Solid electrolytes contain a layer

Abstract

Provided is a solid electrolyte-containing layer capable of preventing short-circuiting due to formation of dendrites. A solid electrolyte-containing layer (30) according to an aspect of the present invention contains: (i) an inorganic solid electrolyte (31); (ii) a heat-resistant resin (32); and (iii) at least one substance selected from the group consisting of an ionic liquid, a mixture of ionic liquid and lithium salt, and a polymer electrolyte.

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte-containing layer. The present invention also relates to an all-solid-state secondary battery, a method for manufacturing an all-solid-state secondary battery, and a method for preventing a short circuit in an all-solid-state secondary battery. [Background technology]

[0002] All-solid-state secondary batteries are secondary batteries that use a solid electrolyte as the electrolyte. Solid electrolytes are broadly classified into inorganic solid electrolytes and organic solid electrolytes, and research and development is underway for both of them to be put to practical use. For an example of an all-solid-state secondary battery that uses an inorganic solid electrolyte, see Patent Document 1. For an example of an all-solid-state secondary battery that uses an organic solid electrolyte, see Patent Document 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-199394 [Patent Document 2] Japanese Patent Publication No. 2019-102301 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional techniques still have room for improvement in terms of preventing short circuits between electrodes caused by dendrites.

[0005] An object of one aspect of the present invention is to provide a solid electrolyte-containing layer that can prevent short circuits caused by the formation of dendrites. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by a solid electrolyte-containing layer in which an inorganic solid electrolyte is composited with another material. That is, the present invention includes the following features. <1> an inorganic solid electrolyte; A heat-resistant resin; At least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte; a solid electrolyte-containing layer comprising: <2> The heat-resistant resin has a glass transition point of 200°C or higher. <1> The solid electrolyte-containing layer according to claim 1. <3> The inorganic solid electrolyte is a sulfide-based solid electrolyte or an oxide-based solid electrolyte. <1> or <2> The solid electrolyte-containing layer according to claim 1. <4> A positive electrode and <1> ~ <3> 10. An all-solid-state secondary battery comprising the solid electrolyte-containing layer according to any one of claims 1 to 9 and a negative electrode. <5> Between the positive and negative electrodes, <1> ~ <3> 10. A method for producing an all-solid-state secondary battery, comprising the step of arranging the solid electrolyte-containing layer according to any one of claims 1 to 9. <5> Between the positive and negative electrodes, <1> ~ <3> 10. A method for preventing a short circuit in an all-solid-state secondary battery, comprising arranging the solid electrolyte-containing layer according to any one of the above items. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a solid electrolyte-containing layer that can prevent short circuits caused by the formation of dendrites. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating a configuration of a solid electrolyte-containing layer according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating the configuration of an all-solid-state secondary battery according to one embodiment of the present invention. [Figure 3] 1 is a schematic diagram illustrating the configuration of an all-solid-state secondary battery according to another embodiment of the present invention. [Figure 4]1 is a schematic diagram illustrating the configuration of an all-solid-state secondary battery according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an example of an embodiment of the present invention will be described in detail, but the present invention is not limited to this.

[0010] Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more and B or less."

[0011] [1. Solid electrolyte-containing layer] Referring to Figure 1, the solid electrolyte-containing layer 30 contains (i) an inorganic solid electrolyte 31, (ii) a heat-resistant resin 32, and (iii) at least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte.

[0012] All-solid-state secondary batteries using a solid electrolyte as the electrolyte have a problem with dendrite formation. That is, metal (e.g., metallic lithium) typically deposits in a dendritic form on the negative electrode side during charge-discharge cycles or constant-voltage charging. This dendritic metal (dendrite) grows along the grain boundaries of the solid electrolyte from the negative electrode side toward the positive electrode side, causing a short circuit between the positive and negative electrodes. In the present invention, this problem is solved by providing a solid electrolyte-containing layer 30.

[0013] The inventors' investigations have revealed that a layer composed of an inorganic solid electrolyte (particularly an oxide-based solid electrolyte) and a heat-resistant resin has low ionic conductivity. This is thought to be because the presence of the heat-resistant resin, which has low ionic conductivity, between the inorganic solid electrolytes causes the inorganic solid electrolytes to be isolated without being in contact with each other, thereby blocking the ionic conduction path.

[0014] In contrast, the solid electrolyte-containing layer 30 contains, in addition to the inorganic solid electrolyte 31 and the heat-resistant resin 32, at least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte. In the solid electrolyte-containing layer 30, at least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte is present between the particles of the inorganic solid electrolyte 31, thereby smoothly forming an ion conduction path. Therefore, the solid electrolyte-containing layer 30 has superior ion conductivity to a layer consisting of an inorganic solid electrolyte and a heat-resistant resin, and is advantageous when applied to the all-solid-state secondary batteries 100a, 100b, and 100c.

[0015] All-solid-state secondary batteries do not use flammable organic solvents as electrolytes, making them inherently safer and less susceptible to fire or combustion. Therefore, unlike conventional liquid-based secondary batteries, they are believed to eliminate the need for a cooling system, allowing them to be used at higher temperatures. To enhance the ionic conductivity of the solid electrolyte, it is also anticipated that all-solid-state secondary batteries may be heated externally using a heating element such as a heater. In this case, the interior of the all-solid-state secondary battery may be exposed to high-temperature conditions (approximately 150°C or higher) due to the heat generated during charging and discharging. The present inventors have newly discovered a problem: if a resin other than a heat-resistant resin is used as the material for the solid electrolyte-containing layer, the resin may soften or melt, or the solid electrolyte-containing layer itself may deform, making it easier for dendrites to penetrate the solid electrolyte-containing layer. Therefore, a heat-resistant resin 32 is used as the resin to be composited with the inorganic solid electrolyte 31.

[0016] The glass transition point of the heat-resistant resin 32 is preferably equal to or higher than 200° C., and more preferably equal to or higher than 250° C. If the glass transition point of the heat-resistant resin 32 is equal to or higher than 200° C., it is possible to prevent short circuits between electrodes due to the generation of dendrites even if the inside of the all-solid-state secondary batteries 100a, 100b, and 100c becomes a high-temperature environment as described above.

[0017] [1.1. Inorganic solid electrolyte] The solid electrolyte-containing layer 30 contains an inorganic solid electrolyte 31. Examples of inorganic solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, and nitride-based solid electrolytes. Among these solid electrolytes, sulfide-based solid electrolytes and oxide-based solid electrolytes are prone to dendrite growth along the grain boundaries of electrolyte particles. The solid electrolyte-containing layer 30 can suppress dendrite formation even when using a sulfide-based solid electrolyte or an oxide-based solid electrolyte, thereby preventing short-circuiting between electrodes due to dendrite formation. Furthermore, while sulfide-based solid electrolytes may generate toxic gases such as hydrogen sulfide when exposed to the atmosphere, oxide-based solid electrolytes do not. Therefore, from the perspective of safety of all-solid-state secondary batteries, it is preferable to use an oxide-based solid electrolyte as the inorganic solid electrolyte 31.

[0018] The sulfide-based solid electrolyte typically contains lithium and sulfur. Furthermore, the sulfide-based solid electrolyte preferably contains one or more elements selected from the group consisting of phosphorus, germanium, tin, and silicon. The sulfide-based solid electrolyte may also contain one or more elements selected from the group consisting of oxygen and halogen elements (e.g., fluorine, chlorine, bromine, and iodine).

[0019] Examples of sulfide-based solid electrolytes include Li2S-P2S5, Li2S-P2S5-GeS2, Li2S-P2S5-SnS2, Li2S-P2S5-SiS2, Li2S-P2S5-LiI, Li2S-P2S5-LiI-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S n (m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y(x and y are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In). Here, the notation "AB" means "a material made using a raw material composition containing A and B." For example, "Li2S-P2S5" means "a material made using a raw material composition containing Li2S and P2S5."

[0020] Examples of oxide-based solid electrolytes include NASICON-type solid electrolytes (e.g., LiTi2(PO4)3 and its elemental substitution products (Li 1+x Al x Ti 2-x (PO4)3, Li 1+x+y Al x Ti 2-x P 3-y Si y O 12 etc.); perovskite-type solid electrolytes (e.g., (LaLi)TiO3 and La 1-3x Li 3x TiO3); LISICON-type solid electrolytes (e.g., Li4SiO4, LiGeO4 and their elemental substitutions (e.g., Li 4-2x Zn x GeO4(Li 14 ZnGeO 16 Glass ceramic solid electrolytes (e.g., Li 1.5 Al 0.5 Ge 1.5 (PO4)3); Li3N and its H-substituted derivatives; Li3PO4 and its N-substituted derivatives (e.g., Li 2.9 PO 3.3 N 0.46 (LIPON));

[0021] An example of an oxide-based solid electrolyte is a garnet-type solid electrolyte having a garnet-type crystal structure. Garnet-type solid electrolytes have high lithium ion conductivity and are stable against moisture, oxygen, lithium metal, etc.

[0022] Garnet-type solid electrolytes can have a cubic crystal structure. Examples of garnet-type solid electrolytes include composite oxides containing Li, La, and Zr, and composite oxides containing Li, La, and Ta. Garnet-type solid electrolytes may contain one or more substitution elements selected from the group consisting of Al, Mg, Ca, Sr, Ba, Ta, Nb, and Yb. A more specific example is Li7La3Zr2O 12 (LLZ), Li6La3Ta 1.5 Y 0.5 O 12 (LLTY), Li6BaLa2Ta2O 12 (LBLT), etc. Examples of elemental substitution products of LLZ include Li 7-3x Al x La3Zr2O 12 , Li 7-x La3Zr 2-y M y O 12 (M is a pentavalent element such as Nb or Ta).

[0023] The inorganic solid electrolyte may be glass, glass ceramic, or a crystalline material. Glass can be obtained by amorphous processing of a raw material composition (e.g., a mixture of Li2S and P2S5). Examples of amorphous processing include mechanical milling. Glass ceramic can be obtained by heat treating glass. Crystalline materials can be obtained by, for example, solid-state reaction of a raw material composition.

[0024] The inorganic solid electrolyte is preferably in the form of particles. 50 The lower limit of the average particle diameter (D 50 The upper limit of the thickness D is, for example, 10 μm or less, and preferably 5 μm or less. 50 The upper and lower limit values ​​may be combined, and an example of such a combination is 0.01 μm or more and 10 μm or less. The lower limit value of the ionic conductivity (e.g., lithium ion conductivity) of the inorganic solid electrolyte at 25° C. is, for example, 1×10 -5S / cm or more, 1×10 -4 The upper limit of the ionic conductivity (e.g., lithium ion conductivity) of the inorganic solid electrolyte at 25°C is, for example, 1 × 10 -2 The upper and lower limits of the ionic conductivity (for example, lithium ion conductivity) of the inorganic solid electrolyte may be combined, and an example of such a combination is 1×10 -5 S / cm or more 1×10 -2 S / cm or less, 1×10 -4 S / cm or more 1×10 -2 S / cm or less.

[0025] Average particle size of inorganic solid electrolyte (D 50 ) is measured by a laser diffraction scattering method. Specifically, it is as follows. 1. 0.1 g of inorganic solid electrolyte powder is added to 50 ml of 0.2 mass % aqueous sodium hexametaphosphate solution to obtain a dispersion liquid in which the powder is dispersed. 2. The particle size distribution of the obtained dispersion is measured using a laser diffraction / scattering particle size distribution measuring device (for example, Microtrac MT3300EXII manufactured by Microtrac-Bell Corporation), and a volume-based cumulative particle size distribution curve is obtained. 3. In the obtained cumulative particle size distribution curve, the particle diameter value at the point where the cumulative volume from the fine particle side is 50% is the average particle diameter (D 50 (μm)).

[0026] Furthermore, the lithium ion conductivity of an inorganic solid electrolyte at 25° C. can be measured by an impedance method, specifically as follows. 1. The measurement sample is compressed, sintered, etc., and molded into a pellet. 2. In a glove box under a dry argon atmosphere, sandwich the measurement sample between two blocking electrodes (e.g., SUS electrodes) to prepare a coin-type lithium battery CR2032 (hereinafter sometimes referred to as a coin cell). Note that gold may be vapor-deposited on the measurement sample to reduce the interfacial resistance between the measurement sample and the blocking electrodes. 3. The obtained coin cell is conditioned in a thermostatic chamber at 25°C for 12 hours. 4. Using an impedance measuring device, measure at the desired temperature in the frequency range of 0.1 Hz to 1 MHz with an amplitude of 10 mV. The ionic conductivity σ can be calculated using the following formula: σ(S·cm -1 )=t(cm)×R(Ω) / A(cm 2 ) In the formula, R represents the impedance value, A represents the area of ​​the sample, and t represents the thickness of the sample.

[0027] [1.2.Heat-resistant resin] The solid electrolyte-containing layer 30 contains a heat-resistant resin. In this specification, "heat-resistant resin" refers to a resin that does not soften, melt, or thermally decompose in a high-temperature environment. Here, "high-temperature environment" refers to an environment of 150°C. The glass transition point of the heat-resistant resin is preferably 200°C or higher, more preferably 250°C or higher, and even more preferably 300°C or higher. Such a resin does not soften, melt, or thermally decompose even when the all-solid-state secondary batteries 100a, 100b, and 100c are heated and used without using a cooling system. The upper limit of the glass transition point of the heat-resistant resin is 450° C. The upper and lower limits of the glass transition point of the heat-resistant resin may be combined, and examples of such combinations include 200° C. or higher and 450° C. or lower, 250° C. or higher and 450° C. or lower, and 300° C. or higher and 450° C. or lower.

[0028] Examples of heat-resistant resins include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyether ether ketone, aromatic polyester, polyethersulfone, polyetherimide, cellulose ethers, polybenzimidazole, polyurethane, melamine resin, etc. These heat-resistant resins may be used alone or in combination of two or more.

[0029] Among the above-mentioned heat-resistant resins, polyamide, polyimide, polyamideimide, aromatic polyester, polyethersulfone, and polyetherimide are preferred from the viewpoint of having higher heat resistance, with polyamide, polyimide, and polyamideimide being more preferred. Among polyamide, polyimide, and polyamideimide, nitrogen-containing aromatic polymers are even more preferred from the viewpoint of heat resistance. Examples of nitrogen-containing aromatic polymers include aromatic polyamides (para-oriented aromatic polyamides, meta-oriented aromatic polyamides, etc.), aromatic polyimides, and aromatic polyamideimides. Of these, aromatic polyamides are even more preferred, with para-oriented aromatic polyamides being particularly preferred. In this specification, aromatic polyamides may be referred to as "aramids," and para-oriented aromatic polyamides may be referred to as "para-aramids."

[0030] Para-aramid is a heat-resistant resin obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide. The repeating unit that essentially constitutes para-aramid has an amide bond at the para position of the aromatic ring. Alternatively, the repeating unit has an amide bond at a position oriented similar to the para position of the aromatic ring. Here, having an amide bond at a position oriented similar to the para position of the aromatic ring means that two amide bonds extending from the aromatic ring are in a collinear or parallel positional relationship.

[0031] Specific examples of para-aramids include poly(paraphenylene terephthalamide), poly(parabenzamide), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylenedicarboxylic acid amide), poly(paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly(2-chloro-paraphenylene terephthalamide), and paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer.

[0032] Examples of aromatic polyimides include wholly aromatic polyimides produced by condensation polymerization of aromatic tetracarboxylic dianhydrides and aromatic diamines. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride. Examples of aromatic diamines include oxydianiline, paraphenylenediamine, benzophenonediamine, 3,3'-methylenedianiline, 3,3'-diaminobenzophenone, 3,3'-diaminodiphenylsulfone, and 1,5'-naphthalenediamine.

[0033] Examples of aromatic polyamide-imides include resins obtained by condensation polymerization of aromatic dicarboxylic acids and aromatic diisocyanates, and resins obtained by condensation polymerization of aromatic tricarboxylic anhydrides and aromatic diisocyanates. Examples of aromatic dicarboxylic acids include isophthalic acid and terephthalic acid. Examples of aromatic tricarboxylic anhydrides include trimellitic anhydride. Examples of aromatic diisocyanates include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, ortho-tolylene diisocyanate, and m-xylene diisocyanate.

[0034] Among the heat-resistant resins exemplified above, examples of resins having a glass transition point of 200° C. or higher include aromatic polyamide, aromatic polyimide, aromatic polyamideimide, aromatic polyester, and polyethersulfone.

[0035] [1.3. Ionic Liquids, Mixtures of Ionic Liquids and Lithium Salts, and Polymer Electrolytes] The solid electrolyte-containing layer 30 contains at least one selected from an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte. From the viewpoint of further increasing the ionic conductivity of the solid electrolyte-containing layer 30 and obtaining a stable voltage output, the solid electrolyte-containing layer 30 preferably contains an ionic liquid or a mixture of an ionic liquid and a lithium salt.

[0036] The solid electrolyte-containing layer 30 may contain at least one selected from an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte. For example, the layer may contain two or more types of ionic liquids, two or more types of polymer electrolytes, or an ionic liquid and a polymer electrolyte.

[0037] An ionic liquid is a substance containing a cation and an anion and having a melting point of 100°C or less (preferably a substance that is liquid at room temperature (e.g., 25°C)). The cation contained in an ionic liquid is generally an organic cation (or may be a complex ion in which an organic ligand coordinates to an inorganic cation). Examples of cations include ammonium-based cations (e.g., imidazolium salts, pyridinium salts), phosphonium-based cations, alkali metal cations, and alkaline earth metal cations. Examples of anions include halogen-based anions (e.g., bromide ion), boron-based anions (e.g., tetrafluoroborate), phosphorus-based anions (e.g., hexafluorophosphate), and sulfonylimide-based anions (e.g., bis(trifluoromethylsulfonyl)imide (TFSI) and bis(fluorosulfonyl)imide (FSI)). Examples of organic ligands coordinated to inorganic cations (e.g., lithium ion) include triglyme and tetraglyme. Ionic liquids may also be mixtures of lithium salts and nonionic organic ligands. For example, a mixture of a lithium salt and tetraglyme can be used. In this case, the cation contained in the ionic liquid is a lithium-containing complex ion, and the anion is the anion contained in the lithium salt.

[0038] Examples of lithium salts in the mixture of ionic liquids and lithium salts include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium bis(fluorosulfonyl)imide (LiFSI:LiN(SO2F)2), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI:LiN(SO2CF3)2), lithium bis(perfluoroethylsulfonyl)imide (LiN(SO2C2F5)2), LiAsF6, LiCF3SO3, and lithium difluoro(oxalato)borate.

[0039] A polymer electrolyte is a mixture of a polymer compound having polarity within its molecule and a lithium salt. Examples of polymer compounds having polarity within its molecule include compounds having an alkylene oxide structure (such as an ethylene oxide structure or a propylene oxide structure), polyethyleneimine-based polymers, polyalkylene sulfide-based polymers, and polyvinylpyrrolidone-based polymers. Such polymer compounds can contain a large amount of lithium salt, thereby increasing ionic conductivity. Examples of lithium salts contained in polymer electrolytes include the compounds exemplified as lithium salts in the mixture of an ionic liquid and a lithium salt.

[0040] 2. Form and manufacturing method of solid electrolyte-containing layer There is no particular limitation on how the heat-resistant resin 32 is distributed in the solid electrolyte-containing layer 30. For example, the heat-resistant resin 32 may be locally distributed or uniformly distributed.

[0041] There are no particular limitations on how at least one selected from the ionic liquid, the mixture of the ionic liquid and the lithium salt, and the polymer electrolyte is distributed in the solid electrolyte-containing layer 30. However, in order to increase the ionic conductivity of the solid electrolyte-containing layer 30, it is preferable that at least one selected from the ionic liquid, the mixture of the ionic liquid and the lithium salt, and the polymer electrolyte be uniformly distributed in the solid electrolyte-containing layer 30.

[0042] Examples of methods for manufacturing the solid electrolyte-containing layer 30 include the following methods (a), (b), (c), and (d). Methods (a) and (c) are methods for manufacturing a solid electrolyte-containing layer 30 containing an ionic liquid or a mixture of an ionic liquid and a lithium salt. Methods (b) and (d) are methods for manufacturing a solid electrolyte-containing layer 30 containing a polymer electrolyte.

[0043] (a) A powder of inorganic solid electrolyte 31 and a powder of heat-resistant resin 32 are mixed. The resulting mixture is compressed to obtain a mass of mixture. The resulting mixture is impregnated with one or more liquids selected from the group consisting of an ionic liquid and a mixture of an ionic liquid and a lithium salt, to obtain a solid electrolyte-containing layer 30.

[0044] (b) Powder of the inorganic solid electrolyte 31, powder of the heat-resistant resin 32, and the polymer electrolyte are mixed together, and the resulting mixture is pressure-molded to obtain the solid electrolyte-containing layer 30.

[0045] (c) A slurry containing an inorganic solid electrolyte 31 and a solvent is applied to a porous substrate (such as a porous film or nonwoven fabric) containing a heat-resistant resin 32. The solvent is then removed by drying or the like. The resulting composite is impregnated with one or more liquids selected from the group consisting of an ionic liquid and a mixture of an ionic liquid and a lithium salt, to obtain a solid electrolyte-containing layer 30.

[0046] (d) A slurry containing an inorganic solid electrolyte 31, a polymer electrolyte, and a solvent is applied onto a porous substrate (porous film, nonwoven fabric, etc.) containing a heat-resistant resin 32. Next, the solvent is removed by drying or the like to obtain a solid electrolyte-containing layer 30.

[0047] The manufacturing methods of the solid electrolyte-containing layer 30 exemplified above in (a) and (b) are based on pressure molding. Such manufacturing methods are preferable to manufacturing methods based on sintering in that they can be manufactured using simpler equipment. Of course, the solid electrolyte-containing layer 30 may also be manufactured by sintering.

[0048] The solid electrolyte-containing layer 30 may contain both (i) a polymer electrolyte and (ii) at least one selected from the group consisting of an ionic liquid and a mixture of an ionic liquid and a lithium salt. Such a solid electrolyte-containing layer 30 can be obtained, for example, by impregnating the material obtained by the production method (b) or (d) with one or more liquids selected from the group consisting of an ionic liquid and a mixture of an ionic liquid and a lithium salt.

[0049] In the production methods (a) and (c), when a mixture of an ionic liquid and a lithium salt is used, the ionic liquid and the lithium salt may be mixed in advance and then impregnated into the composite, or the ionic liquid and the lithium salt may be separately impregnated into the composite.

[0050] The "porous substrate" in the manufacturing methods (c) and (d) refers to a material having a large number of pores, allowing gas and liquid to pass from one side to the other. The pore size of the pores in the porous substrate is not particularly limited, but is preferably 0.3 μm or less, more preferably 0.14 μm or less. The basis weight per unit area of ​​the porous film is not particularly limited, but is 4 to 20 g / m 2 is preferred, and 4 to 12 g / m 2 More preferably, 5 to 12 g / m 2 The air permeability of the porous substrate is preferably 30 to 500 seconds / 100 mL, more preferably 50 to 300 seconds / 100 mL, in terms of Gurley value measured in accordance with JIS P8117.

[0051] Examples of the "porous substrate containing heat-resistant resin 32" in the manufacturing methods (c) and (d) include a porous substrate made of heat-resistant resin 32 and a porous substrate containing heat-resistant resin 32 and another resin (such as a porous substrate in which another resin and a heat-resistant resin are laminated). The porous substrate containing heat-resistant resin 32 and another resin may further contain a filler or the like. The filler material may be a conventionally known material (such as alumina).

[0052] Other resins include, for example, polyolefins. Specific examples of polyolefins include homopolymers and copolymers obtained by polymerizing (or copolymerizing) monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene. Examples of such homopolymers include polyethylene, polypropylene, and polybutene. An example of such a copolymer is an ethylene-propylene copolymer. Among these resins, polyethylene is preferred. Examples of polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultra-high molecular weight polyethylene having a weight-average molecular weight of 1,000,000 or more. Of these, ultra-high molecular weight polyethylene is particularly preferred.

[0053] (short circuit prevention film) In one embodiment, the solid electrolyte-containing layer 30 may be a short-circuit prevention film. In this specification, the term "short-circuit prevention film" refers to a solid electrolyte-containing layer 30 that has a function of preventing short circuits. Here, whether the solid electrolyte-containing layer 30 has a function of preventing short circuits (i.e., whether it is a short-circuit prevention film) can be determined by the following procedure. 1. A coin-type lithium battery CR2032 is used as an evaluation cell (hereinafter, sometimes referred to as a coin cell) and subjected to the following dendrite resistance test 1 or dendrite resistance test 2. Note that the dendrite resistance test 1 is applied to an all-solid-state secondary battery that does not include a solid electrolyte 20, such as the first embodiment (all-solid-state secondary battery 100a shown in FIG. 2) described below. 2. After one hour has elapsed since the start of the test, disassemble any coin cells whose voltage did not indicate 0 V, and remove the solid electrolyte-containing layer (in the case of Dendrite Resistance Test 1), or remove the solid electrolyte layer (in the case of Dendrite Resistance Test 2). 3. The surface of the removed solid electrolyte-containing layer (or solid electrolyte layer) is observed. If the number of black dots (i.e., dendrite marks) present on the surface of the solid electrolyte-containing layer (or solid electrolyte layer) is less than 10, it is determined to be the short-circuit prevention film of the present invention.

[0054] (Dendrite Resistance Test 1: Resistance Test Without Using Solid Electrolyte Layer 20) The following test stack is prepared using a coin cell: 2 A current of 1000 kJ / s is passed through the battery, and metallic Li is continuously deposited on the negative electrode. The test temperature is 60°C. The change in voltage over time is observed.

[0055] The layer structure of the test laminate is as follows: Stainless steel plate, thickness: 500 μm, diameter: 15.5 mm - Metallic lithium foil (positive electrode) on the elution side, thickness: 500 μm, diameter: 13 mm Solid electrolyte-containing layer 30 (short-circuit prevention film), diameter: 15 mm - Metallic lithium foil (negative electrode) on the deposition side, thickness: 500 μm, diameter: 13 mm.

[0056] (Dentrite Resistance Test 2: Resistance Test Using Solid Electrolyte Layer 20) The following test laminates were prepared using coin cells. The other test conditions were the same as in Dendrite Resistance Test 1.

[0057] The layer structure of the test laminate is as follows: Stainless steel plate, thickness: 500 μm, diameter: 15.5 mm - Metallic lithium foil (positive electrode) on the elution side, thickness: 500 μm, diameter: 13 mm Solid electrolyte layer (e.g., Toshima Manufacturing Co., Ltd., Li 6.75 La3Zr 1.75 Nb 0.25 O 12 sintered body, thickness 500 μm, diameter 15 mm) Solid electrolyte-containing layer 30 (short-circuit prevention film), diameter: 15 mm - Metallic lithium foil (negative electrode) on the deposition side, thickness: 500 μm, diameter: 13 mm.

[0058] In dendrite resistance tests 1 and 2, if no short circuit occurs and metallic lithium is stably deposited on the negative electrode, the voltage of the coin cell will not indicate 0 V. On the other hand, if a complete short circuit occurs due to dendrites, the voltage of the coin cell will indicate 0 V. Furthermore, if repeated micro-short circuits occur due to dendrites, the voltage of the coin cell will fluctuate drastically between 0 V and negative values.

[0059] Note that, if there are less than 10 dendrite marks on the surface of the solid electrolyte-containing layer or the solid electrolyte layer after the dendrite resistance test 1 or 2, this indicates that the solid electrolyte-containing layer 30 (short-circuit prevention film) has suppressed the growth of dendrites and prevented the penetration of dendrites into the positive electrode or the solid electrolyte layer.

[0060] The short-circuit prevention film is preferably a solid electrolyte-containing layer 30 that can be handled as a sheet-like object during the manufacturing stage of the all-solid-state secondary batteries 100a, 100b, and 100c. Such a short-circuit prevention film can be distributed as a component of the all-solid-state secondary batteries 100a, 100b, and 100c, or as a finished or semi-finished product.

[0061] The embodiment in which the solid electrolyte-containing layer 30 is a sheet-like short-circuit prevention film has the following advantages, for example.

[0062] (1) The material is easy to handle, facilitating the manufacture of the all-solid-state secondary batteries 100a, 100b, and 100c.

[0063] (2) It is possible to manufacture and laminate a short-circuit prevention film with high film thickness uniformity and no defects such as pinholes, etc. Therefore, it is possible to obtain superior short-circuit prevention properties compared to other methods (for example, a method of applying and drying a solution such as method (γ) described below).

[0064] (3) Unlike the solution coating / drying method such as Method (γ) described below, this method does not use a solvent, so there is no risk of the solid electrolyte being deteriorated by the solvent. In addition, there is no step of removing the solvent, so there is no risk of the solid electrolyte being deteriorated by heating to remove the solvent.

[0065] The lower limit of the weight of the inorganic solid electrolyte in the solid electrolyte-containing layer 30 is preferably 25 wt % or more, more preferably 40 wt % or more. The upper limit of the weight of the inorganic solid electrolyte is preferably 94 wt % or less, more preferably 85 wt % or less. The lower limit of the weight of the heat-resistant resin in the solid electrolyte-containing layer 30 is preferably 1 wt % or more, more preferably 5 wt % or more. The upper limit of the weight of the heat-resistant resin is preferably 70 wt % or less, more preferably 50 wt % or less. The lower limit of the total weight of the ionic liquid, the mixture of the ionic liquid and a lithium salt, and the polymer electrolyte in the solid electrolyte-containing layer 30 is preferably 5 wt % or more, more preferably 10 wt % or more. The upper limit of the total weight of the ionic liquid, the mixture of the ionic liquid and a lithium salt, and the polymer electrolyte is preferably 74 wt % or less, more preferably 55 wt % or less. The total amount of the ionic liquid, the mixture of the ionic liquid and lithium salt, the polymer electrolyte, the inorganic solid electrolyte, and the solid electrolyte-containing layer is 100% by weight. If the components are contained in such proportions, the solid electrolyte-containing layer 30 can suppress dendrites and further prevent short circuits between electrodes due to dendrite formation.

[0066] These lower and upper limits can be combined as appropriate. Examples of weight combinations of inorganic solid electrolytes include 25% by weight or more and 94% by weight or less, and 40% by weight or more and 85% by weight or less. Examples of weight combinations of heat-resistant resins include 1% by weight or more and 70% by weight or less, and 5% by weight or more and 50% by weight or less. Examples of total weight combinations of ionic liquids, mixtures of ionic liquids and lithium salts, and polymer electrolytes include 5% by weight or more and 74% by weight or less, and 10% by weight or more and 55% by weight or less.

[0067] The lower limit of the thickness of the solid electrolyte-containing layer 30 is preferably 5 μm or more, more preferably 10 μm or more. The upper limit of the thickness is preferably 1000 μm or less, more preferably 500 μm or less. The upper and lower limit of the thickness of the solid electrolyte-containing layer 30 may be combined, and examples of such combinations include 5 μm or more and 1000 μm or less, 10 μm or more and 500 μm or less, and 10 μm or more and 1000 μm or less. The lower limit of the ionic conductivity (e.g., ionic conductivity of lithium ions) of the solid electrolyte-containing layer 30 at 60°C is 1×10 -6 S / cm or more is preferable, and 1×10 -5 The upper limit of the ionic conductivity of the solid electrolyte-containing layer 30 is, for example, 1×10 -2 The upper and lower limits of the ionic conductivity of the solid electrolyte-containing layer 30 may be combined. An example of such a combination is 1×10 -6 S / cm or more 1×10 -2 S / cm or less, 1×10 -5 S / cm or more 1×10 -2 S / cm or less.

[0068] The ionic conductivity of the solid electrolyte-containing layer 30 can be measured by an impedance method, which is specifically described below. 1. In a glove box under a dry argon atmosphere, a measurement sample is sandwiched between two blocking electrodes (for example, SUS electrodes) to prepare a coin-type lithium battery CR2032 (hereinafter sometimes referred to as a coin cell). 2. The obtained coin cell is conditioned in a thermostatic chamber at 60°C for 12 hours. 3. Using an impedance measuring device, measure at the desired temperature in the frequency range of 0.1 Hz to 1 MHz with an amplitude of 10 mV. The ionic conductivity σ can be calculated using the following formula: σ(S·cm -1 )=t(cm)×R(Ω) / A(cm 2 ) In the formula, R represents the impedance value, A represents the area of ​​the sample, and t represents the thickness of the sample.

[0069] 3. All-Solid-State Secondary Battery and Laminate for All-Solid-State Secondary Battery An all-solid-state secondary battery according to one embodiment of the present invention includes a solid electrolyte-containing layer 30. This all-solid-state secondary battery includes the following three configurations. The first configuration is a configuration including no solid electrolyte layer 20 and one solid electrolyte-containing layer 30 (all-solid-state secondary battery 100a shown in FIG. 2). The second configuration is a configuration including one solid electrolyte layer 20 and one solid electrolyte-containing layer 30 (all-solid-state secondary battery 100b shown in FIG. 3). The third configuration is a configuration including one solid electrolyte layer 20 and two solid electrolyte-containing layers 30 (all-solid-state secondary battery 100c shown in FIG. 4). Each configuration will be described below.

[0070] (First form) 2, the all-solid-state secondary battery 100a according to the first embodiment includes a positive electrode 10, a solid electrolyte-containing layer 30, and a negative electrode 40.

[0071] (Second form) Referring to Fig. 3, an all-solid-state secondary battery 100b according to the second embodiment includes a positive electrode 10, a solid electrolyte layer 20, a solid electrolyte-containing layer 30, and a negative electrode 40. Here, the solid electrolyte-containing layer 30 is adjacent to the solid electrolyte layer 20 and the negative electrode 40.

[0072] (Third Form) Referring to Fig. 4, an all-solid-state secondary battery 100c according to the third embodiment includes a positive electrode 10, a solid electrolyte-containing layer 30, a solid electrolyte layer 20, a solid electrolyte-containing layer 30, and a negative electrode 40. One side of the solid electrolyte-containing layer 30 is adjacent to the solid electrolyte layer 20 and the negative electrode 40. The other side of the solid electrolyte-containing layer 30 is adjacent to the positive electrode 10 and the solid electrolyte layer 20.

[0073] From the viewpoint of miniaturizing the all-solid-state secondary battery, the first embodiment is most preferable, followed by the second embodiment. On the other hand, from the viewpoint of increasing the mechanical strength of the laminate against bending and folding, and from the viewpoint of increasing the distance between the positive and negative electrodes and improving safety, the second and third embodiments are preferable.

[0074] In this specification, the term "all-solid-state secondary battery" refers to a secondary battery that uses a solid electrolyte as an electrolyte, i.e., a secondary battery that includes a solid electrolyte. In one embodiment, the all-solid-state secondary batteries 100a, 100b, and 100c do not include an electrolytic solution (e.g., an aqueous electrolytic solution or a non-aqueous electrolytic solution).

[0075] The shape of the all-solid-state secondary batteries 100a, 100b, and 100c is not particularly limited. Examples of shapes include coin-type batteries, laminated batteries, cylindrical batteries, and prismatic batteries. All-solid-state secondary batteries can be repeatedly charged and discharged, but can also be used like primary batteries. That is, a charged all-solid-state secondary battery may be used for the purpose of one-time discharge.

[0076] The all-solid-state secondary batteries 100a, 100b, and 100c are, for example, all-solid-state lithium secondary batteries, all-solid-state sodium secondary batteries, etc., and are preferably all-solid-state lithium secondary batteries.

[0077] The applications of the all-solid-state secondary batteries 100a, 100b, and 100c are not particularly limited. Examples of applications include mobile applications (electric vehicles, electric motorcycles, electrically assisted bicycles, trains, etc.), industrial machinery applications (construction machinery, forklifts, elevators, etc.), stationary power sources (solar power generation, wind power generation, UPS, medical equipment, etc.), and consumer applications (mobile PCs, smartphones, etc.).

[0078] Hereinafter, the members other than the solid electrolyte-containing layer 30 that constitute the all-solid-state secondary batteries 100a, 100b, and 100c will be individually described.

[0079] [3.1. Positive electrode] The positive electrode 10 includes, for example, a positive electrode active material layer and a positive electrode current collector.

[0080] The positive electrode active material layer is a layer containing at least a positive electrode active material. Examples of the positive electrode active material include oxide-based active materials and sulfur-based active materials.

[0081] Examples of oxide-based active materials include rock salt layer-structured active materials (such as LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.); spinel-type active materials (such as LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, etc.); olivine-type active materials (such as LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc.). Other examples of oxide-based active materials include Li 1+x Mn 2-x-y M y O4 (M is one or more selected from the group consisting of Al, Mg, Co, Fe, Ni, and Zn, and 0 < x + y < 2), which is a LiMn spinel active material; lithium titanate.

[0082] A coating layer containing a Li-ion conductive oxide may be provided on the surface of the oxide-based active material. By providing the coating layer, the reaction between the oxide-based active material and the solid electrolyte can be suppressed. Examples of the Li-ion conductive oxide include LiNbO3, Li4Ti5O 12 , Li3PO4. The lower limit value of the thickness of the coating layer can be, for example, 0.1 nm or more or 1 nm or more. The upper limit value of the thickness of the coating layer can be, for example, 100 nm or less or 20 nm or less. The coverage rate of the coating layer on the surface of the oxide-based active material is, for example, 70% or more or 90% or more.

[0083] The sulfur-based active material is an active material containing at least sulfur element. The sulfur-based active material may or may not contain Li element. Examples of the sulfur-based active material include elemental sulfur, lithium sulfide (Li2S), polysulfide lithium (Li2S x [[ID=​

[0084] The positive electrode active material layer may optionally contain one or more materials selected from the group consisting of inorganic solid electrolytes, conductive materials, and binders. Examples of inorganic solid electrolytes include those described in Section [1.1]. Examples of conductive materials include acetylene black, ketjen black, and carbon fiber. Examples of binders include rubber-based binders (such as butylene rubber (BR) and styrene butadiene rubber (SBR)) and fluoride-based binders (such as polyvinylidene fluoride (PVDF)).

[0085] The lower limit of the thickness of the positive electrode active material layer is, for example, 0.1 μm or more, and the upper limit of the thickness of the positive electrode active material layer is, for example, 300 μm or less or 100 μm or less.

[0086] Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. Examples of the shape of the positive electrode current collector include foil and plate. The lower limit of the thickness of the positive electrode current collector is, for example, 0.1 μm or more or 1 μm or more. The upper limit of the thickness of the positive electrode current collector is, for example, 1 mm or less or 100 μm or less.

[0087] [3.2. Negative electrode] The negative electrode 40 includes, for example, a negative electrode active material layer and a negative electrode current collector.

[0088] The negative electrode active material layer is a layer containing at least a negative electrode active material, examples of which include lithium metal, lithium alloys, metals that can be alloyed with lithium, carbon-based materials, and oxide-based materials.

[0089] Examples of carbon-based materials include graphite, amorphous carbon, carbon nanotubes, and graphene. Examples of oxide-based materials include Li4Ti5O 12 (LTO), TiO2.

[0090] The negative electrode active material layer may optionally contain one or more substances selected from the group consisting of inorganic solid electrolytes, conductive materials, and binders. Examples of these substances include the inorganic solid electrolytes, conductive materials, and binders that can be contained in the positive electrode active material layer, which are exemplified in Section [3.1.].

[0091] The lower limit of the thickness of the negative electrode active material layer is, for example, 0.1 μm or more, and the upper limit of the thickness of the negative electrode active material layer is, for example, 300 μm or less or 100 μm or less.

[0092] Examples of materials for the negative electrode current collector include materials that do not alloy with Li. More specific examples include stainless steel, copper, nickel, and carbon. Examples of the shape of the negative electrode current collector include foil and plate shapes. The lower limit of the thickness of the negative electrode current collector is, for example, 0.1 μm or more or 1 μm or more. The upper limit of the thickness of the negative electrode current collector is, for example, 1 mm or less or 100 μm or less.

[0093] [3.3. Solid electrolyte layer] The solid electrolyte layer 20 is a layer containing at least a solid electrolyte. The solid electrolyte layer 20 is a layer different from the solid electrolyte-containing layer 30. For example, the weight of the heat-resistant resin in the solid electrolyte 20 is less than 1% by weight, where the total weight of the solid electrolyte layer 20 is 100% by weight. The solid electrolyte contained in the solid electrolyte layer 20 may be an inorganic solid electrolyte or an organic solid electrolyte. Examples of inorganic solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, and nitride-based solid electrolytes. Examples of organic solid electrolytes include polymer electrolytes and gel electrolytes.

[0094] Among these solid electrolytes, sulfide-based solid electrolytes and oxide-based solid electrolytes are prone to dendrite formation along the grain boundaries of electrolyte particles. By providing the solid electrolyte-containing layer 30, dendrite formation can be suppressed even when a sulfide-based solid electrolyte or an oxide-based solid electrolyte is used as the solid electrolyte layer 20, thereby preventing short circuits between electrodes due to dendrite formation. Furthermore, while sulfide-based solid electrolytes may generate toxic gases such as hydrogen sulfide when exposed to the atmosphere, oxide-based solid electrolytes do not. Therefore, from the perspective of safety of all-solid-state secondary batteries, it is preferable to use an oxide-based solid electrolyte as the inorganic solid electrolyte contained in the solid electrolyte layer 20.

[0095] (Inorganic solid electrolyte) The description of the inorganic solid electrolyte and specific examples of the inorganic solid electrolyte are incorporated by reference in Section [1.1]. The inorganic solid electrolyte used in the solid electrolyte layer 20 may be in pellet form. The term "pellet form" refers to a shape formed by compressing or sintering powder, or both. The thickness of the pellet-shaped inorganic solid electrolyte is preferably 1 mm or less, and more preferably 500 μm or less.

[0096] (Organic solid electrolyte) For explanations of polymer electrolytes and specific examples of polymer electrolytes, the descriptions in Section [1.3.] are incorporated herein by reference.

[0097] A gel electrolyte is, for example, a mixture of a polymer compound with gelling properties and a non-aqueous electrolyte. A gel electrolyte is a polymer compound that retains a non-aqueous electrolyte, and has appropriate plasticity and adhesiveness, as well as ionic conductivity close to that of a non-aqueous electrolyte. Therefore, all-solid-state secondary batteries using a gel electrolyte can achieve high charge / discharge efficiency. The mixing ratio of the polymer compound to the non-aqueous electrolyte can be (2:3) to (3:2) from the viewpoint of obtaining appropriate plasticity.

[0098] Examples of polymer compounds having a gelling effect include fluororesins containing vinylidene fluoride units, acrylic resins containing (meth)acrylic acid units (the (meth)acrylic acid units may be esterified), and polyether resins containing polyalkylene oxide units. Examples of fluororesins containing vinylidene fluoride units include polyvinylidene fluoride, copolymers containing vinylidene fluoride units and hexafluoropropylene units, and copolymers containing vinylidene fluoride units and trifluoroethylene units. Polymer compounds used in polymer electrolytes (e.g., compounds having an alkylene oxide structure) can also be used.

[0099] The non-aqueous electrolyte solution contained in the gel electrolyte contains a lithium salt and a non-aqueous solvent that dissolves the lithium salt. Examples of the lithium salt include the substances exemplified in Section [1.3.]. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic acid esters, cyclic ethers, chain ethers, nitriles, and amides.

[0100] 4. Manufacturing method of all-solid-state secondary battery A method for manufacturing all solid state secondary batteries 100a, 100b, and 100c according to one aspect of the present invention includes a step of disposing a solid electrolyte-containing layer 30 between a positive electrode 10 and a negative electrode 40. In one embodiment, the manufacturing method includes a step of disposing a solid electrolyte-containing layer 30 between a solid electrolyte layer 20 and a negative electrode 40 (method for manufacturing all solid state secondary batteries 100b and 100c). In one embodiment, the manufacturing method further includes a step of disposing a solid electrolyte-containing layer 30 between a solid electrolyte layer 20 and a positive electrode 10 (method for manufacturing all solid state secondary battery 100c).

[0101] Hereinafter, a method for manufacturing a laminate represented as the all-solid-state secondary batteries 100a, 100b, and 100c will be described, focusing on a method for arranging the solid electrolyte-containing layer 30.

[0102] (Manufacturing Method of All-Solid-State Secondary Battery 100a) Examples of methods for disposing the solid electrolyte-containing layer 30 between the positive electrode 10 and the negative electrode 40, as in the all-solid-state secondary battery 100a, include the following: By these methods, a laminate (all-solid-state secondary battery 100a) in which the positive electrode 10, the solid electrolyte-containing layer 30, and the negative electrode 40 are laminated in this order can be obtained.

[0103] (α) A method in which the solid electrolyte-containing layer 30 is prepared and then disposed between the positive electrode 10 and the negative electrode 40. For example, (i) a short-circuit prevention film is placed on the positive electrode 10 (or the negative electrode 40), and (ii) the negative electrode 40 (or the positive electrode 10) is placed thereon. Examples of the method for preparing the solid electrolyte-containing layer 30 include the methods (a) to (d) described in Section [2].

[0104] (β) A method of forming a solid electrolyte-containing layer 30 after disposing a film containing an inorganic solid electrolyte 31 and a heat-resistant resin 32 between a positive electrode 10 and a negative electrode 40. For example, a method of (i) placing a film containing an inorganic solid electrolyte 31 and a heat-resistant resin 32 on the positive electrode 10 (or a negative electrode 40), (ii) impregnating or supporting one or more selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte to form a solid electrolyte-containing layer 30, and (iii) stacking the negative electrode 40 (or positive electrode 10) on the solid electrolyte-containing layer 30.

[0105] (γ) A method of producing a solid electrolyte-containing layer 30 by applying a solution containing an inorganic solid electrolyte 31, a heat-resistant resin 32, and at least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte to a positive electrode 10 (or a negative electrode 40). For example, a method of (i) preparing a solution containing an inorganic solid electrolyte 31, a heat-resistant resin 32, and at least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte, and a solvent, (ii) applying the solution to the positive electrode 10 (or a negative electrode 40), (iii) drying to remove the solvent, thereby forming a solid electrolyte-containing layer 30, and (iv) laminating the negative electrode 40 (or positive electrode 10) on the solid electrolyte-containing layer 30.

[0106] (δ) A method of forming a powder mixture containing an inorganic solid electrolyte 31, a heat-resistant resin 32, and at least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte, by placing the powder mixture on the positive electrode 10 (or the negative electrode 40) and molding the mixture to form a solid electrolyte-containing layer 30. For example, a method of (i) preparing a powder mixture containing an inorganic solid electrolyte 31, a heat-resistant resin 32, and at least one selected from the group consisting of an ionic liquid, a mixture of an ionic liquid and a lithium salt, and a polymer electrolyte, (ii) placing the powder between the positive electrode 10 and the negative electrode 40, and (iii) press-molding the powder.

[0107] (Manufacturing method of all-solid-state secondary battery 100b) In the above methods (α) to (δ), if "cathode 10" is read as "solid electrolyte layer 20," the methods are those in which a solid electrolyte-containing layer 30 is disposed between the solid electrolyte layer 20 and the anode 40. These methods provide a laminate in which the solid electrolyte layer 20, the solid electrolyte-containing layer 30, and the anode 40 are laminated in this order. If a cathode 10 is further laminated on the solid electrolyte layer 20 of this laminate, a laminate (all-solid-state secondary battery 100b) in which the positive electrode 10, the solid electrolyte layer 20, the solid electrolyte-containing layer 30, and the anode 40 are laminated in this order can be produced.

[0108] (Manufacturing method of all-solid-state secondary battery 100c) After obtaining a laminate in which the solid electrolyte layer 20, the solid electrolyte-containing layer 30, and the negative electrode 40 are laminated in this order by the above-mentioned method, by further laminating the solid electrolyte-containing layer 30 and the positive electrode 10 on the solid electrolyte layer 20 of the laminate, it is possible to manufacture a laminate (all-solid-state secondary battery 100c) in which the positive electrode 10, the solid electrolyte-containing layer 30, the solid electrolyte layer 20, the solid electrolyte-containing layer 30, and the negative electrode 40 are laminated in this order.

[0109] Alternatively, if "negative electrode 40" is read as "solid electrolyte layer 20" in the above methods (α) to (δ), the method results in a method in which the solid electrolyte-containing layer 30 is disposed between the positive electrode 10 and the solid electrolyte layer 20. These methods produce a laminate in which the positive electrode 10, the solid electrolyte-containing layer 30, and the solid electrolyte layer 20 are laminated in this order. If the solid electrolyte-containing layer 30 and the negative electrode 40 are further laminated on the solid electrolyte layer 20 of this laminate, a laminate (all-solid-state secondary battery 100c) in which the positive electrode 10, the solid electrolyte-containing layer 30, the solid electrolyte layer 20, the solid electrolyte-containing layer 30, and the negative electrode 40 are laminated in this order can be produced.

[0110] In the above-described manufacturing method, the positive electrode 10, the solid electrolyte layer 20, and the negative electrode 40 may each be a precursor. That is, the positive electrode 10, the solid electrolyte layer 20, or the negative electrode 40 may be formed by heating, pressing, or the like after the methods (α) to (δ). The precursor is a compound or mixture that becomes the positive electrode 10, the solid electrolyte layer 20, or the negative electrode 40 by heating, pressing, or the like.

[0111] In the above-described manufacturing method, the positive electrode 10, the solid electrolyte layer 20, and the negative electrode 40 may be manufactured by a known method. For example, these layers can be manufactured by a wet method in which a raw material slurry is dried, or a powder molding method in which a raw material powder is pressed. When the solid electrolyte layer 20 is an organic solid electrolyte layer, the solid electrolyte layer 20 can be manufactured by a known polymerization method or the like.

[0112] Although not shown, the all-solid-state secondary batteries 100a, 100b, and 100c may include a case for storing the laminate, leads for extracting current from the electrodes, etc. These components can be manufactured and the battery product can be assembled using conventionally known methods.

[0113] The contents described in each of the above sections can be appropriately incorporated into other sections. The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Therefore, embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0114] All patent documents mentioned herein are incorporated herein by reference.

[0115] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. [Example]

[0116] The dendrite suppression effect of using a solid electrolyte-containing layer was verified through an experiment. In this experiment, a coin-type lithium battery CR2032 was used as the evaluation cell. Specifically, a test laminate having the following layers (stainless steel plate / metallic lithium foil on the dissolution side / solid electrolyte-containing layer / metallic lithium foil on the deposition side) was fabricated. A current of 0.10 mA / cm was applied to this laminate. 2 The current density was measured using commercially available LLZN sintered pellets (Li 6.75 La3Zr 1.75 Nb 0.25 O 12 The limiting current density is obtained when a Li deposition-dissolution cycle test was performed using a 500 μm thick pellet. The test temperature was 60°C. The test time was 1 hour. Details of each layer are as follows: Stainless steel plate, thickness: 500 μm, diameter: 15.5 mm -Metallic lithium foil on the melting side, thickness: 500 μm, diameter: 13 mm ·Solid electrolyte containing layer, diameter: 15mm Deposition side: metallic lithium foil, thickness: 500 μm, diameter: 13 mm.

[0117] The ionic conductivity of the solid electrolyte-containing layer was measured using an impedance method, specifically as follows. 1. In a glove box under a dry argon atmosphere, a measurement sample was sandwiched between two blocking electrodes (e.g., SUS electrodes) to prepare a coin-type lithium battery CR2032 (coin cell). 2. The obtained coin cell was conditioned in a thermostatic chamber at 60°C for 12 hours. 3. Measurements were made using an impedance measuring device at 60°C, in the frequency range of 0.1 Hz to 1 MHz, and with an amplitude of 10 mV. The ionic conductivity σ was calculated using the following formula: σ(S·cm -1 )=t(cm)×R(Ω) / A(cm 2 ) In the formula, R represents the impedance value, A represents the area of ​​the sample, and t represents the thickness of the sample.

[0118] Example 1 Inorganic solid electrolyte (Li6La3Ta manufactured by Toshima Manufacturing Co., Ltd.) 1.5 Y 0.5 O 12 Powder; LLTY, D 50 1500 mg of cellulose nitrate (2-3 μm) and 500 mg of heat-resistant resin (polyparaphenylene terephthalamide) were mixed in a mortar and pestle for 15 minutes. Next, 111 mg of the resulting mixture was pressure-molded at 200 MPa for about 2 minutes to produce a pellet. This pellet was impregnated with 50 μL (70 mg) of an ionic liquid to obtain a solid electrolyte-containing layer 1. The ionic liquid used was a mixture of tetraglyme (G4) and lithium bis(fluorosulfonyl)imide (LiFSI), [Li(G4)][FSI]. The thickness of the solid electrolyte-containing layer 1 was 293 μm. The ionic conductivity of the resulting solid electrolyte-containing layer 1 at 60°C was 4.2 × 10 -4 It was S / cm.

[0119] Example 2 Inorganic solid electrolyte (Li6La3Ta manufactured by Toshima Manufacturing Co., Ltd.) 1.5 Y 0.5 O 12Powder; LLTY, D 50 1200 mg of polyethylene oxide (PEO) with a particle size of 2-3 μm, 400 mg of a heat-resistant resin (polyparaphenylene terephthalamide), and 400 mg of a polymer electrolyte were mixed in a mortar and pestle for 15 minutes. The polymer electrolyte used was polyethylene oxide (PEO) to which lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) had been added. The mixing ratio was adjusted to Li / ethylene oxide repeating unit = 1 / 24 (molar ratio). Next, 153 mg of the resulting mixture was pressure-molded at 200 MPa for about 2 minutes to produce a pellet. This pellet was used as the solid electrolyte-containing layer 2. The thickness of the solid electrolyte-containing layer 2 was 521 μm. The ionic conductivity of the resulting solid electrolyte-containing layer 2 at 60°C was 3.3 × 10 -6 It was S / cm.

[0120] Example 3 Inorganic solid electrolyte (Li6La3Ta manufactured by Toshima Manufacturing Co., Ltd.) 1.5 Y 0.5 O 12 Powder; LLTY, D 50 1200 mg of a polymer electrolyte (2-3 μm), 400 mg of a heat-resistant resin (polyparaphenylene terephthalamide), and 400 mg of a polymer electrolyte were mixed in a mortar and pestle for 15 minutes. The same polymer electrolyte as in Example 2 was used. Next, 216 mg of the resulting mixture was pressure-molded at 200 MPa for about 2 minutes to produce a pellet. This pellet was impregnated with 50 μL (70 mg) of the same ionic liquid as in Example 1 to obtain a solid electrolyte-containing layer 3. The thickness of the solid electrolyte-containing layer 3 was 655 μm.

[0121] Example 4 Inorganic solid electrolyte (Li6La3Ta manufactured by Toshima Manufacturing Co., Ltd.) 1.5 Y 0.5 O 12 Powder; LLTY, D 501500 mg of a crystalline silicate (2-3 μm) and 500 mg of a heat-resistant resin (aromatic polyamideimide with a glass transition point of approximately 260°C) were mixed in a mortar and pestle for 15 minutes. Next, 110 mg of the resulting mixture was pressure-molded at 200 MPa for approximately 2 minutes to produce a pellet. 50 μL (70 mg) of an ionic liquid was impregnated into this pellet to obtain a solid electrolyte-containing layer 4. The ionic liquid used was a mixture of tetraglyme (G4) and lithium bis(fluorosulfonyl)imide (LiFSI), [Li(G4)][FSI]. The thickness of the solid electrolyte-containing layer 4 was 315 μm.

[0122] Example 5 Inorganic solid electrolyte (Li6La3Ta manufactured by Toshima Manufacturing Co., Ltd.) 1.5 Y 0.5 O 12 Powder; LLTY, D 50 1500 mg of a crystalline silicate (2-3 μm) and 500 mg of a heat-resistant resin (aromatic polyester with a glass transition point of approximately 240°C) were mixed in a mortar and pestle for 15 minutes. Next, 113 mg of the resulting mixture was pressure-molded at 200 MPa for approximately 2 minutes to produce a pellet. 50 μL (70 mg) of an ionic liquid was impregnated into this pellet to obtain a solid electrolyte-containing layer 5. The ionic liquid used was a mixture of tetraglyme (G4) and lithium bis(fluorosulfonyl)imide (LiFSI), [Li(G4)][FSI]. The thickness of the solid electrolyte-containing layer 5 was 302 μm.

[0123] Comparative Example 1 Toshima Manufacturing Co., Ltd. Li6La3Ta 1.5 Y 0.5 O 12 The sintered pellets were used as a comparative solid electrolyte layer, and the thickness of the comparative solid electrolyte layer was 500 μm.

[0124] The solid electrolyte-containing layer 3 contains a polymer electrolyte and corresponds to a "solid electrolyte-containing layer containing a polymer electrolyte." Here, the polymer electrolyte is a substance containing a lithium ion salt, and the solid electrolyte-containing layer 3 also corresponds to a "solid electrolyte-containing layer containing a mixture of an ionic liquid and a lithium salt."

[0125] Comparative Example 2 Inorganic solid electrolyte (Li6La3Ta manufactured by Toshima Manufacturing Co., Ltd.) 1.5 Y 0.5 O 12 Powder; LLTY, D 50 An inorganic solid electrolyte (particle size = 2-3 μm) and a heat-resistant resin (polyparaphenylene terephthalamide) were mixed in a mortar and pestle for 15 minutes. The heat-resistant resin content was 25 wt %. The resulting mixture was then pressure-molded at 200 MPa for approximately 2 minutes to produce a pellet. Gold was then vapor-deposited on both sides of the resulting pellet. When the impedance of the resulting pellet was measured, the Cole-Cole plot was irregular, showing no ionic conductivity and making it unsuitable for use in all-solid-state secondary batteries. Therefore, this pellet was not expected to have a dendrite suppression effect in all-solid-state secondary batteries. Because this pellet contained only an inorganic solid electrolyte and a heat-resistant resin, it is believed that the ionic conduction pathways were disrupted.

[0126] [result] From the start of the test to the end of the test (within 1 hour), the voltage of the test laminates of Examples 1 to 5 never reached 0 V. This suggests that the solid electrolyte-containing layer suppressed short circuits between electrodes caused by the generation of dendrites in the test laminates of Examples 1 to 5. Of the examples, Examples 1 and 3 to 5 maintained stable voltage output until the end. On the other hand, Example 2 showed a decrease in voltage over time.

[0127] In contrast, in the test laminate according to Comparative Example 1, the voltage was close to 0 for several times. This is thought to be because, since a solid electrolyte-containing layer was not used, micro-short circuits occurred due to the grown dendrites.

[0128] These results suggest that the use of a solid electrolyte-containing layer can prevent short circuits between electrodes due to dendrite formation. Furthermore, it also suggests that a solid electrolyte-containing layer containing an ionic liquid or a mixture of an ionic liquid and a lithium salt is preferable from the viewpoint of stabilizing voltage output. [Industrial Applicability]

[0129] The present invention can be used in all-solid-state secondary batteries and the like. [Explanation of symbols]

[0130] 10: Positive electrode 20: Solid electrolyte layer 30: Solid electrolyte containing layer 31: Inorganic solid electrolyte 32: Heat resistant resin 40: Negative electrode 100a: All-solid-state secondary battery 100b: All-solid-state secondary battery 100c: All-solid-state secondary battery

Claims

1. A battery comprising an oxide-based solid electrolyte, a heat-resistant resin having a glass transition point of 200°C or higher, and an ionic liquid, The solid electrolyte-containing layer, wherein the ionic liquid is a mixture of a lithium salt and a non-ionic organic ligand.

2. An all-solid-state secondary battery comprising: a positive electrode; the solid electrolyte-containing layer according to claim 1; and a negative electrode.

3. A method for producing an all-solid-state secondary battery, comprising a step of disposing the solid electrolyte-containing layer according to claim 1 or 2 between a positive electrode and a negative electrode.

4. A method for preventing a short circuit in an all-solid-state secondary battery, comprising disposing the solid electrolyte-containing layer according to claim 1 or 2 between a positive electrode and a negative electrode.

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