Solid electrolyte layer, and method for manufacturing solid state battery

Abstract

To provide a solid electrolyte layer that can suppress increase in resistance, and a method for manufacturing a solid state battery.SOLUTION: It is a solid electrolyte layer for a solid state battery, the solid electrolyte layer includes a non-woven fabric and a solid electrolyte, the solid electrolyte is placed inside the non-woven fabric, and the ratio of the volume of the non-woven fabric to the volume of the solid electrolyte layer is equal to or more than 35% and equal to or less than 54%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a solid electrolyte layer and a method for manufacturing a solid battery.

Background Art

[0002] Various techniques have been proposed regarding a solid electrolyte layer including a nonwoven fabric as disclosed in Patent Documents 1 to 3.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a solid electrolyte layer including a nonwoven fabric, if the basis weight of the nonwoven fabric is too large, the resistance increases, and if the basis weight of the nonwoven fabric is too small, the tensile strength decreases.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a solid electrolyte layer and a method for manufacturing a solid battery capable of suppressing an increase in resistance.

Means for Solving the Problems

[0006] That is, the present disclosure includes the following aspects. <1> A solid electrolyte layer for a solid battery, The solid electrolyte layer includes a nonwoven fabric and a solid electrolyte, The solid electrolyte is disposed inside the nonwoven fabric, A solid electrolyte layer in which the ratio of the volume of the nonwoven fabric to the volume of the solid electrolyte layer is 35% or more and 54% or less.

[0007] <2> The solid electrolyte layer according to <1>, wherein the porosity of the nonwoven fabric is 73% or more and 83% or less.

[0008] <3> The solid electrolyte layer according to <1> or <2>, wherein the nonwoven fabric is made of polyethylene terephthalate.

[0009] <4> The solid electrolyte layer according to any one of <1> to <3>, wherein the solid electrolyte contains a sulfide solid electrolyte.

[0010] <5> A method for manufacturing a solid battery, comprising: a step of obtaining a laminate by disposing the solid electrolyte layer according to any one of <1> to <4> between a negative electrode layer and a positive electrode layer; a step of pressing the laminate.

Advantages of the Invention

[0011] According to the present disclosure, it is possible to provide a solid electrolyte layer and a method for manufacturing a solid battery that can suppress an increase in resistance.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments according to the present disclosure will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present disclosure (for example, a solid electrolyte layer that does not characterize the present disclosure, and general configurations and manufacturing processes of solid-state batteries) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in the art. In the present disclosure, unless otherwise specified, the average particle size of the particles is the value of the median diameter (D50), which is the particle diameter at the integrated value of 50% in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0014] 1. Solid electrolyte layer In the present disclosure, a solid electrolyte layer for a solid-state battery, The solid electrolyte layer includes a non-woven fabric and a solid electrolyte, The solid electrolyte is disposed inside the non-woven fabric, A solid electrolyte layer is provided in which the ratio of the volume of the non-woven fabric to the volume of the solid electrolyte layer is 35% or more and 54% or less.

[0015] In the present disclosure, in a solid electrolyte layer including a non-woven fabric, by setting the ratio of the volume of the non-woven fabric to the volume of the solid electrolyte layer within a predetermined range, the number of fibers of the non-woven fabric decreases and the pore diameter increases. As a result, while maintaining the desired tensile strength of the solid electrolyte layer, the solid electrolyte (SE) particles in the solid electrolyte layer are more likely to come into contact with each other, the ion conduction paths increase, and an increase in resistance due to the inclusion of the non-woven fabric can be suppressed.

[0016] The solid electrolyte layer of the present disclosure includes a non-woven fabric and a solid electrolyte, and may include a binder or the like as necessary. The solid electrolyte layer of the present disclosure is for a solid-state battery. The "non-woven fabric" is a sheet-like material in which fibers are adhered or entangled without weaving, and indicates a planar fiber aggregate having a predetermined level of structural strength obtained by physical methods and / or chemical methods excluding weaving, knitting, and papermaking (JIS L0222:2022). The fiber aggregate has a plurality of pores. "Pore diameter" refers to the maximum pore diameter measured by the bubble point method (JIS K3832). The planar shape of the solid electrolyte layer is not particularly limited, and examples include a rectangle. Examples of the rectangle include a square and a rectangle. The thickness of the solid electrolyte layer depends on the thickness of the nonwoven fabric and may be equal to or greater than the thickness of the nonwoven fabric. From the perspective of reducing the resistance of the solid-state battery, the thickness of the solid electrolyte layer may be 50 μm or less, or may be 30 μm or less. The thickness of the solid electrolyte layer may be 1 μm or more.

[0017] [Nonwoven fabric] The type of nonwoven fabric is not particularly limited. For example, it includes meltblown nonwoven fabric, spunbond nonwoven fabric, carded nonwoven fabric, parallel nonwoven fabric, cross nonwoven fabric, random nonwoven fabric, spunlaced nonwoven fabric, flash spun nonwoven fabric, chemical bonded nonwoven fabric, hydroentangled nonwoven fabric, needle punched nonwoven fabric, stitch bonded nonwoven fabric, thermal bonded nonwoven fabric, burst fiber nonwoven fabric, degummed nonwoven fabric, and film split nonwoven fabric. Examples of the material of the nonwoven fabric include resin and glass. Examples of the resin include polyester resin, polyolefin resin, and polyamide resin. Examples of the polyester resin include polyethylene terephthalate (PET). Examples of the polyolefin resin include polyethylene (PE) and polypropylene (PP). Examples of the polyamide resin include nylon and aramid. From the perspective of high heat resistance and low degradation at high temperatures, the nonwoven fabric may be composed of polyethylene terephthalate. The porosity of the nonwoven fabric is not particularly limited. From the perspective of further reducing the resistance of the solid-state battery, it may exceed 69%, may be 70% or more, or may be 73% or more. From the perspective of reducing the resistance while maintaining the tensile strength of the solid electrolyte layer, it may be less than 84%, may be 83% or less. The porosity of the nonwoven fabric may be 73% or more and 83% or less. The porosity indicates the volume of voids inside the nonwoven fabric with respect to the total volume of the nonwoven fabric. The porosity of the nonwoven fabric can be calculated by calculating the volume of voids from the difference between the actual volume of the nonwoven fabric and the volume calculated from the specific gravity of the material, and obtaining the ratio of the volume of voids to the actual volume of the nonwoven fabric. The average fiber diameter of the nonwoven fabric is not particularly limited. The fibers of the nonwoven fabric may be long fibers or single fibers. The cross-sectional shape of the fibers is not particularly limited, and examples include circular, elliptical, and irregular shapes. The thickness of the nonwoven fabric is not particularly limited, and it may be 10 μm or more, 60 μm or less, or 30 μm or less. When the thickness of the nonwoven fabric is 10 μm to 60 μm, the thickness of the solid electrolyte layer of the solid battery can be made thinner. As a result, the resistance of the solid battery can be further reduced. The basis weight of the nonwoven fabric is not particularly limited, and from the viewpoint of further reducing the battery resistance of the solid battery, etc., it may be 0.10 g / cm 2 or more and 1 g / cm 2 or less. The pore diameter of the nonwoven fabric is not particularly limited, and it may be 1 μm to 15 μm. The nonwoven fabric can be produced by conventionally known methods such as the meltblown method and the spunbond method, and the average fiber diameter, pore diameter, thickness, and porosity of the nonwoven fabric can be controlled by conventionally known methods.

[0018] [Solid electrolyte] The solid electrolyte is disposed inside the nonwoven fabric. As long as the solid electrolyte is disposed inside the nonwoven fabric, it may or may not cover the nonwoven fabric. Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, halide solid electrolytes, and nitride solid electrolytes, and organic polymer electrolytes such as polymer electrolytes. From the viewpoint of suppressing the peeling of the positive electrode layer and the negative electrode layer from the solid electrolyte layer and further reducing the resistance of the solid battery, a relatively soft sulfide solid electrolyte may be used as the solid electrolyte. The solid electrolyte may be used alone as one type, or two or more types may be combined and used. Further, when two or more types of solid electrolytes are used, two or more types of solid electrolytes may be mixed, or layers of two or more solid electrolytes may be formed respectively to form a multilayer structure. The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited, but may be, for example, 50% by mass or more and 99% by mass or less. 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 90% by volume or more.

[0019] Sulfide solid electrolytes include, for example, solid electrolytes containing Li element, A element, and S element. 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 element and halogen element. Examples of the halogen element (X) include F element, Cl element, Br element, and I element. The sulfide solid electrolyte may be glass (amorphous), glass ceramics, or crystalline. When the sulfide solid electrolyte is crystalline, the sulfide solid electrolyte has a crystal phase. Examples of the crystal phase include Thio-LISICON type crystal phase, LGPS type crystal phase, and argyrodite type crystal phase. Examples of the sulfide solid electrolyte include Li2S-P2S5, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, and Li2S-P2S5-GeS2. Note that the description of "Li2S-P2S5" means a material formed using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. The molar ratio of each element in the sulfide solid electrolyte can be controlled by adjusting the content of each element in the raw material. Also, the molar ratio and composition of each element in the sulfide solid electrolyte can be measured, for example, by ICP emission spectrometry.

[0020] Oxide solid electrolytes include, for example, solid electrolytes containing Li element, Z element (Z is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O element. Examples of the oxide solid electrolyte include Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, Li 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 , Li7La3Zr2O 12 , Li6BaLa2Ta2O 12 , Li 3.6 Si 0.6 P 0.4 O4, Li4SiO4, Li3PO4, and Li 3+x PO4-x N x It may be, for example, (1 ≦ x ≦ 3). The hydride solid electrolyte has, for example, Li and a complex anion containing hydrogen. Examples of the complex anion include (BH4) - , (NH2) - , (AlH4) - , and (AlH6) 3- and the like. Examples of the halogenated solid electrolyte include LiF, LiCl, LiBr, LiI, and LiI - Al2O3 and the like. Examples of the nitrided solid electrolyte include Li3N and the like.

[0021] Examples of the binder include rubber - based binders, fluoride - based binders, and the like. Examples of the rubber - based binder include butadiene rubber, hydrogenated butadiene rubber, styrene - butadiene rubber (SBR), hydrogenated styrene - butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, and ethylene - propylene rubber. Examples of the fluoride - based binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - HFP), polytetrafluoroethylene, and fluororubber. When the solid electrolyte layer contains a binder, the content of the binder may be 0 to 3 parts by mass with respect to the total amount of the solid electrolyte layer.

[0022] The solid electrolyte is solid electrolyte particles. The average particle diameter (D50) of the solid electrolyte particles is not particularly limited, but from the viewpoint of reducing the battery resistance, it may be 0.1 μm or more, it may be 0.5 μm or more, it may be 100 μm or less, or it may be 10 μm or less.

[0023] [Ratio of non - woven fabric volume to solid electrolyte layer volume] In the present disclosure, the ratio of the volume of the non - woven fabric to the volume of the solid electrolyte layer is 35% or more and 54% or less. The ratio of the volume of the nonwoven fabric to the volume of the solid electrolyte layer can be changed by controlling the porosity of the nonwoven fabric and the amount of the solid electrolyte deposited on the nonwoven fabric, etc.

[0024] The solid electrolyte layer can be formed, for example, by the following method. A solid electrolyte paste containing a solid electrolyte, a binder, and a solvent may be prepared, a nonwoven fabric may be placed on a release film, and the solid electrolyte layer may be formed by applying the solid electrolyte paste to the nonwoven fabric placed on the release film. Examples of the solvent include butyl acetate, butyl butyrate, heptane, and N-methyl-2-pyrrolidone.

[0025] 2. Solid battery The solid battery of the present disclosure includes a negative electrode including a negative electrode layer, a positive electrode including a positive electrode layer, and the solid electrolyte layer of the present disclosure disposed between the negative electrode layer and the positive electrode layer. In the present disclosure, the solid battery means a battery including a solid electrolyte. The solid battery may be a semi-solid battery that is a solid battery including a solid electrolyte and a liquid-based material, or may be an all-solid battery that is a solid battery not including a liquid-based material. When a set of a positive electrode, a solid electrolyte layer, and a negative electrode is used as a power generation unit, the solid battery may have only one power generation unit or may have two or more power generation units. When the solid battery has two or more power generation units, those power generation units may be connected in series or may be connected in parallel.

[0026] [Positive electrode] The positive electrode includes a positive electrode layer. The positive electrode may include a positive electrode current collector as needed.

[0027] [Positive electrode layer] The positive electrode layer includes a positive electrode active material, and may include a solid electrolyte, a conductive material, a binder, etc. as needed.

[0028] Examples of the positive electrode active material include lithium nickel cobalt aluminum oxide (NCA), LiCoO2, LiNi x Co1-x O2 (0 < x < 1), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, LiMn2O4, LiNiO2, LiVO2, heteroatom-substituted Li-Mn spinel, lithium titanate, lithium metal phosphate, LiCoN, Li2SiO3, and Li4SiO4, etc. can be mentioned. Heteroatom-substituted Li-Mn spinel is, for example, LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4, and LiMn 1.5 Zn 0.5 O4, etc. Lithium titanate is, for example, Li4Ti5O 12 etc. Lithium metal phosphate is, for example, LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4, etc. The positive electrode active material may be an active material containing Ni element and Co element. The shape of the positive electrode active material is not particularly limited, but it may be particulate (positive electrode active material particles). The average particle size of the positive electrode active material particles is not particularly limited and may be 1 nm to 100 μm. A coating layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material. This is because the reaction between the positive electrode active material and the solid electrolyte can be suppressed. Examples of the Li ion conductive oxide include LiNbO3, Li4Ti5O 12 , and Li3PO4, etc. The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coverage rate of the coating layer on the surface of the positive electrode active material is, for example, 70% or more, and may be 90% or more.

[0029] As the conductive material, known materials can be used, for example, carbon materials, metal particles, and the like. Examples of the carbon material include acetylene black (AB), furnace black, VGCF, carbon nanotubes, and carbon nanofibers. Among them, from the viewpoint of electron conductivity, it may be at least one selected from the group consisting of VGCF, carbon nanotubes, and carbon nanofibers. Examples of the metal particles include particles such as Ni, Cu, Fe, and SUS. The content of the conductive material in the positive electrode layer is not particularly limited.

[0030] As the solid electrolyte, the solid electrolytes that can be contained in the above-described solid electrolyte layer can be exemplified. The content of the solid electrolyte in the positive electrode layer is not particularly limited, but when the total mass of the positive electrode layer is 100% by mass, it may be, for example, in the range of 1% to 80% by mass.

[0031] As the binder, the binders that can be contained in the above-described solid electrolyte layer can be exemplified. The content of the binder in the positive electrode layer is not particularly limited.

[0032] The thickness of the positive electrode layer is not particularly limited.

[0033] The positive electrode layer can be formed by a conventionally known method. For example, the positive electrode active material and, if necessary, other components are put into a solvent and stirred to prepare a positive electrode paste. The positive electrode layer is obtained by applying the positive electrode paste on one surface of a support such as a positive electrode current collector and drying it. As the solvent, the solvents that can be used for preparing the above-described solid electrolyte paste can be exemplified. The method of applying the positive electrode paste on one surface of a support such as a positive electrode current collector is not particularly limited, and examples thereof include a doctor blade method, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a gravure coating method, and a screen printing method. As the support, those having self-supporting properties can be appropriately selected and used, and there is no particular limitation. For example, metal foils such as Cu and Al can be used.

[0034] [Positive current collector] As the positive current collector, known metals that can be used as the current collector of the solid battery can be used. Examples of such metals include metal materials containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Examples of the positive current collector include SUS, aluminum, nickel, iron, titanium, and carbon. The form of the positive current collector is not particularly limited and can be various forms such as foil-like and mesh-like.

[0035] [Negative electrode] The negative electrode includes a negative electrode layer. The negative electrode may include a negative current collector as needed.

[0036] [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 needed. Examples of the negative electrode active material include Li-based active materials, carbon-based active materials, oxide-based active materials, and Si-based active materials, and may be 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 Si single substance, Si alloy, and silicon oxide. The shape of the negative electrode active material is, for example, particulate. The average particle size of the negative electrode active material particles is not particularly limited and may be 1 nm to 100 μm. The conductive material, solid electrolyte, and binder used for the negative electrode layer may be the same as those exemplified as the conductive material, solid electrolyte, and binder that may be included in the positive electrode layer. The thickness of the negative electrode layer is not particularly limited and may be, for example, from 0.1 μm to 1000 μm.

[0037] [Negative electrode current collector] The material of the negative electrode current collector may be a material that does not alloy with Li, and examples thereof include SUS, copper, nickel, and the like. Examples of the form of the negative electrode current collector include foil shape and plate shape. The planar shape of the negative electrode current collector is not particularly limited, and examples thereof include circular shape, elliptical shape, rectangular shape, and any polygonal shape. Further, the thickness of the negative electrode current collector varies depending on the shape, but may be, for example, in the range of 1 μm to 50 μm, or may be in the range of 5 μm to 20 μm.

[0038] [Solid electrolyte layer] The solid-state battery includes the solid electrolyte layer of the present disclosure. The nonwoven fabric included in the solid electrolyte layer 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 nonwoven fabric of the solid electrolyte layer and at least one of the positive electrode layer and the negative electrode layer. By disposing another solid electrolyte layer, the internal resistance of the solid-state battery is reduced. Another solid electrolyte layer contains a solid electrolyte and may contain a binder as necessary. Examples of the solid electrolyte and the binder are the same as those exemplified as the solid electrolyte and the binder that may be included in the solid electrolyte layer of the present disclosure. Another solid electrolyte layer does not contain a nonwoven fabric. The thickness of another solid electrolyte layer is not particularly limited.

[0039] The solid-state battery may include an exterior body that houses the positive electrode layer, the negative electrode layer, the solid electrolyte layer, etc., as necessary. The material of the exterior body is not particularly limited as long as it is stable to the solid electrolyte, and examples thereof include resins such as aluminum, polypropylene, polyethylene, and acrylic resin.

[0040] Examples of the shape of the solid battery include a coin type, a laminate type, a cylindrical type, and a rectangular type.

[0041] The solid battery may be a primary battery or a secondary battery. Examples of the uses of the solid battery include power sources for vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), battery electric vehicles (BEV), gasoline vehicles, and diesel vehicles. Among them, it may be used as a driving power source for a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or a battery electric vehicle (BEV). In addition, the solid battery may be used as a power source for moving bodies other than vehicles (e.g., railways, ships, and aircraft), and may also be used as a power source for electrical products such as information processing devices.

[0042] 3. Method for manufacturing a solid battery The method for manufacturing a solid battery according to the present disclosure includes a step of obtaining a laminate by disposing the solid electrolyte layer according to the present disclosure between a negative electrode layer and a positive electrode layer, and a step of pressing the laminate. In the step of obtaining the laminate, the solid electrolyte layer according to the present disclosure may be disposed on one of the first electrodes of the positive electrode layer and the negative electrode layer and pre-pressed. Then, the release film may be peeled off from the non-woven fabric, and the other second electrode of the positive electrode layer and the negative electrode layer may be disposed on the solid electrolyte layer to obtain a laminate. The pressing pressure in the pressing step is not particularly limited, but may be greater than the pressing pressure in the pre-pressing. The pressing method is not particularly limited, and examples include roll pressing. Depending on the pressing in the pressing step, each of the non-woven fabric and the solid electrolyte contained in the solid electrolyte layer is difficult to deform. Therefore, each of the non-woven fabric and the solid electrolyte contained in the solid electrolyte layer after pressing can be regarded as the same as each of the non-woven fabric and the solid electrolyte contained in the solid electrolyte layer before pressing.

Example

[0043] (Example 1) [Preparation of non-woven fabric] A nonwoven fabric made of PET with a thickness of 30 μm and a porosity of 83% shown in Table 1 was prepared. The basis weight of the nonwoven fabric was 1 g / cm 2 was used. [Fabrication of Solid Electrolyte Layer] As the sulfide solid electrolyte, particles of glass ceramics of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle diameter (D50) of 1 μm shown in Table 1 were used. With respect to 100% by mass of the sulfide solid electrolyte, 3% by mass of an SBR (styrene-butadiene rubber) - based binder was weighed, and these were formulated in butyl butyrate to a solid content of 50% by mass, and ultrasonic dispersion treatment was performed for 1 minute using an ultrasonic disperser to obtain a solid electrolyte paste. Next, the nonwoven fabric was placed on a release film (Si - coated PET film) with a thickness of 25 μm, and the solid electrolyte paste was uniformly coated using blade coating with a commercially available applicator so that the basis weight was 3.0 mg / cm 2 was achieved. Thereafter, the obtained coating film was dried at 100 °C for 60 minutes to obtain a solid electrolyte layer including the nonwoven fabric on the release film. Also, the volume ratio (%) of the nonwoven fabric to the volume of the solid electrolyte layer was calculated from the basis weight and specific gravity of the solid electrolyte and the basis weight and specific gravity of the nonwoven fabric. The volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer was 35%. The results are shown in Table 1. [Fabrication of Positive Electrode] As the positive electrode active material, particles of LiNi 2 Mn 1 / 3 Co 1 / 3 O2 with an average particle diameter (D50) of 10 μm and a specific surface area of 1 m 1 / 3 / g were used. Then, LiNbO3 was coated on the surface of the positive electrode active material using the sol - gel method. As the solid electrolyte, the same sulfide solid electrolyte as that of the solid electrolyte layer was used. With respect to 100% by mass of the positive electrode active material, 50% by mass of the sulfide solid electrolyte and a conductive material (CNF, specific surface area 14 m 210% by mass of (g) and 1% by mass of an SBR (styrene-butadiene rubber) - based binder were weighed, and these were formulated in butyl butyrate to a solid content of 60% by mass. By performing ultrasonic dispersion treatment for 1 minute using an ultrasonic dispersing device, a positive electrode paste was obtained. Next, the obtained positive electrode paste was uniformly applied by blade coating using a commercially available applicator onto a positive electrode current collector made of aluminum foil with a thickness of 15 μm at a coating weight of 25 mg / cm 2 so as to be uniform. Thereafter, the obtained coating film was dried at 100 °C for 60 minutes to obtain a positive electrode having a positive electrode layer formed on a positive electrode current collector made of aluminum foil. [Fabrication of Negative Electrode] As the negative electrode active material, Si particles with an average particle diameter (D50) of 3 μm and a specific surface area of 4 m 2 / g were used. As the sulfide solid electrolyte, the same sulfide solid electrolyte as the solid electrolyte layer was used. 100% by mass of the above-mentioned negative electrode active material and 100% by mass of the sulfide solid electrolyte, 10% by mass of a conductive material (CNF, specific surface area 14 m 2 / g), and 2% by mass of an SBR (styrene-butadiene rubber) - based binder were weighed, and these were formulated in butyl butyrate to a solid content of 40% by mass. By performing ultrasonic dispersion treatment for 1 minute using an ultrasonic dispersing device, a negative electrode paste was obtained. Next, the obtained negative electrode paste was uniformly applied by blade coating using a commercially available applicator onto a negative electrode current collector made of surface roughened copper foil with a thickness of 20 μm at a coating weight of 5 mg / cm 2 so as to be uniform. Thereafter, the obtained coating film was dried at 100 °C for 60 minutes to obtain a negative electrode having a negative electrode layer formed on a negative electrode current collector made of surface roughened copper foil. [Fabrication of Solid - State Battery] The negative electrode was cut out into a square shape of 1.2 cm × 1.2, and a solid electrolyte layer with a release film cut out in the same shape was superposed on the negative electrode layer so that the negative electrode layer and the solid electrolyte layer were in contact with each other, and roll - pressed at a pressing pressure of 1 ton / cm. Next, the release film attached to the solid electrolyte layer laminated on the negative electrode was peeled off, the positive electrode was cut out into a square shape of 1.0 cm × 1.0 cm, and the positive electrode layer and the solid electrolyte layer were overlapped so that they were in contact with each other on the solid electrolyte layer laminated on the negative electrode, and roll-pressed at a pressing pressure of 4 tons / cm². The laminate thus obtained was sealed with an exterior body made of an aluminum laminate film provided with a positive electrode terminal and a negative electrode terminal in advance, and a solid battery for testing in Example 1 (all-solid lithium-ion secondary battery) was fabricated.

[0044] (Example 2) A solid battery was fabricated in the same manner as in Example 1 except that a nonwoven fabric made of PET with a thickness of 30 μm and a porosity of 79% was used. The volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer was 42%.

[0045] (Example 3) A solid battery was fabricated in the same manner as in Example 1 except that a nonwoven fabric made of PET with a thickness of 30 μm and a porosity of 77% was used. The volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer was 46%.

[0046] (Example 4) A solid battery was fabricated in the same manner as in Example 1 except that a nonwoven fabric made of PET with a thickness of 30 μm and a porosity of 75% was used. The volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer was 50%.

[0047] (Example 5) A solid battery was fabricated in the same manner as in Example 1 except that a nonwoven fabric made of PET with a thickness of 30 μm and a porosity of 73% was used. The volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer was 54%.

[0048] (Comparative Example 1) A solid battery was fabricated in the same manner as in Example 1 except that no nonwoven fabric was used.

[0049] (Comparative Example 2) A solid battery was fabricated in the same manner as in Example 1 except that a nonwoven fabric made of PET with a thickness of 30 μm and a porosity of 84% was used. The volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer was 32%.

[0050] (Comparative Example 3) A solid battery was fabricated in the same manner as in Example 1 except that a nonwoven fabric made of PET with a thickness of 30 μm and a porosity of 69% was used. The volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer was 62%.

[0051] [Battery Resistance Measurement] Each of the solid batteries fabricated in Examples 1 to 5 and Comparative Examples 1 to 3 was charged in a CCCV manner under the conditions of a current value of 2 mA, an upper limit voltage of 4.5 V, and a lower limit voltage of 2.5 V, and then CCCV discharge was performed. Next, CCCV charging was performed at a current value of 2 mA and an upper limit voltage of 3.6 V. After a 10-minute rest, CC discharge was performed at a current value of 10 mA and a lower limit voltage of 0.0 V for 10 seconds, and the battery (cell) resistance R (=ΔV / I) was calculated according to Ohm's law. The results are shown in Table 1.

[0052] [Tensile Strength Measurement] For each of the solid electrolyte layers fabricated in Examples 1 to 5 and Comparative Examples 2 to 3, the tensile strength was measured by the following method with reference to JIS L 1096. A laminate obtained by further laminating a release film on the solid electrolyte paste coating surface of the solid electrolyte layer on the release film fabricated in the above [Fabrication of Solid Electrolyte Layer] was roll-pressed at a press pressure of 1 ton / cm² to peel off the release films on both sides of the solid electrolyte layer to create a self-standing solid electrolyte layer. The self-standing solid electrolyte layer was cut into strips with a width of 1 cm × a length of 5 cm, and the tensile strength was measured by a predetermined tensile test. The results are shown in Table 1.

[0053]

Table 1

[0054] FIG. 1 is a graph showing the relationship between the volume ratio (%) of the nonwoven fabric in each solid electrolyte layer, the tensile strength of each solid electrolyte layer, and the resistance of each solid battery, which were produced in Examples 1 to 5 and Comparative Examples 2 to 3. As shown in FIG. 1 and Table 1, the volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer is desirably as large as possible from the viewpoint of increasing the tensile strength of the solid electrolyte layer. However, as shown in Comparative Example 3, when the volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer exceeds 54%, the battery resistance significantly increases. As shown in Comparative Example 2, when the volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer is too small, the battery resistance is reduced, but the allowable value of the tensile strength is less than 1.0. When the volume ratio of the nonwoven fabric to the volume of the solid electrolyte layer is 35% or more and 54% or less, the allowable value of the tensile strength is 1.0 or more, and the battery resistance can be reduced to a desired value, achieving both reduction of the battery resistance and ensuring the desired tensile strength.

Claims

1. A solid electrolyte layer for a solid-state battery, wherein the solid electrolyte layer includes a nonwoven fabric and a solid electrolyte, the solid electrolyte is disposed inside the nonwoven fabric, and a ratio of a volume of the nonwoven fabric to a volume of the solid electrolyte layer is 35% or more and 54% or less. The solid electrolyte layer.

2. The solid electrolyte layer according to claim 1, wherein a porosity of the nonwoven fabric is 73% or more and 83% or less.

3. The solid electrolyte layer according to claim 1, wherein the nonwoven fabric is made of polyethylene terephthalate.

4. The solid electrolyte layer according to claim 1, wherein the solid electrolyte includes a sulfide solid electrolyte.

5. A method for manufacturing a solid-state battery, comprising: disposing the solid electrolyte layer according to any one of claims 1 to 4 between a negative electrode layer and a positive electrode layer to obtain a laminate; and pressing the laminate. A method for manufacturing a solid-state battery.

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