Laminate

Abstract

The present invention provides a laminate which prevents short-circuiting caused by the generation of dendrites and with which stable voltage output can be obtained. A laminate (50) according to one embodiment of the present invention includes a solid electrolyte layer (20), and a layer (30) including a heat-resistant resin and an ion-conductive material. The solid electrolyte layer (20) and the layer (30) including the heat-resistant resin and the ion-conductive material are adjacent to each other.

Description

[Technical Field]

[0001] The present invention also relates to an all-solid-state secondary battery, a method for producing the same, a short-circuit prevention film, 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 have room for improvement in terms of preventing short circuits between electrodes and obtaining stable voltage output.

[0005] An object of one aspect of the present invention is to provide a laminate that can prevent short circuits caused by the formation of dendrites and can obtain a stable voltage output. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by using a layer containing a heat-resistant resin and an ion-conductive material. That is, the present invention includes the following features. <1> a solid electrolyte layer and a layer containing a heat-resistant resin and an ion-conductive material; a laminate, wherein the solid electrolyte layer and the layer containing the heat-resistant resin and the ion-conductive material are adjacent to each other. <2> The glass transition point of the heat-resistant resin is 200°C or higher. <1> The laminate according to claim 1. <3> The ion-conductive material is 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. <1> or <2> The laminate according to claim 1. <4> the solid electrolyte contained in the solid electrolyte layer is an inorganic solid electrolyte; <1> ~ <3> The laminate according to any one of the preceding items. <5> The inorganic solid electrolyte is an oxide-based solid electrolyte or a sulfide-based solid electrolyte. <4> The laminate according to claim 1. <6> A positive electrode and <1> ~ <5> and a negative electrode, the layer containing the heat-resistant resin and the ion-conductive material is disposed between the negative electrode and the solid electrolyte layer. <7> A short circuit prevention film comprising a heat-resistant resin and an ion-conductive material, The short-circuit prevention film, wherein the ion-conductive material is 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. <8> <6> A method for producing the all-solid-state secondary battery according to claim 1, and disposing a layer containing the heat-resistant resin and the ion-conductive material between the solid electrolyte layer and the negative electrode. <9> Between the positive and negative electrodes, <1> ~ <4> or <7> A method for preventing a short circuit in an all-solid-state secondary battery, comprising arranging the short-circuit prevention film according to claim 1. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a laminate that can prevent short circuits caused by the generation of dendrites and obtain a stable voltage output. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram schematically illustrating a laminate and an all-solid-state secondary battery according to an embodiment of the present invention. [Figure 2] 1A and 1B are diagrams schematically illustrating a laminate and an all-solid-state secondary battery according to another embodiment of the present invention. [Figure 3] 1 is a graph showing the results of a dendrite resistance test for an all-solid-state secondary battery including a laminate according to an embodiment of the present invention, which uses aramid as the heat-resistant resin and a polymer electrolyte as the ion-conductive material. [Figure 4] 1 is a graph showing the results of a dendrite resistance test for an all-solid-state secondary battery including a laminate according to an embodiment of the present invention, which uses aramid as the heat-resistant resin and an ionic liquid as the ion-conductive material. [Figure 5] 1 is a graph showing the results of a dendrite resistance test for an all-solid-state secondary battery including a laminate according to an embodiment of the present invention, which uses aramid and aromatic polyester as the heat-resistant resin and a polymer electrolyte as the ion-conducting material. [Figure 6] 1 is a graph showing the results of a dendrite resistance test for an all-solid-state secondary battery including a laminate according to an embodiment of the present invention, which uses aramid and aromatic polyester as heat-resistant resins and an ionic liquid as an ion-conducting material. 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. Laminate] 1 and 2 . The laminate 50 includes a solid electrolyte layer 20 and a layer 30 containing a heat-resistant resin and an ion-conductive material. The solid electrolyte layer 20 and the layer 30 containing a heat-resistant resin and an ion-conductive material are adjacent to each other. That is, the laminate 50 is a laminate in which the layer 30 containing a heat-resistant resin and an ion-conductive material is stacked on one or both sides of the solid electrolyte layer 20. At least one of the layers 30 containing a heat-resistant resin and an ion-conductive material is provided between the solid electrolyte layer 20 and the negative electrode 40 (the side of the laminate 50 that contacts the negative electrode 40). In one embodiment, the laminate 50 is a component that constitutes part of an all-solid-state secondary battery.

[0012] 1 shows a laminate 50 in which a layer 30 containing a heat-resistant resin and an ion-conductive material is laminated on one side of a solid electrolyte layer 20. FIG. 2 shows a laminate 50 in which a layer 30 containing a heat-resistant resin and an ion-conductive material is laminated on both sides of a solid electrolyte layer 20. From the viewpoint of miniaturizing the all-solid-state secondary battery, it is preferable that the layer 30 containing a heat-resistant resin and an ion-conductive material is provided on one side of the solid electrolyte layer 20 (that is, the form of an all-solid-state secondary battery 100a is preferable).

[0013] 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. The present invention solves this problem by providing a layer 30 containing a heat-resistant resin and an ion-conductive material.

[0014] Furthermore, because all-solid-state secondary batteries do not use flammable organic solvents as electrolytes, they are inherently safer, with a low risk of 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, 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 become a high-temperature environment (approximately 150°C or higher) due to the heat generated during charging and discharging. The present inventors have newly discovered a problem: even if a resin layer is provided between the solid electrolyte layer 20 and the anode 40 in such a high-temperature environment, if the resin does not have heat resistance, the resin may soften or melt, or the resin layer itself may deform, making it easier for dendrites to penetrate the resin layer. Therefore, it is desirable for the layer provided between the solid electrolyte layer 20 and the anode 40 to resist softening, melting, or deformation even in high-temperature environments.

[0015] Therefore, in the present invention, a layer 30 containing a heat-resistant resin and an ion-conductive material is provided between the solid electrolyte layer 20 and the negative electrode 40. Because the layer 30 containing a heat-resistant resin and an ion-conductive material contains a heat-resistant resin, it is resistant to softening, melting, and deformation even in high-temperature environments. This solves the above-mentioned problems. The layer 30 containing a heat-resistant resin and an ion-conductive material physically blocks dendrites formed in the negative electrode 40 with the heat-resistant resin, preventing short circuits between the electrodes. Furthermore, because the solid electrolyte layer 20 and the negative electrode 40 do not come into direct contact with each other and the negative electrode 40 forms a good interface, dendrite nucleation on the surface of the negative electrode 40 can be suppressed.

[0016] The glass transition point of the heat-resistant resin 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 is equal to or higher than 200° C., melting, softening, and deformation of the layer 30 containing the heat-resistant resin and the ion-conductive material can be more effectively prevented even if the inside of the all-solid-state secondary batteries 100 a, 100 b becomes a high-temperature environment as described above.

[0017] However, the present inventors have also found that when a layer containing only a heat-resistant resin is provided between the solid electrolyte layer 20 and the negative electrode 40, the ionic conductivity decreases, causing the voltage output of the all-solid-state secondary batteries 100a, 100b to decrease or become unstable. For this reason, the present invention provides a layer 30 containing both a heat-resistant resin and an ion-conductive material.

[0018] In summary, the all-solid-state secondary batteries 100a, 100b, each including the layer 30 containing a heat-resistant resin and an ion-conductive material, can be said to be batteries that prevent short circuits caused by dendrites even in high-temperature environments, have sufficient ion conductivity, and can obtain stable voltage output. Whether short circuits caused by dendrites can be prevented in high-temperature environments can be confirmed, for example, by the tests described in the examples below.

[0019] [1.1. Layer containing heat-resistant resin and ion-conductive material] The layer 30 containing a heat-resistant resin and an ion-conductive material contains a heat-resistant resin and an ion-conductive material. In addition, the layer 30 containing a heat-resistant resin and an ion-conductive material may contain other materials (such as other resins).

[0020] When the ion-conductive material contains a polymer electrolyte (described later), the lower limit of the weight of the heat-resistant resin in the layer 30 containing the heat-resistant resin and the ion-conductive material 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 80 wt % or less, more preferably 70 wt % or less. The lower limit of the weight of the ion-conductive material in the layer 30 containing the heat-resistant resin and the ion-conductive material is preferably 20 wt % or more, more preferably 30 wt % or more. The upper limit of the weight of the ion-conductive material is preferably 99 wt % or less, more preferably 95 wt % or less. However, the above-mentioned ratios are based on the total weight of the heat-resistant resin and the ion-conductive material being 100 wt %. If the heat-resistant resin and the ion-conductive material are contained in such ratios, short circuits due to dendrite formation can be more reliably prevented and the voltage output can be more stabilized.

[0021] These lower and upper limits can be combined as appropriate. Examples of weight combinations of the heat-resistant resin include 1% by weight to 80% by weight and 5% by weight to 70% by weight. Examples of weight combinations of the ion-conductive material include 20% by weight to 99% by weight and 30% by weight to 95% by weight.

[0022] When the ion-conductive material contains an ionic liquid (described below), the lower limit of the weight of the heat-resistant resin in the layer 30 containing the heat-resistant resin and the ion-conductive material is preferably 1 wt % or more, more preferably 2 wt % or more. The upper limit of the weight of the heat-resistant resin is preferably 99 wt % or less, more preferably 90 wt % or less. Furthermore, the lower limit of the weight of the ion-conductive material in the layer 30 containing the heat-resistant resin and the ion-conductive material is preferably 1 wt % or more, more preferably 10 wt % or more. The upper limit of the weight of the ion-conductive material is preferably 99 wt % or less, more preferably 98 wt % or less. If the heat-resistant resin and the ion-conductive material are contained in such proportions, short circuits due to sufficient dendrite formation can be more reliably prevented and the voltage output can be more stabilized.

[0023] These lower and upper limits can be combined as appropriate. Examples of weight combinations of the heat-resistant resin include 1% by weight to 99% by weight and 2% by weight to 90% by weight. Examples of weight combinations of the ion-conductive material include 1% by weight to 99% by weight and 10% by weight to 98% by weight.

[0024] The lower limit of the thickness of the layer 30 containing a heat-resistant resin and an ion-conductive material is preferably 5 μm or more, more preferably 10 μm or more. The upper limit of the thickness of the layer 30 containing a heat-resistant resin and an ion-conductive material is preferably 500 μm or less, more preferably 250 μm or less. The upper and lower limits of the thickness of the layer 30 containing a heat-resistant resin and an ion-conductive material may be combined, and example combinations include 5 μm to 500 μm, 10 μm to 250 μm, and 5 μm to 250 μm.

[0025] The lower limit of the ionic conductivity (for example, lithium ion conductivity) of the layer 30 containing the heat-resistant resin and the ion-conductive material 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 layer 30 containing the heat-resistant resin and the ion-conductive material is, for example, 1×10 -2 The upper and lower limits of the ionic conductivity of the layer 30 containing the heat-resistant resin and the ion-conductive material 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.

[0026] The ionic conductivity of the layer 30 containing the heat-resistant resin and the ion-conductive material can be measured by an impedance method, specifically as follows. 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.

[0027] (Heat-resistant resin) As used herein, the term "heat-resistant resin" refers to a resin that does not soften, melt, or thermally decompose in a high-temperature environment. Here, a "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. The upper limit of the glass transition point of the heat-resistant resin can be 450°C or lower. The upper and lower limit values of the glass transition point of the heat-resistant resin can be combined. 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. Such a resin does not soften, melt, or thermally decompose even when the all-solid-state secondary batteries 100a, 100b are heated and used without a cooling system.

[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] (ion-conducting material) In this specification, the term "ionically conductive material" refers to a material having an ionic conductivity of a specific ion (such as lithium ion) of 10 or more at 60°C. -6 S / cm or more. Examples of ion-conductive substances include ionic liquids, mixtures of ionic liquids and lithium salts, polymer electrolytes, and inorganic solid electrolytes. These ion-conductive substances may be used alone or in combination of two or more. The ionic conductivity of ion-conductive substances can be measured by the impedance method, and the specific measurement method is as described above.

[0036] 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.

[0037] Examples of the lithium salt 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(oxalate)borate.

[0038] Examples of the lithium salt in the mixture of the ionic liquid and the lithium salt include the lithium salts mentioned above.

[0039] A polymer electrolyte is a mixture of a polymer compound with polarity in its molecule and a lithium salt. Specifically, it is an electrolyte obtained by dissolving a lithium salt in a polymer compound with polarity in its molecule. Specific examples of polymer electrolytes include the compounds exemplified in Section [1.2.] (organic solid electrolytes).

[0040] The layer containing the heat-resistant resin and the ion-conductive material may contain an inorganic solid electrolyte. Examples of inorganic solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, and nitride-based solid electrolytes. Specific examples of inorganic solid electrolytes include the compounds exemplified in (Inorganic Solid Electrolytes) in Section [1.2.]. The layer 30 containing the heat-resistant resin and the ion-conductive material and containing the inorganic solid electrolyte preferably further contains 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. This configuration can further enhance ionic conductivity.

[0041] [1.1.1. Form and manufacturing method of layer containing heat-resistant resin and ion-conductive material] The layer 30 containing a heat-resistant resin and an ion-conductive material can take various forms. For example, in the layer 30 containing a heat-resistant resin and an ion-conductive material, the heat-resistant resin may be uniformly distributed or localized. An example of the former is a layer in which a porous substrate containing a heat-resistant resin is impregnated with or supports an ion-conductive material. An example of the latter is a layer in which a porous substrate formed by laminating a heat-resistant resin and another resin is impregnated with or supports an ion-conductive material. It is preferable that the ion-conductive material be uniformly distributed in the layer 30 containing a heat-resistant resin and an ion-conductive material.

[0042] Examples of methods for producing the layer 30 containing a heat-resistant resin and an ion-conductive material include the following methods (a), (b), (c) and (d).

[0043] (a) A method in which a porous substrate (porous membrane, nonwoven fabric, etc.) containing a heat-resistant resin is impregnated with or supported by an ion-conductive substance to obtain a layer 30 containing a heat-resistant resin and an ion-conductive substance. From the viewpoint of reducing the thickness of the layer 30 containing a heat-resistant resin and an ion-conductive substance, the porous substrate is preferably a porous membrane.

[0044] (b) A method in which a porous substrate containing a heat-resistant resin and another substance (such as a porous membrane in which a heat-resistant resin and another resin are laminated; a nonwoven fabric in which a heat-resistant resin and another resin are blended, etc.) is impregnated with or made to carry an ion-conductive substance to obtain a layer 30 containing a heat-resistant resin and an ion-conductive substance. For the same reasons as in (a), the porous substrate is preferably a porous membrane.

[0045] (c) A method of forming a layer 30 containing a heat-resistant resin and an ion-conductive material by forming a film from a mixture containing a heat-resistant resin and an ion-conductive material. Examples of the film formation method include a wet method using a solvent and a dry method in which the mixture is pressed together.

[0046] (d) A method of binding an ion-conductive material with a heat-resistant resin to obtain a layer 30 containing a heat-resistant resin and an ion-conductive material. For example, a method of binding an inorganic solid electrolyte with a heat-resistant resin is exemplified, and a preferred method is a method of binding an inorganic solid electrolyte with a heat-resistant resin, and then adding 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.

[0047] Here, the "porous substrate" in the above embodiments (a) and (b) 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 2The 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.

[0048] The "porous substrate containing a heat-resistant resin and other substances" in the production method (b) may further contain a filler, etc. The filler material may be a conventionally known material (such as alumina).

[0049] Furthermore, examples of the "other resin" in aspect (b) include 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. Examples of such copolymers include ethylene-propylene copolymers. 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 with a weight-average molecular weight of 1,000,000 or more. Of these, ultra-high molecular weight polyethylene is particularly preferred.

[0050] [1.1.2. Short-circuit prevention film] In one embodiment, the layer 30 containing a heat-resistant resin and an ion-conductive material may be a short-circuit prevention film. As used herein, the term "short-circuit prevention film" refers to the layer 30 containing a heat-resistant resin and an ion-conductive material that has the function of preventing short circuits. Whether the layer 30 containing a heat-resistant resin and an ion-conductive material has the 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 the following dendrite resistance test is performed. 2. After 20 hours have passed since the start of the test, the coin cell that showed a nearly constant negative voltage was disassembled and the solid electrolyte layer was removed. 3. The surface of the removed solid electrolyte layer is observed. If there are less than 10 black dots (i.e., dendrite marks) on the surface of the solid electrolyte layer, it is determined to be a short-circuit prevention film according to the present invention.

[0051] (Dentrite resistance test) 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.

[0052] 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) Layer 30 (short circuit prevention film) containing heat-resistant resin and ion-conductive material, diameter: 16 mm - Metallic lithium foil (negative electrode) on the deposition side, thickness: 500 μm, diameter: 13 mm.

[0053] In the dendrite resistance test, if no short circuit occurs and metallic lithium is stably deposited on the negative electrode, the coin cell will show a nearly constant negative voltage. On the other hand, if a complete short circuit occurs due to dendrites, the coin cell's voltage will show 0V. Furthermore, if repeated micro-short circuits occur due to dendrites, the coin cell's voltage will fluctuate dramatically between 0V and negative values.

[0054] The fact that there were fewer than 10 dendrite marks on the surface of the solid electrolyte layer after the dendrite resistance test indicates that the layer 30 (short-circuit prevention film) containing the heat-resistant resin and the ion-conductive material suppressed the growth of dendrites and prevented the penetration of dendrites into the solid electrolyte layer.

[0055] For example, in the examples described below, a "membrane in which a heat-resistant resin-polyethylene laminated film is impregnated with an ion-conductive material" is used. When this membrane was subjected to the dendrite resistance test described above, it showed a stable, constant negative voltage (approximately -1.5 V) even 20 hours after the start of the test. In addition, when the coin cell was disassembled after the test and the surface of the solid electrolyte layer was observed, no black dendrite marks were found. These results demonstrate that the "membrane in which a heat-resistant resin-polyethylene laminated film is impregnated with an ion-conductive material" is a short-circuit prevention membrane.

[0056] The short-circuit prevention film is preferably a layer 30 containing a heat-resistant resin and an ion-conductive material, which can be handled as a sheet-like object during the manufacturing stage of the all-solid-state secondary batteries 100 a, 100 b. Such a short-circuit prevention film can be distributed as a component of the laminate 50 or the all-solid-state secondary batteries 100 a, 100 b, or as a finished product or semi-finished product.

[0057] The embodiment in which the layer 30 containing a heat-resistant resin and an ion-conductive material is a sheet-like short-circuit prevention film has the following advantages, for example.

[0058] (1) The material is easy to handle, facilitating the manufacture of the all-solid-state secondary batteries 100a and 100b.

[0059] (2) It is possible to laminate a short-circuit prevention film with a highly uniform film thickness and no defects such as pinholes, which results in better short-circuit prevention properties than other methods (such as the method (γ) described below, which involves applying and drying a solution).

[0060] (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.

[0061] One aspect of the present invention is a short-circuit prevention film containing a heat-resistant resin and an ion-conductive material. In other words, one aspect of the present invention is use of a film containing a heat-resistant resin and an ion-conductive material for preventing a short circuit in an all-solid-state secondary battery (this film may be a component constituting a part of the laminate 50).

[0062] [1.2. 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 layer 30 containing the heat-resistant resin and the ion-conductive material. For example, the weight of the heat-resistant resin in the solid electrolyte layer 20 is less than 1 wt %.

[0063] The lower limit of the thickness of the solid electrolyte layer 20 is, for example, 5 μm or more, and the upper limit is, for example, 500 μm or less. The upper and lower limits of the thickness of the solid electrolyte layer 20 may be combined, and an example of such a combination is 5 μm or more and 500 μm or less.

[0064] The ionic conductivity (e.g., lithium ion conductivity) of the solid electrolyte layer 20 at 25°C is, for example, 1×10 -5 S / cm or more is preferable, and 1×10 -4 The upper limit of the ionic conductivity (e.g., lithium ion conductivity) of the solid electrolyte layer 20 at 25°C is, for example, 1 × 10 -2 The upper and lower limits of the ionic conductivity (e.g., lithium ion conductivity) of the solid electrolyte layer 20 may be combined. 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 -2S / cm or less.

[0065] The lithium ion conductivity of the solid electrolyte layer 20 at 25° C. can be measured by an impedance method, specifically as follows. 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 25°C for 12 hours. 3. Using an impedance measuring device, measurements are taken at 25°C, in the frequency range of 0.1 Hz to 1 MHz, and 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.

[0066] 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.

[0067] 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 a layer 30 containing a heat-resistant resin and an ion-conductive material, 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, 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 in all-solid-state secondary batteries, it is preferable to use an oxide-based solid electrolyte as the inorganic solid electrolyte.

[0068] (Inorganic solid electrolyte) 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).

[0069] 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."

[0070] 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));

[0071] 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.

[0072] 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 Zr. 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).

[0073] 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.

[0074] The inorganic solid electrolyte is preferably in the form of a pellet. The thickness of the pellet-shaped inorganic solid electrolyte is preferably 1 mm or less, more preferably 500 μm or less. The lower limit of the thickness of the inorganic solid electrolyte is, for example, 5 μm or more. The upper and lower limit values of the thickness of the inorganic solid electrolyte may be combined, and examples of such combinations include 5 μm or more and 1 mm or less, and 5 μm or more and 500 μm or less.

[0075] 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 is preferable, and 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.

[0076] 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.

[0077] (Organic solid electrolyte) 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 include those exemplified in the section (Ionically Conductive Materials) in Section [1.1.].

[0078] 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.

[0079] 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.

[0080] 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 lithium salts include the substances exemplified in the item (ion-conductive materials) in Section [1.1.]. Examples of non-aqueous solvents include cyclic carbonates, chain carbonates, carboxylic acid esters, cyclic ethers, chain ethers, nitriles, and amides.

[0081] [2. All-solid-state secondary battery] FIG. 1 is a schematic diagram showing a laminate and an all-solid-state secondary battery according to one embodiment of the present invention. The all-solid-state secondary battery 100a includes a positive electrode 10, a laminate 50, and a negative electrode 40. Here, the laminate 50 is arranged such that a layer 30 containing a heat-resistant resin and an ion-conductive material is located between the solid electrolyte layer 20 and the negative electrode 40. In the laminate 50 shown in FIG. 1, the layer 30 containing a heat-resistant resin and an ion-conductive material is provided on one side of the solid electrolyte layer 20. Therefore, the layer 30 containing a heat-resistant resin and an ion-conductive material is not present between the positive electrode 10 and the solid electrolyte layer 20.

[0082] Fig. 2 is a schematic diagram showing a laminate and an all-solid-state secondary battery according to another embodiment of the present invention. In the laminate 50 shown in Fig. 2, layers 30 containing a heat-resistant resin and an ion-conductive material are provided on both sides of a solid electrolyte layer 20. Therefore, a layer 30 containing a heat-resistant resin and an ion-conductive material is also present between the positive electrode 10 and the solid electrolyte layer 20.

[0083] 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 and 100b do not include an electrolytic solution (e.g., an aqueous electrolytic solution or a non-aqueous electrolytic solution).

[0084] The shape of the all-solid-state secondary batteries 100a and 100b is not particularly limited. Examples of shapes include coin-type batteries, laminated batteries, cylindrical batteries, and square 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.

[0085] The all-solid-state secondary batteries 100a and 100b 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.

[0086] The applications of the all-solid-state secondary batteries 100a and 100b 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.).

[0087] [2.1. Positive electrode] The positive electrode 10 includes, for example, a positive electrode active material layer and a positive electrode current collector.

[0088] The positive electrode active material layer is a layer containing at least a positive electrode active material, examples of which include oxide-based active materials and sulfur-based active materials.

[0089] Examples of oxide active materials include rock salt layered active materials (LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.); spinel-type active materials (LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, etc.); olivine-type active materials (LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc.). Other examples of oxide-based active materials include Li 1+x Mn 2-x-y M yA LiMn spinel active material represented by O4 (where M is one or more selected from the group consisting of Al, Mg, Co, Fe, Ni, and Zn, and 0 < x + y < 2); examples include lithium titanate.

[0090] 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 of the thickness of the coating layer can be, for example, 0.1 nm or more or 1 nm or more. The upper limit 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.

[0091] 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 ; 2 ≤ x ≤ 8).

[0092] The positive electrode active material layer may optionally contain one or more selected from the group consisting of an inorganic solid electrolyte, a conductive material, and a binder. Examples of the inorganic solid electrolyte can be the inorganic solid electrolytes described in [1.2.]. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Examples of the binder include rubber-based binders (such as butadiene rubber (BR), styrene-butadiene rubber (SBR), etc.); fluoride-based binders (such as polyvinylidene fluoride (PVDF), etc.).

[0093] The lower limit of the thickness of the positive electrode active material layer is, for example, 0.1 μm or more. 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.

[0094] 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.

[0095] [2.2. Negative electrode] The negative electrode 40 includes, for example, a negative electrode active material layer and a negative electrode current collector.

[0096] 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.

[0097] Examples of carbon-based materials include graphite, amorphous carbon, carbon nanotubes, and graphene. Examples of oxide-based materials include Li4Ti5O 12 (LTO), TiO2.

[0098] 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 [2.1.].

[0099] 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.

[0100] 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.

[0101] 3. Manufacturing method of all-solid-state secondary battery One aspect of the present invention is a method for producing an all-solid-state secondary battery, which includes a step of disposing a layer 30 containing a heat-resistant resin and an ion-conductive material between a solid electrolyte layer 20 and a negative electrode 40. In one embodiment, the layer 30 containing a heat-resistant resin and an ion-conductive material is a short-circuit prevention film.

[0102] [3.1. Arrangement of Layers Containing Heat-Resistant Resin and Ion-Conductive Material] Examples of methods for disposing the layer 30 containing a heat-resistant resin and an ion-conductive material between the solid electrolyte layer 20 and the negative electrode 40 include the following.

[0103] (α) A method in which a layer 30 (short-circuit prevention film) containing a heat-resistant resin and an ion-conductive material is prepared and then disposed between the solid electrolyte layer 20 and the negative electrode 40. For example, a method in which the layer 30 (short-circuit prevention film) containing a heat-resistant resin and an ion-conductive material is placed on the solid electrolyte layer 20 or the negative electrode 40.

[0104] (β) A method of forming the layer 30 containing a heat-resistant resin and an ion-conductive material after disposing a porous substrate containing a heat-resistant resin (or a porous substrate containing a heat-resistant resin and another material) between the solid electrolyte layer 20 and the negative electrode 40. For example, a method of placing a porous substrate containing a heat-resistant resin on the solid electrolyte layer 20 or the negative electrode 40, and then impregnating or supporting the ion-conductive material in the porous substrate.

[0105] (γ) A method of applying a solution containing a heat-resistant resin and an ion-conductive material onto the solid electrolyte layer 20 or the negative electrode 40 to produce a layer 30 containing a heat-resistant resin and an ion-conductive material. For example, a method of (i) preparing a solution containing a heat-resistant resin, an ion-conductive material, and a solvent, (ii) applying the solution onto the solid electrolyte layer 20 or the negative electrode 40, and (iii) drying to remove the solvent.

[0106] (δ) A method of forming a layer 30 containing a heat-resistant resin and an ion-conductive material by placing a powder of a mixture containing a heat-resistant resin and an ion-conductive material on the solid electrolyte layer 20 or the negative electrode 40 and molding the mixture. For example, a method of (i) preparing a powder of a mixture containing a heat-resistant resin and an ion-conductive material, (ii) placing the powder on the solid electrolyte layer 20 or the negative electrode 40, and (iii) press-molding the powder.

[0107] [3.2. Manufacturing Method of All-Solid-State Secondary Battery 100a] By carrying out any of the above methods (α) to (δ), it is possible to produce a laminate 50 in which a solid electrolyte layer 20, a layer 30 containing a heat-resistant resin and an ion-conductive material, and a negative electrode 40 are laminated in this order, and which has only one layer 30 containing a heat-resistant resin and an ion-conductive material. By further laminating a positive electrode 10 on the solid electrolyte layer 20 of this laminate 50, it is possible to produce a laminate (all-solid-state secondary battery 100a) in which the positive electrode 10, the solid electrolyte layer 20, the layer 30 containing a heat-resistant resin and an ion-conductive material, and a negative electrode 40 are laminated in this order.

[0108] [3.3. Manufacturing Method of All-Solid-State Secondary Battery 100b] By performing any of the above methods (α) to (δ), it is possible to produce a laminate 50 in which a solid electrolyte layer 20, a layer 30 containing a heat-resistant resin and an ion-conductive material, and a negative electrode 40 are laminated in this order, and which has only one layer 30 containing a heat-resistant resin and an ion-conductive material. By further laminating a layer 30 containing a heat-resistant resin and an ion-conductive material and a positive electrode 10 on the solid electrolyte layer 20 of this laminate 50, it is possible to produce a laminate (all-solid-state secondary battery 100b) in which the positive electrode 10, the layer 30 containing a heat-resistant resin and an ion-conductive material, the solid electrolyte layer 20, the layer 30 containing a heat-resistant resin and an ion-conductive material, and a negative electrode 40 are laminated in this order.

[0109] The above-described solid electrolyte layer 20 or 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.

[0110] 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.

[0111] Although not shown, the all-solid-state secondary batteries 100a and 100b may also 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.

[0112] 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.

[0113] All scientific and patent literature mentioned herein is hereby incorporated by reference.

[0114] 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]

[0115] The dendrite suppression effect and voltage stabilization effect of using a layer (short circuit prevention film) containing a heat-resistant resin and an ion-conductive material were verified by a dendrite resistance test. In this test, a coin-type lithium battery CR2032 was used as the evaluation cell. Specifically, a test laminate was prepared by stacking each layer in the following order. A current of 0.10 mA / cm was applied to this laminate. 2 The current density was measured using LLZN sintered pellets (Li 6.75 La3Zr 1.75 Nb 0.25 O 12 The graph shows the limiting current density when a deposition-dissolution cycle test was performed using a 500 μm thick pellet (with a short-circuit prevention film). The graph shows the limiting current density when a deposition-dissolution cycle test was performed without using a short-circuit prevention film. The test temperature was 60°C. Stainless steel plate, thickness: 500 μm, diameter: 15.5 mm - Metallic lithium foil on the elution side, thickness: 500 μm, diameter: 13 mm Solid electrolyte layer (Toshima Manufacturing Co., Ltd., Li 6.75 La3Zr 1.75 Nb 0.25 O 12 Sintered body, thickness 500 μm, diameter 15 mm, ionic conductivity at 25 °C: 1.0 × 10 -5 S / cm) Short circuit prevention membrane, diameter: 16mm Deposition side: metallic lithium foil, thickness: 500 μm, diameter: 13 mm.

[0116] The ionic conductivity of the short-circuit prevention film or the ionic conductive material 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.

[0117] The ionic conductivity of the solid electrolyte was measured in the same manner as above, except that the temperature was changed to 25°C.

[0118] Example 1-1 A polymer electrolyte was used as the ion-conductive material. Specifically, LiTFSI (Sigma Aldrich) was added to a 10 wt % aqueous solution of polyethylene oxide (PEO; Sigma Aldrich, MW: 200,000). The mixing ratio was such that the molar ratio of Li / ethylene oxide repeating units was 1 / 24. The mixture was then heated to 80°C under stirring to dissolve the LiTFSI. An aramid-polyethylene laminated film was impregnated with the resulting aqueous solution and dried to obtain a short-circuit prevention film 1-1. The film thickness of the short-circuit prevention film 1-1 was 28 μm. The polymer electrolyte content of the short-circuit prevention film 1-1 was 73 wt %. The ionic conductivity of the short-circuit prevention film 1-1 at 60°C was 2.3 × 10 -5 It was S / cm.

[0119] The aramid-polyethylene laminated film used here was a laminated film having a polyethylene film (thickness: 12.5 μm) and a layer (thickness: 4.0 μm) containing aramid resin (polyparaphenylene terephthalamide) and alumina in a weight ratio of 1:2. When arranging the short-circuit prevention film 1-1, it was arranged so that the aramid resin layer faced the deposition-side metallic lithium foil.

[0120] Comparative Example 1-1 The dendrite resistance test was carried out without using the short circuit prevention film.

[0121] Comparative Example 1-2 A ceramic-polyethylene laminated film was impregnated with an aqueous solution prepared in the same manner as in Example 1 and dried to obtain a comparative short-circuit prevention film 1-2. The ceramic-polyethylene laminated film used here was a laminated film having a polyethylene film (thickness: 12.5 μm) and a ceramic (alumina: acrylic emulsion binder: sodium polyacrylate = 94 wt %: 5 wt %: 1 wt %) layer (thickness: 2.3 μm). The comparative short-circuit prevention film was arranged so that the ceramic layer faced the deposition-side metallic lithium foil. The film thickness of the comparative short-circuit prevention film 1-2 was 41 μm. The polymer electrolyte content of the comparative short-circuit prevention film 1-2 was 79 wt %. The ionic conductivity of the comparative short-circuit prevention film 1-2 at 60°C was 1.1 × 10 -4 It was.

[0122] Comparative Examples 1-3 A polyethylene monolayer film was impregnated with an aqueous solution prepared in the same manner as in Example 1 and dried to obtain a comparative short-circuit prevention film 1-3. The thickness of the comparative short-circuit prevention film 1-3 was 45 μm. The content of the polymer electrolyte in the comparative short-circuit prevention film 1-1 was 88 wt %. The ionic conductivity of the comparative short-circuit prevention film 1-3 at 60° C. was 6.1×10 -5 It was.

[0123] Comparative Examples 1-4 A comparative short-circuit prevention film 1-4 consisting of only a polymer electrolyte was obtained by removing water as a solvent from the aqueous solution prepared in the same manner as in Example 1. The thickness of the comparative short-circuit prevention film 1-4 was 85 μm. The content of the polymer electrolyte in the comparative short-circuit prevention film 1-4 was 100% by weight. The ionic conductivity of the comparative short-circuit prevention film 1-4 at 60° C. was 2.3×10 -4 It was S / cm.

[0124] Comparative Examples 1-5 The aramid-polyethylene laminated film used in Example 1-1 was used as it was.

[0125] [result] The test results are shown in Figure 3. As can be seen from the figure, the test laminate of Example 1-1 did not experience any short circuits due to dendrite formation for more than 20 hours (until the end of the test), and the voltage behavior was stable. In contrast, in Comparative Example 1-1, the voltage dropped to 0 immediately after the start of the test. This is thought to be because, due to the absence of a short-circuit prevention film, a short circuit occurred between the electrodes due to the grown dendrites. In Comparative Example 1-2, the voltage repeatedly rose and fell, and the voltage behavior was completely unstable. This is thought to be because micro-short circuits caused by dendrites repeatedly occurred between the electrodes. In Comparative Example 1-3, the voltage behavior was also unstable compared to the Examples. In Comparative Example 1-4, the voltage dropped rapidly. This is thought to be because the internal resistance became too high. In Comparative Example 1-5, the internal resistance was so high that measurement was not possible (since it was not possible to measure, it is not shown in Figure 3).

[0126] Example 2-1 An ionic liquid was used as the ion-conductive material. The ionic liquid used was a mixture of tetraglyme (G4) and lithium bis(fluorosulfonyl)imide (LiFSI), [Li(G4)][FSI]. The mixing ratio (molar ratio) was G4:LiFSI=1:1. 50 mL of this ionic liquid was impregnated into the aramid-polyethylene laminated film used in Example 1 to obtain a short-circuit prevention film 2-1. The film thickness of the short-circuit prevention film 2-1 was 17 μm. The short-circuit prevention film was arranged so that the aramid resin layer faced the deposition-side metallic lithium foil. The ionic conductivity of the short-circuit prevention film 2-1 at 60°C was 1.4 × 10 -4 It was S / cm.

[0127] Example 2-2 The short-circuit prevention film 1-1 produced in Example 1-1 was impregnated with 50 mL of the ionic liquid prepared in Example 2-1 to obtain a short-circuit prevention film 2-2. That is, the short-circuit prevention film 2-2 contains both an ionic liquid and a polymer electrolyte as ion-conductive materials. The film thickness of the short-circuit prevention film 2-1 was 55 μm. The short-circuit prevention film was arranged so that the aramid resin layer faced the deposition-side metallic lithium foil.

[0128] Comparative Example 2-1 The dendrite resistance test was carried out without using the short circuit prevention film.

[0129] Comparative Example 2-2 The dendrite resistance test was carried out by impregnating the solid electrolyte layer with ionic liquid without using a short circuit prevention film.

[0130] [result] The test results are shown in Figure 4. As can be seen from the figure, the test laminates of Examples 2-1 and 2-2 did not experience short circuits due to dendrite formation for nearly 50 hours (until the end of the test), and the voltage behavior was stable. Comparing the Examples, Example 2-1 showed more stable voltage behavior. In contrast, in Comparative Example 1-1, the voltage became 0 immediately after the start of the test. This is thought to be because, since there was no short-circuit prevention film, a short circuit occurred between the electrodes due to the grown dendrites. In Comparative Example 1-2, the voltage gradually decreased. This is thought to be because the internal resistance increased over time.

[0131] Example 3-1 A short-circuit prevention film 3-1 was produced in the same manner as in Example 1-1, except that the type of laminated film was changed. Specifically, a laminated film was used as the film to be impregnated with the polymer electrolyte, which had (i) a polyethylene film (thickness: 12.5 μm) and (ii) a layer (thickness: 4.0 μm) containing aramid resin (polyparaphenylene terephthalamide), aromatic polyester (glass transition point: about 240° C.), and alumina in a weight ratio of 3:2:10.

[0132] The short-circuit prevention film 3-1 had a thickness of 69 μm. The polymer electrolyte content of the short-circuit prevention film 3-1 was 90 wt %. The short-circuit prevention film 3-1 was arranged so that the heat-resistant resin layer faced the deposition-side metallic lithium foil.

[0133] Example 3-2 A short-circuit prevention film 3-2 was produced in the same manner as in Example 2-1, except that the type of laminated film was changed. Specifically, a laminated film was used as the film to be impregnated with the ionic liquid, which had (i) a polyethylene film (thickness: 12.5 μm) and (ii) a layer (thickness: 4.0 μm) containing aramid resin (polyparaphenylene terephthalamide), aromatic polyester (glass transition point: about 240°C), and alumina in a weight ratio of 3:2:10.

[0134] The short-circuit prevention film 3-2 had a thickness of 17 μm. The short-circuit prevention film 3-2 was arranged so that the heat-resistant resin layer faced the deposition-side metallic lithium foil.

[0135] [result] The test results for Example 3-1 are shown in Figure 5. As can be seen from the figure, the test laminate according to Example 3-1 did not experience any short circuit due to dendrite formation over a period of 10 hours, and the voltage behavior was stable.

[0136] The test results for Example 3-2 are shown in Figure 6. As can be seen from the figure, the test laminate according to Example 3-2 did not experience any short circuit due to dendrite generation over 50 hours (until the end of the test), and the voltage behavior was stable. [Industrial Applicability]

[0137] The present invention can be used in all-solid-state secondary batteries and the like. [Explanation of symbols]

[0138] 10: Positive electrode 20: Solid electrolyte layer 30: Layer containing heat-resistant resin and ion-conductive material (short-circuit prevention film) 40: Negative electrode 50: Laminate 100a: All-solid-state secondary battery 100b: All-solid-state secondary battery

Claims

1. a solid electrolyte layer and a layer containing a heat-resistant resin and an ion-conductive material; the solid electrolyte layer and the layer containing the heat-resistant resin and the ion-conductive material are adjacent to each other, In the layer containing the heat-resistant resin and the ion-conductive material, the weight of the heat-resistant resin is 1 to 99 wt %, The heat-resistant resin has a glass transition temperature of 200°C or higher.

2. 2. The laminate according to claim 1, wherein the ion-conductive material is 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.

3. 3. The laminate according to claim 1, wherein the solid electrolyte contained in the solid electrolyte layer is an inorganic solid electrolyte.

4. The laminate according to claim 3 , wherein the inorganic solid electrolyte is an oxide-based solid electrolyte or a sulfide-based solid electrolyte.

5. The laminate comprises a positive electrode, the laminate according to any one of claims 1 to 4, and a negative electrode, the layer containing the heat-resistant resin and the ion-conductive material is disposed between the negative electrode and the solid electrolyte layer.

6. A short circuit prevention film comprising a heat-resistant resin and an ion-conductive material, the ion-conductive material is 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; the weight of the heat-resistant resin in the short-circuit prevention film is 1 to 99% by weight; The short circuit prevention film, wherein the heat-resistant resin has a glass transition point of 200°C or higher.

7. A method for producing the all-solid-state secondary battery according to claim 5, and disposing a layer containing the heat-resistant resin and the ion-conductive material between the solid electrolyte layer and the negative electrode.

8. A method for preventing a short circuit in an all-solid-state secondary battery, comprising disposing the laminate according to any one of claims 1 to 4 or the short-circuit prevention film according to claim 6 between a positive electrode and a negative electrode.

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