Solid electrolyte sheet and all-solid-state battery

Abstract

To provide a solid electrolyte sheet capable of preventing the occurrence of a short circuit even when a metal foreign substance is mixed into an all-solid-state battery while suppressing the battery resistance of the all-solid-state battery.SOLUTION: The solid electrolyte sheet of the present disclosure includes a nonwoven fabric and a solid electrolyte disposed inside the nonwoven fabric. The solid electrolyte includes a sulfide solid electrolyte. The pore diameter of the nonwoven fabric is 15 μm or less. The ratio of the pore diameter to the particle diameter of the solid electrolyte (pore diameter / particle diameter) is 5.0 or more and 10.0 or less. The pore size indicates a maximum pore size of the nonwoven fabric measured by a bubble point method in accordance with JIS K 3832. The particle size refers to a particle size corresponding to 50% of a value of a volume-based cumulative particle size distribution of the solid electrolyte measured using a laser diffraction particle size distribution analyzer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a solid electrolyte sheet and an all-solid-state battery. [Background technology]

[0002] BACKGROUND ART All-solid-state batteries having a solid electrolyte layer have been known as lithium ion secondary batteries that are excellent in safety. Patent Document 1 discloses a solid electrolyte sheet used in a solid electrolyte layer. The solid electrolyte sheet disclosed in Patent Document 1 includes a nonwoven fabric and a solid electrolyte. The solid electrolyte is disposed on the surface and inside of the nonwoven fabric. The mass of the nonwoven fabric per square meter is 8 g or less. The thickness of the nonwoven fabric is 10 μm or more and 25 μm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-31789 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, nonwoven fabrics have a plurality of three-dimensional spaces (hereinafter also referred to as "pores") therein, and the distribution of the sizes of the pores (hereinafter also referred to as "pore diameters") is wide. Patent Document 1 does not disclose anything about the pore diameters of nonwoven fabrics. The solid electrolyte sheet disclosed in Patent Document 1 may not be able to retain the solid electrolyte in areas where the pore size of the nonwoven fabric is large, which may result in an increase in the battery resistance of the all-solid-state battery. Furthermore, during the manufacturing process of an all-solid-state battery, there is a risk that metallic foreign matter may be mixed into the materials of the all-solid-state battery. The metallic foreign matter is typically a metal piece having a size of 20 μm. If metallic foreign matter is mixed into the solid electrolyte sheet disclosed in Patent Document 1, the metallic foreign matter may penetrate the solid electrolyte layer during the battery press. The "battery press" refers to the press in which the positive electrode layer, solid electrolyte layer, and negative electrode are laminated and integrated in this order. As a result, there is a risk of a short circuit occurring in the all-solid-state battery.

[0005] The present disclosure has been made in consideration of the above circumstances. An object of an embodiment of the present disclosure is to provide a solid electrolyte sheet that can suppress the battery resistance of an all-solid-state battery and prevent the occurrence of a short circuit even if a metallic foreign matter is mixed into the all-solid-state battery. Another embodiment of the present disclosure aims to solve a problem by providing an all-solid-state battery in which the battery resistance is suppressed and in which a short circuit is unlikely to occur even if metallic foreign matter is mixed inside the all-solid-state battery. [Means for solving the problem]

[0006] The means for solving the above problems include the following embodiments. <1> Nonwoven fabric and a solid electrolyte disposed inside the nonwoven fabric; Equipped with The pore size of the nonwoven fabric is 15 μm or less, A solid electrolyte sheet, wherein the ratio of the pore diameter to the particle diameter of the solid electrolyte (pore diameter / particle diameter) is 5.0 or more. <2> The thickness of the nonwoven fabric is 10 μm or more and 30 μm or less. <1> The solid electrolyte sheet according to claim 1. <3> The particle size is 3.0 μm or less. <1> or <2> The solid electrolyte sheet according to claim 1. <4> the solid electrolyte includes a sulfide solid electrolyte; <1> ~ <3> 10. The solid electrolyte sheet according to claim 9, wherein the first and second electrodes are electrically connected to each other. <5> a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; The solid electrolyte layer is <1> ~ <4> 10. An all-solid-state battery comprising the solid electrolyte sheet according to any one of claims 1 to 9. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, there is provided a solid electrolyte sheet that can suppress the battery resistance of an all-solid-state battery and prevent the occurrence of a short circuit even if a metallic foreign matter is mixed inside the all-solid-state battery. According to another embodiment of the present disclosure, there is provided an all-solid-state battery in which the battery resistance of the all-solid-state battery is suppressed and in which a short circuit is unlikely to occur even if metallic foreign matter is mixed inside the all-solid-state battery. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In the numerical ranges described in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances unless otherwise specified. In the present disclosure, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0009] (1) Solid electrolyte sheet The solid electrolyte sheet of the present disclosure includes a nonwoven fabric and a solid electrolyte disposed inside the nonwoven fabric. The pore size of the nonwoven fabric is 15 μm or less. The ratio (pore size / particle size) is 5.0 or more. The ratio (pore size / particle size) indicates the pore size relative to the particle size of the solid electrolyte.

[0010] "Nonwoven fabric" refers to a sheet-like material in which fibers are bonded or intertwined without being woven, and is a flat fiber assembly that has a predetermined level of structural strength obtained by physical and / or chemical methods other than weaving, knitting, and papermaking (JIS L0222:2022). The fiber assembly has multiple pores. "Pore diameter" refers to the maximum pore diameter measured by the bubble point method (JIS K3832).

[0011] The solid electrolyte sheet of the present disclosure has the above-described configuration, and therefore can suppress the battery resistance of the all-solid-state battery and prevent the occurrence of a short circuit even if metallic foreign matter gets mixed into the inside of the all-solid-state battery. This effect is presumably due to, but not limited to, the following reasons. During the manufacturing process of an all-solid-state battery, there is a risk of foreign metal particles being mixed into the battery. Foreign metal particles are typically metal pieces with a size of 20 μm. In the present disclosure, the pore size of the nonwoven fabric is 15 μm or less, which is smaller than the particle size of the foreign metal particles. Therefore, even if foreign metal particles are mixed into the materials of the all-solid-state battery of the present disclosure, the foreign metal particles are unlikely to penetrate into the nonwoven fabric. Therefore, during the battery fabrication press, the foreign metal particles are unlikely to penetrate the solid electrolyte layer. As a result, it is presumed that the solid electrolyte sheet of the present disclosure can prevent the occurrence of a short circuit even if foreign metal particles are mixed into the all-solid-state battery. Furthermore, in the present disclosure, the ratio (pore size / particle size) is 5.0 or more. Therefore, the solid electrolyte can be arranged more densely inside the nonwoven fabric than when the ratio (pore size / particle size) is not 5.0 or more. Therefore, in the all-solid-state battery of the present disclosure, the gaps between adjacent solid electrolyte particles become smaller. As a result, it is presumed that the solid electrolyte sheet of the present disclosure can suppress the battery resistance of the all-solid-state battery.

[0012] The planar shape of the solid electrolyte sheet is not particularly limited, and examples thereof include a rectangular shape, etc. Examples of the rectangular shape include a square shape and a rectangular shape.

[0013] The thickness of the solid electrolyte sheet depends on the thickness of the nonwoven fabric, and may be equal to or greater than the thickness of the nonwoven fabric. From the viewpoint of further reducing the battery resistance of the all-solid-state battery, the thickness of the solid electrolyte sheet is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, and particularly preferably 15 μm or less. The thickness of the solid electrolyte sheet is preferably 1 μm or more, more preferably 10 μm or more. The thickness of the solid electrolyte sheet is preferably 1 μm to 50 μm.

[0014] (1.1) Nonwoven fabric The solid electrolyte sheet comprises a nonwoven fabric.

[0015] The pore diameter of the nonwoven fabric is 15 μm or less, and from the viewpoint of further reducing the battery resistance of the all-solid-state battery, it is preferably 13 μm or less, more preferably 8 μm or less. From the viewpoint of further reducing the battery resistance of the all-solid-state battery, it is preferably 1 μm or more, more preferably 3 μm or more. The pore diameter of the nonwoven fabric is preferably 1 μm to 15 μm. The pore size of the nonwoven fabric was measured by the same method as described in the examples.

[0016] The basis weight of the nonwoven fabric is not particularly limited, but is preferably 0.10 mg / cm from the viewpoint of further reducing the battery resistance of the all-solid-state battery. 2 More preferably, 0.20 mg / cm 2 More preferably, 0.30 mg / cm 2 The basis weight of the nonwoven fabric is not particularly limited, but is preferably 0.80 mg / cm from the viewpoint of further reducing the battery resistance of the all-solid-state battery. 2 or less, more preferably 0.60 mg / cm 2 or less, more preferably 0.40 mg / cm 2 The basis weight of the nonwoven fabric is preferably 0.10 mg / cm or less. 2 ~0.80mg / cm 2 is. The method for measuring the basis weight of the nonwoven fabric is the same as the method described in the examples.

[0017] The porosity of the nonwoven fabric is not particularly limited, and is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more from the viewpoint of further reducing the battery resistance of the all-solid-state battery. The porosity of the nonwoven fabric is preferably 95% or less, more preferably 90% or less, from the viewpoint of allowing the nonwoven fabric to function as a support. The porosity of the nonwoven fabric is preferably 50% to 95%. The porosity indicates the volume of voids inside the nonwoven fabric relative to the total volume of the nonwoven fabric. The method for measuring the porosity of the nonwoven fabric is the same as that described in the examples.

[0018] The thickness of the nonwoven fabric is not particularly limited, but is preferably 10 μm to 30 μm. By making the thickness of the nonwoven fabric 10 μm to 30 μm, the thickness of the solid electrolyte layer of the all-solid-state battery can be made thinner. As a result, the battery resistance of the all-solid-state battery can be further reduced. The thickness of the nonwoven fabric is more preferably 11 μm or more, even more preferably 12 μm or more, and particularly preferably 13 μm or more. From the viewpoint of further reducing the battery resistance of the all-solid-state battery, the thickness of the nonwoven fabric is more preferably 25 μm or less, even more preferably 20 μm or less, and particularly preferably 18 μm or less. The method for measuring the thickness of the nonwoven fabric is the same as that described in the examples.

[0019] The type of nonwoven fabric is not particularly limited, and examples thereof include meltblown nonwoven fabric, spunbond nonwoven fabric, carded nonwoven fabric, parallel nonwoven fabric, cross nonwoven fabric, random nonwoven fabric, spunlaid nonwoven fabric, flash-spun nonwoven fabric, chemically bonded nonwoven fabric, hydroentangled nonwoven fabric, needle-punched nonwoven fabric, stitch-bonded nonwoven fabric, thermally bonded nonwoven fabric, burst fiber nonwoven fabric, tow-spread nonwoven fabric, and film-split nonwoven fabric. Among these, the type of nonwoven fabric is preferably a meltblown nonwoven fabric. Meltblown nonwoven fabrics are made of ultrafine fibers (for example, fiber diameters of 1 μm to 6 μm). Therefore, even if the basis weight of a meltblown nonwoven fabric is low, the number of fibers contained in the nonwoven fabric is large. As a result, it is easy to obtain a nonwoven fabric whose pore size, basis weight, and porosity are each within the above ranges.

[0020] The fiber diameter and fiber length of the fiber are not particularly limited. The fiber may be a long fiber or a single fiber. The cross-sectional shape of the fiber is not particularly limited, and examples thereof include a circular, elliptical, irregular shape, etc.

[0021] Examples of fiber materials include resins and glass. Examples of resins include polyester resins, polyolefin resins, and polyamide resins. Examples of polyester resins include polyethylene terephthalate (PET). Examples of polyolefin resins include polyethylene (PE) and polypropylene (PP). Examples of polyamide resins include nylon and aramid.

[0022] (1.2) Solid electrolyte The solid electrolyte sheet comprises a solid electrolyte. The solid electrolyte may or may not cover the nonwoven fabric, provided that it is disposed inside the nonwoven fabric.

[0023] The shape of the solid electrolyte may be, for example, particulate. The particle size of the solid electrolyte is preferably 3.0 μm or less. If the particle size of the solid electrolyte is 3.0 μm or less, the battery resistance of the all-solid-state battery can be reduced compared to when the particle size of the solid electrolyte exceeds 3.0 μm. The particle size of the solid electrolyte is preferably 0.05 μm or more, more preferably 0.2 μm or more, even more preferably 1.0 μm or more, and particularly preferably 2.0 μm or more. The particle size of the solid electrolyte is more preferably 2.8 μm or less, even more preferably 2.6 μm or less, and particularly preferably 2.4 μm or less. The particle size of the solid electrolyte is preferably 0.05 μm to 3.0 μm. The particle size of the solid electrolyte is preferably smaller than the thickness of the nonwoven fabric. The ratio of the total volume of the solid electrolyte to the total volume of the voids in the nonwoven fabric may be 50% by volume or more, 70% by volume or more, or even 90% by volume. The particle size of the solid electrolyte was measured by the same method as described in the examples.

[0024] The ratio (pore diameter / particle diameter) is 5.0 or more, and from the viewpoint of the packing efficiency of the solid electrolyte, it is preferably 5.5 or more, more preferably 6.0 or more. From the viewpoint of foreign matter resistance, the ratio (pore diameter / particle diameter) is preferably 55.0 or less, more preferably 40.0 or less, even more preferably 20.0 or less, particularly preferably 10.0 or less, and even more preferably 6.0 or less. The ratio (pore diameter / particle diameter) is preferably 5.0 to 55.0.

[0025] In particular, it is preferable that the thickness of the nonwoven fabric is 20 μm or less and the ratio (pore diameter / particle diameter) is 5.0 to 6.0. If the thickness of the nonwoven fabric is 20 μm or less and the ratio (pore diameter / particle diameter) is 5.0 to 6.0, the battery resistance of the all-solid-state battery can be further reduced.

[0026] Examples of solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, halide solid electrolytes, and nitride solid electrolytes. One type of solid electrolyte may be used alone, or two or more types may be used in combination. The sulfide solid electrolyte preferably contains sulfur (S) as the main anion element. The oxide solid electrolyte preferably contains oxygen (O) as the main anion element. The hydride solid electrolyte preferably contains hydrogen (H) as the main anion element. The halide solid electrolyte preferably contains a halogen element (X) as the main anion element. The nitride solid electrolyte preferably contains nitrogen (N) as the main anion element.

[0027] (1.2.1) Sulfide solid electrolyte The sulfide solid electrolyte preferably contains, for example, Li, A, and S. The A element is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In. The sulfide solid electrolyte may further contain at least one of O and a halogen element. Examples of the halogen element (X) include F, Cl, Br, and I.

[0028] From the perspective of excellent chemical stability, the sulfide solid electrolyte preferably has an ortho-composition anion structure as the main component of the anion structure. Examples of the ortho-composition anion structure include PS4 3- structure, SiS4 4- structure, GeS4 4- structure, AlS3 3- structure or BS3 3- structure. The proportion of the ortho-composition anion structure is preferably 70 mol% or more, more preferably 90 mol% or more, based on the total anion structure in the sulfide solid electrolyte.

[0029] The sulfide solid electrolyte may be amorphous or crystalline. When the sulfide solid electrolyte is crystalline, it has a crystal phase. Examples of the crystal phase include Thio-LISICON type crystal phase, LGPS type crystal phase, and argyrodite type crystal phase.

[0030] The composition of the sulfide solid electrolyte is not particularly limited, and examples include xLi2S·(100-x)P2S5 (70≦x≦80), yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.7≦x≦0.8, 0≦y≦30, 0≦z≦30).

[0031] The sulfide solid electrolyte may have a composition represented by the general formula (1): Li 4-x Ge 1-x P x S4 (0<x<1). In the general formula (1), at least a part of Ge may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the general formula (1), at least a part of P may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the general formula (1), a part of Li may be substituted with at least one of Na, K, Mg, Ca, and Zn. In the general formula (1), a part of S may be substituted with a halogen. The halogen is at least one of F, Cl, Br, and I.

[0032] Other compositions of sulfide solid electrolytes include, for example, Li 7-x-2 Z PS 6-x-y X y , Li 8-x-2y SIS 6-x-y X y , Li 8-z-2y GeS 6-x-y X y In these compositions, X is at least one of F, Cl, Br and I, and x and y are in the range of 0≦x, 0≦y.

[0033] (1.2.2) Oxide solid electrolyte The oxide solid electrolyte contains, for example, Li, Z (Z is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O. Examples of the oxide solid electrolyte include garnet-type solid electrolytes, perovskite-type solid electrolytes, Nasicon-type solid electrolytes, Li-PO-based solid electrolytes, and Li-BO-based solid electrolytes. Examples of the garnet-type solid electrolyte include Li7La3Zr2O 12 , Li 7-x La3(Zr 2-x Nb x )O 12 (0≦x≦2), Li5La3Nb2O 12 Examples of perovskite-type solid electrolytes include (Li,La)TiO3, (Li,La)NbO3, (Li,Sr)(Ta,Zr)O3, etc. Examples of Nasicon-type solid electrolytes include Li(Al,Ti)(PO4)3, Li(Al,Ga)(PO4)3, etc. Examples of Li-PO-based solid electrolytes include Li3PO4 and LIPON (a compound in which part of the O in Li3PO4 is substituted with N), and examples of Li-BO-based solid electrolytes include Li3BO3 and a compound in which part of the O in Li3BO3 is substituted with C, etc.

[0034] (1.2.3) Hydride solid electrolyte The hydride solid electrolyte contains, for example, Li and a complex anion containing hydrogen. The complex anion may be, for example, (BH4).- , (NH2) - , (AlH4) - , (AlH6) 3- etc. can be mentioned.

[0035] (1.2.4) Halogenated solid electrolyte As the halogenated solid electrolyte, Li63z Z z X6 (X is at least one of Cl and Br, and z is 0 < z < 2) can be mentioned.

[0036] (1.2.5) Nitrogenated solid electrolyte As the nitrogenated solid electrolyte, for example, Li3N etc. can be mentioned.

[0037] (1.2.6) Molten salt that is solid at 25°C As another example of the solid electrolyte, a molten salt that is solid at 25°C can be mentioned. The molten salt has a cation and an anion. As the cation, for example, inorganic cations, organic cations, etc. can be mentioned As the inorganic cation, for example, lithium ions etc. can be mentioned. As the organic cation, for example, ammonium-based ions, piperidinium-based cations, pyrrolidinium-based cations, imidazolium-based cations, viridium-based cations, alicyclic amine-based cations, aliphatic amine-based cations, aliphatic phosphonium-based cations, etc. can be mentioned. As the anion, for example, anions having a sulfonylamide structure can be mentioned. As the anion having a sulfoniumamide structure, for example, bis(trifluoromethanesulfonyl)amide, bis(fluorosulfonyl)amide, bis(pentafluoroethanesulfonyl)amide, (fluorosulfonyl)(trifluoromethanesulfonyl)amide, etc. can be mentioned. The melting point of the molten salt is usually 25°C or higher, may be 30°C or higher, and may be 40°C or higher. The melting point of the molten salt is, for example, 200°C or lower, may be 150°C or lower, and may be 120°C or lower.

[0038] (1.2.7) Soft-viscous crystalline solid electrolyte Another example of a solid electrolyte is a plastic crystal solid electrolyte. Plastic crystals are composed of a regularly ordered three-dimensional crystal lattice. In plastic crystals, orientational and rotational disorder exists at the level of molecular species or molecular ions. Plastic crystals have cations and anions. Examples of cations include pyrrolidinium, tetraalkylammonium, and tetraalkylphosphonium. Examples of anions include hexafluorophosphate, tetrafluoroborate, thiocyanate, bis(trifluoromethanesulfonyl)amide, and (fluorosulfonyl)(trifluoromethanesulfonyl)amide.

[0039] In particular, the solid electrolyte preferably contains a sulfide solid electrolyte, and more preferably consists of a sulfide solid electrolyte. When the solid electrolyte contains a sulfide solid electrolyte, the battery resistance of the all-solid-state battery is further reduced.

[0040] (1.3) Binder The solid electrolyte sheet may or may not include a binder. Examples of binders include rubber-based binders, fluoride-based binders, etc. Examples of rubber-based binders include butadiene rubber, hydrogenated butadiene rubber, styrene butadiene rubber (SBR), hydrogenated styrene butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, ethylene propylene rubber, etc. Examples of fluoride-based binders include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, fluororubber, etc. When the solid electrolyte contains a binder, the content of the binder may be 0 to 3 parts by mass relative to the total amount of the solid electrolyte.

[0041] (2) All-solid-state battery The all-solid-state battery of the present disclosure includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer includes the solid electrolyte sheet of the present disclosure.

[0042] The all-solid-state battery of the present disclosure has the above-described configuration, and therefore the battery resistance of the all-solid-state battery is suppressed, and a short circuit is unlikely to occur even if metallic foreign matter is mixed inside the all-solid-state battery. This effect is presumed to be due to the same reason as the effect of the solid electrolyte sheet described above, but is not limited to this.

[0043] When a set of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is defined as a power generation unit, the all-solid-state battery may have only one power generation unit or may have two or more power generation units. When the all-solid-state battery has two or more power generation units, the power generation units may be connected in series or in parallel.

[0044] (2.1) Solid electrolyte layer The all-solid-state battery includes a solid electrolyte layer. The solid electrolyte layer includes the solid electrolyte sheet of the present disclosure, or may consist solely of the solid electrolyte sheet of the present disclosure. The solid electrolyte layer is subjected to a battery pressing.

[0045] From the viewpoint of further reducing the battery resistance of the all-solid-state battery, the thickness of the solid electrolyte layer is preferably 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The thickness of the solid electrolyte layer is preferably 1 μm or more, more preferably 10 μm or more. The thickness of the solid electrolyte layer is preferably 1 μm to 50 μm.

[0046] The solid electrolyte layer has a history of being subjected to a battery press. The nonwoven fabric and the solid electrolyte contained in the solid electrolyte sheet are unlikely to be deformed by the battery press. Therefore, the nonwoven fabric and the solid electrolyte contained in the solid electrolyte sheet after the battery press can be considered to be the same as the nonwoven fabric and the solid electrolyte contained in the solid electrolyte sheet before the battery press. The pore size of the nonwoven fabric contained in the solid electrolyte layer can be obtained, for example, by separating only the nonwoven fabric from the all-solid-state battery by washing with an organic solvent, and measuring the pore size of the obtained nonwoven fabric by a method similar to the method described in the Examples. The particle size of the solid electrolyte contained in the solid electrolyte layer can be obtained, for example, by observing a cross section of the solid electrolyte layer with a scanning electron microscope (SEM), randomly selecting solid electrolyte particles, and measuring the average particle size.

[0047] The nonwoven fabric included in the solid electrolyte may or may not be in direct contact with at least one of the positive electrode layer and the negative electrode layer. Another solid electrolyte layer may be disposed between the nonwoven fabric included in the solid electrolyte nonwoven fabric and at least one of the positive electrode layer and the negative electrode layer. The disposition of the other solid electrolyte layer reduces the internal resistance of the all-solid-state battery. The other solid electrolyte layer contains a solid electrolyte and may contain a binder as needed. Examples of the solid electrolyte and binder include the same as those exemplified as the solid electrolyte and binder that may be contained in the solid electrolyte sheet. The other solid electrolyte layer usually does not have electronic conductivity. The other solid electrolyte layer does not contain a nonwoven fabric. The thickness of the other solid electrolyte layer is not particularly limited.

[0048] (2.2) Positive electrode layer The all-solid-state battery includes a positive electrode layer. The positive electrode layer includes a positive electrode active material. The positive electrode layer may further include at least one of a solid electrolyte, a conductive material, and a binder, as necessary. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include rock salt layered active materials, spinel active materials, and olivine active materials. Examples of the rock salt layered active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Examples of spinel active materials include LiMnO, LiTiO, etc. 12 , Li(Ni 0.5 Mn 1.5)O4, etc. Examples of olivine active materials include LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0049] A protective layer may be formed on the surface of the oxide active material. The protective layer contains a Li-ion conductive oxide. The protective layer can suppress the reaction between the oxide active material and the solid electrolyte. Examples of Li-ion conductive oxides include LiNbO3. The thickness of the protective layer is, for example, 1 nm to 30 nm. For example, Li2S can be used as the positive electrode active material.

[0050] The shape of the positive electrode active material may be, for example, particulate. The particle size of the positive electrode active material is not particularly limited, but is preferably 10 nm or more, more preferably 100 nm or more. The particle size of the positive electrode active material is not particularly limited, but is preferably 50 μm or less, more preferably 20 μm or less. The particle size of the positive electrode active material is preferably 10 nm to 50 μm. The particle size of the positive electrode active material was measured by the same method as described in the examples.

[0051] The positive electrode layer may contain a conductive material. Examples of the conductive material include carbon materials, metal particles, and conductive polymers. Examples of the carbon material include particulate carbon materials and fibrous carbon materials. Examples of the particulate carbon materials include acetylene black (AB) and ketjen black (KB). Examples of the fibrous carbon materials include carbon nanotubes (CNTs) and carbon nanofibers (CNFs).

[0052] The solid electrolyte and binder used in the positive electrode layer may be the same as those exemplified as the solid electrolyte and binder that may be contained in the solid electrolyte sheet. The thickness of the positive electrode layer is not particularly limited, but is preferably 0.1 μm to 1000 μm.

[0053] [2.3] Positive electrode current collector The all-solid-state battery may further include a positive electrode current collector. The positive electrode current collector collects current from the positive electrode layer. The positive electrode current collector is disposed on the opposite side of the positive electrode layer from the solid electrolyte layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, carbon, etc. Examples of shapes for the positive electrode current collector include foil and mesh shapes.

[0054] [2.4] Negative electrode layer The all-solid-state battery includes a negative electrode layer. The negative electrode layer contains a negative electrode active material. The negative electrode layer may contain at least one of a solid electrolyte, a conductive material, and a binder, as necessary. Examples of the negative electrode active material include a Li-based active material, a carbon-based active material, an oxide-based active material, and a Si-based active material. Examples of the Li-based active material include metallic lithium and lithium alloys. Examples of the carbon-based active material include graphite, hard carbon, and soft carbon. Examples of the oxide-based active material include lithium titanate. Examples of the Si-based active material include simple Si, Si alloys, and silicon oxide.

[0055] The shape of the negative electrode active material may be, for example, particulate. The particle size of the negative electrode active material is preferably 10 μm or more, more preferably 100 μm or more. The particle size of the negative electrode active material is preferably 50 μm or more, more preferably 20 μm or more. The particle size of the negative electrode active material is preferably 10 μm to 50 μm. The particle size of the negative electrode active material was measured by the same method as described in the examples.

[0056] The conductive material, solid electrolyte, and binder used in the negative electrode layer may be the same as those exemplified as the conductive material, solid electrolyte, and binder that may be contained in the positive electrode layer. The thickness of the negative electrode layer is not particularly limited, but is preferably 0.1 μm to 1000 μm.

[0057] [2.5] Negative electrode current collector The all-solid-state battery may further include a negative electrode current collector. The negative electrode current collector collects current from the negative electrode layer. The negative electrode current collector is disposed on the opposite side of the negative electrode layer from the solid electrolyte layer. Examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon. Examples of the shape of the negative electrode current collector include a foil shape and a mesh shape.

[0058] [2.6] Exterior body The all-solid-state battery may further include an exterior body that houses at least the power generating unit described above. Examples of the exterior body include a laminate-type exterior body and a case-type exterior body.

[0059] [2.7] Restraining member The all-solid-state battery may further include a restraining member. The restraining member applies a restraining pressure to the positive electrode layer, the solid electrolyte layer, and the negative electrode layer in the thickness direction. The restraining pressure is preferably 0.1 MPa or more, more preferably 1 MPa or more, and even more preferably 5 MPa or more. The restraining pressure is preferably 100 MPa or less, more preferably 50 MPa or less, and even more preferably 20 MPa or less. The restraining pressure is preferably 0.1 MPa to 100 MPa.

[0060] [2.8] Purpose The all-solid-state battery of the present disclosure is typically an all-solid-state lithium-ion secondary battery. Examples of all-solid-state batteries include power sources for vehicles, electronic devices, and electrical storage. Examples of vehicles include electric four-wheeled vehicles, electric two-wheeled vehicles, gasoline-powered automobiles, and diesel-powered automobiles. Examples of electric four-wheeled vehicles include electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), and hybrid vehicles (BEVs). Examples of electric two-wheeled vehicles include electric motorcycles and electrically assisted bicycles. Examples of electronic devices include handheld devices (e.g., smartphones, tablet computers, audio players, etc.), portable devices (e.g., notebook computers, CD (Compact Disc) players, and mobile devices (e.g., power tools, commercial video cameras, etc.). Among these, the all-solid-state battery of the present disclosure is preferably used as a power source for driving hybrid vehicles, plug-in hybrid vehicles, or electric vehicles. [Example]

[0061] The present disclosure will be described in more detail below with reference to examples, but the invention of the present disclosure is not limited to these examples.

[0062] [1]Measurement method The methods for measuring the physical properties of the materials in the examples and comparative examples are as follows.

[0063] [1.1] Pore size of nonwoven fabric The pore size of nonwoven fabrics was measured using the bubble point method (JIS K 3832). Specifically, air pressure is applied to paper completely immersed in the test liquid, and the maximum pore size is calculated from the pressure (bubble point) at which the appearance of bubbles is observed. By using a test liquid with a known surface tension, the maximum pore size d can be calculated using the following formula. d = γ / P (γ: surface tension of test liquid, P: bubble point pressure)

[0064] [1.2] Nonwoven fabric basis weight A sheet of a certain area was cut out from the nonwoven fabric, and the mass per area of ​​the sheet was calculated to determine the basis weight.

[0065] [1.3] Porosity of nonwoven fabric The volume of the voids was calculated from the difference between the actual volume of the sheet and the volume calculated from the specific gravity of the material, and the ratio of the voids to the actual volume of the sheet was determined. The ratio of the voids was taken as the porosity.

[0066] [1.4] Thickness The thickness of the nonwoven fabric was measured with a bench micrometer. The thickness of the solid electrolyte layer was confirmed by synchrotron X-ray laminography and cross-sectional SEM.

[0067] [1.5] Particle size The particle sizes of the sulfide solid electrolyte, the positive electrode active material, the negative electrode active material, and the metallic foreign matter were measured using a laser diffraction particle size distribution analyzer. Specifically, the objects to be measured were dispersed in a dispersion medium, and the volume-based particle size distribution was measured using the particle size distribution analyzer. The particle size was determined as the particle size at which the value of the volume-based cumulative particle size distribution reached 50%.

[0068] [1.6] Specific surface area The specific surface areas of the positive electrode active material, negative electrode active material, positive electrode conductive material, and negative electrode conductive material were measured by the BET method (JIS R1626-1996).

[0069] [2] Solid electrolyte sheet [2.1] Example 1 The following materials were prepared:

[0070] First sulfide solid electrolyte: 15LiBr 10LiI 75 (0.75Li2S 0.25P2S5) glass ceramics with a particle size of 2.2 μm Binder: SBR (styrene-butadiene rubber) binder Dispersion medium: butyl butyrate Base foil: Stainless steel (SUS) foil with a thickness of 15 μm

[0071] A first nonwoven fabric was produced by melt-blowing. The first nonwoven fabric had a thickness of 30 μm and a density of 0.37 mg / cm 2The first nonwoven fabric had a basis weight of 1000, a porosity of 91%, and a pore size of 15 μm. The material of the fibers constituting the first nonwoven fabric was polyethylene terephthalate.

[0072] 100 parts by mass of the first sulfide solid electrolyte and 3 parts by mass of a binder were mixed in a dispersion medium so as to have a solid content of 50% by mass. The resulting mixture was subjected to ultrasonic dispersion treatment using an ultrasonic dispersion device for 1 minute to obtain a solid electrolyte paste.

[0073] The first nonwoven fabric was placed on the base foil. The solid electrolyte paste was applied by blade coating at a concentration of 2.9 mg / cm. 2 The coating was uniformly applied to the first nonwoven fabric so as to achieve a basis weight of 100°C, and then dried at 100°C for 60 minutes. A commercially available applicator was used for blade coating. This resulted in a solid electrolyte sheet with a substrate foil. The solid electrolyte sheet with a substrate foil included the substrate foil and a solid electrolyte sheet disposed on one side of the substrate foil. The solid electrolyte sheet included the first nonwoven fabric and a solid electrolyte. The solid electrolyte was disposed inside and outside the first nonwoven fabric so as to cover the first nonwoven fabric. [2.2] Example 2 A solid electrolyte sheet with a substrate foil was obtained in the same manner as in Example 1, except that the second nonwoven fabric was used instead of the first nonwoven fabric. The second nonwoven fabric had a thickness of 15 μm and a density of 0.37 mg / cm 2 The second nonwoven fabric had a basis weight of 1000, a porosity of 82%, and a pore size of 11 μm. The material of the fibers constituting the second nonwoven fabric was polyethylene terephthalate.

[0074] [2.3] Example 3 A solid electrolyte sheet with a substrate foil was obtained in the same manner as in Example 1, except that the third nonwoven fabric was used instead of the first nonwoven fabric and the second sulfide solid electrolyte was used instead of the first sulfide solid electrolyte. The third nonwoven fabric had a thickness of 15 μm and a capacitance of 0.67 mg / cm 2The third nonwoven fabric had a basis weight of 1000, a porosity of 68%, and a pore size of 5 μm. The fiber material constituting the third nonwoven fabric was polyethylene terephthalate. The second sulfide solid electrolyte was a 15LiBr 10LiI 75 (0.75Li2S 0.25P2S5) glass ceramic with a particle size of 0.1 μm.

[0075] [2.4] Comparative Example 1 Except for not using the first nonwoven fabric, a solid electrolyte sheet with a base foil was obtained in the same manner as in Example 1. The solid electrolyte sheet with a base foil of Comparative Example 1 does not include a nonwoven fabric.

[0076] [2.5] Comparative Example 2 A solid electrolyte sheet with a substrate foil was obtained in the same manner as in Example 1, except that the fourth nonwoven fabric was used instead of the first nonwoven fabric. The fourth nonwoven fabric was produced by the spunbond method. The fourth nonwoven fabric had a thickness of 20 μm and a density of 0.89 mg / m 2 The fourth nonwoven fabric had a basis weight of 100g, a porosity of 68%, and a pore size of 73µm. The material of the fibers constituting the fourth nonwoven fabric was polyethylene terephthalate.

[0077] [2.6] Comparative Example 3 A solid electrolyte sheet with a base foil was obtained in the same manner as in Example 1, except that the third nonwoven fabric was used instead of the first nonwoven fabric.

[0078] [3] Evaluation A plurality of all-solid-state batteries for evaluation were fabricated using each of the solid electrolyte sheets of Examples 1 to 3 and Comparative Examples 1 to 3, each containing metallic foreign matter. Each of the plurality of all-solid-state batteries for evaluation was subjected to foreign matter evaluation and resistance measurement. Details are as follows.

[0079] [3.1] All-solid-state battery for evaluation [3.1.1] Positive electrode The following materials were prepared:

[0080] Positive electrode active material: 10 μm particle size and 1 m 2 LiNi with a specific surface area of ​​ / g 1 / 3 Mn 1 / 3 Co1 / 3 O2 powder Positive electrode solid electrolyte: First sulfide solid electrolyte with the same composition as the sulfide solid electrolyte of the solid electrolyte sheet Positive electrode conductive material: 14m 2 / g specific surface area of ​​cellulose nanofiber (CNF) Positive electrode binder: SBR (styrene-butadiene rubber) binder Positive electrode dispersion medium: butyl butyrate Positive electrode current collector: Aluminum foil with a thickness of 15 μm

[0081] The surface of the positive electrode active material was coated with LiNbO3 using the sol-gel method to obtain a positive electrode active material with a protective layer. 100 parts by mass of the positive electrode active material with a protective layer, 50 parts by mass of a positive electrode sulfide solid electrolyte, 10 parts by mass of a positive electrode conductive material, and 1 part by mass of a positive electrode binder were mixed into a positive electrode dispersion medium so that the solid content was 60% by mass. The resulting mixture was subjected to ultrasonic dispersion treatment using an ultrasonic dispersion device for 1 minute to obtain a positive electrode paste.

[0082] Positive electrode paste was applied by blade coating at 25 mg / cm 2 The coating was uniformly applied to the positive electrode current collector so that the coating weight was 100g, and then dried at 100°C for 60 minutes. A commercially available applicator was used for blade coating. This resulted in a positive electrode layer with a positive electrode current collector. The positive electrode layer with a positive electrode current collector included the positive electrode current collector and a positive electrode layer disposed on one surface of the positive electrode current collector. The positive electrode layer included a positive electrode active material with a protective layer, a positive electrode sulfide solid electrolyte, a positive electrode conductive material, and a positive electrode binder.

[0083] [3.1.2] Negative electrode The following materials were prepared:

[0084] Negative electrode active material: 3 μm particle size, 4 m 2 Si powder with a specific surface area of ​​ / g Anode solid electrolyte: First sulfide solid electrolyte with the same composition as the sulfide solid electrolyte of the solid electrolyte sheet Conductive material for negative electrode: 14m 2CNF with a specific surface area of ​​1000mJ / g Negative electrode binder: SBR binder Dispersion medium for negative electrode: butyl butyrate Negative electrode current collector: 20 μm thick surface-roughened copper foil

[0085] 100 parts by mass of a negative electrode active material, 100 parts by mass of a negative electrode sulfide solid electrolyte, 10 parts by mass of a negative electrode conductive material, and 2 parts by mass of a negative electrode dispersant were mixed into a negative electrode dispersion medium so that the solid content was 40% by mass. The resulting mixture was subjected to ultrasonic dispersion treatment using an ultrasonic dispersion device for 1 minute to obtain a negative electrode paste.

[0086] The negative electrode paste was applied by blade coating at a density of 5 mg / cm 2 The coating was uniformly applied to the negative electrode current collector so that the coating weight was 100g, and then dried at 100°C for 60 minutes. A commercially available applicator was used for blade coating. This resulted in a negative electrode layer with a negative electrode current collector. The negative electrode layer with a negative electrode current collector included the negative electrode current collector and a negative electrode layer disposed on one surface of the negative electrode current collector. The negative electrode layer included a negative electrode active material, a negative electrode sulfide solid electrolyte, a negative electrode conductive material, and a negative electrode binder.

[0087] [3.1.3] Lamination The following materials were prepared:

[0088] Solid electrolyte sheets with substrate foil: solid electrolyte sheets of Examples 1 to 3 and Comparative Examples 1 to 3 Metallic foreign matter: SUS fine powder with a particle size of 20 μm Exterior: Aluminum laminate film with positive and negative terminals attached

[0089] The negative electrode layer with the negative electrode current collector was cut into a 1.2 cm × 1.2 cm square to obtain a negative electrode structure. The solid electrolyte sheet with the base foil was cut into a 1.2 cm × 1.2 cm square to obtain a solid electrolyte structure. The positive electrode layer with the positive electrode current collector was cut into a 1.0 cm × 1.0 cm square to obtain a positive electrode structure. A metal foreign object was placed on the negative electrode layer of the negative electrode structure, and then the negative electrode structure and the solid electrolyte structure were stacked together so that the negative electrode layer and the solid electrolyte sheet faced each other, and then roll-pressed at a pressure of 1 ton / cm. Next, the substrate foil attached to the solid electrolyte layer was peeled off, and the positive electrode structure and the solid electrolyte structure were overlapped with each other so that the positive electrode layer and the solid electrolyte sheet faced each other, and then roll pressed at a pressure of 4 ton / cm to obtain a laminated electrode body. The laminated electrode body was sealed with an outer casing to prepare an all-solid-state battery for evaluation (all-solid-state lithium ion secondary battery). The thickness of the solid electrolyte layer of the all-solid-state battery for evaluation of Example 1 was 15 μm. The thickness of the solid electrolyte layer of the all-solid-state batteries for evaluation of Examples 2 and 3 was 15 μm.

[0090] [3.2] Foreign matter evaluation The voltage of the all-solid-state battery for evaluation was measured while it was restrained under a load of 5 MPa in the stacking direction of the positive electrode layer, solid electrolyte layer, and negative electrode layer, and the all-solid-state battery for evaluation was evaluated for the occurrence of a short circuit according to the following criteria. The evaluation results are shown in Table 1. An "A" in the evaluation criteria indicates that it is determined that no short circuit has occurred. A "B" in the evaluation criteria indicates that it is determined that a short circuit has occurred.

[0091] <Evaluation criteria> A: The voltage is over 0.200V B: The voltage is 0.200V or less

[0092] [3.3] Resistance measurement The all-solid-state battery for evaluation, which was rated "A" for foreign matter, was subjected to constant current-constant voltage (CC-CV) charging and CC-CV discharging at a current of 2 mA, an upper limit voltage of 4.5 V, and a lower limit voltage of 2.5 V. Next, CC-CV charging was performed at a current of 2 mA and an upper limit voltage of 3.6 V, and the CC-CV charging was paused. Ten minutes after the CC-CV charging was paused, constant current (CC) discharging was performed for 10 seconds at a current of 10 mA and a lower limit voltage of 0.0 V. The battery resistance R (= ΔV / I) of the all-solid-state battery for evaluation was calculated according to Ohm's law. ΔV represents the difference between the voltage immediately before CC discharging and the voltage after 10 seconds of discharging. I represents the measured current value of CC discharging. The calculated battery resistance of the all-solid-state battery for evaluation is shown in Table 1. The allowable range of the battery resistance of the all-solid-state battery for evaluation is 110% or less compared to Example 1.

[0093] [Table 1]

[0094] In Table 1, "SE" indicates a solid electrolyte. "Evaluation (20 μm)" indicates the evaluation of an all-solid-state battery for evaluation in which metallic foreign matter having a particle size of 20 μm was mixed.

[0095] The solid electrolyte sheet of Comparative Example 1 did not include a nonwoven fabric. Therefore, the foreign matter evaluation of Comparative Example 1 was rated as "B." In other words, a short circuit occurred in the all-solid-state battery for evaluation of Comparative Example 1. In the solid electrolyte sheet of Comparative Example 2, the pore size of the nonwoven fabric was not 15 μm or less but was larger than the particle size of the metallic foreign matter. Therefore, the foreign matter evaluation of Comparative Example 2 was rated "B." In other words, a short circuit occurred in the all-solid-state battery for evaluation of Comparative Example 2. In the solid electrolyte sheet of Comparative Example 3, the ratio (pore diameter / particle diameter) was not 5.0 or more, and therefore the battery resistance of Comparative Example 3 was 1547%, which was significantly high.

[0096] The solid electrolyte sheets of Examples 1 to 3 included a nonwoven fabric and a solid electrolyte disposed inside the nonwoven fabric, and the pore size of the nonwoven fabric was 15 μm or less, and the ratio (pore size / particle size) was 5.0 or more. Therefore, the foreign matter evaluation of Examples 1 to 3 was "A." In other words, no short circuit occurred in the all-solid-state evaluation batteries of Examples 1 to 3. Furthermore, the battery resistance of Examples 1 to 3 was 103% or less. These results demonstrate that the solid electrolyte sheets of Examples 1 to 3 can suppress the battery resistance of the all-solid-state battery and prevent the occurrence of a short circuit even if metallic foreign matter gets mixed into the all-solid-state battery.

[0097] Comparing Examples 1 to 3 with Comparative Example 3, it is found that by setting the pore size of the nonwoven fabric to 15 μm or less, metallic foreign matter having a particle size larger than the pore size is less likely to penetrate into the nonwoven fabric during pressing to form a battery. In other words, metallic foreign matter is less likely to penetrate the solid electrolyte layer. As a result, it is presumed that the all-solid-state batteries for evaluation of Examples 1 to 3 are less likely to develop short circuits. Comparing Examples 1 to 3 with Comparative Example 2, it is found that when the ratio (pore diameter / particle diameter) is 5.0 or more, the solid electrolyte is more densely arranged inside the nonwoven fabric than when the ratio (pore diameter / particle diameter) is not 5.0 or more. In other words, after pressing to form a battery, the gaps between adjacent particles of the solid electrolyte become smaller. As a result, it is estimated that the battery resistance of the all-solid-state batteries for evaluation in Examples 1 to 3 was 103% or less.

Claims

1. A nonwoven fabric, a solid electrolyte disposed inside the nonwoven fabric; Equipped with the solid electrolyte includes a sulfide solid electrolyte, The pore size of the nonwoven fabric is 15 μm or less, a ratio of the pore diameter to the particle diameter of the solid electrolyte (pore diameter / particle diameter) of 5.0 to 10.0, the pore diameter is the maximum pore diameter of the nonwoven fabric measured by a bubble point method in accordance with JIS K 3832, a solid electrolyte sheet, wherein the particle size is a particle size corresponding to 50% of a value of a volume-based cumulative particle size distribution of the solid electrolyte measured using a laser diffraction particle size distribution analyzer.

2. 2. The solid electrolyte sheet according to claim 1, wherein the nonwoven fabric has a thickness of 10 μm or more and 30 μm or less.

3. 3. The solid electrolyte sheet according to claim 1, wherein the particle size is 3.0 μm or less.

4. a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; 3. An all-solid-state battery, wherein the solid electrolyte layer comprises the solid electrolyte sheet according to claim 1.

5. A solid electrolyte sheet as described in claim 1, wherein the nonwoven fabric is made of a polyester-based resin or a polyamide-based resin.

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