Solid electrolyte layer, solid state battery and method for manufacturing solid state battery

Abstract

To provide a solid electrolyte layer that can suppress increase in resistance, a solid state battery and a method for manufacturing the 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, the solid electrolyte is solid electrolyte particles, and the ratio of the average fiber diameter of the non-woven fabric to the average particle diameter of the solid electrolyte particles is equal to or more than 25 and equal to or less than 100.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Various techniques have been proposed regarding solid electrolyte layers including nonwoven fabrics as disclosed in Patent Documents 1 and 2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

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, a solid battery, and a method for manufacturing the solid battery that can suppress 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, The solid electrolyte is solid electrolyte particles, A solid electrolyte layer in which the ratio of the average fiber diameter of the nonwoven fabric to the average particle diameter of the solid electrolyte particles is 25 or more and 100 or less.

[0007] <2> The solid electrolyte layer according to <1>, wherein the ratio of the average fiber diameter of the nonwoven fabric to the average particle diameter of the solid electrolyte particles is 25 or more and 50 or less.

[0008] <3> The solid electrolyte layer according to <1> or <2>, wherein the porosity of the nonwoven fabric is 73% or more and less than 91%.

[0009] <4> The solid electrolyte layer according to any one of <1> to <3>, wherein the average fiber diameter of the nonwoven fabric is 3 μm or more and 10 μm or less.

[0010] <5> The solid electrolyte layer according to any one of <1> to <4>, wherein the average particle diameter of the solid electrolyte particles is 0.1 μm or more and less than 0.5 μm.

[0011] <6> The solid electrolyte layer according to any one of <1> to <5>, wherein the nonwoven fabric is made of polyethylene terephthalate.

[0012] <7> The solid electrolyte layer according to any one of <1> to <6>, wherein the solid electrolyte contains a sulfide solid electrolyte.

[0013] <8> A solid battery having a negative electrode layer, a positive electrode layer, and the solid electrolyte layer according to any one of <1> to <7> disposed between the negative electrode layer and the positive electrode layer.

[0014] <9> The solid battery according to <8>, wherein the negative electrode layer contains an Si-based active material as a negative electrode active material.

[0015] <10> The positive electrode layer contains a positive electrode active material, The positive electrode active material contains Ni element and Co element, the solid battery according to <8> or <9>.

[0016] <11> A method for manufacturing a solid battery, A step of obtaining a laminate by disposing the solid electrolyte layer described in any one of <1> to <7> between the negative electrode layer and the positive electrode layer; A method for manufacturing a solid battery, comprising: a step of pressing the laminate.

Advantages of the Invention

[0017] According to the present disclosure, it is possible to provide a solid electrolyte layer, a solid battery, and a method for manufacturing the solid battery, which can suppress an increase in resistance.

Brief Description of the Drawings

[0018]

Figure 1

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments according to the present disclosure will be described. In addition, matters other than those specifically mentioned in this specification and matters 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 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 relevant field. In the present disclosure, unless otherwise specified, the average particle diameter of the particles is the value of the median diameter (D50), which is the particle diameter at 50% of the integrated value in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0020] 1. Solid Electrolyte Layer In the present disclosure, 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, The solid electrolyte is solid electrolyte particles, A solid electrolyte layer is provided in which the ratio of the average fiber diameter of the nonwoven fabric to the average particle diameter of the solid electrolyte particles is 25 or more and 100 or less.

[0021] In the present disclosure, in a solid electrolyte layer including a nonwoven fabric, by increasing the average fiber diameter of the nonwoven fabric while maintaining a high porosity of the nonwoven fabric, the number of fibers of the nonwoven fabric decreases and the pore diameter increases. The average particle diameter of the solid electrolyte particles is made sufficiently smaller than the average fiber diameter of the nonwoven fabric. 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 including the nonwoven fabric can be suppressed.

[0022] The solid electrolyte layer of the present disclosure includes a nonwoven 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 battery. A "nonwoven fabric" is a sheet-like material in which fibers are adhered or intertwined without being woven, and is a planar fiber aggregate having a predetermined level of structural strength obtained by physical and / or chemical methods excluding weaving, knitting, and papermaking (JIS L0222:2022). The fiber aggregate has a plurality of pores. The "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 viewpoint of reducing the resistance of the solid battery, the thickness of the solid electrolyte layer may be 50 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. The thickness of the solid electrolyte layer may be 1 μm or more or 10 μm or more.

[0023] [Nonwoven fabric] The type of non-woven fabric is not particularly limited. For example, it may include melt-blown non-woven fabric, spunbond non-woven fabric, carded non-woven fabric, parallel non-woven fabric, cross non-woven fabric, random non-woven fabric, spunlaced non-woven fabric, flash-spun non-woven fabric, chemically bonded non-woven fabric, hydroentangled non-woven fabric, needle-punched non-woven fabric, stitch-bonded non-woven fabric, thermal-bonded non-woven fabric, burst fiber non-woven fabric, degummed non-woven fabric, and film-split non-woven fabric, etc. Examples of the material of the non-woven fabric include resin and glass, etc. Examples of the resin include polyester-based resin, polyolefin-based resin, and polyamide-based resin, etc. Examples of the polyester-based resin include polyethylene terephthalate (PET), etc. Examples of the polyolefin-based resin include polyethylene (PE) and polypropylene (PP), etc. Examples of the polyamide-based resin include nylon and aramid, etc. From the viewpoint of high heat resistance and being less likely to deteriorate even at high temperatures, the non-woven fabric may be composed of polyethylene terephthalate. The porosity of the non-woven fabric is not particularly limited. From the viewpoint of further reducing the resistance of the solid-state battery, it may be 50% or more, 60% or more, 70% or more, or 73% or more. From the viewpoints such as being able to reduce the resistance while maintaining the tensile strength of the solid electrolyte layer, the porosity of the non-woven fabric may be less than 91%, less than 90%, or less than 77%. The porosity of the non-woven fabric may be 73% or more and less than 91%. The porosity indicates the volume of the voids inside the non-woven fabric with respect to the total volume of the non-woven fabric. The porosity of the non-woven fabric can be calculated by calculating the volume of the voids from the difference between the actual volume of the non-woven fabric and the volume calculated from the specific gravity of the material, and obtaining the ratio of the volume of the voids to the actual volume of the non-woven fabric. The average fiber diameter of the non-woven fabric is not particularly limited and may be 3 μm or more and 10 μm or less. If the average fiber diameter of the non-woven fabric is too large, the thickness of the solid electrolyte layer will become large. If the average fiber diameter of the non-woven fabric is too small, the support for the solid electrolyte will not be possible. Therefore, within the above range, it is possible to support the solid electrolyte while keeping the thickness of the solid electrolyte layer small. The average fiber diameter of the nonwoven fabric may be calculated by measuring the fiber diameters of 100 fibers at any location on the nonwoven fabric in an electron micrograph and taking their arithmetic mean value. 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.

[0024] [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 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 types of 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 proportion 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, may be 70% by volume or more, or may be 90% by volume or more.

[0025] Examples of the sulfide solid electrolyte include 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), may be glass ceramics, or may be 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. The description of "Li2S-P2S5" above means a material obtained 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.

[0026] Examples of the oxide solid electrolyte include 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, Li1.3 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 PO 4-x N x (1 ≦ x ≦ 3) etc. may also be acceptable. 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- etc. Examples of the halogenated solid electrolyte include LiF, LiCl, LiBr, LiI, and LiI - Al2O3 etc. Examples of the nitrided solid electrolyte include Li3N etc.

[0027] Examples of the binder include rubber - based binders, fluoride - based binders, etc. 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, etc. Examples of the fluoride - based binder include polyvinylidene fluoride (PVDF), polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - HFP), polytetrafluoroethylene, and fluororubber, etc. When the solid electrolyte layer contains a binder, the content of the binder may be 0 to 3 parts by mass based on the total amount of the solid electrolyte layer.

[0028] The solid electrolyte is solid electrolyte particles. The average particle size (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, may be less than 0.5 μm, or may be 0.2 μm or less.

[0029] [Average fiber diameter of nonwoven fabric / Average particle size of solid electrolyte particles] In the present disclosure, the ratio of the average fiber diameter of the nonwoven fabric to the average particle size of the solid electrolyte particles (average fiber diameter of nonwoven fabric / average particle size of solid electrolyte particles) may be 25 or more and 100 or less, or may be 25 or more and 50 or less. If it is within this range, the resistance can be reduced while suppressing an increase in the thickness of the solid electrolyte layer due to an increase in the average fiber diameter of the nonwoven fabric.

[0030] 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.

[0031] 2. Solid battery The solid battery of the present disclosure has 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 which is a solid battery including a solid electrolyte and a liquid-based material, or may be an all-solid battery which 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 in parallel.

[0032] [Positive electrode] The positive electrode includes a positive electrode layer. The positive electrode may include a positive electrode current collector as required.

[0033] [Positive electrode layer] The positive electrode layer contains a positive electrode active material, and may contain a solid electrolyte, a conductive material, a binder, etc. as required.

[0034] Examples of the positive electrode active material include lithium nickel cobalt aluminum oxide (NCA), LiCoO2, LiNi x Co 1-x O2 (0 < x < 1), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, LiMn2O4, LiNiO2, LiVO2, hetero-element substituted Li-Mn spinel, lithium titanate, lithium metal phosphate, LiCoN, Li2SiO3, and Li4SiO4, etc. can be mentioned. Examples of the hetero-element substituted Li-Mn spinel include 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, for example, LiNbO3, Li4Ti5O12 、and examples thereof include Li3PO4 and the like. 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.

[0035] As the conductive material, known materials can be used, and examples thereof include carbon materials and metal particles. 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.

[0036] As the solid electrolyte, 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.

[0037] As the binder, 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.

[0038] The thickness of the positive electrode layer is not particularly limited.

[0039] 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, and the positive electrode paste is applied onto one surface of a support such as a positive electrode current collector and dried to obtain the positive electrode layer. Examples of the solvent include solvents that can be used for preparing the above-described solid electrolyte paste. 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-supportability can be appropriately selected and used, and there is no particular limitation. For example, metal foils such as Cu and Al can be used.

[0040] [Positive Electrode Current Collector] As the positive electrode current collector, known metals that can be used as the current collector of a 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 electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. The form of the positive electrode current collector is not particularly limited, and it can be in various forms such as a foil shape and a mesh shape.

[0041] [Negative Electrode] The negative electrode includes a negative electrode layer. The negative electrode may include a negative electrode current collector as required.

[0042] [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 required. 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 an Si-based active material may be used. The Si-based active material has a high discharge capacity, but has a large expansion rate. When the Si-based active material is used, stress is applied to the solid electrolyte layer, and the solid electrolyte layer may be damaged. In the present disclosure, since the solid electrolyte layer has a high tensile strength, even when an Si-based active material is used, the occurrence of damage to the solid electrolyte layer can be suppressed, and a solid battery having a high discharge capacity can be obtained. 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 elemental Si, Si alloys, and silicon oxide. Examples of the shape of the negative electrode active material include particulate shape. 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 in 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 0.1 μm to 1000 μm.

[0043] [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, and nickel. 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.

[0044] [Solid electrolyte layer] The solid battery includes the solid electrolyte layer of the present disclosure. The nonwoven fabric contained 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 contained in 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 battery is reduced. Another solid electrolyte layer contains a solid electrolyte and may contain a binder as required. Examples of the solid electrolyte and the binder are the same as those exemplified as the solid electrolyte and the binder that can be contained 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.

[0045] The solid battery may include an exterior body that houses a positive electrode layer, a negative electrode layer, a solid electrolyte layer, etc. as required. 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.

[0046] Examples of the shape of the solid battery include coin type, laminate type, cylindrical type, and square type.

[0047] 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), 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 an electric vehicle (BEV). In addition, the solid battery may be used as a power source for moving bodies other than vehicles (for example, railways, ships, and aircraft), and may be used as a power source for electrical products such as information processing devices.

[0048] 3. Manufacturing method of solid battery The method for manufacturing a solid-state battery of the present disclosure includes a step of obtaining a laminate by disposing the solid electrolyte layer of 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 of 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 thereof 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.

Examples

[0049] (Example 1) [Preparation of non-woven fabric] A non-woven fabric made of PET having an average fiber diameter of 5 μm and a porosity of 73% shown in Table 1 was prepared. The basis weight of the non-woven fabric was 1 g / cm 2 and the thickness of the non-woven fabric was 30 μm. [Fabrication of solid electrolyte layer] Particles of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) glass ceramics having an average particle diameter (D50) of 0.2 μm shown in Table 1 were used as the sulfide solid electrolyte. 3% by mass of an SBR (styrene-butadiene rubber) binder was weighed with respect to 100% by mass of the sulfide solid electrolyte, and these were formulated in butyl butyrate so that the solid content was 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 applied by blade coating using a commercially available applicator to a basis weight of 3.0 mg / cm 2 such that it became. Thereafter, the obtained coating film was dried at 100 °C for 60 minutes to obtain a solid electrolyte layer containing the nonwoven fabric on the release film. [Fabrication of positive electrode] As the positive electrode active material, particles of LiNi 2 with an average particle diameter (D50) of 10 μm and a specific surface area of 1 m 1 / 3 Mn 1 / 3 Co 1 / 3 O2 were used. And 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 the solid electrolyte layer was used. The positive electrode active material, 50% by mass of the sulfide solid electrolyte, 10% by mass of a conductive material (CNF, specific surface area 14 m 2 / g), and 1% by mass of an SBR (styrene-butadiene rubber) - based binder were weighed based on 100% by mass of the positive electrode active material, and these were formulated in butyl butyrate to a solid content of 60% by mass and subjected to ultrasonic dispersion treatment for 1 minute using an ultrasonic disperser to obtain a positive electrode paste. Next, the obtained positive electrode paste was uniformly applied by blade coating using a commercially available applicator to a positive electrode current collector made of aluminum foil with a thickness of 15 μm to a basis weight of 25 mg / cm 2 such that it became. 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 the aluminum foil - made positive electrode current collector. [Fabrication of negative electrode] As the negative electrode active material, particles of Si with an average particle diameter (D50) of 3 μm and a specific surface area of 4 m 2 / g were used, and as the sulfide solid electrolyte, the same sulfide solid electrolyte as the solid electrolyte layer was used. The above - mentioned negative electrode active material and, based on 100% by mass of the negative electrode active material, 100% by mass of the sulfide solid electrolyte, a conductive material (CNF, specific surface area 14 m2 10% by mass of (g) and 2% by mass of an SBR (styrene-butadiene rubber) - based binder were weighed, and these were formulated in butyl butyrate so that the solid content became 40% by mass, and ultrasonic dispersion treatment was performed for 1 minute using an ultrasonic disperser to obtain a negative electrode paste. Next, the obtained negative electrode paste was uniformly applied onto a negative electrode current collector made of a surface - roughened copper foil with a thickness of 20 μm by blade coating using a commercially available applicator so that the basis weight was 5 mg / cm 2 was achieved. 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 a 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, and roll - pressed at a pressing pressure of 1 ton / cm². 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 was superposed on the solid electrolyte layer laminated on the negative electrode so that the positive electrode layer and the solid electrolyte layer were in contact, and roll - pressed at a pressing pressure of 4 ton / cm². The laminate thus obtained was sealed with an exterior body made of an aluminum - made laminate film to which a positive electrode terminal and a negative electrode terminal were previously attached, and a solid - state battery (all - solid - state lithium - ion secondary battery) for testing in Example 1 was fabricated.

[0050] (Example 2) A solid - state battery was fabricated in the same manner as in Example 1, except that a non - woven fabric made of PET with an average fiber diameter of 3 μm and a porosity of 77% was used, and particles of glass ceramics of 15LiBr·10LiI·75(0.75Li₂S·0.25P₂S₅) with an average particle diameter (D50) of 0.1 μm were used as the sulfide solid electrolyte.

[0051] (Example 3) A solid battery was fabricated in the same manner as in Example 1, except that glass ceramic particles of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle size (D50) of 0.1 μm were used as the sulfide solid electrolyte.

[0052] (Example 4) A solid battery was fabricated in the same manner as in Example 1, except that a nonwoven fabric made of PET with an average fiber diameter of 10 μm and a porosity of 75% was used.

[0053] (Example 5) A solid battery was fabricated in the same manner as in Example 1, except that a nonwoven fabric made of PET with an average fiber diameter of 10 μm and a porosity of 75% was used, and glass ceramic particles of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle size (D50) of 0.1 μm were used as the sulfide solid electrolyte.

[0054] (Comparative Example 1) A solid battery was fabricated in the same manner as in Example 1, except that no nonwoven fabric was used, and glass ceramic particles of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle size (D50) of 0.5 μm were used as the sulfide solid electrolyte.

[0055] (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 an average fiber diameter of 3 μm and a porosity of 77% was used, and glass ceramic particles of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle size (D50) of 0.5 μm were used as the sulfide solid electrolyte.

[0056] (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 an average fiber diameter of 5 μm and a porosity of 21% was used, and glass ceramic particles of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle size (D50) of 0.5 μm were used as the sulfide solid electrolyte.

[0057] (Comparative Example 4) A solid-state battery was fabricated in the same manner as in Example 1, except that a nonwoven fabric made of PET with an average fiber diameter of 5 μm and a porosity of 48% was used, and particles of glass ceramics of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle diameter (D50) of 0.5 μm were used as the sulfide solid electrolyte.

[0058] (Comparative Example 5) A solid-state battery was fabricated in the same manner as in Example 1, except that a nonwoven fabric made of PET with an average fiber diameter of 5 μm and a porosity of 75% was used, and particles of glass ceramics of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle diameter (D50) of 0.5 μm were used as the sulfide solid electrolyte.

[0059] (Comparative Example 6) A solid-state battery was fabricated in the same manner as in Example 1, except that a nonwoven fabric made of PET with an average fiber diameter of 5 μm and a porosity of 91% was used, and particles of glass ceramics of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle diameter (D50) of 0.5 μm were used as the sulfide solid electrolyte.

[0060] (Comparative Example 7) A solid-state battery was fabricated in the same manner as in Example 1, except that a nonwoven fabric made of PET with an average fiber diameter of 3 μm and a porosity of 77% was used.

[0061] (Comparative Example 8) A solid-state battery was fabricated in the same manner as in Example 1, except that a nonwoven fabric made of PET with an average fiber diameter of 10 μm and a porosity of 77% was used, and particles of glass ceramics of 15LiBr·10LiI·75(0.75Li2S·0.25P2S5) with an average particle diameter (D50) of 0.5 μm were used as the sulfide solid electrolyte.

[0062] [Battery Resistance Measurement] Each of the solid-state batteries fabricated in Examples 1 to 5 and Comparative Examples 1 to 8 was charged by CCCV 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 carried out at a current value of 2 mA and an upper limit voltage of 3.6 V. After a 10-minute rest, CC discharge was carried out at a current value of 10 mA and a lower limit voltage of 0.0 V for 10 seconds, and the battery resistance R (=ΔV / I) was calculated according to Ohm's law. The results are shown in Table 1.

[0063] <Tensile Strength Measurement> For each solid electrolyte layer prepared in Examples 1 to 5 and Comparative Examples 2 to 8, the tensile strength was measured by the following method with reference to JIS L 1096. The laminate obtained by further laminating a release film on the solid electrolyte paste coating surface of the solid electrolyte layer on the release film prepared in the above [Preparation of Solid Electrolyte Layer] was roll-pressed at a press pressure of 1 ton / cm², and the release films on both sides of the solid electrolyte layer were peeled off to create a self-standing solid electrolyte layer. The self-standing solid electrolyte layer was cut into strips with a width of 1 cm and a length of 5 cm, and the tensile strength was measured by a predetermined tensile test. The results are shown in Table 1.

[0064]

Table 1

[0065] Figure 1 is a graph showing the relationship between the average fiber diameter of the non-woven fabric / solid electrolyte particle average particle diameter and the resistance of each solid battery prepared in Examples 1 to 5 and Comparative Examples 2, 5, 7, and 8. As shown in Comparative Examples 3 to 6 of Table 1, when the average particle diameter of the solid electrolyte particles and the average fiber diameter of the non-woven fabric are constant, it can be seen that as the porosity of the non-woven fabric increases, the battery resistance decreases, but the tensile strength of the solid electrolyte layer decreases. As shown in Fig. 1 and Table 1, it can be seen that when the nonwoven fabric average fiber diameter / average particle diameter of the solid electrolyte particles is less than 25, the battery resistance increases rapidly. On the other hand, if the nonwoven fabric average fiber diameter / average particle diameter of the solid electrolyte particles is 25 or more, it can be seen that the battery resistance decreases rapidly. In Examples 1 to 5, adjustments were made to maintain a high porosity, and the nonwoven fabric average fiber diameter / average particle diameter of the solid electrolyte particles was adjusted to be 25 or less. As a result, while ensuring the desired tensile strength, the battery resistance can be lowered to a desired value. This is considered to be because the average particle diameter of the solid electrolyte particles is sufficiently smaller than the nonwoven fabric average fiber diameter, making it easier for the solid electrolyte particles to connect with each other within the solid electrolyte layer.

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, the solid electrolyte is solid electrolyte particles, and a ratio of an average fiber diameter of the nonwoven fabric to an average particle diameter of the solid electrolyte particles is 25 or more and 100 or less. A solid electrolyte layer.

2. The solid electrolyte layer according to claim 1, wherein a ratio of an average fiber diameter of the nonwoven fabric to an average particle diameter of the solid electrolyte particles is 25 or more and 50 or less.

3. The solid electrolyte layer according to claim 1, wherein a porosity of the nonwoven fabric is 73% or more and less than 91%.

4. The solid electrolyte layer according to claim 1, wherein an average fiber diameter of the nonwoven fabric is 3 μm or more and 10 μm or less.

5. The solid electrolyte layer according to claim 1, wherein an average particle diameter of the solid electrolyte particles is 0.1 μm or more and less than 0.5 μm.

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

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

8. A solid-state battery having a negative electrode layer, a positive electrode layer, and the solid electrolyte layer according to any one of claims 1 to 7 disposed between the negative electrode layer and the positive electrode layer.

9. The solid-state battery according to claim 8, wherein the negative electrode layer includes an Si-based active material as a negative electrode active material.

10. The positive electrode layer includes a positive electrode active material, and the positive electrode active material includes Ni element and Co element. The solid-state battery according to claim 8.

11. A method for manufacturing a solid-state battery, including a step of disposing the solid electrolyte layer according to any one of claims 1 to 7 between a negative electrode layer and a positive electrode layer to obtain a laminate, and a step of pressing the laminate. A method for manufacturing a solid-state battery.

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