by mass of the conductive substance, Preferably it is 0.5-10 mass parts, More preferably, it is the range of 0.8-5 mass parts.

  Carbon particles that are preferably used as the conductive material of the conductive adhesive layer include graphite having high conductivity due to the presence of delocalized π electrons (specifically, natural graphite, artificial graphite, etc.); Carbon black (specifically, acetylene black, ketjen black, other furnace blacks, channel blacks, thermal lamp blacks, etc.), which is a spherical aggregate in which several layers of carbon microcrystals are gathered to form a turbulent layer structure; Carbon whiskers, etc., among these, the carbon particles of the conductive adhesive layer are filled with high density, the electron transfer resistance can be reduced, and further the internal resistance of the battery can be reduced, graphite or carbon black, Particularly preferred.

  As the carbon particles, those listed above may be used alone, or two kinds may be used in combination. Specific examples include graphite and carbon black, graphite and carbon fiber, graphite and carbon whisker, carbon black and carbon fiber, carbon black and carbon whisker, and preferably graphite and carbon black, graphite and carbon fiber, and carbon black. And carbon fiber, particularly preferably graphite and carbon black, and a combination of graphite and carbon fiber. When carbon particles are used in this combination, the carbon particles of the conductive adhesive layer are filled with high density, so that the electron transfer resistance is reduced and the internal resistance of the battery is reduced.

The electrical resistivity of the carbon particles is preferably 0.0001 to 1 Ω · cm, more preferably 0.0005 to 0.5 Ω · cm, and particularly preferably 0.001 to 0.1 Ω · cm. When the electrical resistivity of the carbon particles is within this range, the electron transfer resistance of the conductive adhesive layer can be reduced and the internal resistance can be reduced. Here, the electrical resistivity is measured by using a powder resistance measurement system (MCP-PD51 type; manufactured by Dia Instruments Co., Ltd.) while measuring the resistance value while applying pressure to the carbon particles, and the resistance value converged with respect to the pressure. The electrical resistivity ρ (Ω · cm) = R × (S / d) is calculated from R (Ω), the area S (cm ² ) and the thickness d (cm) of the compressed carbon particle layer.

  The volume average particle diameter of the carbon particles is preferably 0.01 to 20 μm, more preferably 0.05 to 15 μm, and particularly preferably 0.1 to 10 μm. When the volume average particle diameter of the carbon particles is within this range, the carbon particles of the conductive adhesive layer are filled with high density, so that the electron transfer resistance is reduced and the internal resistance of the battery is reduced. The volume average particle diameter is a volume average particle diameter calculated by measuring with a laser diffraction particle size distribution analyzer (SALD-3100; manufactured by Shimadzu Corporation).

<Method for producing all-solid-state secondary battery>
[Step of Forming Positive Electrode Active Material Layer (1)]
A method for forming the positive electrode active material layer is not particularly limited. For example, a method of applying a slurry composition for a positive electrode active material layer containing a positive electrode active material, a binder a, and a solid electrolyte on a current collector a and drying it. And a method of pressure-forming composite particles obtained by granulating the slurry composition for the positive electrode active material layer. The slurry composition for the positive electrode active material layer is produced by kneading the positive electrode active material, the binder a, the solid electrolyte, the organic solvent, and other components added as necessary.

  The positive electrode active material layer slurry composition is obtained by mixing the above-described components. The mixing method is not particularly limited, and examples thereof include a method using a mixing apparatus such as a stirring type, a shaking type, and a rotary type. In addition, a method using a dispersion kneader such as a homogenizer, a ball mill, a bead mill, a planetary mixer, a sand mill, a roll mill, and a planetary kneader may be used, and a planetary mixer, ball mill or A method using a bead mill is preferred.

  The method for applying the slurry composition for the positive electrode active material layer to the current collector is not particularly limited. For example, the doctor blade method, the dip method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, the brush coating, etc. Applied. The amount to be applied is not particularly limited, but is such an amount that the thickness of the positive electrode active material layer formed after removing the organic solvent is usually 5 to 300 μm, preferably 10 to 250 μm. The drying method is not particularly limited, and examples thereof include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying conditions are adjusted so that the organic solvent volatilizes as soon as possible within a speed range that normally causes stress concentration and cracks in the positive electrode active material layer or does not peel from the current collector. To do. Furthermore, the positive electrode active material layer after drying may be pressed to stabilize the positive electrode. Examples of the pressing method include, but are not limited to, a mold press and a calendar press.

  The drying temperature is a temperature at which the organic solvent is sufficiently volatilized. Specifically, 50 to 250 ° C is preferable, and 80 to 200 ° C is more preferable. By setting it as the said range, it becomes possible to form a favorable positive electrode active material layer, without thermal decomposition of the binder a. Although it does not specifically limit about drying time, Usually, it is performed in the range for 10 to 60 minutes.

  Moreover, the positive electrode active material layer in the all-solid-state secondary battery is formed by a method of pressure-molding composite particles (composite particles for positive electrode) obtained by granulating the slurry composition for positive electrode active material layer. Is preferred. By forming the positive electrode active material layer in this way, it is possible to suppress the uneven distribution of the binder a in the slurry composition for the positive electrode active material layer and to obtain a positive electrode having a high peel strength.

(Manufacture of composite particles for positive electrode)
The manufacturing method of the composite particle for positive electrodes is not specifically limited, In addition to the method used when manufacturing the composite particle for solid electrolyte layers described above, it can be manufactured by a known granulation method such as a wet granulation method. Among these, the wet granulation method and the spray drying granulation method are preferable, and the spray drying granulation method is more preferable. According to the said manufacturing method, drying of the slurry composition for positive electrode active material layers is easy, and the lifetime characteristic of a battery can be improved. In addition, since the spherical composite particles having good fluidity can be obtained by the above granulation method, a uniform positive electrode active material layer can be formed and the life characteristics of the battery can be improved.

  The manufacturing method of the composite particles for positive electrodes by the spray drying granulation method is as described above except that the positive electrode active material layer slurry composition is used. Below, the manufacturing method of the composite particle for positive electrodes which uses a wet granulation method is demonstrated.

  The wet granulation method is a step of mixing a binder a, a solid electrolyte and other components such as a conductive agent as required in an organic solvent to obtain a slurry composition, fluidizing the positive electrode active material, The slurry composition is sprayed and fluidized and granulated, the particles obtained in the fluidized granulation process are tumbled and granulated, and if necessary, heat treated.

  First, the binder a, the solid electrolyte, and other components such as a conductive agent as necessary are dispersed or dissolved in an organic solvent to obtain a slurry composition. When an organic solvent having a lower boiling point than water is used, the drying rate can be increased during fluid granulation. In addition, when an organic solvent having a boiling point lower than that of water is used, the solubility of the binder a is changed, and the viscosity and fluidity of the slurry composition can be adjusted depending on the amount or type of the solvent, thereby improving the production efficiency. Can do.

  The amount of the organic solvent used when preparing the slurry composition is such that the solid content concentration of the slurry composition is usually 10 to 70 mass%, preferably 20 to 60 mass%, more preferably 30 to 50 mass%. The amount is in the range. When the amount of the organic solvent is within this range, the binder a and the solid electrolyte are uniformly dispersed, which is preferable.

  The method and procedure for dispersing or dissolving the binder a, the solid electrolyte and other components such as a conductive agent in an organic solvent are not particularly limited. For example, the binder a, the solid electrolyte, A method of adding and mixing other components such as a conductive agent; after adding the binder a dissolved in an organic solvent to the organic solvent, adding and mixing other components such as a conductive agent, and finally a solid electrolyte A method in which other components are added and mixed; a method in which other components such as a solid electrolyte and a conductive agent are added and mixed in an organic solvent, and a binder a dissolved in the organic solvent is added thereto and mixed. And so on. Examples of the mixing means include mixing equipment such as a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer. Mixing is usually performed in the range of room temperature to 80 ° C. for 10 minutes to several hours.

  Next, the positive electrode active material is fluidized, and the slurry composition is sprayed thereon for fluid granulation. Examples of fluidized granulation include a fluidized bed, a deformed fluidized bed, and a spouted bed. In the fluidized bed, the positive electrode active material is fluidized with hot air, and the slurry composition is sprayed from the spray or the like to perform agglomeration and granulation. The modified fluidized bed is the same as the fluidized bed, but is a method of giving a circulating flow to the powder in the bed and discharging the granulated material that has grown relatively large by using the classification effect. In addition, the method using the spouted bed is a method in which a slurry composition from a spray or the like is attached to coarse particles using the characteristics of the spouted bed, and granulated while simultaneously drying. As a method for producing composite particles for positive electrode in the present invention, a fluidized bed or a deformed fluidized bed is preferred among these three methods.

  The temperature of the sprayed slurry composition is usually room temperature, but it may be heated to room temperature or higher. The temperature of the hot air used for fluidization is usually 70 to 300 ° C, preferably 80 to 200 ° C.

  Particles obtained by fluid granulation (hereinafter referred to as “fluid granulated particles”) may be those completely dried with hot air, but in order to increase the granulation efficiency in the next rolling granulation step. In addition, it is preferable that it is in a wet state.

  Next, the fluidized granulated particles obtained in the fluidized granulation step are tumbled and granulated. There are various types of rolling granulation, such as a rotating coarse method, a rotating cylindrical method, and a rotating truncated cone method. Rotational roughness is produced by spraying the binder a or the slurry composition onto the fluidized granulated particles supplied into the inclined rotating texture, if necessary, to produce an agglomerated granulated product, and the classification effect of the rotating texture. This is a method of discharging a granulated material that has grown relatively large from the rim. In the rotating cylinder system, wet granulated particles are supplied to an inclined rotating cylinder, which rolls in the cylinder, and if necessary, the binder a or the slurry composition is sprayed to form an agglomerated granulated product. It is a method to obtain. The rotating truncated cone method is the same as the operating method of the rotating cylinder, but is a method in which the granulated material that has grown relatively large is discharged by utilizing the classification effect of the aggregated granulated material by the truncated cone shape.

  Although the temperature at the time of rolling granulation is not specifically limited, in order to remove the organic solvent which comprises a slurry composition, it is normally 80-300 degreeC, Preferably it carries out at 100-200 degreeC. Furthermore, heat treatment is performed to cure the surface of the composite particles. The heat treatment temperature is usually 80 to 300 ° C.

  By the above manufacturing method, composite particles for a positive electrode including electrode active material particles, binder a, solid electrolyte particles, and other components such as a conductive agent as required can be obtained.

  The composite particles for the positive electrode are mixed with other binders and other additives that are added as necessary, and a material for forming the positive electrode active material layer (hereinafter referred to as “positive electrode material”) Used).

  The amount of the composite particles for positive electrode contained in the positive electrode material is usually 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more.

  Examples of the other binder contained as necessary include the same binders as those mentioned as the binder a used for obtaining the positive electrode composite particles. Since the composite particles for positive electrode already contain the binder a, it is not necessary to add them separately when preparing the positive electrode material, but other binders are added to increase the binding force between the composite particles. You may add when preparing positive electrode material. The amount of the other binder added when preparing the positive electrode material is a total of the binder a in the composite particles for positive electrode and is usually 0.1 to 50 with respect to 100 parts by mass of the positive electrode active material. It is the range of 1 to 10 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass. Other additives include molding aids such as water and alcohol, and can be appropriately selected in an amount that does not impair the effects of the present invention.

  The water content of the composite particles for positive electrode thus obtained is preferably 400 ppm or less, more preferably 100 ppm or less. By setting the moisture content of the composite particles for positive electrode within the above range, the charge / discharge cycle characteristics of the all-solid secondary battery can be improved.

  Moreover, the weight average particle diameter of the composite particles for positive electrode is preferably 0.1 to 1000 μm, more preferably 1 to 500 μm, and particularly preferably 10 to 100 μm. By setting the weight average particle diameter of the composite particles for positive electrode in the above range, the film thickness accuracy of the positive electrode active material layer is excellent, and the productivity of the battery can be improved. The weight average particle diameter can be measured using a laser diffraction particle size distribution analyzer.

(Pressure molding of composite particles for positive electrode)
In the manufacturing method of the all-solid-state secondary battery of this invention, it is preferable to press-mold the said composite particle for positive electrodes, and to obtain a positive electrode active material layer. The pressure forming method is a method of forming a positive electrode active material layer by applying pressure to a positive electrode material composed of composite particles to perform densification by rearrangement and deformation of the positive electrode material. The pressure molding method can be performed with simple equipment.

  Examples of the pressure molding method include a method in which a positive electrode material is supplied to a roll-type pressure molding apparatus with a supply device such as a screw feeder, and a positive electrode active material layer is formed on a current collector or a substrate. Is applied to the current collector or the base material, the thickness of the positive electrode material is adjusted with a blade or the like, the thickness is then adjusted, the positive electrode material is filled in the mold, and the mold is pressurized. There are methods such as molding.

  In the manufacturing method of the all-solid-state secondary battery of the present invention, since it is excellent in productivity, the positive electrode material is supplied to a roll-type pressure molding device with a supply device such as a screw feeder, and then on the current collector or the substrate. A method of forming the positive electrode active material layer is preferable. In this method, a current collector or a base material to be described later is fed into a roll simultaneously with the supply of the positive electrode material, whereby a positive electrode active material layer is laminated directly on the current collector or the base material, and a current collector with a positive electrode active material layer is collected. A body or a substrate with a positive electrode active material layer can be obtained. The temperature of the roll at the time of shaping | molding is 25-200 degreeC normally, Preferably it is 70-150 degreeC, More preferably, it is 50-120 degreeC. Moreover, the press linear pressure of the roll at the time of shaping | molding is 10-1,000 kN / m normally, Preferably it is 200-900 kN / m, Most preferably, it is 300-600 kN / m. When the temperature of the roll and the press linear pressure during molding are within the above ranges, the positive electrode active material layer can be uniformly bonded onto the current collector or the substrate, and a positive electrode having excellent strength can be obtained.

  In the method for producing an all solid state secondary battery of the present invention, the positive electrode active material layer may be formed on a substrate, but is preferably formed directly on a current collector. By forming the positive electrode active material layer on the current collector, a more uniform positive electrode active material layer can be formed. As a result, the internal resistance of the battery can be suppressed and the charge / discharge cycle characteristics can be improved. When the positive electrode active material layer is formed on the substrate, the positive electrode active material layer formed on the substrate is then transferred onto the current collector to form the positive electrode.

  The base material used for this invention supports a positive electrode active material layer, and uses it for bonding a positive electrode active material layer to a collector. The base material preferably has a roughened surface in contact with the positive electrode active material layer. As a material constituting the base material, any inorganic material, organic material, etc. can be used without limitation as long as the positive electrode active material layer can be formed on the base material. For example, metal foil such as aluminum foil and copper foil; plastic film; paper; thermoplastic resin film and the like can be mentioned. A film having a multilayer structure in which the above films and the like are stacked may be used. Among these, paper and thermoplastic resin film are preferable from the viewpoint of versatility and handling, and among paper and thermoplastic resin film, in particular, PET (polyethylene terephthalate) film, polyolefin film, PVA (polyvinyl alcohol) film, PVB (Polyvinyl butyral film) and PVC (polyvinyl chloride) film are preferable. In addition, the collector used for a positive electrode is not included in the base material in this invention.

  Although the thickness of a base material is not specifically limited, 10-200 micrometers is preferable, 20-150 micrometers is more preferable, 20-100 micrometers is especially preferable.

(Process for integrating positive electrode active material layer and current collector)
Further, in the method for producing an all-solid-state secondary battery according to the present invention, in order to eliminate the variation in the thickness of the formed positive electrode active material layer and increase the density of the positive electrode active material layer to increase the capacity, further post-addition is required. It is preferable to include a step of applying pressure to integrate the positive electrode active material layer and the current collector.

  As the post-pressurization method, a hot press method is generally used. Specific examples of the hot press method include a batch hot press and a continuous hot roll press, and a continuous hot roll press capable of improving productivity is preferable. In a continuous hot roll press, two cylindrical rolls are arranged vertically in parallel with a narrow interval, and each is rotated in the opposite direction, and the positive electrode active material layer and the current collector are sandwiched and pressed between them. . The temperature of the hot press is usually 25 to 200 ° C, preferably 70 to 150 ° C, more preferably 50 to 120 ° C. The linear pressure of the hot press is usually 10 to 1,000 kN / m, preferably 200 to 900 kN / m, particularly preferably 300 to 600 kN / m. When the temperature and linear pressure of the hot press are in the above ranges, the positive electrode active material layer can be uniformly bonded to the current collector, and a positive electrode having excellent strength can be obtained.

  In the case where the positive electrode active material layer is formed on the substrate, the current collector and the positive electrode active material layer are laminated, hot-pressed, and attached to the positive electrode active material layer and the current collector. It is preferable to integrate and then peel the substrate. The method for peeling the base material from the positive electrode active material layer is not particularly limited. For example, after the positive electrode active material layer is pasted on the current collector, the current collector on which the positive electrode active material layer is pasted and the base material are separated. The substrate can be easily peeled off by winding on a roll. Thus, the positive electrode active material layer and the current collector are integrated.

  Also, an electrode in which an electrode active material layer is formed on both sides of the current collector by bonding the base material on which the positive electrode active material layer is formed to the other surface of the current collector on which the positive electrode active material layer is formed by hot pressing. Can also be manufactured.

  In the production method of the present invention, the thickness of the positive electrode active material layer in the positive electrode is usually 10 to 500 μm, preferably 20 to 400 μm, particularly preferably 30 to 200 μm. When the thickness of the positive electrode active material layer is in this range, a battery having a balance between internal resistance and energy density can be obtained.

[Step of Forming Negative Electrode Active Material Layer (2)]
The method for forming the negative electrode active material layer is not particularly limited, and is formed on a current collector b different from the current collector a on which the positive electrode active material layer is formed, using each of the above-described components constituting the negative electrode active material layer. Except for this, it is the same as the above step (1).

[Step of forming solid electrolyte layer (3)]
The solid electrolyte layer is formed by pressure-molding the composite particles for the solid electrolyte layer on the positive electrode active material layer and / or the negative electrode active material layer formed in the above steps (1) and (2). In the manufacturing method of the all-solid-state secondary battery of this invention, it is preferable to have the process of charging the composite particle for solid electrolyte layers. The charging step is performed prior to pressure molding described later.

(Step of charging the composite particles for the solid electrolyte layer)
In the present invention, to charge the composite particles means to charge the composite particles positively or negatively by treating the composite particles. The method for charging the composite particles is not particularly limited, and examples thereof include a method in which a voltage is directly applied to the composite particles for charging, and a method in which the composite particles are charged by friction.

  Examples of a method for charging a composite particle by directly applying a voltage include a charging method using corona discharge. The charging method using corona discharge is a method of charging composite particles by passing the vicinity of the corona discharge electrode when spraying the composite particles on the positive electrode active material layer and / or the negative electrode active material layer or on the substrate. Alternatively, a method of charging the composite particles in a fluidized state (fluidized bed) and installing a corona discharge electrode therein may be used.

  As a method for frictionally charging the composite particles, a method in which the composite particles and a substance that easily charges the particles are brought into contact with each other by using a charging train is used. The charged column is inherent to a substance and has a relative order of easiness of charging from a material that is easily charged negatively to a material that is easily charged positively. As the two substances to be rubbed are separated from each other in the charged row, the larger the charge is, the more easily the composite particles can be easily brought into contact with the composite particles by bringing the charged row away from the charged particles. Can be charged. When charging composite particles positively, contact the composite particles with polytetrafluoroethylene, vinyl chloride, etc., and when charging composite particles negatively, contact the composite particles with asbestos, nylon, etc. Can be charged respectively.

(Pressure molding of composite particles for solid electrolyte layer)
The pressure forming method is the pressure forming method described in the above step (1) except that the composite electrolyte for the solid electrolyte layer is used and the solid electrolyte layer is formed on the positive electrode active material layer and / or the negative electrode active material layer. It is the same. Alternatively, the composite particles may be pressure-molded on the above-described base material to form a solid electrolyte layer, and transferred onto the positive electrode active material layer and / or the negative electrode active material layer.

(Process for integrating the solid electrolyte layer and the electrode)
Further, in the method for producing an all-solid-state secondary battery according to the present invention, post-pressurization is further performed in order to eliminate the variation in the thickness of the formed solid electrolyte layer and increase the density of the solid electrolyte layer to increase the capacity. It is preferable to have a step of performing and integrating the solid electrolyte layer and the electrode. The post-pressurization method is the same as the method described in the step (1).

  In the production method of the present invention, the thickness of the solid electrolyte layer in the all-solid secondary battery is preferably 0.1 to 30 μm, more preferably 1 to 20 μm, and particularly preferably 3 to 15 μm. By setting the thickness of the solid electrolyte layer in the above range, a battery having low internal resistance and free from self-discharge and short circuit can be obtained.

[Lamination process]
Thereafter, the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode obtained as described above are laminated via a solid electrolyte layer to obtain an all-solid secondary battery element. The lamination method is not particularly limited. Furthermore, you may pressurize said all-solid-state secondary battery element. The pressurizing method is not particularly limited, and examples thereof include a flat plate press, a roll press, and CIP (Cold Isostatic Press). The pressure for pressing is preferably 5 to 700 MPa, more preferably 7 to 500 MPa. This is because by setting the pressure of the pressure press within the above range, the resistance at each interface between the electrode and the solid electrolyte layer, and further, the contact resistance between particles in each layer is lowered, and good battery characteristics are exhibited. Note that the solid electrolyte layer and the electrode active material layer may be compressed by pressing, and may be thinner than before pressing. When pressing is performed, the thickness of the solid electrolyte layer and the electrode active material layer in the present invention may be within the above range after the pressing.

  The obtained all-solid-state secondary battery element is put into a battery container as it is or wound or folded according to the shape of the battery, and sealed to obtain an all-solid-state secondary battery. If necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate or the like can be placed in the battery container to prevent an increase in pressure inside the battery and overcharge / discharge. The shape of the battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these Examples. In addition, the part and% in an Example and a comparative example are mass references | standards unless there is particular notice. In the examples and comparative examples, various physical properties are evaluated as follows.

(Measurement of iodine value)
The iodine value was determined according to JIS K 0070; 1992.

(Coating efficiency)
The application efficiency to the positive electrode active material layer and / or the negative electrode active material layer is calculated from the mass of the supplied composite particles and the mass of the composite particles forming the solid electrolyte layer according to the following formula. The higher the coating efficiency, the higher the adhesive strength between the composite particles, and the lower the internal resistance of the battery, which is preferable because the output characteristics and cycle characteristics are improved.
Coating efficiency (%) = mass of composite particles forming a solid electrolyte layer / mass of supplied composite particles × 100

(Peel strength)
Each electrode on which the solid electrolyte layer is laminated is cut into a rectangle having a width of 1 cm and a length of 10 cm to form a test piece, and fixed with the solid electrolyte layer surface facing up. After applying the cellophane tape to the surface of the solid electrolyte layer of the test piece, the stress was measured when the cellophane tape was peeled from the end of the test piece in the direction of 180 ° at a speed of 50 mm / min. The measurement was performed 10 times, the average value was obtained, and this was used as the peel strength. It shows that the adhesiveness of the solid electrolyte layer with respect to an electrode is so favorable that peel strength is large.
A: 20 N / m or more B: 15 N / m or more and less than 20 N / m C: 10 N / m or more and less than 15 N / m D: 4 N / m or more and less than 10 N / m E: Less than 4 N / m

(Battery characteristics; output characteristics)
A 10-cell all-solid-state secondary battery is charged to 4.3 V by a constant current method of 0.1 C, and then discharged to 3.0 V at 0.1 C to obtain a 0.1 C discharge capacity. Thereafter, the battery is charged to 4.3 V at 0.1 C, and then discharged to 3.0 V at 5 C to obtain the 5 C discharge capacity. The average value of 10 cells is a measured value (0.1C discharge capacity a, 5C discharge capacity b), and is expressed as a ratio of electric capacity between 5C discharge capacity b and 0.1C discharge capacity a (b / a (%)). Capacity retention ratio is obtained, and this is used as an evaluation criterion for output characteristics, and is evaluated according to the following criteria. Higher values indicate better output characteristics, that is, lower internal resistance.
A: 50% or more B: 30% or more and less than 50% C: 10% or more and less than 30% D: 1% or more and less than 10% E: Less than 1%

(Battery characteristics; high-temperature cycle characteristics)
Using the obtained all-solid-state secondary battery, charging / discharging which was charged from 3 V to 4.3 V at 0.1 C at 60 ° C. and then discharged from 4.3 V to 3 V at 0.1 C was repeated 100 cycles. . A value obtained by calculating the percentage of the 0.1C discharge capacity at the 100th cycle with respect to the 0.1C discharge capacity at the 5th cycle as a percentage is determined as the capacity maintenance rate, and the following criteria are used. The larger this value is, the less the discharge capacity is reduced, and the higher the cycle characteristics at high temperature.
A: 60% or more B: 50% or more and less than 60% C: 40% or more and less than 50% D: 30% or more and less than 40% E: 20% or more and less than 30% F: Less than 20%

Example 1
<Manufacture of binder>
A reaction vessel was charged with 240 parts of water, 16 parts of acrylonitrile, and 2.5 parts of sodium dodecylbenzenesulfonate (emulsifier), and the temperature was adjusted to 5 ° C. Next, after the gas phase was depressurized and sufficiently deaerated, 86 parts of 1,3-butadiene, 0.06 part of paramentane hydroperoxide as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, and sulfuric acid first First stage reaction of emulsion polymerization was started by adding 0.006 part of iron (7 water salt) and 0.06 part of sodium formaldehyde sulfoxylate and 1 part of t-dodecyl mercaptan as a chain transfer agent. After the start of the reaction, when the polymerization conversion ratio with respect to the charged monomer reaches 34 mass% and 58 mass%, 20 parts and 20 parts of 1,3-butadiene are added to the reaction vessel, respectively, and the second and third stages. An eye polymerization reaction was performed. Thereafter, when the polymerization conversion rate with respect to all charged monomers reached 75% by mass, 0.3 part of hydroxylamine sulfate and 0.2 part of potassium hydroxide were added to stop the polymerization reaction. After the reaction was stopped, the contents in the reaction vessel were heated to 70 ° C., and unreacted monomers were recovered by steam distillation under reduced pressure to obtain an aqueous dispersion of a nitrile group-containing unsaturated polymer (solid content: 24 mass). %).

  When the content ratio of each monomer constituting the obtained nitrile group-containing unsaturated polymer was measured using a FTNMR apparatus (JNM-EX400WB) manufactured by JEOL Ltd., an acrylonitrile monomer unit (nitrile group was converted). Monomer unit) and 15% by mass, and 1,3-butadiene unit by 85% by mass.

(Hydrogenation reaction)
400 ml of an aqueous dispersion of a nitrile group-containing unsaturated polymer adjusted to a solid content concentration of 12% by mass (total solid content of 48 g) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to disperse in water. After removing dissolved oxygen in the liquid, 75 mg of palladium acetate was dissolved in 180 ml of water to which 4 times moles of nitric acid had been added to Pd as a hydrogenation catalyst and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. .) At this time, the iodine value of the nitrile group-containing unsaturated polymer was 35.

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate was further dissolved and added as a hydrogenation catalyst in 60 ml of water to which 4 times moles of nitric acid had been added relative to Pd. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. .) Thereafter, the contents are returned to room temperature, the inside of the system is made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration is about 40% by mass to obtain an aqueous dispersion of a highly saturated nitrile polymer. It was. The obtained aqueous dispersion was dried to obtain a highly saturated nitrile polymer (hydrogenated NBR) A as a binder. The iodine value of the highly saturated nitrile polymer A was 7.

<Manufacture of slurry for forming conductive adhesive layer>
100 parts of carbon black having a volume average particle size of 0.7 μm, and 4 parts of a 4.0% aqueous solution (DN-10L; manufactured by Daicel Chemical Industries, Ltd.) of ammonium salt of carboxymethyl cellulose as a dispersing agent, resin component As a (binder), a 40% aqueous dispersion of an acrylic polymer (2-ethylhexyl acrylate: acrylonitrile = 75: 25 (mass ratio)) having a number average particle size of 0.25 μm and 8 parts solid equivalent and ions The exchange water was mixed so that the total solid content concentration was 30% to prepare a slurry for forming a conductive adhesive layer.

<Formation of conductive adhesive layer>
As the positive electrode current collector (current collector a), an aluminum foil having a thickness of 20 μm was prepared. Further, a copper foil having a thickness of 20 μm was prepared as a negative electrode current collector (current collector b). A slurry for forming a conductive adhesive layer was applied to each of the current collectors a and b, and dried at 120 ° C. for 10 minutes to form a conductive adhesive layer having a thickness of 2 μm.

<Production of positive electrode>
100 parts of lithium cobaltate having a layered rock salt structure (average particle diameter of 11.5 μm) as the positive electrode active material, 5 parts of a toluene solution of the above highly saturated nitrile polymer A as the binder, and a solid electrolyte. 150 parts of a sulfide glass composed of Li ₂ S and P ₂ S ₅ (Li ₂ S: P ₂ S ₅ = 70: 30 (molar ratio), average particle diameter 0.4 μm), an average particle diameter of 0. After adding 7.5 parts of 7 μm acetylene black (Denka black powder; manufactured by Denki Kagaku Kogyo Co., Ltd.) and further adjusting the solid content concentration to 30% using toluene as an organic solvent, “TK Homomixer” (manufactured by Primix Co. ) To obtain a slurry composition for the positive electrode active material layer. Using this slurry composition, a spray dryer (OC-16; manufactured by Okawara Chemical Co., Ltd.), rotating disk type atomizer (diameter 65 mm), rotation speed 25,000 rpm, hot air temperature 160 ° C., temperature at particle recovery outlet Was spray-dried and granulated under the condition of 90 ° C. to obtain composite particles for the positive electrode. The weight average particle diameter of the composite particles was 45 μm.

Using a quantitative feeder (Nikka, Nikka Spray K-V), the above-mentioned composite particles for positive electrode were fed at a feed rate of 800 g / min, and a roll for press of a roll press machine (pressed rough surface heat roll; manufactured by Hirano Giken Kogyo Co., Ltd.) (Roll temperature 100 ° C., press linear pressure 500 kN / m). Then, an aluminum foil on which a conductive adhesive layer is formed is inserted between the rolls for pressing, and the composite particles supplied from the quantitative feeder are adhered onto the conductive adhesive layer and pressed at a molding speed of 15 m / min. Molding was performed to obtain a positive electrode on which a positive electrode active material layer having an average thickness of 100 μm and an average single-sided density of 3.5 g / cm ³ was formed.

<Manufacture of negative electrode>
100 parts of graphite (average particle diameter 10 μm) as the negative electrode active material, 5 parts of toluene solution of the above-mentioned highly saturated nitrile polymer A as the binder b in solids, Li ₂ S and P ₂ S as the solid electrolyte 150 parts of sulfide glass (Li ₂ S: P ₂ S ₅ = 70: 30 (molar ratio), average particle size 0.4 μm) consisting of ₅ and a solid content concentration of 25% using toluene as an organic solvent. Then, the mixture was stirred and mixed with a “TK homomixer” (manufactured by Primex) to obtain a slurry composition for a negative electrode active material layer. Using this slurry composition, a spray dryer (OC-16; manufactured by Okawara Chemical Co., Ltd.), rotating disk type atomizer (diameter 65 mm), rotation speed 25,000 rpm, hot air temperature 160 ° C., temperature at particle recovery outlet Was spray-dried and granulated under the condition of 90 ° C. to obtain composite particles for the negative electrode. The composite particles had a weight average particle diameter of 54 μm.

Using a quantitative feeder (Nikka Spray, Nikka Spray K-V), the negative electrode composite particles were fed at a feed rate of 300 g / min, and a roll for press of a roll press machine (pressed rough surface heat roll; manufactured by Hirano Giken Kogyo Co., Ltd.) (Roll temperature 100 ° C., press linear pressure 500 kN / m). Then, a copper foil on which a conductive adhesive layer is formed is inserted between the rolls for pressing, and the composite particles supplied from the quantitative feeder are adhered onto the conductive adhesive layer and pressed at a molding speed of 15 m / min. Molding was performed to obtain a negative electrode on which a negative electrode active material layer having an average thickness of 100 μm and an average single-side density of 1.5 g / cm ³ was formed.

<Manufacture of solid electrolyte layer>
As a binder c, a toluene solution of the above-mentioned highly saturated nitrile polymer A in a solid content equivalent to 5 parts, and a sulfide glass (Li ₂ S: P ₂ S) composed of Li ₂ S and P ₂ S ₅ as a solid electrolyte. ₅ = 70: 30 (molar ratio), average particle diameter 0.4 μm) 100 parts were added, and further, the solid content concentration was adjusted to 25% using toluene as an organic solvent, followed by “TK Homomixer” (manufactured by Primics) The mixture was stirred and mixed to obtain a slurry composition. Using this slurry composition, a spray dryer (OC-16; manufactured by Okawara Chemical Co., Ltd.), rotating disk type atomizer (diameter 65 mm), rotation speed 25,000 rpm, hot air temperature 160 ° C., temperature at particle recovery outlet Was spray dried and granulated under the condition of 90 ° C. to obtain composite particles for the solid electrolyte layer. The composite particles had a weight average particle diameter of 30 μm.

 100 parts of the composite particles for a solid electrolyte layer and 0.5 part of a positive charge control resin “FCA207-P” (styrene acrylic resin; manufactured by Fujikura Kasei Co., Ltd.) are mixed with a Henschel mixer (manufactured by Mitsui Miike). Mixing for minutes, composite particles (externally added particles) to which the charge control resin was adhered were obtained.

 Next, friction charging electrostatic powder coating machine MTR-100VTmini manufactured by Asahi Sunac Co., Ltd. and friction charging electrostatic powder manual gun T-2m type L7 manufactured by Asahi Sunac Co., Ltd. (the inner sleeve and outer sleeve are made of polytetrafluoroethylene) Was used to charge the external additive particles. Thereafter, the charged externally added particles were supplied onto the negative electrode active material layer of the negative electrode produced by the above-described method to form a solid electrolyte layer. Specifically, the external additive particles were put into a hopper of the powder coating machine, the number of rotations of a screw feeder for quantitative supply was adjusted, and the external additive particles were supplied at 100 g / min. The carrier air pressure from the powder manual gun was set to 0.4 MPa, and external additive particles were supplied to the negative electrode from above. The external additive particles were charged by friction when passing through the gap between the inner sleeve and the outer sleeve of the powder manual gun. The coating efficiency was 35%.

  The negative electrode on which this solid electrolyte layer is formed is supplied to a roll (roll temperature 100 ° C., press linear pressure 500 kN / m) of a roll press machine (pressed rough surface heat roll, manufactured by Hirano Giken Kogyo Co., Ltd.) An electrode in which the solid electrolyte layer and the negative electrode active material layer were integrated was obtained.

<Production of measurement cell>
The electrode and the positive electrode in which the solid electrolyte layer and the negative electrode active material layer produced above were integrated were slit so that the portion where the active material layer was formed was 5 cm and the portion where the active material layer was not formed was 2 cm. Furthermore, the electrode in which the solid electrolyte layer and the negative electrode active material layer are integrated and the positive electrode are overlapped with each other so that the active material layers overlap with each other through the solid electrolyte layer. The positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material are supplied to a roll (roll temperature 120 ° C., press linear pressure 500 kN / m) of a roll press machine (pressed rough surface heat roll, manufactured by Hirano Giken Kogyo Co., Ltd.). An electrode integrated with the material layer was obtained. The thickness of this solid electrolyte layer was 10 μm.

The electrode prepared above is cut to a width of 5 cm, and the active material layer is formed of a tab material of length 7 cm × width 1 cm × thickness 0.01 cm, made of aluminum for the positive electrode and nickel for the negative electrode. An all solid-state battery for measurement was produced by ultrasonic welding to the unexposed portion. The measurement battery was vacuum-dried at 200 ° C. for 24 hours, placed inside an aluminum laminate film, fused on the three sides, and then fused on the other side under reduced pressure to produce a measurement cell.
Table 1 shows the determination results of this measurement cell.

(Example 2)
Spray drying granulation was carried out under the same conditions as in Example 1 except that the solid content concentration of the slurry composition was 15% using toluene and the rotational speed of a rotating disk type atomizer (diameter 65 mm) was 35,000 rpm. Then, composite particles for a solid electrolyte layer having a weight average particle diameter of 8 μm were obtained.

  A measurement cell was produced in the same manner as in Example 1 except that the composite particles for a solid electrolyte layer were used. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 30%. The thickness of the solid electrolyte layer in the measurement cell was 13 μm.

Example 3
Spray drying granulation was carried out under the same conditions as in Example 1 except that the solid content concentration of the slurry composition was 35% using toluene and the rotational speed of a rotating disk type atomizer (diameter 65 mm) was 15,000 rpm. Then, composite particles for a solid electrolyte layer having a weight average particle diameter of 85 μm were obtained.

  A measurement cell was produced in the same manner as in Example 1 except that the composite particles for a solid electrolyte layer were used. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 15%. Further, the thickness of the solid electrolyte layer in the measurement cell was 18 μm.

Example 4
A measurement cell was produced in the same manner as in Example 1 except that the press linear pressure of the roll for supplying the negative electrode on which the solid electrolyte layer was formed was 250 kN / m. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 34%. Further, the thickness of the solid electrolyte layer in the measurement cell was 16 μm.

(Example 5)
A measurement cell was produced in the same manner as in Example 1 except that the press linear pressure of the roll for supplying the negative electrode on which the solid electrolyte layer was formed was 150 kN / m. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 35%. Further, the thickness of the solid electrolyte layer in the measurement cell was 23 μm.

(Example 6)
A measurement cell was produced in the same manner as in Example 1 except that the roll temperature of the roll for supplying the negative electrode on which the solid electrolyte layer was formed was 150 ° C. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 33%. The thickness of the solid electrolyte layer in the measurement cell was 8 μm.

(Example 7)
A measurement cell was produced in the same manner as in Example 1 except that the roll temperature of the roll for supplying the negative electrode on which the solid electrolyte layer was formed was 25 ° C. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 36%. The thickness of the solid electrolyte layer in the measurement cell was 27 μm.

(Example 8)
As binders a, b, and c, hydrogenated NBR which is a highly saturated nitrile polymer (Zetpol3310 manufactured by Nippon Zeon Co., Ltd. (content ratio of monomer unit having nitrile group: 23.6% by mass, iodine value of 15)) (Hereinafter, it may be referred to as “highly saturated nitrile polymer B”) was used in the same manner as in Example 1 to produce a measurement cell. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 30%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

Example 9
As binders a, b, and c, hydrogenated NBR which is a highly saturated nitrile polymer (Zetpol 4320 manufactured by Nippon Zeon Co., Ltd. (content ratio of monomer unit having nitrile group: 18.6% by mass, iodine value of 27)) (Hereinafter, it may be referred to as “highly saturated nitrile polymer C”) was used in the same manner as in Example 1 to produce a measurement cell. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 34%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

(Example 10)
A measurement cell was prepared in the same manner as in Example 1 except that the following binder (highly saturated nitrile polymer (hydrogenated NBR) D) was used as the binders a, b, and c. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 32%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

<Manufacture of binder>
A reaction vessel was charged with 240 parts of water, 9 parts of acrylonitrile, and 2.5 parts of sodium dodecylbenzenesulfonate (emulsifier), and the temperature was adjusted to 5 ° C. Next, after the gas phase was depressurized and sufficiently degassed, 93 parts of 1,3-butadiene, 0.06 part of paramentane hydroperoxide as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, sulfuric acid first First stage reaction of emulsion polymerization was started by adding 0.006 part of iron (7 water salt) and 0.06 part of sodium formaldehyde sulfoxylate and 1 part of t-dodecyl mercaptan as a chain transfer agent. After the start of the reaction, when the polymerization conversion ratio with respect to the charged monomer reaches 34 mass% and 58 mass%, 20 parts and 20 parts of 1,3-butadiene are added to the reaction vessel, respectively, and the second and third stages. An eye polymerization reaction was performed. Thereafter, when the polymerization conversion rate with respect to all charged monomers reached 75% by mass, 0.3 part of hydroxylamine sulfate and 0.2 part of potassium hydroxide were added to stop the polymerization reaction. After the reaction was stopped, the contents in the reaction vessel were heated to 70 ° C., and unreacted monomers were recovered by steam distillation under reduced pressure to obtain an aqueous dispersion of a nitrile group-containing unsaturated polymer (solid content: 24 mass). %).

  When the content ratio of each monomer constituting the obtained nitrile group-containing unsaturated polymer was measured using a FTNMR apparatus (JNM-EX400WB) manufactured by JEOL Ltd., an acrylonitrile monomer unit (nitrile group was converted). Monomer unit)) and 8 mass% of 1,3-butadiene units.

(Hydrogenation reaction)
400 ml of an aqueous dispersion of a nitrile group-containing unsaturated polymer adjusted to a solid content concentration of 12% by mass (total solid content of 48 g) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes to disperse in water. After removing dissolved oxygen in the liquid, 75 mg of palladium acetate was dissolved in 180 ml of water to which 4 times moles of nitric acid had been added to Pd as a hydrogenation catalyst and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. .) At this time, the iodine value of the nitrile copolymer was 35.

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate was further dissolved and added as a hydrogenation catalyst in 60 ml of water to which 4 times moles of nitric acid had been added relative to Pd. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. .) Thereafter, the contents are returned to room temperature, the inside of the system is made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration is about 40% by mass to obtain an aqueous dispersion of a highly saturated nitrile polymer. It was. The obtained aqueous dispersion was dried to obtain a highly saturated nitrile polymer (hydrogenated NBR) D as a binder. The iodine value of the highly saturated nitrile polymer D was 5.

(Example 11)
A measurement cell was prepared in the same manner as in Example 1 except that the following binder (styrene-ethylene-butylene-styrene block copolymer (SEBS)) was used as the binders a, b, and c. did. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 25%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

<Manufacture of binder>
A reaction vessel was charged with 240 parts of water, 21 parts of styrene, and 2.5 parts of sodium dodecylbenzenesulfonate (emulsifier), and the temperature was adjusted to 5 ° C. Next, after depressurizing and sufficiently degassing the gas phase, 81 parts of 1,3-butadiene, 0.06 part of paramentane hydroperoxide as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, first sulfuric acid sulfate First stage reaction of emulsion polymerization was started by adding 0.006 part of iron (7 water salt) and 0.06 part of sodium formaldehyde sulfoxylate and 1 part of t-dodecyl mercaptan as a chain transfer agent. After the start of the reaction, when the polymerization conversion ratio with respect to the charged monomer reaches 34 mass% and 58 mass%, 20 parts and 20 parts of 1,3-butadiene are added to the reaction vessel, respectively, and the second and third stages. An eye polymerization reaction was performed. Thereafter, when the polymerization conversion rate with respect to all charged monomers reached 75% by mass, 0.3 part of hydroxylamine sulfate and 0.2 part of potassium hydroxide were added to stop the polymerization reaction. After the reaction was stopped, the contents of the reaction vessel were heated to 70 ° C., and unreacted monomers were recovered by steam distillation under reduced pressure, and an aqueous dispersion of styrene-butadiene-styrene block copolymer (SBS). (Solid content 24% by mass) was obtained.

  When the content rate of each monomer which comprises the obtained styrene-butadiene-styrene block copolymer was measured using the JEOL FTNMR apparatus (JNM-EX400WB), the styrene monomer unit 20 mass. %, 1,3-butadiene unit was 80% by mass.

(Hydrogenation reaction)
400 ml of an aqueous dispersion of styrene-butadiene-styrene block copolymer adjusted to a solid content concentration of 12% by mass (total solid content 48 g) was put into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was allowed to flow for 10 minutes. After removing dissolved oxygen in the latex, 75 mg of palladium acetate was added as a hydrogenation catalyst after dissolving it in 180 ml of water to which nitric acid of 4 times moles of Pd was added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. To obtain a precursor of a styrene-ethylene-butylene-styrene block copolymer. At this time, the iodine value of the precursor was 35.

  Next, the autoclave was returned to atmospheric pressure, and 25 mg of palladium acetate was further dissolved and added as a hydrogenation catalyst in 60 ml of water to which 4 times moles of nitric acid had been added relative to Pd. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. .) Thereafter, the contents are returned to room temperature, and the inside of the system is made into a nitrogen atmosphere. Then, using an evaporator, the content is concentrated to a solid content concentration of about 40% by mass, and a styrene-ethylene-butylene-styrene block copolymer is obtained. An aqueous dispersion was obtained. The obtained aqueous dispersion was dried to obtain a styrene-ethylene-butylene-styrene block copolymer as a binder. The iodine value of the styrene-ethylene-butylene-styrene block copolymer was 9.

(Example 12)
Thio-LISICON (thiolysicon (GeS ₂ -Li ₂ S—P ₂ S ₅ , Li: 3.75, Ge: 0.25, P: 0.75, S: 4, average particle diameter 0.6 μm) as a solid electrolyte A measurement cell was prepared in the same manner as in Example 1 except that. Table 1 shows the determination results of this measurement cell. The weight average particle size of the composite particles for positive electrode was 53 μm, the weight average particle size of the composite particles for negative electrode was 60 μm, and the average particle size of the composite particles for solid electrolyte layer was 40 μm. The coating efficiency of the composite particles for the solid electrolyte layer was 23%, and the thickness of the solid electrolyte layer in the measurement cell was 16 μm.

(Example 13)
Li ₇ La ₃ Zr ₂ O ₁₀ (average particle size 0.8 μm) having a garnet-type structure as a solid electrolyte, and lithium titanate “LT-106” (average particle size 6.9 μm, manufactured by Ishihara Sangyo Co., Ltd.) as a negative electrode active material A measurement cell was prepared in the same manner as in Example 1 except that aluminum foil was used as the negative electrode current collector. Table 1 shows the determination results of this measurement cell. The weight average particle size of the composite particles for positive electrode was 57 μm, the weight average particle size of the composite particles for negative electrode was 45 μm, and the average particle size of the composite particles for solid electrolyte layer was 35 μm. The average thickness of the negative electrode active material layer was 200 μm, and the electrode density was 1.7 g / cm ³ . Moreover, the coating efficiency of the composite particles for the solid electrolyte layer was 20%, and the thickness of the solid electrolyte layer in the measurement cell was 17 μm.

(Example 14)
A measurement cell was prepared in the same manner as in Example 1 except that cyclohexane was used as the organic solvent for producing the positive electrode composite particles, the negative electrode composite particles, and the solid electrolyte layer composite particles. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 28%, and the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

(Example 15)
A measurement cell was prepared in the same manner as in Example 1 except that the external additive particles were not charged. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 15%, and the thickness of the solid electrolyte layer in the measurement cell was 35 μm.

(Example 16)
A measurement cell was produced in the same manner as in Example 1 except that the conductive adhesive layer was not formed on the current collectors a and b. Table 1 shows the determination results of this measurement cell. The application efficiency of the solid electrolyte layer composite particles was 29%, and the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

(Example 17)
A measurement cell was produced in the same manner as in Example 1 except that the following binder (acrylic polymer A) was used as the binders a, b, and c. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 30%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

<Manufacture of binder>
In a reaction vessel equipped with a stirrer, 21 parts of acrylonitrile, 78 parts of butyl acrylate and 1 part of acrylic acid, 1 part of sodium dodecylbenzenesulfonate as a dispersant, 200 parts of ion-exchanged water and 1 part of potassium persulfate as a polymerization initiator Then, the mixture was sufficiently stirred, and then heated to 80 ° C. for polymerization. When the monomer consumption reached 99.0%, the reaction was stopped by cooling to obtain an aqueous dispersion of acrylic polymer A (solid content 28%). The obtained aqueous dispersion of acrylic polymer A was dried to obtain acrylic polymer A. The content ratio of the monomer unit having a nitrile group in the acrylic polymer A was 21% by mass, and the iodine value of the acrylic polymer A was 0.

(Example 18)
A measurement cell was produced in the same manner as in Example 1 except that the following binder (acrylic polymer B) was used as the binders a, b, and c. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 31%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

<Manufacture of binder>
In a reaction vessel equipped with a stirrer, 30 parts of acrylonitrile, 69 parts of butyl acrylate and 1 part of acrylic acid, 1 part of sodium dodecylbenzenesulfonate as a dispersant, 200 parts of ion-exchanged water and 1 part of potassium persulfate as a polymerization initiator Then, the mixture was sufficiently stirred, and then heated to 80 ° C. for polymerization. When the monomer consumption reached 99.0%, the reaction was stopped by cooling to obtain an aqueous dispersion of acrylic polymer B (solid content 28%). The obtained aqueous dispersion of acrylic polymer B was dried to obtain acrylic polymer B. The content ratio of the monomer unit having a nitrile group in the acrylic polymer B was 30% by mass, and the iodine value of the acrylic polymer B was 0.

(Comparative Example 1)
As binders a, b and c, hydrogenated NBR which is a nitrile group-containing polymer (Zetpol 2030L manufactured by Nippon Zeon Co., Ltd. (content ratio of monomer unit having nitrile group: 36.2% by mass, iodine value 56)) A measurement cell was prepared in the same manner as in Example 1 except that was used. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 33%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

(Comparative Example 2)
SBR (acrylonitrile monomer unit: 5% by mass, styrene monomer unit: 50% by mass, butadiene monomer unit: 45% by mass, iodine value 130) was used as binders a, b, and c. A measurement cell was produced in the same manner as in Example 1 except for the above. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 31%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

(Comparative Example 3)
As the binders a and b, NBR which is a nitrile polymer (Nipol LX550L manufactured by Nippon Zeon Co., Ltd. (content ratio of monomer units having a nitrile group: 15 mass%, iodine value 200)) is used. As c, a measurement cell was produced in the same manner as in Example 1 except that the following binder (NBR) was used. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte layer composite particles was 28%. Further, the thickness of the solid electrolyte layer in the measurement cell was 10 μm.

<Manufacture of binder>
A reaction vessel was charged with 240 parts of water, 16 parts of acrylonitrile, and 2.5 parts of sodium dodecylbenzenesulfonate (emulsifier), and the temperature was adjusted to 5 ° C. Next, after the gas phase was depressurized and sufficiently deaerated, 86 parts of 1,3-butadiene, 0.06 part of paramentane hydroperoxide as a polymerization initiator, 0.02 part of sodium ethylenediaminetetraacetate, and sulfuric acid first First stage reaction of emulsion polymerization was started by adding 0.006 part of iron (7 water salt) and 0.06 part of sodium formaldehyde sulfoxylate and 1 part of t-dodecyl mercaptan as a chain transfer agent. After the start of the reaction, when the polymerization conversion ratio with respect to the charged monomer reaches 34 mass% and 58 mass%, 20 parts and 20 parts of 1,3-butadiene are added to the reaction vessel, respectively, and the second and third stages. An eye polymerization reaction was performed. Thereafter, when the polymerization conversion rate with respect to all charged monomers reached 75% by mass, 0.3 part of hydroxylamine sulfate and 0.2 part of potassium hydroxide were added to stop the polymerization reaction. After the reaction was stopped, the contents in the reaction vessel were heated to 70 ° C., and unreacted monomers were recovered by steam distillation under reduced pressure to obtain an aqueous dispersion of a nitrile group-containing unsaturated polymer (solid content: 24 mass). %). The obtained aqueous dispersion was dried to obtain a nitrile copolymer rubber (NBR) which is a nitrile group-containing unsaturated polymer as a binder. The iodine value of the nitrile copolymer rubber was 200. In addition, when the content rate of each monomer which comprises the obtained nitrile copolymer rubber was measured using the FTNMR apparatus (JNM-EX400WB) by JEOL Ltd., the acrylonitrile monomer unit (nitrile group is shown. Monomer unit) and 15 mass% of 1,3-butadiene monomer unit.

(Comparative Example 4)
The binder c was not used and composite particles were not formed. Then, a measurement cell was produced in the same manner as in Example 1 except that a solid electrolyte having a charge control resin attached to the surface was used. Table 1 shows the determination results of this measurement cell. The coating efficiency of the solid electrolyte was 18%. The thickness of the solid electrolyte layer in the measurement cell was 12 μm.

(Comparative Example 5)
A slurry composition was prepared without using the binder c, and the slurry composition was applied onto the negative electrode active material layer and dried (120 ° C., 20 minutes) to form a solid electrolyte layer having a thickness of 7 μm. A measurement cell was produced in the same manner as in Example 1 except that. Table 1 shows the determination results of this measurement cell. Note that no charge control resin is used.

(Comparative Example 6)
The composite particles for the solid electrolyte layer are dispersed in an organic solvent to prepare a slurry composition (solid content concentration 40%), and the slurry composition is applied on the negative electrode active material layer and dried (120 ° C., 20 minutes). A measurement cell was prepared in the same manner as in Example 1 except that a 27 μm thick solid electrolyte layer was formed. Table 1 shows the determination results of this measurement cell. In addition, the charge control resin is not used, and the process of charging the composite particles is not performed.

From Table 1, it can be seen that the all-solid secondary batteries of Examples 1 to 18 are excellent in the balance of peel strength, output characteristics, and high-temperature cycle characteristics. On the other hand, the all-solid secondary batteries of Comparative Examples 1 to 3 using the binder c having a high iodine value, the all-solid secondary batteries of Comparative Examples 4 and 5 not using the binder c, and the solid electrolyte layer The all-solid-state secondary battery of Comparative Example 6 formed by coating the slurry composition is inferior in peel strength, output characteristics, and high-temperature cycle characteristics.

Claims (9)

In the method for producing an all-solid secondary battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer,
(1) forming a positive electrode active material layer including a positive electrode active material, a binder a and a solid electrolyte on the current collector a;
(2) forming a negative electrode active material layer including a negative electrode active material, a binder b and a solid electrolyte on the current collector b; and (3) on the positive electrode active material layer and / or the negative electrode active material layer. All-solid secondary including a step of press-molding composite particles containing solid electrolyte particles and a binder c comprising a polymer having an iodine value of 0 to 30 mg / 100 mg to form a solid electrolyte layer Battery manufacturing method. The binder a contains 10 to 28% by mass of a monomer unit having a nitrile group,
The method for producing an all-solid-state secondary battery according to claim 1, comprising a polymer having an iodine value of 0 to 30 mg / 100 mg.   The manufacturing method of the all-solid-state secondary battery of Claim 1 or 2 which the said binder c consists of a polymer containing 10-28 mass% of monomer units which have a nitrile group.   The manufacturing method of the all-solid-state secondary battery in any one of Claims 1-3 in which the said process (3) has the process of charging a composite particle.   The manufacturing method of the all-solid-state secondary battery of Claim 4 with which the said composite particle contains charge control resin further.   The method for producing an all-solid-state secondary battery according to any one of claims 1 to 5, wherein the composite particles are obtained by granulating a slurry composition containing a solid electrolyte, a binder c and an organic solvent. .   The method for producing an all-solid secondary battery according to claim 1, wherein the solid electrolyte is a sulfide containing Li and P. The method for producing an all-solid-state secondary battery according to claim 1, wherein the solid electrolyte is a sulfide glass composed of Li ₂ S and P ₂ S ₅ .   The manufacturing method of the all-solid-state secondary battery in any one of Claims 1-8 in which a conductive adhesive layer is formed in the at least single side | surface of the said collector a and / or the collector b.