All-solid-state batteries

Abstract

The main purpose of the present disclosure is to provide an all-solid-state battery with good cycle characteristics. The present disclosure solves the above-mentioned problems by providing the following all-solid-state battery, which includes an electrode structure, the electrode structure having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer, the electrode structure having an opposing portion in which the positive electrode layer and the negative electrode layer are opposed to each other, and in a plan view observed along the thickness direction, the shape of the opposing portion is a rectangle having a long side and a short side, and the ratio of the length of the long side to the length of the short side is greater than 1.5, the solid electrolyte layer contains a non-woven fabric and a solid electrolyte arranged inside the non-woven fabric, and in the plan view, the angle between the long side direction of the opposing portion and the fiber direction of the non-woven fabric is greater than 0° and less than 30°.

Description

Technical Field

[0001] The present disclosure relates to an all-solid-state battery. Background Art

[0002] All-solid-state batteries have a solid electrolyte layer between the positive and negative electrode layers. Compared to liquid-type batteries with an electrolyte solution containing a flammable organic solvent, they offer the advantage of simplified safety features. Patent Document 1 discloses a solid electrolyte sheet for an all-solid-state secondary battery comprising a nonwoven fabric and a solid electrolyte on and within the nonwoven fabric.

[0003] Patent Document 2 discloses a method for manufacturing a solid electrolyte membrane for an all-solid-state battery, comprising a step of forming a nonwoven fabric comprising fibers made of a resin. Patent Document 3 also discloses an electrode assembly comprising a first electrode, a second electrode, and a separator membrane, wherein the first electrode comprises a plurality of fibrous first structures extending in a first direction, the second electrode comprises a plurality of fibrous second structures extending in a second direction different from the first direction, and the separator membrane is disposed between the first and second structures.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-031789

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-181758

[0007] Patent Document 3: Japanese Patent Application No. 2013-534704 Summary of the Invention

[0008] From the perspective of improving battery performance, all-solid-state batteries with excellent cycle characteristics are required. The present disclosure has been made in view of the above-mentioned situation, and its main object is to provide an all-solid-state battery with excellent cycle characteristics.

[0009] In the present disclosure, an all-solid-state battery is provided, which has an electrode structure, the electrode structure having a positive electrode layer, a negative electrode layer and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer, the electrode structure having an opposing portion in which the positive electrode layer and the negative electrode layer are opposed to each other, and in a plan view observed along the thickness direction, the opposing portion has a shape of a rectangle having a long side and a short side, and the ratio of the length of the long side to the length of the short side is greater than 1.5, the solid electrolyte layer contains a non-woven fabric and a solid electrolyte arranged inside the non-woven fabric, and in the plan view, the angle between the long side direction of the opposing portion and the fiber direction of the non-woven fabric is greater than 0° and less than 30°.

[0010] According to the present disclosure, the angle between the longitudinal direction of the facing portion and the fiber direction of the nonwoven fabric is within a predetermined range, thereby achieving an all-solid-state battery with excellent cycle characteristics.

[0011] In the above disclosure, the angle may be greater than or equal to 0° and less than or equal to 10°.

[0012] In the above disclosure, the porosity of the nonwoven fabric may be 70% or more and 90% or less.

[0013] In the above disclosure, in the above nonwoven fabric, the tensile strength in the fiber direction may be greater than the tensile strength in a direction perpendicular to the fiber direction.

[0014] In the above disclosure, the above solid electrolyte may be an inorganic solid electrolyte.

[0015] In the above disclosure, the above-mentioned inorganic solid electrolyte may be at least one of a sulfide solid electrolyte, an oxide solid electrolyte, and a hydride solid electrolyte.

[0016] In the above disclosure, the solid electrolyte may be a molten salt (meltable salt) that is solid at 25°C.

[0017] In the above disclosure, the above solid electrolyte may be a plastic crystalline solid electrolyte.

[0018] The all-solid-state battery disclosed herein has an effect of good cycle characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic cross-sectional view illustrating an all-solid-state battery in the present disclosure.

[0020] Figure 2 This is a schematic perspective view illustrating a battery structure in the present disclosure.

[0021] Description of Reference Numerals

[0022] 1…positive electrode layer

[0023] 2…Negative electrode layer

[0024] 3…Solid electrolyte layer

[0025] 4…Positive electrode collector

[0026] 5…Negative electrode current collector

[0027] 10…Electrode structure

[0028] 100…All-solid-state batteries DETAILED DESCRIPTION

[0029] The following figures illustrate the all-solid-state battery disclosed herein in detail. Each of the following figures is a schematic diagram, and the size and shape of the components are exaggerated for ease of understanding. Furthermore, hatching indicating component cross-sections is omitted in each figure.

[0030] Figure 1 This is a schematic cross-sectional view illustrating the all-solid-state battery of the present disclosure. Figure 1 The illustrated all-solid-state battery 100 includes an electrode structure 10 having a positive electrode layer 1, a negative electrode layer 2, a solid electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 for collecting current from the positive electrode layer 1, and a negative electrode current collector 5 for collecting current from the negative electrode layer 2. Furthermore, although not specifically shown, the all-solid-state battery 100 may also include an exterior body and a restraining member, which will be described later. The electrode structure 10 includes an opposing portion α where the positive electrode layer 1 and the negative electrode layer 2 face each other.

[0031] Figure 2 This is a schematic perspective view illustrating an electrode structure in the present disclosure. Figure 2 The electrode structure 10 shown includes a positive electrode layer 1 , a negative electrode layer 2 , and a solid electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2 . Figure 2 In the electrode structure 10 shown, the negative electrode layer 2 and the solid electrolyte layer 3 have the same shape in plan view. T In a plan view, the outer edges of the negative electrode layer 2 and the solid electrolyte layer 3 are located outside the outer edge of the positive electrode layer 1. In other words, the area of ​​the negative electrode layer 2 and the solid electrolyte layer 3 is larger than the area of ​​the positive electrode layer 1. Therefore, the plan view shape of the opposing portion is consistent with the plan view shape of the positive electrode layer 1, and is a rectangle with long and short sides.

[0032] In addition, if Figure 2 As shown, in the present disclosure, the direction in which the long side of the opposing portion extends is defined as the long side direction D of the opposing portion. L , and will be in the direction of the long side D L The orthogonal direction is defined as the short side direction D of the opposing parts. S On the other hand, the solid electrolyte layer 3 contains a nonwoven fabric and a solid electrolyte disposed inside the nonwoven fabric. T In the plan view, the long side direction D of the opposing portion is L The angle with the fiber direction D1 of the nonwoven fabric included in the solid electrolyte layer 3 is within a predetermined range. L The angle with D1 indicates the angle on the acute angle side.

[0033] According to the present disclosure, the angle between the long side direction of the opposing portion and the fiber direction of the nonwoven fabric is within a predetermined range, so a fully solid-state battery with good cycle characteristics is obtained. As described in the above-mentioned patent document 1, a solid electrolyte sheet (solid electrolyte layer) containing a solid electrolyte inside a nonwoven fabric is known. By containing a nonwoven fabric in the solid electrolyte layer, for example, there is an advantage in being able to reduce the thickness of the solid electrolyte layer while maintaining insulating properties.

[0034] On the other hand, when the multiple fibers constituting the nonwoven fabric extend in one direction, their tensile strength is not isotropic, but anisotropic. Here, the direction in which the multiple fibers mainly extend is defined as the fiber direction. The fiber direction is usually consistent with the MD (Machine Direction, longitudinal) direction corresponding to the direction of travel (flow direction) in the manufacturing process of the nonwoven fabric. In addition, generally speaking, the direction orthogonal to the MD direction is called the CD (Cross Direction, transverse) direction. The MD direction and the CD direction can be determined by observing the nonwoven fabric with a microscope and confirming the direction in which the fibers extend. When the multiple fibers constituting the nonwoven fabric extend in one direction, the tensile strength in the fiber direction (MD direction) is usually greater than the tensile strength in the direction orthogonal to the fiber direction (CD direction).

[0035] If the tensile strength in the MD direction is different from the tensile strength in the CD direction in the nonwoven fabric, the uniformity of the solid electrolyte layer is reduced whenever stress associated with charge and discharge is applied to the solid electrolyte layer. As a result, internal short circuits such as micro short circuits are likely to occur, and the cycle characteristics are deteriorated. In addition, when the plan view shape of the opposing portion is a rectangle with long sides and short sides, a volume change in the long side direction (such as a volume change caused by elongation) is likely to occur. In contrast, in the present disclosure, the solid electrolyte layer is configured in a manner that is consistent with the fiber direction (MD direction) with a large tensile strength in the long side direction where volume change is likely to occur. Thus, the anisotropy of tensile strength is alleviated. As a result, the uniformity of the solid electrolyte layer can be maintained and the cycle characteristics are improved.

[0036] like Figure 2 As shown, the long side direction of the opposing portion is set as D L Similarly, the fiber direction of the nonwoven fabric included in the solid electrolyte layer 3 is defined as D1. L The angle with D1 is usually less than 30°, but can be less than 20° or less than 10°. L The angle with D1 can be 0° or greater than 0°.

[0037] 1. Electrode structure

[0038] The electrode structure disclosed in the present invention has a positive electrode layer, a negative electrode layer, and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer. In addition, the electrode structure has an opposing portion in which the positive electrode layer and the negative electrode layer are opposed to each other. In a plan view observed along the thickness direction, the shape of the opposing portion is a rectangle having a long side and a short side. The plan view shape of the opposing portion is typically a rectangle. In addition, the ratio of the length of the long side to the length of the short side is generally greater than 1.5, may be greater than 2.0, or may be greater than 2.5. On the other hand, the ratio of the length of the long side to the length of the short side is, for example, less than 20, or may be less than 15.

[0039] (1) Solid electrolyte layer

[0040] The solid electrolyte layer of the present disclosure is a layer disposed between the positive electrode layer and the negative electrode layer. The solid electrolyte layer comprises a nonwoven fabric and a solid electrolyte disposed within the nonwoven fabric.

[0041] (i) Non-woven fabrics

[0042] Non-woven fabrics usually have multiple fibers with pores formed between the multiple fibers. In addition, the multiple fibers extend along the fiber direction. The multiple fibers can extend linearly along the fiber direction, or can extend in a serpentine or zigzag manner. As the material of the fiber, for example, resins such as polyester resins, polyolefin resins, and polyamide resins can be mentioned. As polyester resins, for example, polyethylene terephthalate (PET) can be mentioned. As polyolefin resins, for example, polyethylene (PE) and polypropylene (PP) can be mentioned. As polyamide resins, for example, nylon and aromatic polyamide can be mentioned. In addition, glass can be used as the material of the fiber. That is, the non-woven fabric can be a glass fiber non-woven fabric. The fiber diameter and fiber length of the fibers constituting the non-woven fabric are not particularly limited.

[0043] The porosity of the nonwoven fabric is not particularly limited, and may be, for example, 50% or more, 60% or more, or 70% or more. If the porosity of the nonwoven fabric is too small, the internal resistance tends to increase. On the other hand, the porosity of the nonwoven fabric may be, for example, 95% or less, or 90% or less. If the porosity of the nonwoven fabric is too large, it may not function as a support. The porosity of the nonwoven fabric can be determined, for example, by observing a cross-section of the nonwoven fabric. In addition, the size of the pores is not particularly limited.

[0044] In a nonwoven fabric, the tensile strength in the fiber direction (MD direction) is set to TS1, and the tensile strength in the direction perpendicular to the fiber direction (CD direction) is set to TS2. Preferably, TS1 is greater than TS2. In this case, due to the anisotropy of the tensile strength, the cycle characteristics are easily reduced. In contrast, in the present disclosure, the anisotropy of the tensile strength can be alleviated by setting the angle between the long side direction of the opposing portion and the fiber direction of the nonwoven fabric within a predetermined range. TS1 is, for example, greater than 1 N / cm, may be greater than 3 N / cm, or may be greater than 5 N / cm. On the other hand, TS1 is, for example, less than 50 N / cm. In addition, TS2 is, for example, greater than 0.1 N / cm, may be greater than 0.5 N / cm, or may be greater than 1 N / cm. On the other hand, TS2 is, for example, less than 30 N / cm. In addition, the ratio of TS1 to TS2 (TS1 / TS2) is, for example, greater than 1.1, may be greater than 1.5, may be greater than 2.0, or may be greater than 5.0. On the other hand, TS1 / TS2 is, for example, less than 50.

[0045] Examples of nonwoven fabrics include chemically bonded nonwovens, thermally bonded nonwovens, air-laid nonwovens, spunlace nonwovens, spunbond nonwovens, meltblown nonwovens, needle-punched nonwovens, and stitchbonded nonwovens. The thickness of the nonwoven fabric is not particularly limited and may be, for example, 1 μm or greater, 5 μm or greater, or 10 μm or greater. Alternatively, the thickness of the nonwoven fabric may be, for example, 50 μm or less.

[0046] (ii) Solid electrolyte

[0047] The solid electrolyte layer contains a solid electrolyte disposed inside the non-woven fabric. The solid electrolyte layer may contain only one solid electrolyte or may contain two or more. As solid electrolytes, for example, inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, halide solid electrolytes, and nitride solid electrolytes may be cited. The sulfide solid electrolyte preferably contains sulfur (S) as the main component of the anion element. The oxide solid electrolyte preferably contains oxygen (O) as the main component of the anion element. The hydride solid electrolyte preferably contains hydrogen (H) as the main component of the anion element. The halide solid electrolyte preferably contains a halogen (X) as the main component of the anion. The nitride solid electrolyte preferably contains nitrogen (N) as the main component of the anion element.

[0048] The sulfide solid electrolyte preferably contains, for example, Li, A (A is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. Furthermore, the sulfide solid electrolyte may further contain at least one of O and a halogen element. Examples of the halogen element include F, Cl, Br, and I.

[0049] The sulfide solid electrolyte preferably has an original composition (e.g. PS4 3- Structure, SiS4 4- Structure, GeS4 4- Structure, AlS3 3- Structure or BS3 3- The anionic structure is the main component of the sulfide solid electrolyte. This is because of its high chemical stability. The proportion of the anionic structure in the original composition relative to the total anionic structure in the sulfide solid electrolyte is, for example, 70 mol% or more, or 90 mol% or more.

[0050] Sulfide solid electrolytes can be either amorphous or crystalline. In the latter case, the sulfide solid electrolyte has a crystalline phase. Examples of crystalline phases include Thio-LISICON, LGPS, and Argentite.

[0051] The composition of the sulfide solid electrolyte is not particularly limited, and examples thereof include xLi2S·(100-x)P2S5 (70≤x≤80), yLiI·zLiBr·(100-yz)(xLi2S·(1-x)P2S5)(0.7≤x≤0.8, 0≤y≤30, 0≤z≤30).

[0052] The sulfide solid electrolyte may have a general formula (1): Li 4-x Ge 1-x P x A composition represented by S4 (0<x<1). In the general formula (1), at least a portion of Ge may be substituted by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the general formula (1), at least a portion of P may be substituted by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the general formula (1), a portion of Li may be substituted by at least one of Na, K, Mg, Ca, and Zn. In the general formula (1), a portion of S may be substituted by a halogen (at least one of F, Cl, Br, and I).

[0053] Other compositions of the sulfide solid electrolyte include, for example, Li 7-x-2y PS 6-x-y X y 、Li 8-x-2y SiS 6-x- y X y 、Li 8-x-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 satisfy 0≤x, 0≤y.

[0054] As an example of an oxide solid electrolyte, there can be mentioned a solid electrolyte containing Li element, Y element (Y is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W and S) and O element. As a specific example of an oxide solid electrolyte, there can be mentioned Li7La3Zr2O 12 、Li 7-x La3(Zr 2-x Nb x )O 12 (0≤x≤2), Li5La3Nb2O 12 Garnet-type solid electrolytes; perovskite-type solid electrolytes such as (Li,La)TiO3, (Li,La)NbO3, (Li,Sr)(Ta,Zr)O3; sodium superion conductor-type solid electrolytes such as Li(Al,Ti)(PO4)3 and Li(Al,Ga)(PO4)3; Li-PO-based solid electrolytes such as Li3PO4 and LIPON (compounds in which part of the O in Li3PO4 is replaced by N); Li-BO-based solid electrolytes such as Li3BO3 and compounds in which part of the O in Li3BO3 is replaced by C.

[0055] The hydride solid electrolyte has, for example, Li and a complex anion containing hydrogen. As the complex anion, for example, (BH4) - NH2 - 、(AlH4) - and (AlH6) 3- As a halide solid electrolyte, for example, Li 6-3z Y z X6 (X is at least one of Cl and Br, and z satisfies 0<z<2). Examples of the nitride solid electrolyte include Li3N.

[0056] As another example of a solid electrolyte, a molten salt that is solid at 25°C can be cited. The molten salt has cations and anions. Examples of cations include inorganic cations such as lithium ions; ammonium cations, piperidinium cations, pyridinium cations, imidazolium cations, pyridinium cations, alicyclic amine cations, aliphatic amine cations, aliphatic An organic cation such as a cation. Examples of anions include anions having a sulfonamide structure. Examples of anions having a sulfonamide structure include bis(trifluoromethanesulfonyl)amide, bis(fluorosulfonyl)amide, bis(pentafluoroethanesulfonyl)amide, and (fluorosulfonyl)(trifluoromethanesulfonyl)amide. The melting point of the molten salt is generally above 25°C, may be above 30°C, or may be above 40°C. On the other hand, the melting point of the molten salt is, for example, below 200°C, may be below 150°C, or may be below 120°C.

[0057] As another example of solid electrolyte, plastic crystal solid electrolyte can be cited. Plastic crystal is composed of a regularly arranged three-dimensional lattice, and has orientational and rotational disorder at the level of molecular species or molecular ions. Plastic crystal has cations and anions. Examples of cations include pyrrolidine, tetraalkylammonium and tetraalkyl Examples of the anion include hexafluorophosphate, tetrafluoroborate, thiocyanate, bis(trifluoromethanesulfonyl)amide, bis(fluorosulfonyl)amide, bis(pentafluoroethanesulfonyl)amide, and (fluorosulfonyl)(trifluoromethanesulfonyl)amide.

[0058] The shape of the solid electrolyte may be, for example, a granular shape. The average particle size (D 50 ) is not particularly limited, and may be, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less. The average particle size (D 50 ) is preferably smaller than the thickness of the nonwoven fabric. Average particle size (D 50 ) can be calculated by, for example, a laser diffraction particle size distribution analyzer or a scanning electron microscope (SEM). The ratio of the total volume of the solid electrolyte to the total volume of the pores in the nonwoven fabric is, for example, 50% by volume or more, 70% by volume or more, or 90% by volume or more.

[0059] (iii) Solid electrolyte layer

[0060] The solid electrolyte layer may or may not contain a binder. As the binder, for example, rubber-based binders such as butadiene rubber, hydrogenated butadiene rubber, styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, and ethylene-propylene rubber can be cited; fluoride-based binders such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and fluororubber can be cited. The proportion of the binder in the solid electrolyte layer is, for example, 0 parts by weight or more and 3 parts by weight or less relative to 100 parts by weight of the solid electrolyte.

[0061] The plan view shape of the solid electrolyte layer is preferably a rectangle having long sides and short sides. The plan view shape of the solid electrolyte layer may be the same as the plan view shape of the negative electrode layer or the same as the plan view shape of the positive electrode layer. The Young's modulus of the solid electrolyte layer is, for example, 1 GPa or more. The thickness of the solid electrolyte layer is not particularly limited, and may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. On the other hand, the thickness of the solid electrolyte layer may be, for example, 150 μm or less, or 100 μm or less.

[0062] The nonwoven fabric in the solid electrolyte layer can be in direct contact with the positive electrode layer. Alternatively, a positive electrode solid electrolyte portion can be placed between the nonwoven fabric and the positive electrode layer. This placement of a positive electrode solid electrolyte portion can reduce internal resistance. The positive electrode solid electrolyte portion contains at least a solid electrolyte and, if necessary, a binder. The solid electrolyte and binder are the same as described above. The positive electrode solid electrolyte portion generally does not have electronic conductivity.

[0063] The nonwoven fabric in the solid electrolyte layer can be in direct contact with the negative electrode layer. Alternatively, a negative electrode solid electrolyte portion can be placed between the nonwoven fabric and the negative electrode layer. This placement of a negative electrode solid electrolyte portion can reduce internal resistance. The negative electrode solid electrolyte portion contains at least a solid electrolyte and, if necessary, a binder. The solid electrolyte and binder are the same as described above. The negative electrode solid electrolyte portion generally does not have electronic conductivity.

[0064] (2) Positive electrode layer

[0065] The positive electrode layer is a layer containing at least a positive electrode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder as needed. Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layered active materials, LiMn2O4, Li4Ti5O 12 、Li(Ni 0.5 Mn 1.5 )O4 and other spinel active materials, LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4 and other olivine active materials.

[0066] A protective layer containing a Li-ion-conducting oxide can be formed on the surface of the oxide active material. This can inhibit the reaction between the oxide active material and the solid electrolyte. Examples of Li-ion-conducting oxides include LiNbO3. The thickness of the protective layer is, for example, from 1 nm to 30 nm. Alternatively, Li2S can be used as the positive electrode active material.

[0067] The shape of the positive electrode active material may be, for example, a granular shape. The average particle size (D 50 ) is not particularly limited, and may be, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D 50 ) is, for example, less than 50 μm, or less than 20 μm.

[0068] 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 granular carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs). In addition, the solid electrolyte and binder used in the positive electrode layer are the same as those described in the above-mentioned "(1) Solid Electrolyte Layer", so they are omitted here. The thickness of the positive electrode layer is, for example, greater than 0.1 μm and less than 1000 μm. The shape of the positive electrode layer in plan view is preferably a rectangle having long sides and short sides.

[0069] (3) Negative electrode layer

[0070] The negative electrode layer contains at least a negative electrode active material and, if necessary, may contain at least one of a solid electrolyte, a conductive material, and a binder. Examples of negative electrode active materials include lithium-based active materials such as metallic lithium and lithium alloys; carbon-based active materials such as graphite, hard carbon, and soft carbon; oxide-based active materials such as lithium titanate; and silicon-based active materials such as elemental Si, Si alloys, and silicon oxide.

[0071] The shape of the negative electrode active material can be granular, for example. The average particle size (D 50 ) is, for example, 10 nm or more, or 100 nm or more. On the other hand, the average particle size (D 50 ) is, for example, less than 50 μm, or less than 20 μm.

[0072] The conductive material, solid electrolyte, and binder used in the negative electrode layer are the same as those described in "(1) Solid Electrolyte Layer" and "(2) Positive Electrode Layer" above, so their description is omitted here. The thickness of the negative electrode layer is, for example, 0.1 μm to 1000 μm. The plan view of the negative electrode layer preferably has a rectangular shape having long and short sides.

[0073] (4) Electrode structure

[0074] The electrode structure comprises a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. When the assembly of the positive electrode layer, solid electrolyte layer, and negative electrode layer serves as a power generation unit, the electrode structure may comprise only one power generation unit or may comprise two or more power generation units. When the electrode structure comprises two or more power generation units, these power generation units may be connected in series or in parallel.

[0075] The electrode structure may include a positive electrode current collector for collecting current from the positive electrode layer. Typically, the positive electrode current collector is positioned on the opposite side of the solid electrolyte layer relative to the positive electrode layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. Examples of shapes for the positive electrode current collector include foil and mesh.

[0076] The electrode structure may include a negative electrode current collector for collecting current from the negative electrode layer. Typically, the negative electrode current collector is positioned on the opposite side of the solid electrolyte layer relative to the negative electrode layer. Examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon. Examples of shapes for the negative electrode current collector include foil and mesh.

[0077] 2. All-solid-state batteries

[0078] The all-solid-state battery disclosed herein may include an outer casing that houses at least the electrode structure. Examples of the outer casing include a laminated outer casing and a shell-type outer casing.

[0079] The all-solid-state battery may include a constraining member that applies a constraining pressure to the electrode structure along the thickness direction. The constraining pressure is, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. On the other hand, the constraining pressure is, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0080] The all-solid-state battery of the present disclosure is typically an all-solid-state lithium ion secondary battery. The purpose of the all-solid-state battery is not particularly limited, and for example, the power supply of vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), electric vehicles (BEV), gasoline vehicles, diesel vehicles, etc. can be cited. It is particularly preferably used as a driving power supply for hybrid electric vehicles, plug-in hybrid electric vehicles or electric vehicles. In addition, the all-solid-state battery of the present disclosure can be used as a power supply for mobile bodies (such as railways, ships, aircraft) other than vehicles, and can also be used as a power supply for electronic products such as information processing equipment.

[0081] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely illustrative, and any configuration having substantially the same structure and effect as the technical concept described in the claims of the present disclosure is encompassed within the technical scope of the present disclosure.

[0082] [Example]

[0083] [Example 1]

[0084] (Production of positive electrode)

[0085] As the positive electrode active material, the average particle size (D 50 ) is 5μm LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 powder. Then, the surface of the positive electrode active material is coated with LiNbO3 using the sol-gel method. In addition, as a sulfide solid electrolyte, an average particle size (D50 ) is 15LiBr·10LiI·75 (0.75Li2S·0.25P2S5) glass ceramic with a thickness of 2.5 μm.

[0086] Next, the positive electrode active material and the sulfide solid electrolyte were weighed and mixed at a weight ratio of 75:25, forming a first mixture. Next, 3 parts by weight of an SBR (styrene-butadiene rubber) binder and 10 parts by weight of a conductive material (carbon nanofiber, CNF) were weighed for 100 parts by weight of the positive electrode active material and added to the first mixture to form a second mixture. A dispersion medium (butyl butyrate) was then added to the second mixture, and the solids concentration was adjusted to 60% by weight. Ultrasonic dispersion was then performed for one minute to form a positive electrode slurry.

[0087] The obtained positive electrode slurry was coated with a doctor blade at a density of 15 mg / cm 2 The coating amount was evenly applied on a positive electrode current collector (aluminum foil, thickness 15 μm) and dried at 100° C. for 60 minutes. Thus, a positive electrode (positive electrode structure) having a positive electrode current collector and a positive electrode layer was obtained.

[0088] (Fabrication of negative electrode)

[0089] As the negative electrode active material, the average particle size (D 50 ) is 5 μm Si powder. In addition, as the sulfide solid electrolyte, the average particle size (D 50 ) is a glass ceramic of 15LiBr·10LiI·75 (0.75Li2S·0.25P2S5) with a thickness of 2.5μm.

[0090] Next, the negative electrode active material and the sulfide solid electrolyte were weighed and mixed at a weight ratio of 50:50, yielding a third mixture. Next, 3 parts by weight of an SBR-based binder and 10 parts by weight of a conductive material (CNF) were weighed per 100 parts by weight of the negative electrode active material and added to the third mixture to yield a fourth mixture. A dispersion medium (butyl butyrate) was then added to the fourth mixture, and the solids concentration was adjusted to 40% by weight. Ultrasonic dispersion was then performed for 1 minute to yield a negative electrode slurry.

[0091] The obtained negative electrode slurry was coated with a doctor blade at a density of 3 mg / cm 2 The coating amount was evenly applied on a negative electrode current collector (roughened copper foil, thickness 25 μm, Rz=5 μm) and dried at 100° C. for 60 minutes. Thus, a negative electrode (negative electrode structure) having a negative electrode current collector and a negative electrode layer was obtained.

[0092] (Fabrication of Solid Electrolyte Layer)

[0093] As the sulfide solid electrolyte, the average particle size (D 50 ) is 15LiBr·10LiI·75 (0.75Li2S·0.25P2S5) glass ceramic with a particle size of 2.5 μm. In addition, an SBR-based binder was used as the binder.

[0094] Next, the sulfide solid electrolyte and binder were weighed and mixed at a weight ratio of sulfide solid electrolyte:binder = 99:1 to obtain a fifth mixture. A dispersion medium (butyl butyrate) was then added to the fifth mixture to adjust the solid content concentration to 50% by weight, followed by ultrasonic dispersion treatment for 1 minute to obtain a slurry for the solid electrolyte layer.

[0095] Then, a polyester nonwoven fabric (thickness 15 μm, porosity 80%, tensile strength 5 N / cm in MD direction, tensile strength 1 N / cm in CD direction) was placed on the aluminum foil. 2 The obtained slurry was evenly applied to a polyester nonwoven fabric in an amount of 100 μm (the thickness including the nonwoven fabric was 15 μm), and dried at 100° C. for 60 minutes. Thus, a transfer member having an aluminum foil and a solid electrolyte layer was obtained.

[0096] (Fabrication of all-solid-state batteries)

[0097] Cut the transfer member into a 7.5 cm x 5.1 cm rectangle. Cut the transfer member so that the fiber direction (MD) is parallel to the long side of the rectangle. Also, cut the negative electrode structure into a 7.5 cm x 5.1 cm rectangle. Also, cut the positive electrode structure into a 7.3 cm x 4.9 cm rectangle.

[0098] Then, the negative electrode layer in the negative electrode structure and the solid electrolyte layer in the transfer member were overlapped and the negative electrode layer was stacked at 1 ton / cm 2 The roller is rolled with a pressing pressure of 3 tons / cm. At this time, the roller is rolled in a manner such that the fiber direction (MD direction) in the solid electrolyte layer is parallel to the direction of the roller. Next, the aluminum foil is peeled off from the transfer member. Thus, a structure X having a negative electrode current collector, a negative electrode layer and a solid electrolyte layer is obtained. Next, the solid electrolyte layer in the structure X is overlapped with the positive electrode layer in the positive electrode structure, and the roller is rolled with a pressing pressure of 3 tons / cm. 2The roller was rolled with a pressing pressure of 1000 rpm. At this time, the roller was rolled in such a way that the fiber direction (MD direction) in the solid electrolyte layer was parallel to the direction of the roller. Thus, a structure Y having a negative electrode collector, a negative electrode layer, a solid electrolyte layer, a positive electrode layer and a positive electrode collector was obtained. Furthermore, the area of ​​the opposing portion in the structure Y was 36.0 cm 2 Next, the structure Y was sealed with an exterior body (aluminum laminate film) on which a positive electrode terminal and a negative electrode terminal were previously provided, thereby obtaining an all-solid-state battery.

[0099] [Example 2]

[0100] A full solid-state battery was obtained in the same manner as in Example 1 except that the transfer member and the negative electrode structure were cut into rectangles of 8.6 cm×4.5 cm, and the positive electrode structure was cut into a rectangle of 8.4 cm×4.3 cm.

[0101] [Example 3]

[0102] A full solid-state battery was obtained in the same manner as in Example 1 except that the transfer member and the negative electrode structure were cut into a rectangle of 9.7 cm×4.0 cm, and the positive electrode structure was cut into a rectangle of 9.5 cm×3.8 cm.

[0103] [Example 4]

[0104] A full solid-state battery was obtained in the same manner as in Example 1 except that the transfer member and the negative electrode structure were cut into a rectangle of 10.7 cm×3.6 cm, and the positive electrode structure was cut into a rectangle of 10.5 cm×3.4 cm.

[0105] [Example 5]

[0106] A full solid-state battery was obtained in the same manner as in Example 1 except that the transfer member and the negative electrode structure were cut into a rectangle of 12.2 cm×3.2 cm, and the positive electrode structure was cut into a rectangle of 12.0 cm×3.0 cm.

[0107] [Comparative Example 1]

[0108] A full solid-state battery was obtained in the same manner as in Example 5 except that the transfer member was cut so that the fiber direction (MD direction) was parallel to the short side of the rectangle.

[0109] [Comparative Example 2]

[0110] A full solid-state battery was obtained in the same manner as in Example 1 except that the transfer member and the negative electrode structure were cut into 6.2 cm×6.2 cm squares, and the positive electrode structure was cut into 6.0 cm×6.0 cm squares.

[0111] [evaluate]

[0112] A cycle test was performed using the all-solid-state batteries prepared in Examples 1 to 5 and Comparative Examples 1 and 2. The measurement was performed in the following order. First, the all-solid-state battery was constrained at a pressure of 100 MPa and CCCV charged to 4.5 V at a current rate of 36 mA (current cutoff value: 0.36 mA). Then, CCCV discharged to 3.0 V at a current rate of 36 mA (current cutoff value: 0.36 mA). The charge and discharge were performed 100 cycles to determine the capacity retention rate. The results are shown in Table 1.

[0113] Capacity retention rate (%) = discharge capacity at the 100th cycle / discharge capacity at the 1st cycle × 100

[0114] Table 1

[0115]

[0116] As shown in Table 1, Examples 1 to 5 have greater capacity retention rates than Comparative Examples 1 and 2. This is presumably because the anisotropy of tensile strength can be mitigated by reducing the angle between the longitudinal direction of the facing portion and the fiber direction of the nonwoven fabric.

Claims

1. An all-solid-state battery comprising an electrode structure comprising 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 electrode structure includes an opposing portion where the positive electrode layer and the negative electrode layer face each other. In a plan view viewed in the thickness direction, the opposing portion has a rectangular shape having long sides and short sides, The ratio of the length of the long side to the length of the short side is greater than 1.5, The solid electrolyte layer includes a non-woven fabric and a solid electrolyte disposed inside the non-woven fabric. In the plan view, the solid electrolyte layer is arranged so that the longitudinal direction of the opposing portion coincides with the fiber direction of the nonwoven fabric. In the nonwoven fabric, the tensile strength in the fiber direction is greater than the tensile strength in a direction orthogonal to the fiber direction.

2. The all-solid-state battery according to claim 1, The nonwoven fabric has a porosity of 70% or more and 90% or less.

3. The all-solid-state battery according to claim 1 or 2, The solid electrolyte is an inorganic solid electrolyte.

4. The all-solid-state battery according to claim 3, The inorganic solid electrolyte is at least one of a sulfide solid electrolyte, an oxide solid electrolyte, and a hydride solid electrolyte.

5. The all-solid-state battery according to claim 1 or 2, The solid electrolyte is a molten salt that is solid at 25°C.

6. The all-solid-state battery according to claim 1 or 2, The solid electrolyte is a plastic crystalline solid electrolyte.

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