JP5652344B2 - All solid state secondary battery - Google Patents

Description

  The present invention relates to an all solid state secondary battery such as an all solid state lithium ion secondary battery.

  2. Description of the Related Art In recent years, secondary batteries such as lithium secondary batteries have been used in various applications such as portable power terminals such as portable information terminals and portable electronic devices, as well as small household electric power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles. Demand is increasing. 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 a solid electrolyte instead of an organic solvent electrolyte having high flammability and extremely high ignition risk at the time of leakage are effective.

For example, Patent Document 1 discloses an all-solid secondary battery using sulfide glass and / or sulfide glass ceramics made of Li ₂ S and P ₂ S ₅ as a solid electrolyte.

JP 2009-176484 A

  However, in the above-mentioned Patent Document 1, since a thermoplastic elastomer or a resin having an ethylene oxide skeleton is used as a binder for holding a solid electrolyte, the binder covers the solid electrolyte. When the all-solid-state secondary battery is obstructed in electronic conduction, the internal resistance becomes high, and there is a problem that the rate characteristics are inferior.

  An object of the present invention is to provide an all-solid-state secondary battery having a high binding property between particles in each layer constituting the battery and excellent in rate characteristics. Another object of the present invention is to provide a slurry for an all solid state secondary battery used for producing such an all solid state secondary battery.

  As a result of diligent research to achieve the above object, the present inventors have used an inorganic solid electrolyte in combination with a binder composed of a particulate polymer containing a surfactant having a polyoxyethylene chain. The inventors have found that an all-solid secondary battery having a high binding property between particles in each layer constituting the battery and excellent in rate characteristics can be obtained, and the present invention has been completed.

  That is, according to the present invention, an all-solid secondary battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer, the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer An all-solid-state secondary battery is provided, wherein at least one of them comprises a binder composed of a particulate polymer containing an inorganic solid electrolyte and a surfactant having a polyoxyethylene chain.

In the all solid state secondary battery of the present invention, preferably, the surfactant having a polyoxyethylene chain is a nonionic surfactant.
In the all solid state secondary battery of the present invention, preferably, the particulate polymer contains 0.1 to 3% by weight of a monomer unit having an acidic functional group.
In the all solid state secondary battery of the present invention, preferably, the acidic functional group is a carboxylic acid group or a sulfonic acid group.
In the all solid state secondary battery of the present invention, preferably, the inorganic solid electrolyte is a sulfide glass containing Li, P and S and / or a sulfide glass ceramic containing Li, P and S.

  Further, according to the present invention, a binder composed of an inorganic solid electrolyte and a particulate polymer containing a surfactant having a polyoxyethylene chain is dissolved or dispersed in a nonpolar solvent having a boiling point of 100 to 220 ° C. An all-solid secondary battery slurry is provided.

  According to the present invention, an all-solid secondary battery having high binding properties between particles in each layer constituting the battery and excellent in rate characteristics, and an all-solid secondary battery for producing such an all-solid secondary battery. A slurry for a solid secondary battery can be provided.

  The all solid state secondary battery of the present invention has a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer, and at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer is And a binder comprising a particulate polymer containing an inorganic solid electrolyte and a surfactant having a polyoxyethylene chain.

(Inorganic solid electrolyte)
First, the inorganic solid electrolyte used in the present invention will be described.
The inorganic solid electrolyte is not particularly limited as long as it has lithium ion conductivity, sulfide glass containing Li, P and S, sulfide glass ceramics containing Li, P and S, and Li ₃ N. , LIICON (Li ₁₄ Zn (GeO ₄ ) ₄ , perovskite-type Li _0.5 La _0.5 TiO ₃ , LIPON (Li _{3 + y} PO _4−x N _x ), Thio-LISON (Li _3.25 Ge _0.25 P Examples include crystalline inorganic lithium ion conductors such as _0.75 S ₄ ), and among these, sulfide glass containing Li, P and S and / or Li, P and S are contained. Sulfide glass ceramics are preferred.

A sulfide glass containing Li, P, and S (hereinafter, referred to as “Li-PS glass” as appropriate) is a glass containing Li ₂ S and P ₂ S ₅ , and Li ₂ S and It can be manufactured by mixing P ₂ S ₅ at a predetermined ratio. Further, a sulfide glass ceramic containing Li, P and S (hereinafter referred to as “Li-PS glass glass ceramic” as appropriate) is a glass ceramic containing Li ₂ S and P ₂ S ₅ . , Li ₂ S and P ₂ S ₅ can be produced by firing Li—PS—S-based glass obtained by mixing at a predetermined ratio at 150 to 360 ° C.

The ratio of Li ₂ S to P ₂ S ₅ in the Li—PS glass and the Li—PS glass glass ceramic is a molar ratio of Li ₂ S: P ₂ S ₅ , preferably 65:35 to 35:35. 75:25, more preferably 68:32 to 74:26. By making the ratio of Li ₂ S and P ₂ S ₅ within this range, the lithium ion conductivity can be increased. Specifically, the lithium ion conductivity can be preferably 1 × 10 ⁻⁴ S / cm or more, more preferably 1 × 10 ⁻³ S / cm or more.

The Li-PS-based glass and the Li-PS-based glass ceramic are selected from the group consisting of Al ₂ S ₃ , B ₂ S ₃ and SiS _{2 as long as} they do not cause a decrease in ionic conductivity. Or at least one lithium orthooxoate 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. Good. By including such a sulfide or lithium orthooxo acid, the glass component in the Li-PS-based glass and the Li-PS-based glass ceramic can be stabilized.

  Moreover, the average particle diameter of Li-PS-based glass and Li-PS-based glass ceramics is preferably 0.1 to 50 μm, more preferably 0.1 to 20 μm. If the average particle size is too small, the handling may be difficult. On the other hand, if the average particle size is too large, the dispersibility may be deteriorated.

(Binder)
Next, the binder used in the present invention will be described.
The binder used in the present invention is a particulate polymer containing a surfactant having a polyoxyethylene chain.

  The particulate polymer containing a surfactant having a polyoxyethylene chain used in the present invention (hereinafter, appropriately referred to as “particulate polymer”) uses, for example, a surfactant having a polyoxyethylene chain as an emulsifier. Produced by polymerizing a monomer that will form a particulate polymer by emulsion polymerization, and having a polyoxyethylene chain by using a surfactant having a polyoxyethylene chain at the time of emulsion polymerization A surfactant can be included in the particulate polymer.

  In particular, the particulate polymer used in the present invention is in a state in which the particulate state is maintained in the all-solid secondary battery, that is, on the inorganic solid electrolyte particles, on the positive electrode active material particles, and / or on the negative electrode active material particles. In this state, the inorganic solid electrolyte particles, the positive electrode active material particles and / or the negative electrode active material particles can be satisfactorily bound without hindering electron conduction and ion conduction. is there. Further, in the present invention, by adding a surfactant having a polyoxyethylene chain to the particulate polymer, the binding force as a binder is made favorable, thereby making the reliability high, Ion conductivity can be improved.

  In the present invention, the “state in which the particle state is maintained” does not have to be a state in which the particle shape is completely maintained, and may be in a state in which the particle shape is maintained to some extent. For example, inorganic solid electrolyte particles As a result of binding each other (or between the positive electrode active material particles and between the negative electrode active material particles), the particles may be crushed to some extent by these particles.

  The particulate polymer used in the present invention preferably contains at least a monomer unit having an acidic functional group. Examples of the monomer having an acidic functional group include monomers having various acidic functional groups such as a carboxylic acid group, a sulfonic acid group, and a phosphinyl group. Among these, a monomer having a carboxylic acid group A monomer having a sulfonic acid group is preferred.

  Monomers having a carboxylic acid group include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; fumaric acid, maleic acid, citraconic acid, metaconic acid, glutaconic acid, itaconic acid, tetrahydrophthalic acid, and croton. And unsaturated polyvalent carboxylic acids such as acid, isocrotonic acid, nadic acid and butenetricarboxylic acid; partially esterified products of unsaturated polyvalent carboxylic acids such as monobutyl fumarate, monoethyl maleate and monomethyl itaconate;

  Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, styrene sulfonic acid, (meth) acryl sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-hydroxy. Examples include propane sulfonic acid.

  These monomers having an acidic functional group can be used alone or in combination of two or more. Among these, methacrylic acid and sulfonic acid are preferable, and methacrylic acid is particularly preferable.

  The content ratio of the monomer unit having an acidic functional group in all the monomer units constituting the particulate polymer is preferably 0.1 to 3% by weight, more preferably 0.3 to 2.%. 5% by weight, more preferably 0.5 to 2% by weight. By setting the content ratio of the monomer unit having an acidic functional group within this range, the binding force is further improved and the reliability is increased, and the stability of the slurry is also improved.

  The particulate polymer used in the present invention may contain other monomer units copolymerizable with the monomer having an acidic functional group in addition to the monomer unit having an acidic functional group. . Other monomer units capable of copolymerization may be contained. Examples of other copolymerizable monomers include styrene; styrene derivatives such as vinyltoluene and α-methylstyrene; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, acrylic acid Acrylic acid esters such as dimethylaminoethyl; Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dimethylaminoethyl methacrylate; Amide compounds such as acrylamide and methacrylamide Olefins such as ethylene, propylene, butylene; aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; allyl methacrylate, ethylene glycol dimethacrylate, Ethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate; N, N-divinyl aniline, divinyl compounds such as divinyl ether; and the like. These other copolymerizable monomers can be used alone or in combination of two or more.

  Surfactants having polyoxyethylene chains contained in the particulate polymer, that is, surfactants having polyoxyethylene chains used as an emulsifier for emulsion polymerization include anionic surfactants and nonionic surfactants. Etc.

  Examples of the anionic surfactant include polyoxyethylene alkyl ether sulfate salt surfactants such as sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether sulfate triethanolamine; Reactive surfactants such as ammonium oxyalkylene alkenyl ether sulfate; polyoxyethylene alkyl ether phosphate ester surfactants such as potassium polyoxyethylene alkyl ether phosphate; and the like.

  Nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, polyoxyethylene myristyl ether, polyoxyethylene octyldodecyl Polyoxyethylene alkyl ether surfactants such as ether; polyoxyethylene alkylene alkyl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene tribenzylphenyl ether, polyoxyethylene polyoxypropylene glycol, and other polyoxyethylene Reactive surfactants such as alkylene derivatives and polyoxyalkylene alkenyl ethers; Polyoxyethylene sorbitol fatty acid ester surfactants such as bits; Polyoxyethylene fatty acid ester surfactants such as polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate; And polyoxyethylene hydrogenated castor oil surfactants such as oxyethylene hydrogenated castor oil; polyoxyethylene alkylamine surfactants such as polyoxyethylene alkylamine; and the like.

  Among these, from the viewpoint that the charge / discharge cycle characteristics of the obtained all-solid-state secondary battery can be improved, nonionic surfactants are preferred, and polyoxyethylene alkyl ether surfactants are more preferred. preferable. Of the polyoxyethylene alkyl ether surfactants, those having an HLB value of 8 to 16 are preferred. Alternatively, among the polyoxyethylene alkyl ether surfactants, those having 10 to 18 carbon atoms in the alkyl group are preferable, and those having 12 to 16 carbon atoms are more preferable.

  In addition, the amount of the surfactant having a polyoxyethylene chain as an emulsifier in the emulsion polymerization of the monomer that forms the particulate polymer is preferably based on 100 parts by weight of the total monomers. Is 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight, still more preferably 1 to 5 parts by weight. By setting the blending amount of the surfactant having a polyoxyethylene chain in the above range, the ion conductivity can be improved while the binding force of the particulate polymer is improved. The content of the surfactant having a polyoxyethylene chain in the particulate polymer is preferably 0.1 to 10% by weight, more preferably 0.5 to 8% by weight, and still more preferably in the particulate polymer. 1 to 5% by weight.

  Moreover, the average particle diameter of the particulate polymer used in the present invention is preferably 30 to 300 nm, more preferably 50 to 250 m, still more preferably 70 to 200 nm. By setting the average particle size of the particulate polymer within this range, the slurry can be more stable and the internal resistance can be further reduced. The average particle diameter of the particulate polymer can be controlled, for example, by adjusting the amount of emulsifier used when producing the particulate polymer by emulsion polymerization. Moreover, the average particle diameter of a particulate polymer can be measured, for example using a laser diffraction type particle size distribution measuring apparatus.

  The particulate polymer used in the present invention can be produced by an emulsion polymerization method using the above-described monomer using water as a dispersion medium and the above-described surfactant having a polyoxyethylene chain as an emulsifier.

  In the present invention, the aqueous dispersion of the particulate polymer obtained by emulsion polymerization using water as a dispersion medium is subjected to solvent substitution with a nonpolar solvent having a boiling point of 100 to 220 ° C., and the boiling point is 100 to A nonpolar solvent solution or dispersion at 220 ° C. is preferred. By performing solvent substitution with a nonpolar solvent having a boiling point of 100 to 220 ° C., it is possible to efficiently remove moisture by heating and drying in the production process. The amount of moisture can be reduced. In addition, as a nonpolar solvent used for solvent substitution, a thing with a boiling point of 100-220 degreeC is desirable, Preferably it is 120-210 degreeC, More preferably, it is 140-200 degreeC. If a nonpolar solvent having a boiling point too low is used, it may be difficult to remove moisture in the production process. On the other hand, if a nonpolar solvent having a boiling point too high is used, it may take too much time for drying in the production process. There is.

The nonpolar solvent used for solvent replacement preferably has an SP value (solubility parameter) of 14 to 20 MPa ^1/2 , more preferably 15 to 19 MPa ^1/2 , and even more preferably 16 to 18 MPa ^1/2 . is there. By using a nonpolar solvent having an SP value in the above range, the dispersibility of the polymer particles can be improved.

  Specific examples of the nonpolar solvent used for such solvent substitution include n-octane (boiling point 125 ° C., SP value 15.6), isooctane (boiling point 117 ° C., SP value 14.1), toluene (boiling point 111 ° C., SP value 18.2), o-xylene (boiling point 144 ° C., SP value 18.5), m-xylene (boiling point 139 ° C., SP value 18.0), p-xylene (boiling point 138 ° C., SP value 18.0) ), Styrene (boiling point 145 ° C., SP value 19.0), ethylbenzene (boiling point 136 ° C., SP value 18.0), decalin (boiling point 185 ° C., SP value 18.0), and the like.

(Solid electrolyte layer)
The solid electrolyte layer constituting the all solid state secondary battery of the present invention contains a solid electrolyte. In the present invention, the solid electrolyte layer preferably contains the inorganic solid electrolyte described above and the particulate polymer as the binder described above. The binding property of the electrolyte particles can be increased, and the obtained all-solid-state secondary battery can be excellent in rate characteristics.

  The content of the particulate polymer in the solid electrolyte layer is preferably 0.05 to 8 parts by weight, more preferably 0.1 to 6 parts by weight, further preferably 100 parts by weight of the inorganic solid electrolyte. 0.2 to 4 parts by weight. By setting the content of the particulate polymer in the above range, the binding force in the solid electrolyte layer can be made sufficient while keeping the internal resistance of the obtained all-solid-state secondary battery low.

  Examples of the method for forming the solid electrolyte layer include a method in which a solid electrolyte layer slurry containing an inorganic solid electrolyte, a particulate polymer, and an organic solvent is prepared, the prepared solid electrolyte layer slurry is applied to a substrate, and dried. .

  As the particulate polymer, as described above, it is preferable to use a solution or dispersion dissolved or dispersed in a nonpolar solvent having a boiling point of 100 to 220 ° C. In this case, it is contained in the solid electrolyte layer slurry. As the organic solvent to be used, it is preferable to use a nonpolar solvent having a boiling point of 100 to 220 ° C. That is, the solid electrolyte layer slurry preferably contains an inorganic solid electrolyte, a particulate polymer, and a nonpolar solvent having a boiling point of 100 to 220 ° C.

  The method for mixing the above-described components in preparing the solid electrolyte layer slurry is not particularly limited, but for example, dispersion kneading such as a homogenizer, ball mill, bead mill, planetary mixer, sand mill, roll mill, and planetary kneader The method using an apparatus is mentioned, The method using a planetary mixer, a ball mill, or a bead mill from a viewpoint that aggregation of an inorganic solid electrolyte can be suppressed is preferable.

  The content of the nonpolar solvent having a boiling point of 100 to 220 ° C. in the solid electrolyte layer slurry is preferably 5 to 70 parts by weight, more preferably 10 to 60 parts by weight with respect to 100 parts by weight of the inorganic solid electrolyte. More preferably, it is 20-50 weight part. If the content of the nonpolar solvent is too small, it may be difficult to form a film with a desired film thickness. On the other hand, if the content is too large, it may take time to remove the solvent.

  In addition to the above components, the solid electrolyte layer slurry may further contain other components such as a dispersant, a leveling agent, and an antifoaming agent. These are not particularly limited as long as they do not affect the battery reaction.

  Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound. The content of the dispersing agent in the solid electrolyte layer slurry is preferably within a range that does not affect the battery characteristics. Specifically, it is preferably 10 parts by weight or less with respect to 100 parts by weight of the inorganic solid electrolyte.

  Examples of the leveling agent include surfactants such as alkyl surfactants, silicone surfactants, fluorine surfactants, and metal surfactants. By containing the leveling agent, repelling that occurs when the solid electrolyte layer slurry is applied to the surface of the positive electrode active material layer or the negative electrode active material layer can be prevented. The content of the leveling agent in the solid electrolyte layer slurry is preferably in a range that does not affect the battery characteristics. Specifically, it is preferably 10 parts by weight or less with respect to 100 parts by weight of the inorganic solid electrolyte.

  Examples of antifoaming agents include mineral oil antifoaming agents, silicone antifoaming agents, and polymer antifoaming agents. The content of the leveling agent in the solid electrolyte layer slurry is preferably in a range that does not affect the battery characteristics. Specifically, it is preferably 10 parts by weight or less with respect to 100 parts by weight of the inorganic solid electrolyte.

(Positive electrode active material layer)
The positive electrode active material layer constituting the all solid state secondary battery of the present invention contains a positive electrode active material. In the present invention, the positive electrode active material layer preferably contains the inorganic solid electrolyte described above and the particulate polymer as the binder described above in addition to the positive electrode active material. By doing so, the binding property of the inorganic solid electrolyte particles and the positive electrode active material particles can be increased, and the obtained all-solid-state secondary battery can be excellent in rate characteristics.

  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. Examples of the transition metal include Fe, Co, Ni, Mn, and the like. Specific examples of the positive electrode active material made of an inorganic compound include lithium-containing composite metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO ₄ ; TiS ₂ , TiS ₃ , amorphous transition metal sulfides such as _{MoS2; Cu 2 V 2 O 3} , transition metal oxides such as amorphous _{V 2 O-P 2 O 5} , MoO 3, V 2 O5, V 6 O 13; and the like. 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. Moreover, as a positive electrode active material, the mixture of the inorganic compound mentioned above and an organic compound may be sufficient.

  The average particle diameter of the positive electrode active material is preferably 0.1 to 50 μm, more preferably 1 to 20 μm, from the viewpoint of improving battery characteristics such as rate characteristics and charge / discharge cycle characteristics. When the average particle size is in the above range, the charge / discharge capacity of the obtained all-solid-state secondary battery can be increased, and handling at the time of producing the positive electrode active material layer becomes easy. The average particle size of the positive electrode active material can be obtained by measuring the particle size distribution by laser diffraction.

  The content of the inorganic solid electrolyte in the positive electrode active material layer is preferably 5 to 95 parts by weight, more preferably 10 to 90 parts by weight, and further preferably 20 to 80 parts by weight with respect to 100 parts by weight of the positive electrode active material. Part. By setting the content of the inorganic solid electrolyte in the above range, the ionic conductivity in the positive electrode active material layer can be made sufficient, and thereby the capacity of the obtained all-solid-state secondary battery is sufficiently high. It can be.

  The content of the particulate polymer in the positive electrode active material layer is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts by weight with respect to a total of 100 parts by weight of the positive electrode active material and the inorganic solid electrolyte. Part by weight, more preferably 1 to 5 parts by weight. By setting the content of the particulate polymer in the above range, the binding force in the positive electrode active material layer can be made sufficient while keeping the internal resistance of the obtained all-solid-state secondary battery low.

  In addition to the above components, the positive electrode active material layer further includes other components such as a conductivity imparting material, a reinforcing material, a dispersant, a leveling agent, an antioxidant, a thickener, and an electrolyte decomposition inhibitor. It may be.

  Examples of the conductivity imparting material include conductive carbon such as acetylene black, ketjen black, carbon black, and graphite, and fibers and foils of various metals. By including a conductivity-imparting material in the positive electrode active material layer, the rate characteristics of the obtained all-solid-state secondary battery can be improved. The content of the conductivity imparting material in the positive electrode active material layer is preferably 0.01 to 20 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode active material.

  As a method for forming a positive electrode active material layer, a positive electrode active material layer slurry containing a positive electrode active material, an inorganic solid electrolyte, a particulate polymer, an organic solvent, and other components such as a conductivity-imparting material added as necessary And a method of applying the prepared positive electrode active material layer slurry on a current collector and drying it.

  As the particulate polymer, as described above, it is preferable to use a solution or dispersion dissolved or dispersed in a nonpolar solvent having a boiling point of 100 to 220 ° C. In this case, in the positive electrode active material layer slurry, As the organic solvent to be contained, it is preferable to use a nonpolar solvent having a boiling point of 100 to 220 ° C. as described above. That is, the positive electrode active material layer slurry is added to other materials such as a positive electrode active material, an inorganic solid electrolyte, a particulate polymer, a nonpolar solvent having a boiling point of 100 to 220 ° C., and a conductivity-imparting material added as necessary. It is preferable to contain a component.

  In preparing the positive electrode active material layer slurry, a method for mixing the above-described components is not particularly limited. For example, dispersion such as a homogenizer, ball mill, bead mill, planetary mixer, sand mill, roll mill, and planetary kneader A method using a kneading apparatus can be mentioned, and a method using a planetary mixer, a ball mill or a bead mill is preferable from the viewpoint that aggregation of the positive electrode active material layer and the inorganic solid electrolyte can be suppressed.

  The content of the nonpolar solvent having a boiling point of 100 to 220 ° C. in the positive electrode active material layer slurry is preferably 5 to 70 parts by weight, more preferably 100 parts by weight of the positive electrode active material layer and the inorganic solid electrolyte. It is 10-60 weight part, More preferably, it is 20-50 weight part. If the content of the nonpolar solvent is too small, it may be difficult to form a film with a desired film thickness. On the other hand, if the content is too large, it may take time to remove the solvent.

  In addition to the above components, the positive electrode active material layer slurry may contain other components such as a dispersant, a leveling agent, and an antifoaming agent in the same manner as the above-described solid electrolyte layer slurry. These are not particularly limited as long as they do not affect the battery reaction.

(Negative electrode active material layer)
The negative electrode active material layer constituting the all solid state secondary battery of the present invention contains a negative electrode active material. In the present invention, the negative electrode active material layer preferably contains the above-described inorganic solid electrolyte and the above-described particulate polymer as a binder in addition to the negative electrode active material. By doing so, the binding property of the inorganic solid electrolyte particles and the negative electrode active material particles can be increased, and the obtained all solid secondary battery can be excellent in rate characteristics.

  The negative electrode active material is a carbonaceous material such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads, pitch-based carbon fiber; conductive polymer such as polyacene; metal such as silicon, tin, zinc, manganese, iron, nickel Or alloys thereof; oxides or sulfates of the above metals or alloys; metallic lithium; lithium alloys such as Li—Al, Li—Bi—Cd, Li—Sn—Cd; lithium transition metal nitrides; silicon; be able to. In the present invention, a negative electrode active material having a conductivity imparting material attached to the surface by a mechanical modification method can also be used.

  The average particle diameter of the negative electrode active material is preferably 1 to 50 μm, more preferably 15 to 30 μm, from the viewpoint of improving battery characteristics such as initial charge / discharge efficiency, rate characteristics, and charge / discharge cycle characteristics. When the average particle size is in the above range, the charge / discharge capacity of the obtained all-solid-state secondary battery can be increased, and handling in producing the negative electrode active material layer is facilitated. The average particle size of the negative electrode active material can be determined by measuring the particle size distribution by laser diffraction.

  The content of the inorganic solid electrolyte in the negative electrode active material layer is preferably 5 to 95 parts by weight, more preferably 10 to 90 parts by weight, and still more preferably 20 to 80 parts by weight with respect to 100 parts by weight of the negative electrode active material. Part. By setting the content of the inorganic solid electrolyte in the above range, the ionic conductivity in the negative electrode active material layer can be made sufficient, and thereby the capacity of the obtained all-solid-state secondary battery is sufficiently high. It can be.

  The content of the particulate polymer in the negative electrode active material layer is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 8 parts with respect to 100 parts by weight in total of the negative electrode active material and the inorganic solid electrolyte. Part by weight, more preferably 1 to 5 parts by weight. By setting the content of the particulate polymer in the above range, the binding force in the negative electrode active material layer can be made sufficient while keeping the internal resistance of the obtained all-solid-state secondary battery low.

  In addition to the above-mentioned components, the negative electrode active material layer is further provided with a conductivity imparting material, a reinforcing material, a dispersant, a leveling agent, an antioxidant, a thickener, and an electrolytic solution decomposition inhibitor. Other components such as may be included.

  As a method for forming the negative electrode active material layer, a negative electrode active material layer slurry containing a negative electrode active material, an inorganic solid electrolyte, a particulate polymer, an organic solvent, and other components such as a conductivity imparting agent added as necessary And a method of applying the prepared negative electrode active material layer slurry onto a negative electrode current collector and drying it.

  As the particulate polymer, as described above, it is preferable to use a solution or dispersion dissolved or dispersed in a nonpolar solvent having a boiling point of 100 to 220 ° C. In this case, in the negative electrode active material layer slurry, As the organic solvent to be contained, it is preferable to use a nonpolar solvent having a boiling point of 100 to 220 ° C. as described above. That is, the negative electrode active material layer slurry is added to other materials such as a negative electrode active material, an inorganic solid electrolyte, a particulate polymer, a nonpolar solvent having a boiling point of 100 to 220 ° C., and a conductivity-imparting material added as necessary. It is preferable to contain a component.

  In preparing the negative electrode active material layer slurry, the method of mixing the above-described components is not particularly limited. For example, dispersion such as a homogenizer, a ball mill, a bead mill, a planetary mixer, a sand mill, a roll mill, and a planetary kneader A method using a kneading apparatus can be mentioned, and a method using a planetary mixer, a ball mill or a bead mill is preferable from the viewpoint that aggregation of the negative electrode active material layer and the inorganic solid electrolyte can be suppressed.

  The content of the nonpolar solvent having a boiling point of 100 to 220 ° C. in the negative electrode active material layer slurry is preferably 5 to 70 parts by weight, more preferably 100 parts by weight of the negative electrode active material layer and the inorganic solid electrolyte. It is 10-60 weight part, More preferably, it is 20-50 weight part. If the content of the nonpolar solvent is too small, it may be difficult to form a film with a desired film thickness. On the other hand, if the content is too large, it may take time to remove the solvent.

  In addition to the above components, the negative electrode active material layer slurry may contain other components such as a dispersant, a leveling agent, and an antifoaming agent in the same manner as the above-described solid electrolyte layer slurry. These are not particularly limited as long as they do not affect the battery reaction.

(All-solid secondary battery)
The all solid state secondary battery of the present invention has the above-described positive electrode active material layer, negative electrode active material layer, and solid electrolyte layer.

  In the all solid state secondary battery of the present invention, the thickness of the solid electrolyte layer is preferably 1 to 15 μm, more preferably 2 to 13 μm, and further preferably 3 to 10 μm. By setting the thickness of the solid electrolyte layer within the above range, the internal resistance of the all-solid-state secondary battery can be kept low while preventing the occurrence of a short circuit.

  The all-solid-state secondary battery of the present invention forms the positive electrode active material layer and the negative electrode active material layer by separately applying the positive electrode active material layer slurry and the negative electrode active material layer slurry on the current collector and drying them. And applying the solid electrolyte layer slurry to the surface of one of the obtained positive electrode active material layer and negative electrode active material layer and drying to form the solid electrolyte layer, and the active material layer having the solid electrolyte layer formed thereon, In addition, the active material layer in which the solid electrolyte layer is not formed can be manufactured by pasting together through the solid electrolyte layer.

  The method of applying the positive electrode active material layer slurry and the negative electrode active material layer slurry onto 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 It is applied by the method or brushing. The coating amount of the positive electrode active material layer slurry and the negative electrode active material layer slurry is not particularly limited, but the thickness of the positive electrode active material layer and the negative electrode active material layer formed after removing the solvent is preferably 5 to 300 μm. More preferably, the amount is about 10 to 250 μm. Although it does not specifically limit as a drying method, For example, drying by warm air, a hot air, low-humidity air, vacuum drying, irradiation by irradiation of (far) infrared rays, an electron beam, etc. is mentioned. The drying temperature is preferably 50 to 250 ° C, more preferably 80 to 200 ° C, and the drying time is preferably in the range of 10 to 60 minutes. Furthermore, you may press the positive electrode active material layer and negative electrode active material layer after drying by methods, such as a metal mold press and a calendar press.

  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 steel, titanium, tantalum, gold, and platinum are preferable. In particular, aluminum is suitably used for the positive electrode and copper is suitably used for the negative electrode. 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. In order to increase the adhesive strength between the positive electrode active material layer and the negative electrode active material layer, the current collector is preferably used after roughening in advance. 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.

  In addition, when the active material layer in which the solid electrolyte layer is formed and the active material layer in which the solid electrolyte layer is not formed are bonded through the solid electrolyte layer, the laminate obtained by bonding them is pressurized. May be. 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 at the time of pressing is preferably 5 to 700 MPa, more preferably 7 to 500 MPa. By setting the pressure of the pressure press in the above range, the resistance at each interface between the positive electrode active material layer and the negative electrode active material layer and the solid electrolyte layer, and further, the contact resistance between the particles in each layer can be reduced. Thereby, the battery characteristics can be improved.

  In addition, when apply | coating a solid electrolyte layer slurry to either one surface of a positive electrode active material layer and a negative electrode active material layer, you may apply to any of a positive electrode active material layer and a negative electrode active material layer, but use. It is preferable to apply the solid electrolyte layer slurry to the active material layer having the larger active material particle size. When the particle diameter of the active material is large, irregularities are formed on the surface of the active material layer. Therefore, the irregularities on the surface of the active material layer can be reduced by applying the slurry composition. Therefore, when the active material layer formed with the solid electrolyte layer and the active material layer not formed with the solid electrolyte layer are laminated and laminated, the contact area between the solid electrolyte layer and the active material layer is increased, and the interface resistance is increased. Can be suppressed.

  Moreover, the all-solid-state secondary battery of this invention is good also as a state sealed by putting in a battery container by winding, folding, etc. according to a desired battery shape. Moreover, the all-solid-state secondary battery of this invention may attach an expanded metal, an overcurrent prevention element, such as a fuse and a PTC element, a lead board, etc. as needed. 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.

  In the all solid state secondary battery of the present invention, the water content in the all solid state secondary battery is preferably 300 ppm or less, more preferably 200 ppm or less, and still more preferably 100 ppm or less. If the amount of water is too high, the inorganic solid electrolyte reacts due to the action of water, and the battery characteristics may deteriorate. In the present invention, as a solvent for the positive electrode active material layer slurry, the negative electrode active material layer slurry, and the solid electrolyte layer slurry, which is used for manufacturing an all solid state secondary battery, a nonpolarity having a boiling point of 100 to 220 ° C. By using the solvent, water can be appropriately removed in the production process, and thereby the amount of water contained in the all-solid secondary battery can be reduced.

  Moreover, the all-solid-state secondary battery of this invention contains the particulate polymer containing the surfactant which has the polyoxyethylene chain mentioned above as a binder, and has such a polyoxyethylene chain. The particulate polymer containing the surfactant is present in a state in which the particle state is maintained in the all solid secondary battery (in the positive electrode active material layer, in the negative electrode active material layer, or in the solid electrolyte layer). And, by maintaining the particle state, the components constituting the all-solid-state secondary battery are well bound without hindering ion conduction and electron conduction in the all-solid-state secondary battery. is there.

  The all-solid-state secondary battery of the present invention thus obtained has high binding properties of active material particles and inorganic solid electrolyte particles in each layer, thereby having excellent reliability and excellent rate characteristics. It is a thing. Therefore, it can be suitably used for various applications such as portable terminals such as portable information terminals and portable electronic devices, small household electric power storage devices, motorcycles, electric vehicles, and hybrid electric vehicles.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Parts and% in each example are based on weight unless otherwise specified.
In addition, the definition and evaluation method of each characteristic are as follows.

<Peel strength>
The solid electrolyte layer slurry was applied onto the aluminum foil by a doctor blade method and dried at 120 ° C. for 20 minutes to form a solid electrolyte layer. The obtained solid electrolyte layer and stainless steel foil were cut out to a width of 10 mm, and this was attached to a glass plate to which a double-sided tape had been previously attached to obtain a test piece (glass plate / double-sided tape / solid electrolyte layer / stainless foil). And the peel strength of this test piece was measured using a peel strength measuring machine according to JIS K6894. In addition, when the state after peeling was confirmed in this example and the comparative example, it was confirmed that peeling due to cohesive failure occurred in the solid electrolyte layer in all evaluations. Therefore, it can be evaluated that the higher the peel strength in this evaluation, the stronger the binding between the solid electrolyte materials in the solid electrolyte layer, that is, the higher the binding force of the binder.
A: Peel strength is 40 N / m or more B: Peel strength is 30 N / m or more and less than 40 N / m C: Peel strength is 20 N / m or more and less than 30 N / m D: Peel strength is 10 N / m or more, 20 N / m Less than E: Peel strength is less than 10 N / m

<Rate characteristics>
About the secondary battery obtained in each Example and Comparative Example, after charging to 4.2 V by a constant current method with a charging rate of 0.1 C, discharging to 3.0 V at a discharging rate of 0.1 C Thus, the battery capacity at the time of 0.1 C discharge was obtained. Next, the battery was charged to 4.2 V by a constant current method with a charging rate of 0.1 C, and then discharged to 3.0 V at a discharging rate of 5 C to obtain the battery capacity at the time of 5 C discharging. Then, the same measurement is performed on 10 cells, and the average value of the battery capacity at the time of 0.1 C discharge and at the time of 5 C discharge is obtained for 10 cells, and the average battery capacity at the time of 0.1 C discharge Cap _{0.1 C} And 5C discharge capacity retention ratio, which is a ratio ((Cap _5C / Cap _0.1C ) × 100%) to the average battery capacity Cap _5C during 5C discharge. Based on the obtained 5C discharge capacity retention rate, the rate characteristics were evaluated according to the following criteria. In addition, since it is judged that the capacity maintenance rate at the time of 5C discharge is high, the discharge capacity at the time of high rate (5C) discharge is high and it can be judged that it is excellent in a rate characteristic, It is preferable.
A: Capacity maintenance ratio during 5C discharge is 70% or more B: Capacity maintenance ratio during 5C discharge is 60% or more and less than 70% C: Capacity maintenance ratio during 5C discharge is 40% or more and less than 60% D: Capacity during 5C discharge Maintenance rate is 20% or more and less than 40% E: Capacity maintenance rate during 5C discharge is less than 20%

Example 1
Production of polymer particles A In a pressure-resistant autoclave of 50 kgf / cm ² with a stirrer, 700 parts of n-butyl acrylate, 200 parts of styrene, 5 parts of methacrylic acid, 10 parts of divinylbenzene, polyoxyethylene lauryl ether as an emulsifier (manufactured by Kao Corporation) Emulgen 108, nonionic surfactant, alkyl group 12 carbon atoms, HLB value 12.1) 25 parts, ion exchange water 1500 parts, azobisbutyronitrile 15 parts as a polymerization initiator, charged sufficiently Then, the polymerization was carried out by heating to 80 ° C. Then, after the start of polymerization, when the consumption of the monomer reached 99.8%, the polymerization reaction was stopped by cooling to obtain a latex of polymer particles A. The latex concentration of the obtained polymer particle A latex was 38%. Further, the particle size of the polymer particle A was 120 nm.

  Next, 12,000 parts of decalin was added to the latex of polymer particles A obtained above, and after sufficiently dispersing, water was removed by drying under reduced pressure to obtain a decalin dispersion of polymer particles A. The resulting dispersion had a solid content of 7%. The water content of the obtained polymer dispersion was measured and found to be 72 ppm.

Preparation of positive electrode active material layer slurry In a stirring tank, a sulfide comprising 100 parts of lithium cobaltate (average particle size: 11.5 μm) as a positive electrode active material and Li ₂ S and P ₂ S ₅ as inorganic solid electrolyte particles 150 parts of glass (Li ₂ S / P ₂ S ₅ = 70 mol% / 30 mol%, average particle diameter: 5 μm), 13 parts of acetylene black as a conductive agent, polymer particles A as a binder obtained above Add 71.4 parts of decalin dispersion (5 parts in terms of solid content), add decalin so that the solid content concentration becomes 78%, and mix for 60 minutes with a planetary mixer. Decalin was further added so that it might become 74%, and it mixed for 10 minutes, and obtained the positive electrode active material layer slurry.

Preparation of negative electrode active material layer slurry In a stirring tank, sulfide glass (Li ₂ ) comprising 100 parts of graphite (average particle size: 20 μm) as a negative electrode active material and Li ₂ S and P ₂ S ₅ as solid electrolyte particles. 50 parts of S / P ₂ S ₅ = 70 mol% / 30 mol%, average particle size: 5 μm) and 42.8 parts of decalin dispersion of polymer particles A as the binder obtained above (in terms of solid content) 3 parts) was added, decalin was added so that the solid content concentration was 60%, and the mixture was mixed for 60 minutes with a planetary mixer to obtain a negative electrode active material layer slurry.

Preparation of solid electrolyte layer slurry In a stirring tank, sulfide glass composed of Li ₂ S and P ₂ S ₅ as solid electrolyte particles (Li ₂ S / P ₂ S ₅ = 70 mol% / 30 mol%, average particle diameter: 5 μm) ) 100 parts and 14.3 parts decalin dispersion (1 part in terms of solid content) of polymer particles A as the binder obtained above are added, so that the solid content concentration is 30%. Decalin was added to and mixed with a planetary mixer for 60 minutes to obtain a solid electrolyte layer slurry. And the peel strength of the solid electrolyte layer was measured according to the said method using the obtained solid electrolyte layer slurry. The results are shown in Table 1.

Production of all-solid-state secondary battery The positive electrode active material layer slurry obtained above was applied to the surface of the aluminum current collector, dried at 120 ° C. for 20 minutes, and a positive electrode having a positive electrode active material layer having a thickness of 50 μm was obtained. Obtained. Separately, the negative electrode active material layer slurry obtained above was applied to the surface of the copper current collector, dried at 120 ° C. for 20 minutes, and a negative electrode having a negative electrode active material layer having a thickness of 30 μm was obtained. Obtained.

  Next, the solid electrolyte layer slurry obtained above is applied to the surface of the positive electrode active material layer of the positive electrode obtained above, and dried at 120 ° C. for 20 minutes to obtain a solid electrolyte layer having a thickness of 11 μm. It was. Then, the solid electrolyte layer formed on the surface of the positive electrode active material layer and the negative electrode active material layer of the negative electrode obtained above were bonded together and pressed at 10 MPa to obtain an all-solid secondary battery. In addition, the thickness of the solid electrolyte layer of the all-solid-state secondary battery after pressing was 9 μm. Then, using the obtained all solid state secondary battery, the rate characteristics were evaluated according to the method described above. The results are shown in Table 1.

(Example 2)
As an emulsifier, 25 parts of polyoxyethylene cetyl ether (manufactured by Kao Corporation, Emulgen 210P, nonionic surfactant, carbon number of alkyl group, HLB value 10.7) was used instead of polyoxyethylene lauryl ether. Except for the above, a decalin dispersion of polymer particles B was obtained in the same manner as in Example 1. The average particle diameter of the obtained polymer particles B was 130 nm. Each slurry was prepared in the same manner as in Example 1 except that the resulting polymer particle B decalin dispersion was used as the binder, and an all-solid secondary battery was produced. Evaluation was performed in the same manner as above. The results are shown in Table 1.

Example 3
As an emulsifier, 25 parts of polyoxyethylene stearyl ether (manufactured by Kao Corporation, Emulgen 320P, nonionic surfactant, carbon number of alkyl group 18, HLB value 13.9) was used instead of polyoxyethylene lauryl ether. Except for the above, a decalin dispersion of polymer particles C was obtained in the same manner as in Example 1. The average particle diameter of the obtained polymer particles C was 150 nm. Then, each slurry was prepared in the same manner as in Example 1 except that the obtained polymer particle C decalin dispersion was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 1.

Example 4
As in Example 1, instead of polyoxyethylene lauryl ether, 25 parts of polyoxyethylene lauryl ether sodium sulfate (manufactured by Kao Corporation, Emar E-27C, anionic surfactant) was used. A decalin dispersion of polymer particles D was obtained. The average particle diameter of the obtained polymer particles D was 100 nm. Then, each slurry was prepared in the same manner as in Example 1 except that the resulting polymer particle D decalin dispersion was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 1.

(Example 5)
As in Example 1, instead of polyoxyethylene lauryl ether, 25 parts of polyoxyethylene alkyl ether sulfate triethanolamine (Kao Co., Ltd., EMAL 20T, anionic surfactant) was used. A decalin dispersion of polymer particles E was obtained. The average particle diameter of the obtained polymer particles E was 130 nm. And each slurry was prepared like Example 1 except having used the decalin dispersion liquid of the obtained polymer particle E as a binder, and an all-solid-state secondary battery was manufactured, Example 1 Evaluation was performed in the same manner as above. The results are shown in Table 1.

(Example 6)
The same procedure as in Example 1 was conducted except that 25 parts of polyoxyethylene alkyl ether potassium phosphate (manufactured by Kao Corporation, electrostripper F, anionic surfactant) was used as an emulsifier instead of polyoxyethylene lauryl ether. A decalin dispersion of polymer particles F was obtained. The average particle diameter of the obtained polymer particles F was 140 nm. Then, each slurry was prepared in the same manner as in Example 1 except that the obtained polymer particle F decalin dispersion was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 1.

(Example 7)
A decalin dispersion of polymer particles G was obtained in the same manner as in Example 1 except that the amount of polyoxyethylene lauryl ether as an emulsifier was changed from 25 parts to 2 parts. The average particle diameter of the obtained polymer particles G was 120 nm. Then, each slurry was prepared in the same manner as in Example 1 except that the obtained polymer particle G decalin dispersion was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 1.

(Example 8)
A decalin dispersion of polymer particles H was obtained in the same manner as in Example 1 except that the amount of polyoxyethylene lauryl ether as an emulsifier was changed from 25 parts to 6 parts. The average particle diameter of the obtained polymer particles H was 120 nm. Then, each slurry was prepared in the same manner as in Example 1 except that the obtained polymer particle H decalin dispersion was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 1.

Example 9
A decalin dispersion of polymer particles I was obtained in the same manner as in Example 1 except that the amount of polyoxyethylene lauryl ether as an emulsifier was changed from 25 parts to 43 parts. The average particle diameter of the obtained polymer particles I was 120 nm. Each slurry was prepared in the same manner as in Example 1 except that the obtained polymer particle I decalin dispersion was used as a binder, and an all-solid secondary battery was produced. Evaluation was performed in the same manner as above. The results are shown in Table 1.

(Example 10)
When preparing the positive electrode active material layer slurry, the blending amount of the decalin dispersion of polymer particles A is changed from 71.4 parts (5 parts in terms of solids) to 25 parts (1.75 parts in terms of solids). Except for the changes, each slurry was prepared in the same manner as in Example 1 to produce an all-solid secondary battery, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 11)
When preparing the positive electrode active material layer slurry, the blending amount of the decalin dispersion of polymer particles A is changed from 71.4 parts (5 parts in terms of solid content) to 142.8 parts (10 parts in terms of solid content). Except for the changes, each slurry was prepared in the same manner as in Example 1 to produce an all-solid secondary battery, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 12)
A decalin dispersion of polymer particles J was obtained in the same manner as in Example 1 except that methacrylic acid as a monomer having an acidic functional group was not used. The average particle diameter of the obtained polymer particles J was 130 nm. Each slurry was prepared in the same manner as in Example 1 except that the obtained polymer particle J decalin dispersion was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 2.

(Example 13)
A decalin dispersion of polymer particles K was obtained in the same manner as in Example 1 except that 5 parts of acrylamide-2-methylpropanesulfonic acid was used in place of methacrylic acid as the monomer having an acidic functional group. . The average particle diameter of the obtained polymer particles K was 130 nm. Then, each slurry was prepared in the same manner as in Example 1 except that the obtained polymer particle K decalin dispersion was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 2.

(Example 14)
A xylene dispersion of polymer particles A was obtained in the same manner as in Example 1 except that 12,000 parts of xylene was used instead of 12,000 parts of decalin as the solvent used for solvent substitution of the latex of polymer particles A. It was. Each slurry was prepared in the same manner as in Example 1 except that the xylene dispersion of the obtained polymer particles A was used as a binder, and an all-solid secondary battery was produced. Evaluation was performed in the same manner as above. The results are shown in Table 2.

(Example 15)
A toluene dispersion of polymer particles A is obtained in the same manner as in Example 1 except that 12,000 parts of toluene is used instead of 12,000 parts of decalin as a solvent used for solvent substitution of the latex of polymer particles A. It was. Then, each slurry was prepared in the same manner as in Example 1 except that the obtained toluene dispersion of polymer particles A was used as a binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 2.

(Comparative Example 1)
A 50 kgf / cm ² pressure-resistant autoclave with a stirrer was charged with 300 parts of ethyl acrylate, 300 parts of n-butyl acrylate, 100 parts of acrylonitrile, 5,000 parts of decalin, and 15 parts of benzoyl peroxide as an initiator at 80 ° C. The decalin solution of the ethyl acrylate-n-butyl acrylate-acrylonitrile copolymer L was obtained by hold | maintaining for 5 hours and performing solution polymerization. In addition, the obtained ethyl acrylate-n-butyl acrylate-acrylonitrile copolymer L was dissolved in decalin and did not have a particle shape. Next, decalin was added to the resulting solution to prepare a solid concentration of 7%, and moisture was removed by drying under reduced pressure.

  Each slurry was obtained in the same manner as in Example 1 except that the decalin solution of ethyl acrylate-n-butyl acrylate-acrylonitrile copolymer L after dehydration obtained above was used as the binder. Was prepared, and an all-solid secondary battery was produced and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 2)
Example, except that 25 parts of sodium dodecylbenzenesulfonate (manufactured by Kao Corporation, Neoperex GS, anionic surfactant having no polyoxyethylene chain) was used as an emulsifier instead of polyoxyethylene lauryl ether In the same manner as in No. 1, a decalin dispersion of polymer particles M was obtained. The average particle diameter of the obtained polymer particles M was 130 nm. Then, each slurry was prepared in the same manner as in Example 1 except that the decalin dispersion of the obtained polymer particles M was used as the binder, and an all-solid secondary battery was manufactured. Evaluation was performed in the same manner as above. The results are shown in Table 2.

(Comparative Example 3)
A decalin dispersion of polymer particles N was obtained in the same manner as in Example 1, except that 25 parts of polyvinyl alcohol was used as an emulsifier instead of polyoxyethylene lauryl ether. The average particle diameter of the obtained polymer particles N was 140 nm. Each slurry was prepared in the same manner as in Example 1 except that the resulting polymer particle N decalin dispersion was used as the binder, and an all-solid secondary battery was produced. Evaluation was performed in the same manner as above. The results are shown in Table 2.

(Comparative Example 4)
When polymerization was carried out in the same manner as in Example 1 except that 25 parts of polyethylene glycol was used instead of polyoxyethylene lauryl ether as an emulsifier, a polymer could not be obtained. Therefore, in Comparative Example 4, each slurry and all-solid secondary battery could not be obtained.

(Comparative Example 5)
In a pressure-resistant autoclave with a stirrer and 50 kgf / cm ² , 300 parts of n-butyl acrylate, 40 parts of polyethylene glycol monomethacrylate (manufactured by NOF Corporation, BLEMMER PE-200), 20 parts of acrylonitrile, t-butyl par as a polymerization initiator After charging 1 part of oxy-2-ethylhexanate and 1500 parts of decalin and stirring sufficiently, the solution was heated to 90 ° C. for solution polymerization. Then, after the start of the polymerization, when the consumption of the monomer reaches 95%, the polymerization reaction is stopped by cooling, and water is removed by drying under reduced pressure, whereby n-butyl acrylate-polyethylene glycol monomethacrylate-acrylonitrile is removed. A decalin solution of copolymer O was obtained. The obtained n-butyl acrylate-polyethylene glycol monomethacrylate-acrylonitrile copolymer O obtained was dissolved in decalin and had no particle shape. Moreover, the solid content concentration of the obtained solution was 19%.

  Then, as the binder, in the same manner as in Example 1, except that the decalin solution of n-butyl acrylate-polyethylene glycol monomethacrylate-acrylonitrile copolymer O after dehydration obtained above was used. A slurry was prepared to produce an all-solid secondary battery, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 6)
Add a copolymer of ethylene oxide and propylene oxide (EO: PO = 90: 10 (molar ratio)) to decalin to a solid content concentration of 5%, and after sufficiently stirring, remove water by drying under reduced pressure. Thus, a decalin solution of a copolymer P of ethylene oxide and propylene oxide was obtained. In addition, the obtained copolymer P of ethylene oxide and propylene oxide was dissolved in decalin and did not have a particle shape.

  Then, as the binder, each slurry was prepared in the same manner as in Example 1 except that the decalin solution of the copolymer P of dehydrated ethylene oxide and propylene oxide obtained above was used. A solid secondary battery was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

表１、表２中、乳化剤の使用量は、単量体の使用量に対する％で示した。
また、表１、表２中、正極活物質層中の結着剤の含有量は、正極活物質と無機固体電解質粒子との合計を１００部とした場合における含有量を、負極活物質層中の結着剤の含有量は、負極活物質と無機固体電解質粒子との合計を１００部とした場合における含有量を、固体電解質層中の結着剤の含有量は、無機固体電解質粒子１００部とした場合における含有量を、それぞれ示した。
さらに、表２中、粒子状のポリマーが得られなかった比較例１，４，５，６については、粒子状ポリマーの組成の欄に、重合条件の要約を記載した。

In Tables 1 and 2, the amount of emulsifier used is shown as a percentage of the amount of monomer used.
In Tables 1 and 2, the content of the binder in the positive electrode active material layer is the same as that in the negative electrode active material layer when the total of the positive electrode active material and the inorganic solid electrolyte particles is 100 parts. The content of the binder is the content when the total of the negative electrode active material and the inorganic solid electrolyte particles is 100 parts, and the content of the binder in the solid electrolyte layer is 100 parts of the inorganic solid electrolyte particles. In each case, the contents are shown.
Furthermore, in Table 2, for Comparative Examples 1, 4, 5, and 6 in which the particulate polymer was not obtained, a summary of the polymerization conditions was described in the column for the composition of the particulate polymer.

  As shown in Table 1, when a particulate polymer containing a surfactant having a polyoxyethylene chain is used as the binder, the peel strength of the solid electrolyte layer is high (that is, the polyoxyethylene chain is The particulate polymer containing the surfactant having high binding power as a binder, and the obtained all-solid-state secondary battery was excellent in rate characteristics (Examples 1 to 12). ). Further, when a particulate polymer containing a surfactant having a polyoxyethylene chain is used as the binder, these particulate polymers are contained in the all-solid-state secondary battery (in the positive electrode active material layer, the negative electrode active material). Both in the material layer and in the solid electrolyte layer) existed in a state where the particle state was maintained.

On the other hand, when a non-particulate polymer is used as the binder, the peel strength of the obtained solid electrolyte layer is low, and in the case of an all-solid secondary battery, the binder is positive electrode active material particles, The negative electrode active material particles and the solid electrolyte particles were covered, and electronic conductivity and ionic conductivity were inhibited, resulting in poor rate characteristics (Comparative Examples 1, 5, and 6).
In addition, when a particulate polymer not containing a surfactant having a polyoxyethylene chain is used as a binder, the peel strength of the obtained solid electrolyte layer is low, and an all-solid secondary battery is obtained. In addition, the binder coats the positive electrode active material particles, the negative electrode active material particles, and the solid electrolyte particles, resulting in inhibition of electronic conductivity and ionic conductivity, resulting in poor rate characteristics (Comparative Example 2). , 3).
Furthermore, when polyethylene glycol was used instead of the emulsifier, a polymer could not be obtained and each evaluation could not be performed (Comparative Example 4).

Claims (6)

An all-solid secondary battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer,
At least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer includes a binder composed of an inorganic solid electrolyte and a particulate polymer containing a surfactant having a polyoxyethylene chain. All-solid-state secondary battery characterized by.   The all-solid-state secondary battery according to claim 1, wherein the surfactant having a polyoxyethylene chain is a nonionic surfactant.   The all-solid-state secondary battery according to claim 1, wherein the particulate polymer contains 0.1 to 3% by weight of a monomer unit having an acidic functional group.   The all-solid-state secondary battery according to claim 3, wherein the acidic functional group is a carboxylic acid group or a sulfonic acid group.   The inorganic solid electrolyte is a sulfide glass containing Li, P and S and / or a sulfide glass ceramic containing Li, P and S, according to any one of claims 1 to 4. All-solid secondary battery.   An all-solid secondary battery obtained by dissolving or dispersing an inorganic solid electrolyte and a binder composed of a particulate polymer containing a surfactant having a polyoxyethylene chain in a nonpolar solvent having a boiling point of 100 to 220 ° C Slurry.