Electrolyte sheet, solid electrolyte coated fiber, and lithium ion battery

Abstract

To provide an electrolyte sheet that is easy to handle because detachment (powdering) of a solid electrolyte is suppressed, and that can be used to efficiently manufacture lithium ion batteries because cracks and powdering are suppressed during folding processing.SOLUTION: An electrolyte sheet according to the present invention includes a plurality of inorganic fibers and a solid electrolyte, and in a thickness direction cross section cut perpendicular to the surface stretching direction of the electrolyte sheet, the proportion of inorganic fibers present is 60% or more. The content of the solid electrolyte is preferably 60 to 95 mass%, and the total amount of the inorganic fibers and the solid electrolyte is 100 mass%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrolyte sheet containing a solid electrolyte and suitable for forming an electrolyte layer or the like that constitutes a lithium ion battery, a solid electrolyte-coated fiber, and a lithium ion battery. [Background technology]

[0002] Lithium-ion batteries are secondary batteries in which lithium ions are released from the positive electrode and transferred to the negative electrode for storage during charging, and then re-inserted from the negative electrode and re-inserted back into the positive electrode during discharging. Because of their high energy density and long life, lithium-ion batteries have been widely used as power sources for various electronic devices, including personal computers and cameras, portable electronic devices and communication devices, and power tools. Recently, they have also been applied to large-scale batteries installed in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Using solid electrolytes instead of flammable organic solvents in lithium-ion batteries not only simplifies safety devices but also improves manufacturing costs and productivity. Therefore, research into various materials, particularly sulfide solid electrolytes with high electrical conductivity (lithium ion conductivity), has been actively conducted.

[0003] Sulfide solid electrolytes are usually in powder form, but in the production of lithium ion batteries, they are required to be in sheet form for ease of handling. However, since it is often difficult to form a single-layer thin film sheet made of powdered solid electrolyte, a solid electrolyte sheet in which the solid electrolyte is attached to fibers such as electronically insulating inorganic fibers has been proposed as an alternative (see Patent Document 1).

[0004] Patent Document 1 discloses a solid electrolyte sheet for lithium batteries, which includes a solid electrolyte and a support having a plurality of openings, the openings of the support being filled with the solid electrolyte, the support being made of glass (glass fiber fabric), the opening ratio of the support being 40 to 90%, the solid electrolyte being made from lithium sulfide and diphosphorus pentasulfide as raw materials, the molar ratio of lithium sulfide to diphosphorus pentasulfide being 68:32 to 80:20, and which is obtained by applying a slurry of the solid electrolyte dissolved in a solvent to the support and drying it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-127982 Summary of the Invention [Problem to be solved by the invention]

[0006] Lithium-ion batteries have diverse internal structures, with electrolyte layers that are either flat or curved. In the latter case, the solid electrolyte sheet must be folded, which requires a structure that prevents cracks or fissures from occurring on the surface. Furthermore, the solid electrolyte sheet for lithium batteries disclosed in Patent Document 1 sometimes suffers from detachment of solid electrolyte particles during transportation, resulting in inconsistent performance when mass-produced lithium-ion batteries are produced. The present invention aims to provide an electrolyte sheet that is easy to handle because detachment (powder shedding) of the solid electrolyte is suppressed, and that suppresses cracks and powder shedding during folding, allowing for efficient production of lithium-ion batteries. Another objective of the present invention is to provide an electrolyte sheet-containing product that includes this electrolyte sheet and has excellent transportability. [Means for solving the problem]

[0007] The present invention is illustrated below. 1. An electrolyte sheet comprising a plurality of inorganic fibers and a solid electrolyte, An electrolyte sheet, wherein the inorganic fibers account for 60% or more of the thickness direction cross section of the electrolyte sheet cut perpendicular to the surface stretching direction. 2. The electrolyte sheet according to item 1, wherein the content of the solid electrolyte is 60 to 95% by mass, where the total amount of the inorganic fibers and the solid electrolyte is 100% by mass. 3. The electrolyte sheet according to item 1 or 2, wherein the inorganic fibers include glass fibers. 4. The electrolyte sheet according to any one of items 1 to 3, wherein the solid electrolyte contains a compound containing lithium, phosphorus, and sulfur elements. 5. The electrolyte sheet according to any one of items 1 to 3, wherein the solid electrolyte contains a compound containing lithium, phosphorus, sulfur, and a halogen element. 6. The electrolyte sheet according to any one of items 1 to 5, wherein the solid electrolyte is amorphous. 7. The electrolyte sheet according to any one of items 1 to 5, wherein the solid electrolyte has crystallinity. 8. The electrolyte sheet according to any one of items 1 to 7, wherein the inorganic fibers include fibers having a fiber diameter of 50 μm or less. 9. An electrolyte sheet according to any one of items 1 to 8, wherein the proportion of voids in a cross section of the electrolyte sheet is 20% or less. 10. An electrolyte sheet-containing product, characterized in that the electrolyte sheet according to any one of items 1 to 9 above is contained in a package. 11. A lithium ion battery comprising the electrolyte sheet according to any one of items 1 to 9 above. 12. A solid electrolyte-coated fiber comprising a fiber portion made of fiber and a solid electrolyte coating layer containing a solid electrolyte and coating at least a portion of the surface of the fiber portion. [Effects of the Invention]

[0008] The electrolyte sheet of the present invention is easy to handle because it is resistant to detachment (powdering) of the solid electrolyte and has excellent shape stability. Furthermore, when bending or other processes are performed during the production of lithium ion batteries, cracks and powdering are unlikely to occur, making it possible to efficiently produce lithium ion batteries with the desired performance. The electrolyte sheet-containing product of the present invention can be opened at the lithium ion battery manufacturing site to remove the electrolyte sheet, and can be used to manufacture lithium ion batteries while maintaining the excellent effects of the electrolyte sheet. The lithium ion battery of the present invention exhibits excellent battery performance because it includes an electrolyte sheet with high lithium ion conductivity. The solid electrolyte-coated fiber of the present invention is suitable for forming an electrolyte sheet with high lithium ion conductivity because the fiber and the solid electrolyte are not bonded together via an adhesive. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing an example of an electrolyte sheet of the present invention. [Figure 2] 1 is a cross-sectional image of the electrolyte sheet obtained in Example 1. [Figure 3] This is a Si element map of the area surrounded by the dotted line in FIG. [Figure 4] 4 is a graph showing a profile of Si in the thickness direction of an electrolyte sheet based on the Si element map of FIG. 3. [Figure 5] 1 is a cross-sectional image of the electrolyte sheet obtained in Comparative Example 1. [Figure 6] This is a Si element map of the area surrounded by the dotted line in FIG. 5. [Figure 7] 7 is a graph showing a profile of Si in the thickness direction of an electrolyte sheet based on the Si element map of FIG. 6. [Figure 8] FIG. 1 is a schematic cross-sectional view showing an example of a lithium ion battery. [Figure 9] 1 is a schematic perspective view showing an example of a solid electrolyte-coated fiber of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The electrolyte sheet of the present invention is a sheet containing a plurality of inorganic fibers and a solid electrolyte, and may contain other fibers as necessary. The electrolyte sheet of the present invention has a structure in which the proportion of the inorganic fibers present is 60% or more in a thickness direction cross section cut perpendicular to the surface stretching direction. In this specification, the term "sheet" includes not only single sheets but also long ones.

[0011] The inorganic fibers are not particularly limited as long as they contain a portion made of an inorganic compound. Examples include fibers made solely of inorganic compounds and fibers having a film or granular portion containing an inorganic material on at least a portion of the surface of resin fibers. The inorganic fibers of the present invention are preferably fibers made solely of inorganic compounds. The inorganic compounds are not particularly limited, but are preferably oxides, nitrides, carbonates, titanates, etc. Specific inorganic fibers include glass fibers, silica fibers, alumina fibers, silica-alumina fibers, silica-alumina-magnesia fibers, silica-alumina-zirconia fibers, silica-magnesia-calcia fibers, rock wool, slag wool, potassium titanate whiskers, calcium carbonate whiskers, basalt fibers, sepilite, apalargite, and other mineral fibers. Among these, glass fibers are preferred. The glass constituting the glass fiber is not particularly limited, but C glass, B glass, E glass, etc. are preferred because they have excellent chemical resistance when the electrolyte sheet of the present invention is used to form the electrolyte layer of a lithium ion battery.

[0012] The fiber diameter of the inorganic fibers is not particularly limited, but from the viewpoints of the mechanical strength and flexibility to bending of the electrolyte sheet of the present invention, the upper limit is preferably 50 μm, more preferably 10 μm, and the lower limit is preferably 0.01 μm, more preferably 0.1 μm. Furthermore, the fiber length is not particularly limited, but from the viewpoints of the productivity of the nonwoven fabric of the electrolyte sheet of the present invention and the uniformity of the mesh size, it is preferably in the range of 0.1 to 10 mm, more preferably 0.5 to 6 mm. The electrolyte sheet of the present invention contains multiple inorganic fibers, and in the present invention, the size (diameter or length) of each fiber may be either uniform or nonuniform among inorganic fibers containing the same material. Furthermore, when the electrolyte sheet contains multiple types of inorganic fibers made of different materials, the diameter or length between fibers made of one material and fibers made of another material may be either uniform or nonuniform.

[0013] As described above, the electrolyte sheet of the present invention may contain other fibers. When the electrolyte sheet of the present invention contains other fibers, the upper limit of the content of such fibers relative to the total fiber content is preferably 65% ​​by mass, more preferably 55% by mass. Examples of other fibers include organic fibers and natural fibers, with organic fibers being preferred.

[0014] Resin fibers are preferred as organic fibers. Examples of materials constituting resin fibers include polyester resins (such as polyethylene terephthalate), aliphatic polyamide resins, aramid resins, polyolefin resins, cyclic olefin resins, acrylic resins, polyacrylonitrile resins, polyvinyl alcohol resins, polyacetal resins, polyvinyl chloride resins, polyvinylidene chloride resins, ethylene-vinyl acetate copolymers, fluororesins, polyethersulfone resins, polyphenylene sulfide resins, and cellulose. Resin fibers can be single-phase fibers containing one or more types of resin, or multi-phase fibers having a low-melting-point resin portion and a high-melting-point resin portion (hereinafter referred to as "composite resin fibers"). Composite resin fibers can be, for example, sheath-core fibers or side-by-side fibers. Examples of resin combinations for composite resin fibers include PET / low-melting-point copolymer polyester, PET / PE, PP (polypropylene) / PE (polyethylene), and PP / low-melting-point copolymer PP. Here, examples of low-melting point copolyesters include modified resins having a basic skeleton such as PET, PPT (polypropylene terephthalate), or PBT (polybutylene terephthalate), i.e., modified copolymers of these polyesters with aromatic dicarboxylic acids such as isophthalic acid, 5-sodium sulfoisophthalic acid, and naphthalenedicarboxylic acid, and / or aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aliphatic polyhydric alcohols such as diethylene glycol, propylene glycol, and 1,4-butanediol. As the organic fiber (resin fiber), polyester fiber is particularly preferable.

[0015] The fiber diameter and fiber length of the organic fibers are not particularly limited, but may be the same as the fiber diameter and fiber length of the inorganic fibers.

[0016] The fibers in the electrolyte sheet of the present invention may be either simply entangled or entangled and bonded together, preferably with an adhesive at their contact points.

[0017] Next, the solid electrolyte is not particularly limited as long as it is a conventionally known material for lithium ion batteries, and examples thereof include sulfide-based solid electrolytes, garnet-based solid electrolytes, nitride-based solid electrolytes, perovskite-based solid electrolytes, zeolite-based solid electrolytes, phosphoric acid-based solid electrolytes, and NASICON-type solid electrolytes. In the present invention, Li3PS4, Li7P2S8X, and Li7P3S are used because of their excellent lithium ion conductivity. 11 , Li2P2S5, Li6PS5X, Li 9.6 P3S 12 Preferred are sulfide-based solid electrolytes such as those listed above. X is Cl, Br, or I. The electrolyte sheet of the present invention may contain one or more solid electrolytes. The crystallinity of the solid electrolyte is not particularly limited, and the solid electrolyte contained in the electrolyte sheet may be either crystalline or amorphous, or may be both.

[0018] The volume ratios of all the fibers and the solid electrolyte contained in the electrolyte sheet of the present invention are not particularly limited. From the viewpoints of lithium ion conductivity, mechanical strength, and flexibility, the volume ratios of the fibers and the solid electrolyte, when the total of the two is taken as 100 volume%, are preferably 5 to 60 volume% and 40 to 95 volume%, more preferably 5 to 50 volume% and 50 to 95 volume%, respectively.

[0019] The mass ratio of the inorganic fibers and the solid electrolyte contained in the electrolyte sheet of the present invention is not particularly limited. From the viewpoint of mechanical strength and flexibility, the contents of the inorganic fibers and the solid electrolyte are preferably 5 to 50 mass% and 50 to 95 mass%, more preferably 5 to 40 mass% and 60 to 95 mass%, respectively, when the total of the inorganic fibers and the solid electrolyte is 100 mass%.

[0020] The electrolyte sheet of the present invention is essentially a solid sheet mainly composed of fibers including inorganic fibers and a solid electrolyte. As shown in FIG. 1 , the electrolyte sheet may be a sheet 1 having a structure in which fibers 3 and a solid electrolyte (not shown) are uniformly contained from one side to the other side, or a sheet (not shown) having a structure in which fibers and a solid electrolyte are uniformly contained inside, while the surface layer on one side and the surface layer on the other side are coating layers made of a solid electrolyte.

[0021] The thickness of the electrolyte sheet of the present invention is preferably 5 to 100 μm, more preferably 10 to 75 μm. As described above, the electrolyte sheet of the present invention has a structure in which the proportion of the inorganic fibers present is 60% or more in a thickness direction cross section cut perpendicular to the surface stretching direction. This proportion is preferably 70% or more. The method for measuring this proportion is shown in [Examples], but is performed by the following procedure. (1) An electron microscope is used to photograph the electrolyte sheet so that the entire cross section in the thickness direction is included in the image (see Figures 2 and 5). (2) In a region (hereinafter referred to as the "measurement region") set to include the entire cross section in the thickness direction, a mapping analysis is performed by energy dispersive X-ray analysis on elements constituting the inorganic fibers contained in the electrolyte sheet but not contained in the solid electrolyte. The measurement element is preferably Si element when the inorganic fibers are glass fibers containing Si element and Si element is not contained in the solid electrolyte. The measurement region preferably has a horizontal length of at least 40 μm. (3) Based on the Si element maps obtained by mapping analysis, such as those shown in Figures 3 and 6, software is used to determine the range of Si element presence using the following method. Specifically, the Si element map is converted into an 8-bit grayscale image, which is then binarized with a lower threshold of 0 and an upper threshold of 10. The gray values ​​of each pixel are converted to 255 for locations where Si element is present and 0 for locations where Si element is not present. Next, the software is used to set a range that fits exactly from the top to the bottom of the Si element map, and a profile of the range from the top to the bottom is created and graphed (see Figures 4 and 7). The horizontal axis represents the vertical distance in the Si element map, and the vertical axis represents the average horizontal gray value of the Si element map. The percentage (area percentage) of the measured area where 20% or more of the pixels are determined to be Si element presence areas, i.e., the area where the average horizontal gray value is 51 or more, is then calculated.

[0022] As described above, the electrolyte sheet of the present invention is essentially a solid sheet mainly composed of fibers including inorganic fibers and a solid electrolyte, and since the solid electrolyte is less likely to fall off (powder off) and has excellent shape stability, the proportion (abundance) of voids is low. The proportion of voids is preferably 20% or less, more preferably 10% or less. The proportion of voids can be calculated within any range based on an image of the cross section obtained by cutting the electrolyte sheet in the thickness direction and using, for example, an optical microscope, a laser microscope, or an electron microscope.

[0023] The electrolyte sheet of the present invention has excellent lithium ion conductivity, and the conductivity measured at 25°C by an AC impedance method is preferably 10 -4 S / cm or more.

[0024] The method for producing the electrolyte sheet of the present invention is not particularly limited, but a preferred production method is shown below. Method (1): A method in which a sheet-shaped aggregate of fibers including inorganic fibers (hereinafter referred to as a "fiber sheet"), a solid electrolyte-forming raw material, and an organic solvent are placed in a container, the solid electrolyte-forming raw material is reacted to form a solid electrolyte, the fiber surface is coated with the solid electrolyte, and the gaps between the fibers are filled with the solid electrolyte, thereby producing a solid sheet. Method (2): A method in which a container is filled with a plurality of fibers containing a plurality of inorganic fibers that are not fixed to each other, a solid electrolyte-forming raw material, and an organic solvent, and then the solid electrolyte-forming raw material is reacted to form a solid electrolyte, and the fiber surfaces are coated with the solid electrolyte, filling all of the voids between the fibers with the solid electrolyte, thereby producing a solid sheet. Method (3): A method in which the above-mentioned fiber sheet and a solid electrolyte solution obtained by dissolving a solid electrolyte in an organic solvent, or a solid electrolyte dispersion obtained by dispersing a solid electrolyte in a dispersion medium consisting of an organic solvent, are placed in a container, the organic solvent is then volatilized off, and the surfaces of the fibers constituting the fiber sheet are coated with the solid electrolyte, filling the gaps between the fibers with the solid electrolyte, thereby producing a solid sheet. Method (4): A method in which a container is charged with a plurality of fibers containing a plurality of inorganic fibers that are not fixed to one another, and a solid electrolyte solution in which a solid electrolyte is dissolved in an organic solvent, or a solid electrolyte dispersion in which a solid electrolyte is dispersed in a dispersion medium made of an organic solvent, and then the organic solvent is volatilized off to coat the fiber surfaces with the solid electrolyte, filling all of the gaps between the fibers with the solid electrolyte, thereby producing a solid sheet. In all of the above methods, after forming the sheet, heat treatment, pressing treatment, etc. may be carried out as necessary.

[0025] The fiber sheet used in the above methods (1) and (3) is not particularly limited and may be a fiber deposit, a nonwoven fabric, a woven fabric, a textile, etc. The fiber sheet may consist of only fibers, or may be a plurality of fibers bound together with an adhesive.

[0026] The fiber sheet preferably contains 35% by mass or more of inorganic fibers, and the inorganic fibers preferably contain glass fibers, thereby obtaining an electrolyte sheet suitable as a material for forming the electrolyte layer of a lithium ion battery.

[0027] The porosity and basis weight of the fiber sheet are not particularly limited. The porosity is preferably 50 to 95%, more preferably 60 to 90%. The basis weight is preferably 1 to 100 g / m 2 , more preferably 1 to 20 g / m 2 is.

[0028] In the above methods (1) and (3), the fiber sheet is preferably a nonwoven fabric. The nonwoven fabric may be one in which the fibers are simply entangled with each other, or one in which the fibers are entangled and bonded with each other. In the latter case, it is preferable that the fibers are bonded with an adhesive at their contact points.

[0029] When the nonwoven fabric contains fibers bonded with an adhesive, the content of the adhesive relative to the entire nonwoven fabric is preferably 15% by mass or less, and more preferably 12% by mass or less, in order to provide an electrolyte sheet with excellent conductivity.

[0030] The thickness of the nonwoven fabric is usually 20 μm or more, but is preferably 5 to 100 μm, more preferably 10 to 75 μm, because the resulting electrolyte sheet is suitable as an electrolyte layer forming material that provides a lithium ion battery with excellent performance.

[0031] The term "plurality of fibers not fixed to each other" used in the above methods (2) and (4) means that most of the fibers are in a dispersed state before a solid electrolyte is formed on the surface of the fibers by placing the plurality of fibers in a container together with a raw material for forming a solid electrolyte and an organic solvent, an organic solution of a solid electrolyte, or a solid electrolyte dispersion obtained by dispersing a solid electrolyte in a dispersion medium comprising an organic solvent. The inorganic fibers used in the above methods (2) and (4) are preferably glass fibers including C-glass, B-glass, E-glass, etc. The preferred size of the inorganic fibers is as described above. In addition, in methods (2) and (4), inorganic fibers can be used in combination with organic fibers or natural fibers. In this case, the proportion of inorganic fibers to the total fibers is preferably 35 mass% or more.

[0032] In the above methods (1) and (2), the solid electrolyte-forming raw materials used to form the solid electrolyte in the presence of an organic solvent usually consist of a plurality of compounds. The solid electrolyte is formed by catalytically reacting the plurality of compounds in the organic solvent. As described above, the preferred solid electrolyte is a sulfide-based solid electrolyte, and the solid electrolyte-forming raw materials are Li3PS4, Li7P2S8X, Li7P3S 11 , Li2P2S5, Li6PS5X, Li 9.6 P3S 12 It is preferable that the compound contains a compound that forms the following: wherein X is Cl, Br or I.

[0033] Examples of raw materials for forming a sulfide-based solid electrolyte include lithium sulfide, phosphorus sulfide, and lithium halides. Examples of phosphorus sulfide include diphosphorus pentasulfide (P2S5), tetraphosphorus trisulfide (P4S3), tetraphosphorus heptasulfide (P4S7), and tetraphosphorus pentasulfide (P4S5). Of these, diphosphorus pentasulfide is preferred. Examples of lithium halides include lithium fluoride, lithium chloride, lithium bromide, and lithium iodide. Of these, lithium iodide is preferred. The solid electrolyte-forming raw material preferably contains lithium sulfide and diphosphorus pentasulfide, and in another preferred embodiment, it contains lithium sulfide, diphosphorus pentasulfide, and a lithium halide.

[0034] The solid electrolyte used in the above methods (3) and (4) is preferably the sulfide-based solid electrolyte, such as Li3PS4, Li7P2S8X, Li7P3S 11 , Li2P2S5, Li6PS5X, Li 9.6 P3S 12 etc.

[0035] Examples of organic solvents that can be used in the above methods (1), (2), (3), and (4) include alcohols (aliphatic alcohols, alicyclic alcohols, aromatic alcohols, etc.), carboxylic acids, carboxylic acid esters (saturated fatty acid esters, etc.), ethers (including cyclic ethers), aldehydes, ketones, carbonates (dialkyl carbonates, etc.), nitriles, amides, nitros, phosphate esters, and halogenated hydrocarbons. Among these, alcohols, carboxylic acid esters, and carbonate esters are preferred, and carboxylic acid esters and carbonate esters are particularly preferred. The above organic solvents may be used alone or in combination of two or more.

[0036] The containers used in the above methods (1), (2), (3), and (4) are not particularly limited, and for example, the shape and size are appropriately selected depending on the size of the fiber sheet, the size of the sheet formed from inorganic fibers, etc. In methods (1) and (3), in order to efficiently coat the fibers constituting the fiber sheet with the solid electrolyte and efficiently fill the gaps between the fibers with the solid electrolyte without suspending the solid electrolyte formed by the reaction alone in the organic solvent, it is preferable to use a container in which the contact angle of the organic solvent on the inner surface of the container is at least 5 degrees higher than the contact angle of the organic solvent on at least one type of fiber (preferably inorganic fiber) constituting the fiber sheet. When the fiber sheet contains multiple fibers made of multiple materials, it is sufficient that the contact angle of the fiber made of at least one type of material (preferably inorganic fiber) is at least 5 degrees lower than the contact angle on the inner surface of the container. In methods (2) and (4), in order to efficiently coat the fiber surfaces with the solid electrolyte and efficiently fill the gaps between the fibers with the solid electrolyte, it is preferable to use a container whose inner surface has a contact angle of the organic solvent that is 5 degrees or more higher than the contact angle of the organic solvent on at least one type of fiber (preferably inorganic fiber). When the fibers include multiple types of fibers made of multiple materials, it is sufficient that the contact angle of the fiber made of at least one type of material (preferably inorganic fiber) is 5 degrees or more lower than the contact angle on the inner surface of the container.

[0037] In the above methods (1), (2), (3), and (4), the inner surface of the container before the electrolyte sheet is formed is in contact with at least one of the fiber sheet, the inorganic fiber-containing loose fibers, the solid electrolyte-forming raw material, the solid electrolyte, and the organic solvent. Therefore, the material constituting the inner surface is preferably a fluororesin, a silicone resin, or the like. Among these, fluororesins are preferred, such as polytetrafluoroethylene (hereinafter sometimes referred to as "PTFE"), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene copolymer, perfluoroethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene-perfluoroalkoxyethylene copolymer, polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and chlorotrifluoroethylene-ethylene copolymer (ECTFE). The container may be made of these materials, or may be a container formed from a film or sheet of these materials and placed on the inner surface of a container made from another material, or a container made from another material may have a coating made from these materials on the inner surface.

[0038] In the above methods (1) and (3), the volume ratio of the fiber sheet to the solid electrolyte-forming raw material or solid electrolyte placed in the container is preferably 5:95 to 60:40, more preferably 5:95 to 50:50. In the above methods (2) and (4), the volume ratio of the total amount of the fibers to the solid electrolyte-forming raw material or solid electrolyte placed in the container is preferably 5:95 to 60:40, more preferably 5:95 to 50:50. Furthermore, in the above methods (1), (2), (3) and (4), the mass ratio of the solid electrolyte-forming raw material or solid electrolyte to the organic solvent is preferably 1:10 to 1:22, more preferably 1:14 to 1:18.

[0039] In the above methods (1) and (2), the reaction conditions for reacting the solid electrolyte-forming raw materials to form a solid electrolyte are not particularly limited. The reaction temperature is appropriately selected depending on the type of solid electrolyte to be formed, but is preferably 20°C to 200°C, more preferably 120°C to 180°C. The solid electrolyte may be formed in an organic solvent. Depending on the type of organic solvent, the reaction temperature may be the same as or close to the boiling point of the organic solvent. In this case, if the organic solvent is volatilized at the reaction temperature, the solid electrolyte can be formed as a result of this volatilization. In the above method (2), multiple fibers that are not immobilized to each other are used, so all the manufacturing raw materials are placed in a container and thoroughly mixed, and then the solid electrolyte is formed by reaction. Then, by volatilizing the organic solvent while the contents are in the container, an integrated sheet can be obtained in which all the fibers are coated and bound by the solid electrolyte and densely packed. In the above methods (1) and (2), the atmosphere inside the container can be an argon atmosphere with a dew point of −30° C. or lower.

[0040] In the above method (1), in order to efficiently produce an electrolyte sheet that fully exhibits the effects of the present invention, a method of reacting the solid electrolyte-forming raw material in two stages can be applied. In this case, the production method can include a first step of contacting a fiber sheet with a solution obtained by dissolving at least a portion of the solid electrolyte-forming raw material (e.g., lithium sulfide) (hereinafter referred to as the "nucleation component") in the organic solvent in the container to form nuclei containing the nucleation component on at least a portion of the fiber surface, thereby obtaining a nucleus-attached fiber sheet, and a second step of contacting the nucleus-attached fiber sheet with a solution obtained by dissolving the remainder of the solid electrolyte-forming raw material in an organic solvent in the container. In the above method (2), a production method including the first and second steps can also be applied, using a plurality of fibers that are not fixed to each other instead of the fiber sheet in method (1).

[0041] In the above method (3), the fiber sheet and the solid electrolyte solution are in sufficient contact with each other in the container. Therefore, by volatilizing off the organic solvent contained in the solid electrolyte solution while the contents are in the container, an integrated sheet can be obtained in which all the fibers constituting the fiber sheet are coated and bound by the solid electrolyte and are densely packed. In addition, in the above method (4), since a plurality of fibers that are not fixed to each other are used, when all the raw materials for production are placed in a container and thoroughly mixed, the surfaces of all the fibers are evenly contacted with the solid electrolyte solution. Then, by volatilizing off the organic solvent contained in the solid electrolyte solution while the contents are in the container, an integrated sheet can be obtained in which all the fibers are coated and bound by the solid electrolyte and are densely packed.

[0042] In the above methods (1), (2), (3), and (4), if an organic solvent is present on the obtained electrolyte sheet, it is preferable to remove the organic solvent by natural drying, heat drying, vacuum drying, or the like. The electrolyte sheet can then be heat-treated to obtain a solid electrolyte having desired chemical or physical properties. This heat treatment may be performed during the heat drying or vacuum drying. This heat treatment can, for example, crystallize or decrystallize the solid electrolyte.

[0043] The electrolyte sheet after devolatilization or heat treatment may be subjected to a press treatment. The heat treatment may be performed after the press treatment.

[0044] The electrolyte sheet of the present invention is suitable for forming an electrolyte layer of a lithium ion battery, and can also be used for forming an electrode layer.

[0045] When the electrolyte sheet of the present invention is used to form an electrolyte layer or an electrode layer of a lithium-ion battery, it is a precision component regardless of its size. Therefore, when transporting the electrolyte sheet from the electrolyte sheet manufacturing site to the lithium-ion battery manufacturing site, it is preferable to keep it isolated from the outside air. In such cases, the electrolyte sheet-containing product (electrolyte sheet-packaged product) of the present invention, in which the electrolyte sheet is housed in a package, is useful because it is possible to prevent deterioration and the like of the electrolyte sheet. For example, it is preferable to house the electrolyte sheet and an inert gas such as argon in the package and seal it. The electrolyte sheet-containing product of the present invention can be a package containing two films forming a space between them, with the electrolyte sheet contained in the space. In this case, for example, a resin film or a metal-deposited resin film (such as an aluminum-deposited resin film) can be used to form a structure in which the periphery of one electrolyte sheet is sealed so that it is held between the two films. The electrolyte sheet-containing product of the present invention can also be a package containing a container having a recess and a flange, and a lid that seals at least the recess, with the electrolyte sheet contained in the recess. In this case, the product can be obtained using a resin container and a resin film lid.

[0046] The lithium ion battery of the present invention includes the electrolyte sheet of the present invention described above. Its structure is not particularly limited, but may have, for example, the laminated structure shown in FIG. 8. The lithium ion battery 10 of FIG. 8 includes a positive electrode layer 11, a negative electrode layer 13, and an electrolyte layer 15 disposed between the positive electrode layer 11 and the negative electrode layer 13, and the electrolyte layer 15 may be made of the electrolyte sheet of the present invention described above. The electrolyte layer 15 is a layer that can move lithium ions by an externally applied electric field. The thickness of the electrolyte layer 15 is preferably 5 to 100 μm, and more preferably 10 to 75 μm.

[0047] The positive electrode layer 11 is an electrode layer containing a positive electrode active material that releases lithium ions during charging and absorbs lithium ions during discharging. Examples of the positive electrode active material include oxides, sulfides, and phosphates containing at least one metal element selected from manganese (Mn), cobalt (Co), nickel (Ni), iron (Fe), molybdenum (Mo), and vanadium (V). Specifically, MoO x , WO x ,VO x , Li x CoO y (LiCoO2 etc.), Li x MnO y (LiMnO2, LiMn2O4, etc.), Li x NiO y (LiNiO2 etc.), Li x VO y (LiVO2 etc.), Li x Mn y Ni z Co w O(LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.), Li x FeP x O y (LiFePO4, etc.), Li x MnP x O y (LiMnPO4, etc.), Li x NiP x O y (LiNiPO4 etc.), Li x CuP x O y (LiCuPO4 etc.), MoS x ,CuS x ,TiS x ,WS x , Li x S y , Li x P y S z The positive electrode layer 11 may also be a composite positive electrode layer that further contains a solid electrolyte, a conductive additive, and the like.

[0048] The negative electrode layer 13 is an electrode layer containing a negative electrode active material that absorbs lithium ions during charging and releases lithium ions during discharging. Examples of the negative electrode active material include carbon materials; metals such as lithium (Li), indium (In), aluminum (Al), and silicon (Si), or alloys containing these; Sn x O y , MoO x , WO x , Li x CoO y (LiCoO2 etc.), Li x Mn y Ni z Co w O(LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.), Li x CuP x O y The negative electrode layer 13 may be a composite negative electrode layer further containing a solid electrolyte, a conductive additive, and the like.

[0049] The conductive additive may be a carbon material, a metal powder, a metal compound, or the like, and among these, a carbon material is preferably used. Examples of the carbon material include plate-like conductive materials such as graphene; linear conductive materials such as carbon nanotubes and carbon fibers; carbon blacks such as ketjen black, acetylene black, thermal black, and channel black; and granular conductive materials such as graphite.

[0050] In addition to the configuration of FIG. 8, the lithium ion battery of the present invention can further include a positive electrode current collector that collects current from the positive electrode layer 11 and a negative electrode current collector that collects current from the negative electrode layer 15 (not shown). The positive electrode current collector or the negative electrode current collector may be made of, for example, stainless steel, gold, platinum, copper, zinc, nickel, tin, aluminum, or an alloy thereof, and may have a plate-like, foil-like, mesh-like, or other shape.

[0051] The solid electrolyte-coated fiber of the present invention is a composite fiber including a fiber portion made of a fiber and a solid electrolyte coating layer containing a solid electrolyte and coating at least a portion of the surface of the fiber portion. The structure of the solid electrolyte-coated fiber of the present invention is not particularly limited, but may be, for example, the structure shown in FIG. 9. FIG. 9 shows a solid electrolyte-coated fiber 20 having a fiber portion 21 and a solid electrolyte coating portion 23 coating the surface of the fiber portion 21. Although not shown, the solid electrolyte-coated fiber may have the solid electrolyte coating portion 23 formed on all side surfaces of the fiber portion 21. The mass proportion of the solid electrolyte in the solid electrolyte-coated fiber of the present invention depends on the constituent material of the fiber portion, but is preferably 50 to 95 mass%.

[0052] The fiber portion 21 constituting the solid electrolyte-coated fiber of the present invention may be derived from any of inorganic fibers, organic fibers, and natural fibers. These fibers may be fibers made of the materials exemplified above. The solid electrolyte contained in the solid electrolyte coating portion 23 is not particularly limited, but is preferably a sulfide-based solid electrolyte, and particularly preferably Li3PS4, Li7P2S8X, or Li7P3S 11 , Li2P2S5, Li6PS5X, Li 9.6 P3S 12 etc. X is Cl, Br, or I. The solid electrolyte coating 23 may contain only one type of solid electrolyte, or two or more types of solid electrolytes.

[0053] The method for producing the solid electrolyte-coated fiber of the present invention is not particularly limited. A preferred production method is, for example, a method in which fibers, a solid electrolyte-forming raw material, and an organic solvent are placed in a container, and the solid electrolyte-forming raw material is reacted in the organic solvent to form and coat the surface of the fiber. This production method can use fibers instead of the fiber sheet used in the above-mentioned method for producing an electrolyte sheet. If heat treatment is performed after the reaction to form the solid electrolyte, the method can be the same as in the above-mentioned method for producing an electrolyte sheet, and the description will be omitted.

[0054] A nonwoven fabric containing a solid electrolyte-coated fiber can be produced by subjecting the solid electrolyte-coated fiber of the present invention to a conventionally known nonwoven fabric production process, etc. The obtained nonwoven fabric containing a solid electrolyte-coated fiber can further be subjected to a heat treatment process, a pressing process, etc. [Example]

[0055] Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples and comparative examples.

[0056] 1. Nonwoven fabric In the production of the electrolyte sheet, glass fibers (fiber diameter: 0.3 μm, fiber length: approximately 0.1–1 mm) produced by flame annealing B-glass were used as the inorganic fibers, and polyester resin fibers (fiber diameter: 2 μm, fiber length: 3 mm) were used as the organic fibers. The resulting wet-sheet fabric was then dip-coated with styrene-butadiene rubber as a binder. This nonwoven fabric (hereinafter referred to as “nonwoven fabric (N1)”) contained 52 mass%, 37 mass%, and 11 mass% of the inorganic fibers, organic fibers, and binder, respectively, assuming a total of 100 mass%. Its porosity was 73 vol%, its thickness was 22 μm, and its basis weight was 10 g / m. 2 is.

[0057] 2. Fabrication and Evaluation of Electrolyte Sheets Electrolyte sheets of Examples and Comparative Examples were produced using the nonwoven fabric (N1) or the glass fibers, and various evaluations were carried out.

[0058] Example 1 Under an argon atmosphere, Li2S powder was added to 5 ml of ethanol and stirred to obtain a Li2S solution. Next, this Li2S solution and a circular nonwoven fabric (N1) with a diameter of 30 mm were placed in a polytetrafluoroethylene dish and left to stand at 25°C for 30 minutes, after which it was vacuum dried (150°C, 1 hour). This resulted in a nucleus-attached nonwoven fabric in which Li2S was attached to the surface of the fibers of the nonwoven fabric (N1). Next, Li2S powder, P2S5 powder, and LiI powder were weighed and mixed in a 1:1:1 molar ratio, with the P2S5 powder accounting for 1 / 3 of the total Li2S, consisting of the Li2S attached to the nucleus-attached nonwoven fabric and the Li2S powder. The mixed powders and 10 ml of ethyl propionate were then stirred under ultrasonic irradiation to dissolve the Li2S powder, P2S5 powder, and LiI powder. The resulting solution was then placed in a polytetrafluoroethylene petri dish, followed by the addition of the nucleus-attached nonwoven fabric, and allowed to stand at room temperature for 6 hours. Vacuum drying (170°C, 2 hours) was then performed. As a result, an electrolyte-containing sheet (A1) was obtained in which the voids in the nonwoven fabric (N1) were filled with the solid electrolyte Li7P2S8I (crystalline) and both sides were coated with Li7P2S8I. The volume ratio of the nonwoven fabric (N1) to the solid electrolyte in this electrolyte-containing sheet (A1) was 11:89. The mass ratio of the glass fiber to the solid electrolyte was 8:92.

[0059] The resulting electrolyte-coated sheet (A1) was punched out to a diameter of 10 mm using a punch, and the resulting test specimen was placed inside a polyetheretherketone (PEEK) cylinder (inner diameter 10 mm). Stainless steel pins with a diameter of 10 mm and flat surfaces at the tip were inserted into both sides of the cylinder to clamp the test specimen, and the cylinder was pressed at 250 MPa using a hydraulic press to obtain a 52 μm-thick electrolyte sheet. To observe the cross section of this electrolyte sheet, the sheet was cut perpendicular to the surface extension direction at a temperature of -70 °C and an accelerating voltage of 4 kW using a JEOL cross-sectional specimen preparation device (model number IB-19520CCP). Images shown in Figure 2 were obtained using a JEOL scanning electron microscope (model number JSM-7800F). Then, a mapping analysis of the Si element contained in the glass fibers constituting the nonwoven fabric (N1) was performed using energy dispersive X-ray spectroscopy. The area to be analyzed is the area surrounded by the dotted line in Figure 2 (width: approximately 54 μm, height: approximately 52 μm). The image surrounded by the dotted line was cut out and shown in Figure 3 as a mapping image of Si elements (Si element map). In Figure 3, the black areas are areas containing Si elements.

[0060] Based on Figure 3, the range of Si element abundance was determined using the software "ImageJ" as follows. First, the Si element map in Figure 3 was converted into an 8-bit grayscale image, and then binarized with a lower threshold of 0 and an upper threshold of 10. As a result, the gray value of each pixel was converted to 255 for areas where Si elements were present and 0 for areas where Si elements were not present. Next, a range was set so that it exactly covered the area from the top to the bottom of the cross section in Figure 3, and the "Plot profile" function of the software was used to create a profile of the selected range, resulting in the graph shown in Figure 4. In the profile in Figure 4, the horizontal axis represents the vertical distance in the image in Figure 3, and the vertical axis represents the average gray value in the horizontal direction in the image in Figure 3. In this profile, the percentage of the area where the average gray value in the horizontal direction was 51 or more (i.e., 20% or more of the pixels were determined to be locations where Si elements were present) relative to the cross section thickness was calculated, and found to be 73% (see Table 1).

[0061] In addition, a powder shedding test, a bending test and electrical conductivity measurement were carried out by the following methods, and the results are shown in Table 1. (1) Powder shedding test The electrolyte sheet was moved slightly on a black sheet, and whether or not the solid electrolyte powder fell off was confirmed by visual observation and weight change to determine the powder falling property. The weight change based on weight loss was investigated using the following method. Specifically, the solid electrolyte sheet was punched into a circle (φ10 mm) using a punch, which was designated "test piece A." The weight (mg) of test piece A was then measured, and it was placed in a cylindrical screw cap vial (manufactured by Maruemu Co., Ltd., No. 5, internal volume 20 ml). This screw cap vial was shaken 200 times in the minor axis direction (left and right) at an amplitude of 150 mm. Test piece A was then removed, its weight (mg) was measured, and the weight loss rate was calculated. 〇: No powder fallout at all ×: Powder falls and weight loss of 5% or more is confirmed (2) Bending test On top of the black sheet, the electrolyte sheet was wrapped around a cylindrical substrate with a radius of 35 mm (R35), and the occurrence of cracks, breaks, or powder falling off was visually observed to determine the bending resistance. 〇: No cracks, breaks or powder falling off ×: Cracks, breakage, or powder falling occurred (3) Conductivity measurement The electrolyte sheet was used as a test piece for conductivity measurement and placed in a measurement unit (a PEEK cylindrical body with stainless steel pins inserted from both sides) under an argon gas atmosphere. The conductivity at 25°C was measured using an Impedance Analyzer "S1260" (model name) manufactured by SOLATRON.

[0062] Example 2 Under an argon atmosphere, Li2S powder, P2S5 powder, and LiI powder were weighed out in a molar ratio of 3:1:1 to obtain a total of 1.37 g of mixed powder. Next, this mixed powder, 10 ml of ethyl propionate, and 30 g of zirconia balls (4 mm diameter) were placed in a resin conical tube (50 ml capacity) and shaken at 25°C and 1500 rpm for 3 hours using an AS ONE shaker (model name: ASCM-1), to obtain a slurry (suspension) containing a precursor of the solid electrolyte Li7P2S8I. Next, a dispersion of 0.15 g of glass fibers (fiber diameter: 0.3 μm, fiber length: approximately 0.1 to 1 mm) produced by flame annealing B glass was added to this slurry and thoroughly dispersed in ethyl propionate, followed by thorough mixing. This mixture was then placed in a polytetrafluoroethylene Petri dish and allowed to stand at room temperature for 1 hour, after which it was vacuum dried (170°C, 2 hours). This resulted in an electrolyte-attached sheet (A2) in which glass fibers were contained as a dispersed phase in a matrix phase consisting of the solid electrolyte Li7P2S8I, with no glass fibers protruding from either side of the sheet. The mass ratio of glass fibers to solid electrolyte in this electrolyte-attached sheet (A2) was 10:90.

[0063] Thereafter, the electrolyte-attached sheet (A2) was pressed to obtain an electrolyte sheet having a thickness of 20 μm in the same manner as in Example 1. Then, a graph (not shown) showing the profile of Si in the thickness direction of the electrolyte sheet was created in the same manner as in Example 1, and the proportion of the region where the average gray value in the horizontal direction was 51 or more (i.e., the number of pixels determined to be the presence of Si element was 20% or more) relative to the cross-sectional thickness was calculated, and found to be 100% (see Table 1). Further, in the same manner as in Example 1, a powder falling test, a bending test and a conductivity measurement were carried out, and the results are also shown in Table 1.

[0064] Comparative Example 1 Under an argon atmosphere, Li2S powder and P2S5 powder were weighed out to a molar ratio of 3:1. These powders, ethyl propionate, and zirconia balls were placed in a centrifuge tube and shaken to obtain a slurry (suspension) containing a solid electrolyte precursor. The zirconia balls were then removed from the centrifuge tube and desolvated by drying under reduced pressure at 170°C to obtain a solid electrolyte powder. XRD confirmed that the obtained solid electrolyte contained a peak due to the Li3PS4 crystalline phase. The lithium ion conductivity of this solid electrolyte was 1.5 x 10 -4 S / cm (room temperature). Next, to prepare a solid electrolyte-containing slurry, the solid electrolyte powder was ground using a pestle and mortar until the average particle size was 10 μm or less. The obtained solid electrolyte particles were then dispersed in dehydrated heptane under an argon atmosphere to obtain a solid electrolyte-containing slurry. The mass ratio of the solid electrolyte particles to dehydrated heptane in this solid electrolyte-containing slurry was 1:1.

[0065] Thereafter, the solid electrolyte-containing slurry was applied to a nonwoven fabric (N1) having a size of 30 mm x 90 mm using a four-sided film applicator manufactured by Allgood Co., Ltd., by the following procedure. The nonwoven fabric (N1) was placed on a fluororesin plate, and a solid electrolyte-containing slurry was applied to one surface of the nonwoven fabric (N1) with a gap of 200 μm between the nonwoven fabric (N1) and an applicator roll. After air-drying, a solid electrolyte-containing slurry was applied to the other surface of the nonwoven fabric (N1) under the same conditions and air-dried. The obtained solid electrolyte-coated sheet was then placed on a hot plate at 100°C for desolvation, yielding an electrolyte-containing sheet (B1). The volume ratio of the nonwoven fabric (N1) to the solid electrolyte in this electrolyte-containing sheet (B1) was 12:88. The mass ratio of the glass fiber to the solid electrolyte was 9:91.

[0066] Thereafter, the electrolyte-attached sheet (B1) was press-formed in the same manner as in Example 1 to obtain an electrolyte sheet with a thickness of 88 μm. To observe the cross section of the obtained electrolyte sheet, the image shown in FIG. 5 was obtained using a scanning electron microscope in the same manner as in the electrolyte sheet of Example 1. Then, a mapping analysis of the Si element contained in the glass fiber constituting the nonwoven fabric (N1) was performed using energy dispersive X-ray analysis. The analysis target was the area surrounded by the dotted line in FIG. 5 (width: approximately 142 μm, length: approximately 88 μm). The image surrounded by the dotted line was cut out and shown in FIG. 6 as an Si element map. In FIG. 6, the black area indicates the area containing Si element. Next, in the same manner as in Example 1, the percentage of the area where the average horizontal gray value was 51 or more (i.e., 20% or more of the pixels were determined to be the location where Si element was present) relative to the cross-sectional thickness was calculated using FIG. 7, and was found to be 50% (see Table 1). Further, in the same manner as in Example 1, a powder falling test, a bending test and a conductivity measurement were carried out, and the results are also shown in Table 1.

[0067] [Table 1]

[0068] As is clear from Table 1, in Comparative Example 1, the proportion of inorganic fibers in the electrolyte sheet was less than 60%, so that detachment (powdering) of the solid electrolyte was significant, resulting in poor appearance, and detachment (powdering) of the solid electrolyte was also confirmed in the bending test. On the other hand, Examples 1 and 2 are examples of the electrolyte sheet of the present invention, and there was no detachment (powdering) of the solid electrolyte, and no cracks or breaks were confirmed in the bending test.

[0069] The present invention is not limited to the above-mentioned Examples 1 and 2, and the electrolyte sheet may be obtained by improving each of the steps. For example, in Example 2, a slurry containing LiS powder, P2S5 powder, and LiI powder is obtained and then mixed with a dispersion of glass fiber. However, the glass fiber may be added during the preparation of this slurry to produce a mixed liquid, or the glass fiber may be used together with the LiS powder, P2S5 powder, and LiI powder from the beginning to produce a mixed liquid. [Industrial Applicability]

[0070] The electrolyte sheet of the present invention is suitable for forming electrolyte layers for lithium ion batteries that constitute the structures of home appliances such as personal computers and cameras, power storage devices, portable electronic devices or communication devices such as mobile phones, electric tools such as power tools, electric bicycles, passenger vehicles such as electric cars, wind power generation, stationary storage batteries for solar cell devices, wristwatches, eyeglasses, wearable terminals, drones, aircraft, robots, etc., which take advantage of their high level of safety. [Explanation of symbols]

[0071] 1: Electrolyte sheet 3: Fiber (inorganic fiber) 10: Lithium-ion battery 11: Positive electrode layer 13: Negative electrode layer 15: Electrolyte layer 20: Solid electrolyte coated fiber 21: Fiber 23: Solid electrolyte

Claims

1. An electrolyte sheet including a plurality of inorganic fibers and a solid electrolyte, The inorganic fibers have a fiber diameter of 0.01 to 50 μm and a fiber length of 0.1 to 10 mm, An electrolyte sheet, wherein the inorganic fibers account for 60% or more of the cross section of the electrolyte sheet taken perpendicular to the surface stretching direction.

2. 2. The electrolyte sheet according to claim 1, wherein the content of the solid electrolyte is 60 to 95% by mass, where the total amount of the inorganic fibers and the solid electrolyte is 100% by mass.

3. 3. The electrolyte sheet according to claim 1, wherein the inorganic fibers comprise glass fibers.

4. 4. The electrolyte sheet according to claim 1, wherein the solid electrolyte contains a compound containing lithium, phosphorus, and sulfur elements.

5. 4. The electrolyte sheet according to claim 1, wherein the solid electrolyte contains a compound containing lithium, phosphorus, sulfur, and a halogen element.

6. The electrolyte sheet according to claim 1 , wherein the solid electrolyte is amorphous.

7. The electrolyte sheet according to claim 1 , wherein the solid electrolyte has crystallinity.

8. 8. The electrolyte sheet according to claim 1, wherein a void ratio is 20% or less when viewed in cross section of the electrolyte sheet.

9. 9. An electrolyte sheet-containing product, comprising the electrolyte sheet according to claim 1 housed in a package.

10. A lithium ion battery comprising the electrolyte sheet according to any one of claims 1 to 8.

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