WO2021241402A1

WO2021241402A1 - Electrolyte sheet, solid-electrolyte-coated fiber, and lithium-ion battery

Info

Publication number: WO2021241402A1
Application number: PCT/JP2021/019212
Authority: WO
Inventors: 厚範松田; 和浩引間; 貴宏小原; 康史高橋
Original assignee: 日本板硝子株式会社; 国立大学法人豊橋技術科学大学
Priority date: 2020-05-29
Filing date: 2021-05-20
Publication date: 2021-12-02
Also published as: JPWO2021241402A1

Abstract

The present invention addresses the problem of providing an electrolyte sheet in which dislodgement of a solid electrolyte (grain shedding) is minimized so as to facilitate handling, and cracking and grain shedding during bending work are minimized so as to enable efficient manufacture of a lithium-ion battery. This electrolyte sheet contains a plurality of inorganic fibers and a solid electrolyte. The inorganic fibers are present in a ratio of at least 60% in said sheet in a thickness-direction cross-section cut perpendicular to the direction of surface stretching of the electrolyte sheet. The solid electrolyte content is preferably 60-95 mass%, where 100 mass% represents the total amount of the inorganic fibers and the solid electrolyte.

Description

Electrolyte sheet, solid electrolyte coated fiber and lithium ion battery

The present invention relates to an electrolyte sheet, a solid electrolyte-coated fiber, and a lithium ion battery, which contain a solid electrolyte and are suitable for forming an electrolyte layer or the like constituting a lithium ion battery.

A lithium-ion battery is a secondary battery having a structure in which lithium is desorbed as ions from the positive electrode during charging, moves to the negative electrode and is stored, and lithium ions are inserted from the negative electrode to the positive electrode and returned during discharge. Since this lithium-ion battery has features such as high energy density and long life, it has been conventionally used for home appliances such as personal computers and cameras, portable electronic devices or communication devices such as mobile phones, and power tools. It is widely used as a power source for electric tools and the like, and has recently been applied to large batteries mounted on electric vehicles (EV), hybrid electric vehicles (HEV), and the like. In such a lithium ion battery, if a solid electrolyte is used instead of the electrolytic solution containing a flammable organic solvent, not only the safety device can be simplified but also the manufacturing cost and productivity are excellent. Research on various materials, especially sulfide solid electrolytes with high conductivity (lithium ion conductivity), is being actively pursued.

The sulfide solid electrolyte is usually in the form of powder. When manufacturing a lithium-ion battery, it is required to form a sheet for convenience of handling, but it is often difficult to form a single-layer thin sheet made of a powdered solid electrolyte. As an alternative, a solid electrolyte sheet in which a solid electrolyte is attached to a fiber such as an electronically insulating inorganic fiber has been proposed (see Patent Document 1).

Patent Document 1 includes a solid electrolyte and a support having a plurality of openings, the solid electrolyte is filled in the openings of the support, the support is made of glass (glass fiber woven fabric), and the opening ratio of the support is high. The solid electrolyte is 40 to 90%, the solid electrolyte is made of lithium sulfide and diphosphorus pentasulfide as raw materials, and the molar ratio of lithium sulfide to diphosphorus pentasulfide is 68:32 to 80:20, and the solid electrolyte is dissolved in a solvent. Disclosed is a solid electrolyte sheet for a lithium battery obtained by applying the above to a support and drying it.

Japanese Unexamined Patent Publication No. 2013-127892

The internal structure of the lithium-ion battery is diverse, and the electrolyte layer may be flat or curved. In the latter case, it is necessary to bend the solid electrolyte sheet, so that it is necessary to have a structure in which cracks and cracks do not occur on the surface. Further, in the solid electrolyte sheet for a lithium battery shown in Patent Document 1, solid electrolyte particles may be detached during transportation or the like, and stable performance cannot be obtained when a lithium ion battery is mass-produced. There was something. The problem of the present invention is that the desorption (powder falling) of the solid electrolyte is suppressed and it is easy to handle, and the generation of cracks and the powder falling during the bending process are suppressed so that the lithium ion battery can be efficiently manufactured. To provide a sheet. Another object of the present invention is to provide a product containing the electrolyte sheet and having excellent transportability.

The present invention is shown below.
1. 1. In an electrolyte sheet containing a plurality of inorganic fibers and a solid electrolyte,
An electrolyte sheet characterized in that the proportion of the inorganic fibers present is 60% or more in a cross section in the thickness direction cut perpendicular to the surface stretching direction of the electrolyte sheet.
2. 2. Item 2. The electrolyte sheet according to Item 1, wherein the content ratio of the solid electrolyte is 60 to 95% by mass when the total amount of the inorganic fibers and the solid electrolyte is 100% by mass.
3. 3. Item 2. The electrolyte sheet according to Item 1 or 2, wherein the inorganic fiber contains glass fiber.
4. Item 2. The electrolyte sheet according to any one of Items 1 to 3, wherein the solid electrolyte contains a compound containing a lithium element, a phosphorus element and a sulfur element.
5. Item 2. The electrolyte sheet according to any one of Items 1 to 3, wherein the solid electrolyte contains a compound containing a lithium element, a phosphorus element, a sulfur element and a halogen element.
6. The electrolyte sheet according to any one of Items 1 to 5, wherein the solid electrolyte has amorphous properties.
7. The electrolyte sheet according to any one of Items 1 to 5, wherein the solid electrolyte has crystallinity.
8. Item 2. The electrolyte sheet according to any one of Items 1 to 7, wherein the inorganic fiber contains a fiber having a fiber diameter of 50 μm or less.
9. The electrolyte sheet according to any one of Items 1 to 8 above, wherein the proportion of voids is 20% or less when the cross section of the electrolyte sheet is viewed.
10. A product containing an electrolyte sheet, wherein the electrolyte sheet according to any one of the above items 1 to 9 is housed in a package.
11. A lithium ion battery comprising the electrolyte sheet according to any one of the above items 1 to 9.
12. A solid electrolyte-coated fiber comprising a fiber portion made of a fiber and a solid electrolyte-coated layer containing a solid electrolyte and covering at least a part of the surface of the fiber portion.

The electrolyte sheet of the present invention is easy to handle because it is difficult for the solid electrolyte to come off (powder fall off) and has excellent shape stability. In addition, cracks and powder falling are less likely to occur when bending or the like is performed during the manufacture of a lithium ion battery, so that a lithium ion battery having the desired performance can be efficiently manufactured.
According to the electrolyte sheet-containing product of the present invention, the electrolyte sheet can be opened at the manufacturing site of the lithium ion battery, and the electrolyte sheet can be taken out and used for manufacturing the lithium ion battery while maintaining the above-mentioned excellent effects of the electrolyte sheet.
Since the lithium ion battery of the present invention contains an electrolyte sheet having high lithium ion conductivity, it exhibits excellent battery performance.
Since the solid electrolyte-coated fiber of the present invention is not a bond between the fiber and the solid electrolyte via an adhesive, it is suitable for forming an electrolyte sheet having high lithium ion conductivity.

It is a schematic sectional drawing which shows an example of the electrolyte sheet of this invention. 6 is a cross-sectional image of the electrolyte sheet obtained in Example 1. It is a Si element map of the part surrounded by the dotted line in FIG. It is a graph which shows the profile of Si in the thickness direction of an electrolyte sheet based on the Si element map of FIG. It is a cross-sectional image of the electrolyte sheet obtained in Comparative Example 1. It is a Si element map of the part surrounded by the dotted line in FIG. It is a graph which shows the profile of Si in the thickness direction of an electrolyte sheet based on the Si element map of FIG. It is a schematic sectional drawing which shows an example of a lithium ion battery. It is a schematic perspective view which shows an example of the solid electrolyte coating fiber of this invention.

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 needed. 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 cross section in the thickness direction cut perpendicular to the surface stretching direction. In addition, in this specification, a "sheet" includes not only a sheet but also a long one.

The inorganic fiber is not particularly limited as long as it contains a portion made of an inorganic compound. For example, a fiber composed of only an inorganic compound, a fiber having a film containing an inorganic material on at least a part of the surface of the resin fiber, or a fiber having a granular portion can be mentioned. The inorganic fiber according to the present invention is preferably a fiber composed of only an inorganic compound. The inorganic compound is not particularly limited, but is preferably an oxide, a nitride, a carbonate, a titanate or the like. Specific inorganic fibers include glass fiber, silica fiber, alumina fiber, silica-alumina fiber, silica-alumina-magnesia fiber, silica-alumina-zirconia fiber, silica-magnesia-calcia fiber, rock wool, slag wool, and titanium. Examples thereof include potassium acid whiskers, calcium carbonate whiskers, basalt fibers, sepilite, mineral fibers such as apparaljite and the like. Of these, glass fiber is preferable.
The glass constituting the glass fiber is not particularly limited, but when the electrolyte sheet of the present invention is used for forming the electrolyte layer of the lithium ion battery, C glass, B glass, E glass and the like are preferable because they are excellent in chemical resistance.

The fiber diameter of the inorganic fiber is not particularly limited, but the upper limit is preferably 50 μm, more preferably 10 μm, and the lower limit is from the viewpoint of the mechanical strength of the electrolyte sheet of the present invention, flexibility against bending, and the like. It is preferably 0.01 μm, more preferably 0.1 μm. The fiber length is not particularly limited, but is preferably in the range of 0.1 to 10 mm, more preferably 0.5 to 6 mm from the viewpoint of productivity of the nonwoven fabric of the electrolyte sheet of the present invention and uniformity of opening. be. The electrolyte sheet of the present invention contains a plurality of inorganic fibers, and in the present invention, the size (diameter or length) of each fiber is uniform or non-uniform among the inorganic fibers containing the same material. But it may be. Further, when the constituent materials include a plurality of types of inorganic fibers different from each other, the diameter or length between the fibers made of one material and the fibers made of another material may be uniform or non-uniform.

The electrolyte sheet of the present invention may contain other fibers as described above. When the electrolyte sheet of the present invention contains other fibers, the upper limit of the content ratio thereof with respect to the entire fibers is preferably 65% by mass, more preferably 55% by mass.
Examples of other fibers include organic fibers and natural fibers, and organic fibers are preferable.

As the organic fiber, a resin fiber is preferable. As the constituent materials of the resin fiber, polyester resin (polyethylene terephthalate, etc.), aliphatic polyamide resin, aramid resin, polyolefin resin, cyclic olefin resin, acrylic resin, polyacrylonitrile resin, polyvinyl alcohol resin, polyacetal resin, polyvinyl chloride resin, etc. Examples thereof include polyvinylidene chloride resin, ethylene / vinyl acetate copolymer, fluororesin, polyether sulfone resin, polyphenylene sulfide resin, cellulose and the like. The resin fiber is a fiber composed of a single phase containing only one type of resin or a plurality of types of resin, or a fiber having a double-phase structure including a low melting point resin portion and a high melting point resin portion (hereinafter referred to as "composite resin fiber"). And so on. In the case of the composite resin fiber, for example, a core-sheath type fiber, a side-by-side type fiber, or the like can be used. Examples of the resin combination in the case of the composite resin fiber include PET / low melting point copolymerized polyester, PET / PE, PP (polypropylene) / PE (polyethylene), PP / low melting point copolymerized PP and the like. Here, as the low melting point copolymerized polyester, a modified resin having PET, PPT (polypropylene terephthalate), PBT (polybutylene terephthalate) or the like as a basic skeleton, that is, these polyesters, isophthalic acid, 5-sodium sulfoisophthalic acid, etc. , Aromatic dicarboxylic acids such as 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. Examples include copolymers.
As the organic fiber (resin fiber), polyester fiber is particularly preferable.

The fiber diameter and fiber length of the organic fiber are not particularly limited, but can be the same as the fiber diameter and fiber length of the inorganic fiber.

The fibers in the electrolyte sheet of the present invention may be either those in which the fibers are simply entangled with each other or those in which the fibers are intertwined with each other and the fibers are joined to each other. In the latter case, it is preferable that the fibers are in a bonded state by an adhesive at the contact point between the fibers.

Next, the solid electrolyte is not particularly limited as long as it is conventionally known as a constituent material of the lithium ion battery, and is a sulfide-based solid electrolyte, a garnet-based solid electrolyte, a nitride-based solid electrolyte, and a perovskite-based solid. Examples thereof include an electrolyte, a zeolite-based solid electrolyte, a phosphoric acid-based solid electrolyte, and a NASICON-type solid electrolyte. In the present invention, since it is excellent in lithium ion conductivity, Li ₃ PS ₄ , Li ₇ P ₂ S ₈ X, Li ₇ P ₃ S ₁₁ , Li ₂ P ₂ S ₅ , Li ₆ PS ₅ X, Li _9. A sulfide-based solid electrolyte such as ₆ P ₃ S _{12 is preferable.} In addition, X is Cl, Br or I. The solid electrolyte contained in the electrolyte sheet of the present invention may be only one type or two or more types. Further, 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.

The volume ratio of all fibers and solid electrolytes contained in the electrolyte sheet of the present invention is not particularly limited. From the viewpoint of lithium ion conductivity, mechanical strength and flexibility, the volume ratios of the fiber and the solid electrolyte are preferably 5 to 60% by volume and 40 to 95% by volume, respectively, when the total of the two is 100% by volume. , More preferably 5 to 50% by volume and 50 to 95% by volume.

The mass ratio of the inorganic fiber 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 content ratios of the inorganic fiber and the solid electrolyte are preferably 5 to 50% by mass and 50 to 95% by mass, respectively, more preferably when the total of both is 100% by mass. It is 5 to 40% by mass and 60 to 95% by mass.

The electrolyte sheet of the present invention is substantially a medium-solid sheet mainly composed of a fiber containing an inorganic fiber and a solid electrolyte, and as shown in FIG. 1, the fiber 3 from one surface side to the other surface side. And the sheet 1 having a structure in which the solid electrolyte (unsigned) is uniformly contained, and the fiber and the solid electrolyte are uniformly contained in the sheet 1, while the surface layer on the one side and the surface layer on the other side are uniformly contained. May be a sheet (not shown) having a structure as a coating layer made of a solid electrolyte.

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 the cross section in the thickness direction cut perpendicular to the surface stretching direction. This ratio is preferably 70% or more. The method for measuring this ratio is shown in [Example], but is as follows.
(1) The electrolyte sheet is photographed with an electron microscope so that the entire cross section in the thickness direction is included in the image (see FIGS. 2 and 5).
(2) An element constituting an inorganic fiber contained in an electrolyte sheet by an energy dispersive X-ray analysis method in a region set so as to include the entire cross section in the thickness direction (hereinafter referred to as “measurement region”). Perform mapping analysis on elements not contained in the solid electrolyte. As the measurement element, the inorganic fiber is a glass fiber containing a Si element, and when the Si element is not contained in the solid electrolyte, it is preferable to select the Si element. The measurement region preferably has a lateral length of at least 40 μm.
(3) Based on, for example, the Si element map shown in FIGS. 3 and 6 obtained by mapping analysis, the existence range of the Si element is determined by the following method using software. That is, after converting the Si element map into an 8-bit grayscale image, this is binarized with a lower limit threshold value of 0 and an upper limit threshold value of 10, and the gray value of each pixel is set to 255 where the Si element is present and non-Si element. Converts the existing location to 0. Next, in the operation of the software, the range is set so that the upper end to the lower end of the Si element map fits exactly, and the profile of the range from the upper end to the lower end is created and graphed (see FIGS. 4 and 7). The horizontal axis is the vertical distance of the Si element map, and the vertical axis is the average value of the horizontal gray values of the Si element map. After that, in this graph, the ratio of the region where the pixel determined to be the presence of the Si element is 20% or more, that is, the region where the average value of the horizontal gray values is 51 or more is relative to the measurement region. Calculate whether it is (area ratio).

As described above, the electrolyte sheet of the present invention is a medium-solid sheet mainly composed of fibers containing inorganic fibers and a solid electrolyte, and has a shape that makes it difficult for the solid electrolyte to come off (powder fall off). Due to its excellent stability, the percentage of voids (presence rate) is low. The percentage of voids is preferably 20% or less, more preferably 10% or less. The void ratio can be calculated in an arbitrary range based on an image of a cross section obtained by cutting the electrolyte sheet in the thickness direction with, for example, an optical microscope, a laser microscope, an electron microscope, or the like. ..

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

The method for producing the electrolyte sheet of the present invention is not particularly limited. Preferred manufacturing methods are shown below.
Method (1): In a container, an aggregate of fibers containing inorganic fibers, which has a sheet shape (hereinafter referred to as "fiber sheet"), a solid electrolyte forming raw material, and an organic solvent are put into a container to form a solid electrolyte. A method in which raw materials are reacted to form a solid electrolyte, the surface of the fiber is coated with the solid electrolyte, and the voids between the fibers are filled with the solid electrolyte to prepare a solid sheet.
Method (2): A container contains a plurality of inorganic fibers that are not immobilized on each other, a solid electrolyte forming raw material, and an organic solvent, and then the solid electrolyte forming raw material is reacted to cause a solid electrolyte. A method in which the surface of a fiber is coated with a solid electrolyte, and the voids between all the fibers are filled with the solid electrolyte to prepare a solid sheet.
Method (3): In a container, the fiber sheet 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. A method in which the organic solvent is devolatile, the surface of the fiber constituting the fiber sheet is coated with a solid electrolyte, and the voids between the fibers are filled with the solid electrolyte to prepare a solid sheet.
Method (4): A solid electrolyte solution containing a plurality of inorganic fibers in a container and not immobilized with each other and a solid electrolyte dissolved in an organic solvent, or a dispersion in which the solid electrolyte is composed of an organic solvent. After adding the solid electrolyte dispersion liquid dispersed in the medium, the organic solvent is devolatile and the fiber surface is coated with the solid electrolyte to fill the voids between all the fibers with the solid electrolyte. How to make a medium solid sheet.
In all of the above methods, heat treatment, press treatment, or the like may be performed after forming the sheet, if necessary.

The fiber sheet used in the above methods (1) and (3) is not particularly limited, and may be a fiber deposit, a non-woven fabric, a woven fabric, a woven fabric, or the like. The fiber sheet may be composed of only fibers, or may be one in which a plurality of fibers are bonded by an adhesive.

The fiber sheet preferably contains 35% by mass or more of inorganic fibers with respect to the whole, and the inorganic fibers preferably contain glass fibers. This makes it possible to obtain an electrolyte sheet suitable as an electrolyte layer forming material for a lithium ion battery.

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 .

In the above methods (1) and (3), the above fiber sheet is preferably a non-woven fabric. The non-woven fabric may be either one in which the fibers are simply entangled with each other, or one in which the fibers are intertwined with each other and the fibers are joined to each other. In the case of the latter non-woven fabric, it is preferable that the fibers are in a bonded state by an adhesive at the contact point between the fibers.

When the non-woven fabric contains fibers bonded by an adhesive, the content ratio of the adhesive to the entire non-woven fabric is preferably 15% by mass or less, more preferably 15% by mass or less, in order to make the obtained electrolyte sheet excellent in conductivity. Is 12% by mass or less.

The thickness of the nonwoven fabric is usually 20 μm or more, but the obtained electrolyte sheet is suitable as an electrolyte layer forming material for giving a lithium ion battery having excellent performance, so it is preferably 5 to 100 μm, more preferably. It is 10 to 75 μm.

In the "plurality of fibers not immobilized with each other" used in the above methods (2) and (4), a plurality of fibers are used as a solid electrolyte forming raw material and an organic solvent, an organic solution of a solid electrolyte, or a solid electrolyte is an organic solvent. It means that most of the fibers are scattered before being placed in a container together with the solid electrolyte dispersion liquid dispersed in the dispersion medium consisting of the above to form the solid electrolyte on the fiber surface.
The inorganic fiber used in the above methods (2) and (4) is preferably a glass fiber containing C glass, B glass, E glass and the like. The preferred size of the inorganic fiber is as described above. Further, in the methods (2) and (4), the inorganic fiber and the organic fiber or the natural fiber can be used in combination, and in this case, the ratio of the inorganic fiber to the whole fiber is preferably 35% by mass or more. be.

In the above methods (1) and (2), the solid electrolyte forming raw material used for forming the solid electrolyte in the presence of the organic solvent is usually composed of a plurality of kinds of compounds. Then, in the organic solvent, a plurality of kinds of compounds are contact-reacted to form a solid electrolyte. As described above, the preferred solid electrolyte is a sulfide-based solid electrolyte, and the raw materials for forming the solid electrolyte are Li ₃ PS ₄ , Li ₇ P ₂ S ₈ X, Li ₇ P ₃ S ₁₁ , Li ₂ P ₂ S. ₅ , Li ₆ PS ₅ X, Li _9.6 P ₃ S _{12 and the} like are preferably contained. In addition, X is Cl, Br or I.

Examples of the raw material for forming the sulfide-based solid electrolyte include lithium sulfide, phosphorus sulfide, lithium halide and the like. Examples of phosphorus sulfide include diphosphorus pentasulfide (P ₂ S ₅ ), tetraphosphorus trisulfide (P ₄ S ₃ ), tetraphosphorus sesquioxide (P ₄ S ₇ ), and tetraphosphorus pentasulfide (P ₄ S ₅ ). Can be mentioned. Of these, diphosphorus pentasulfide is preferable. Examples of lithium halide include lithium fluoride, lithium chloride, lithium bromide, lithium iodide and the like. Of these, lithium iodide is preferred.
The solid electrolyte forming raw material preferably contains lithium sulfide and diphosphorus pentasulfide, and it is also preferable that it contains lithium sulfide, diphosphorus pentasulfide and lithium halide.

The solid electrolyte used in the above methods (3) and (4) is preferably the above sulfide-based solid electrolyte, and is Li ₃ PS ₄ , Li ₇ P ₂ S ₈ X, Li ₇ P ₃ S ₁₁ , Li ₂ P. ₂ S ₅ , Li ₆ PS ₅ X, Li _9.6 P ₃ S _{12 and the} like.

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

The container used in the above methods (1), (2), (3) and (4) is not particularly limited, and for example, the shape and size are the size of the fiber sheet, the size of the sheet formed of inorganic fibers and the like. Is selected as appropriate.
In the methods (1) and (3), the solid electrolyte formed by the reaction is not suspended alone in the organic solvent, and the fibers constituting the fiber sheet are efficiently coated with the solid electrolyte, and the voids between the fibers are solid. In order to efficiently fill with the electrolyte, use a container in which the contact angle of the organic solvent on the inner surface of the container is 5 degrees or more higher than the contact angle of the organic solvent in at least one kind of fiber (preferably inorganic fiber) constituting the fiber sheet. Is preferable. When the fiber sheet contains various kinds of fibers made of a plurality of kinds of materials, the contact angle with respect to the fibers made of at least one kind of material (preferably inorganic fibers) is 5 degrees or more lower than the contact angle with respect to the inner surface of the container. good.
Further, in the methods (2) and (4), the contact angle of the organic solvent on the inner surface of the container is at least at least in order to efficiently fill the voids between the fibers with the solid electrolyte while efficiently covering the fiber surface with the solid electrolyte. It is preferable to use a container having a contact angle of 5 degrees or more higher than the contact angle of the organic solvent in one type of fiber (preferably inorganic fiber). When the fiber contains various kinds of fibers made of a plurality of kinds of materials, the contact angle with respect to the fiber made of at least one kind material (preferably an inorganic fiber) may be 5 degrees or more lower than the contact angle with respect to the inner surface of the container. ..

In the above methods (1), (2), (3) and (4), a plurality of non-immobilized fiber sheets or inorganic fibers are contained on the inner surface of the container before the electrolyte sheet is formed. Since at least the organic solvent of the fiber, the solid electrolyte forming raw material, the solid electrolyte and the organic solvent comes into contact with the fiber, a fluororesin; a silicone resin or the like is preferable as the material constituting the inner surface thereof. Of these, fluororesins are preferable, and for example, polytetrafluoroethylene (hereinafter, may be referred to as “PTFE”), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / hexafluoropropylene are used together. Polymer, perfluoroethylene / propylene copolymer, ethylene / tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / perfluoroalkoxyethylene copolymer , Polyfluoride vinylidene (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE) and the like. The container may be made of these materials, or a film or sheet made of these materials may be processed into a container shape and arranged on the inner surface of a container made of another material. May be good. Further, the inner surface of the container made of other materials may have a film made of these materials.

In the above methods (1) and (3), the volume ratio of the fiber sheet and the solid electrolyte forming raw material or the solid electrolyte to be put in the container is preferably 5:95 to 60:40, more preferably 5:95 to 50:50. Is. Further, in the above methods (2) and (4), the total amount of the plurality of fibers and the volume ratio of the solid electrolyte forming raw material or the solid electrolyte to be put in the container are preferably 5:95 to 60:40, more preferably 5. : 95 to 50:50.
Further, in the above methods (1), (2), (3) and (4), the mass ratio of the solid electrolyte forming raw material or the solid electrolyte and the organic solvent is preferably 1:10 to 1:22, more preferably 1. : 14 to 1:18.

In the above methods (1) and (2), the reaction conditions for reacting the solid electrolyte forming raw materials to form the 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, and depending on the type of the organic solvent, the reaction temperature may be the same as or close to the boiling point of the organic solvent. When the organic solvent is volatilized at the reaction temperature of No. 1, a solid electrolyte can be formed by this volatilization. In the above method (2), since a plurality of fibers that are not immobilized on each other are used, all the production raw materials are contained in the container and sufficiently mixed, and then a solid electrolyte is formed by the reaction. Then, by devolving the organic solvent with the contents in the container, it is possible to obtain an integrated sheet in which all the fibers are coated and bound by the solid electrolyte and contained at a high density.
Further, in the above methods (1) and (2), the atmosphere in the container can be an argon atmosphere, a dew point: −30 ° C. or lower, or the like.

In the above method (1), in order to efficiently produce an electrolyte sheet that fully exerts the effect of the present invention, a method of reacting a solid electrolyte forming raw material in two steps can be applied. In this case, in the above container, a solution obtained by dissolving at least a part (for example, lithium sulfide) component (hereinafter referred to as “nucleation component”) of the solid electrolyte forming raw material in the above organic solvent, and a fiber sheet. In the first step of forming a nucleation containing the nucleation component on at least a part of the surface of the fiber to obtain a nucleation-attached fiber sheet, and in the container, the rest of the solid electrolyte forming raw material is organically prepared. It can be a manufacturing method including a second step of bringing the solution dissolved in the solvent into contact with the nucleated fiber sheet. Also in the above method (2), instead of the fiber sheet in the method (1), a manufacturing method including a first step and a second step can be applied by using a plurality of fibers that are not immobilized on each other.

In the above method (3), since the fiber sheet and the solid electrolyte solution are sufficiently in contact with each other in the container, the organic solvent contained in the solid electrolyte solution is volatilized while the contents are in the container. As a result, it is possible to obtain an integrated sheet in which all the fibers constituting the fiber sheet are coated and bound by the solid electrolyte and contained in a high density.
Further, in the above method (4), since a plurality of fibers that are not immobilized on each other are used, when all the manufacturing raw materials are contained in the container and sufficiently mixed, the surfaces of all the fibers are evenly solid. It will come into contact with the electrolyte solution. Then, by devolatile the organic solvent contained in the solid electrolyte solution while the contents are in the container, all the fibers are covered and bound by the solid electrolyte, and the integrated sheet is contained at high density. Can be obtained.

In the above methods (1), (2), (3) and (4), when the organic solvent adheres to the obtained electrolyte sheet, the organic solvent is applied by natural drying, heat drying, vacuum drying or the like. It is preferable to evaporate. After that, the electrolyte sheet can be heat-treated in order to obtain a solid electrolyte having the desired chemical properties or physical properties. This heat treatment may be performed in the above-mentioned heat drying or vacuum drying. By this heat treatment, for example, the solid electrolyte can be crystallized or non-crystallized.

Further, the electrolyte sheet after devolatile or heat treatment may be pressed. The above heat treatment may be performed after the press treatment.

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.

When the electrolyte sheet of the present invention is used for forming an electrolyte layer or an electrode layer of a lithium ion battery, it is a precision component regardless of its size, so that it is transported from the electrolyte sheet manufacturing site to the lithium ion battery manufacturing site. It is preferable that the air is shut off from the outside air. In such a case, since it is possible to suppress deterioration, deterioration, etc. of the electrolyte sheet, the electrolyte sheet-containing product of the present invention (electrolyte sheet packaging product) in which the electrolyte sheet is housed in the package. Is useful. For example, it is preferable to seal the package with the electrolyte sheet and an inert gas such as argon contained therein.
In the electrolyte sheet-containing product of the present invention, two films can be used, and the electrolyte sheet can be accommodated in the space of the package forming a space between them. In this case, for example, a resin film or a metal-deposited resin film (aluminum-deposited resin film, etc.) is used, and the peripheral portion thereof is sealed so that one electrolyte sheet is held between the two films. Can be. Further, in the electrolyte sheet-containing product of the present invention, the electrolyte sheet may be housed in the recess of the package having a container portion having a recess and a flange portion and a lid portion for at least sealing the recess. can. In this case, it can be obtained by using the resin container portion and the resin film lid portion.

The lithium ion battery of the present invention includes the above-mentioned electrolyte sheet of the present invention, and the structure thereof is not particularly limited, but can have, for example, the laminated structure shown in FIG. The lithium ion battery 10 of FIG. 8 includes a positive electrode layer 11, a negative electrode layer 13, and an electrolyte layer 15 arranged between the positive electrode layer 11 and the negative electrode layer 13, and the electrolyte layer 15 is the electrolyte sheet of the present invention. Can consist of. The electrolyte layer 15 is a layer capable of moving lithium ions by an electric field applied from the outside. The thickness of the electrolyte layer 15 is preferably 5 to 100 μm, more preferably 10 to 75 μm.

The positive electrode layer 11 is an electrode layer containing a positive electrode active material that emits lithium ions during charging and occludes lithium ions during discharging. The positive electrode active material is an oxide containing at least one metal element selected from manganese (Mn), cobalt (Co), nickel (Ni), iron (Fe), molybdenum (Mo) and vanadium (V). Examples include sulfides and phosphor oxides. Specifically, MoO _x , WO _x , VO _x , Li _x CoO _y (LiCoO ₂ etc.), Li _x MnO _y (LiMnO ₂ , LiMn ₂ O ₄ etc.), Li _x NiO _y (LiNiO ₂ etc.), Li _x VO _y (LiVO _2, _{_{_{_{etc.), Li x Mn y Ni z}}}} Co w O (LiNi 1/3 Co 1/3 Mn 1/3 O 2 , _{_{_{etc.), Li x FeP x O y}}} (LiFePO 4 , etc.), Li _x MnP _x O _y (LiMnPO _4, _{_{_{etc.), Li x NiP x O y}}} (LiNiPO 4 , _{_{_{etc.), Li x CuP x O y}}} (LiCuPO 4 , _{_{_{etc.), MoS x, CuS x,}}} TiS x, WS x, Li x S y , Li _x P _y S _{z and the} like. Further, the positive electrode layer 11 may be a composite positive electrode layer further containing a solid electrolyte, a conductive auxiliary agent, and the like.

The negative electrode layer 13 is an electrode layer containing a negative electrode active material that occludes lithium ions during charging and releases lithium ions during discharging. As the negative electrode active material, a carbon material; lithium (Li), indium (In), aluminum (Al), silicon (Si) or the like of a metal or an alloy containing _{_{_{_{these; Sn x O y, MoO x}}}} , WO x, Li x Oxides _{such as CoO y} (LiCoO ₂ etc.), Li _x Mn _y Ni _z Co _w O (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc.), Li _x CuP _x O _y ( _{LiCuPO 4} etc.) And so on. Further, the negative electrode layer 13 may be a composite negative electrode layer further containing a solid electrolyte, a conductive auxiliary agent and the like.

As the conductive auxiliary agent, a material made of a carbon material, a metal powder, a metal compound, or the like can be used, and among these, the carbon material is preferably used. As carbon materials, plate-like conductive substances such as graphene; linear conductive substances such as carbon nanotubes and carbon fibers; carbon black such as Ketjen black, acetylene black, thermal black and channel black, and granular conductivity such as graphite. Substances and the like can be mentioned.

In addition to the configuration shown in FIG. 8, the lithium ion battery of the present invention may further include a positive electrode collector that collects electricity from the positive electrode layer 11 and a negative electrode collector that collects electricity 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 be a plate-like body or a foil-like body. , A mesh-like body and the like can be provided.

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-coated layer containing a solid electrolyte and covering at least a part 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. FIG. 9 is a solid electrolyte-coated fiber 20 having a fiber portion 21 and a solid electrolyte-coated portion 23 that covers the surface of the fiber portion 21. Further, although not shown, the solid electrolyte-coated portion 23 may be a solid electrolyte-coated fiber formed on all the side surfaces of the fiber portion 21. The mass ratio 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% by mass.

The fiber portion 21 constituting the solid electrolyte-coated fiber of the present invention may be derived from any of inorganic fiber, organic fiber and natural fiber. These fibers can 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 Li ₃ PS ₄ , Li ₇ P ₂ S ₈ X, Li ₇ P _3. S ₁₁ , Li ₂ P ₂ S ₅ , Li ₆ PS ₅ X, Li _9.6 P ₃ S _{12 and the} like. In addition, X is Cl, Br or I. The solid electrolyte contained in the solid electrolyte coating portion 23 may be only one type or two or more types.

The method for producing the solid electrolyte-coated fiber of the present invention is not particularly limited. A preferred production method is, for example, to put the fiber, the solid electrolyte forming raw material, and the organic solvent in a container, and react the solid electrolyte forming raw material in the organic solvent to form a solid electrolyte on the surface of the fiber. It is a method of covering. In this manufacturing method, fibers can be used in place of the fiber sheet used in the above-mentioned method for manufacturing an electrolyte sheet. In the case of heat treatment after the reaction for forming the solid electrolyte, the same method as in the above-mentioned method for producing an electrolyte sheet can be used, and the description thereof will be omitted.

By subjecting the solid electrolyte-coated fiber of the present invention to a conventionally known nonwoven fabric manufacturing process or the like, a nonwoven fabric containing a solid electrolyte-coated fiber can be produced. The obtained solid electrolyte-coated fiber-containing nonwoven fabric can be further subjected to a heat treatment step, a pressing step, or the like.

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples and Comparative Examples.

1. 1. In the production of non-woven fabric electrolyte sheets, glass fibers (fiber diameter: 0.3 μm, fiber length: about 0.1 to 1 mm) produced by subjecting B glass to the flame method as inorganic fibers, and polyester resin as organic fibers. A non-woven fabric (hereinafter referred to as "nonwoven fabric (N1)") obtained by wet-making using fibers (fiber diameter: 2 μm, fiber length: 3 mm) and then dip-coated with styrene / butadiene rubber as a binder is used. Using. This non-woven fabric (N1) contains inorganic fibers, organic fibers and a binder in proportions of 52% by mass, 37% by mass and 11% by mass, respectively, when the total of these is 100% by mass, and the void ratio is It is 73% by volume, has a thickness of 22 μm, and has a basis weight of 10 g / m ² .

2. 2. Production and Evaluation of Electrolyte Sheets Electrolyte sheets of Examples and Comparative Examples were produced using the above-mentioned non-woven fabric (N1) or the above-mentioned glass fibers, and various evaluations were performed.

Example 1
Under an argon atmosphere, charged with Li ₂ S powder of ethanol 5 ml, and stirred to obtain a Li ₂ S solution. Then, the polytetrafluoroethylene in the Petri dish, put and the Li ₂ S solution and a circular nonwoven diameter 30 mm (N1), allowed to stand for 30 minutes at 25 ° C., vacuum dried (0.99 ° C., 1 hour) Was done. Thus, the surface of the fibers of the nonwoven fabric (N1) Li 2 _S was obtained impregnated nuclear adhered nonwoven fabric.
Then, a Li ₂ S powder and _P 2 _{S 5} powder and LiI powders, 1: 1: 1 (molar ratio), and, Li ₂ This _P 2 _{S 5} powder was impregnated in the above nucleus adhesion nonwoven Each was weighed and mixed so as to have a molar ratio of 1/3 with respect to the total Li ₂ S composed of S and the above Li _{2 S powder.} Then, the ethyl propionate of the mixed powder and 10 ml, and stirred while irradiating ultrasonic waves, Li ₂ S powder _was dissolved P 2 _{S 5} powder and LiI powders.
Then, the obtained solution was put into a petri dish made of polytetrafluoroethylene, and then the above-mentioned non-woven fabric with nuclei was put in, and the mixture was allowed to stand at room temperature for 6 hours. Then, vacuum drying (170 ° C., 2 hours) was performed. As a result, a sheet (A1) with an electrolyte is obtained in which the voids of the nonwoven fabric (N1) are _{filled with the solid electrolyte Li 7} P ₂ S ₈ I (crystalline) and both sides are _{coated with Li 7} P ₂ S _{8 I.} rice field. The volume ratio of the non-woven fabric (N1) to the solid electrolyte in the sheet with electrolyte (A1) was 11:89. The mass ratio of the glass fiber and the solid electrolyte was 8:92.

A test piece obtained by punching the obtained sheet with electrolyte (A1) to φ10 mm with a punch is filled inside a tubular body (inner diameter 10 mm) made of polyetheretherketone (PEEK), and then a flat surface having a diameter of 10 mm. The test piece was inserted from both sides of the tubular body and pressed at 250 MPa with a hydraulic press to obtain an electrolyte sheet with a thickness of 52 μm. Then, in order to observe the cross section of this electrolyte sheet, the surface of the sheet was used under the conditions of a temperature of -70 ° C. and an acceleration voltage of 4 kW using a cross-section sample preparation device "IB-19520CCP" (model name) manufactured by JEOL Ltd. It was cut perpendicular to the stretching direction, and the image of FIG. 2 was obtained with a scanning electron microscope "JSM-7800F" (model name) manufactured by JEOL Ltd. Then, by the energy dispersive X-ray analysis method, mapping analysis on the Si element contained in the glass fiber constituting the nonwoven fabric (N1) was performed. The analysis target is the portion surrounded by the dotted line in FIG. 2 (horizontal: about 54 μm, vertical: about 52 μm). The image surrounded by the dotted line was cut out and shown in FIG. 3 as a mapping image of Si element (Si element map). In FIG. 3, the black portion is a portion having a Si element.

Based on this FIG. 3, the existence range of the Si element was determined by the following procedure using the software "ImageJ".
First, the Si element map of FIG. 3 was converted into an 8-bit grayscale image, which was binarized with a lower limit threshold value of 0 and an upper limit threshold value of 10. As a result, as the gray value of each pixel, the location where the Si element was present was converted to 255, and the location where the Si element was not present was converted to 0.
Next, the range was set so that the upper end to the lower end of the cross section of FIG. 3 fit exactly, and the profile of the selected range was created by using the "Plot profile" function of the above software, and the graph of FIG. 4 was obtained. In the profile of FIG. 4, the horizontal axis is the vertical distance of the image of FIG. 3, and the vertical axis is the average value of the horizontal gray values of the image of FIG. In this profile, the ratio of the region where the average value of the gray values in the horizontal direction is 51 or more (that is, the number of pixels determined to be the presence of the Si element is 20% or more) to the cross-sectional thickness is calculated to be 73. Was% (see Table 1).

In addition, the powder drop test, bending test and conductivity measurement were performed by the following methods, and the results are also shown in Table 1.
(1) Powder drop test The electrolyte sheet was finely moved on the black sheet, and at this time, whether or not the solid electrolyte powder fell was visually observed and the weight change was confirmed to determine the powder drop property. The weight change due to the weight loss was investigated by the following method. That is, the solid electrolyte sheet was punched into a circular shape (φ10 mm) by punching, and this was designated as “test piece A”. Then, the weight (mg) of the test piece A is measured, placed in a cylindrical screw tube bottle (Maruem Co., Ltd., No. 5, internal volume 20 ml), and the screw tube bottle is placed in the minor axis direction. (Left and right), shaken 200 times with an amplitude of 150 mm. Then, the test piece A was taken out, the weight (mg) was measured, the weight was measured, and the weight loss rate was calculated.
〇: No powder fell off ×: Powder fell and weight loss of 5% by mass or more was confirmed. (2) Bending test On a black sheet, the electrolyte sheet was placed in a columnar shape with a radius of 35 mm (R35). It was wound around a base material, and at this time, it was visually observed whether cracks, cracks, and powder falling occurred, and the bending resistance was determined.
〇: No cracks, cracks, or powder falling ×: Cracks, cracks, or powder falling occurred (3) Conductance measurement Using an electrolyte sheet as a test piece for conductivity measurement, a measurement unit (made of stainless steel) in an argon gas atmosphere. The conductivity at 25 ° C. was measured using an Impedance ANALYZER "S1260" (model name) manufactured by SOLATRON with the pins inserted in a PEEK tubular body inserted from both sides.

Example 2
Under an argon atmosphere, the Li ₂ S powder, the P ₂ S ₅ powder, and the Li I powder were weighed to a ratio of 3: 1: 1 (molar ratio) 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 (diameter 4 mm) were placed in a resin conical tube (capacity 50 ml), and the shaker "ASCM-1" (model name) manufactured by AS ONE Co., Ltd. was placed. ) Was shaken at 25 ° C. at 1500 times / minute for 3 hours to obtain a slurry (suspension) containing a precursor of _{the solid electrolyte Li 7} P ₂ S _{8 I.}
Then, in this slurry, 0.15 g of glass fiber (fiber diameter: 0.3 μm, fiber length: about 0.1 to 1 mm) produced by subjecting B glass to the flame method was well dispersed in ethyl propionate. The dispersion was added and mixed well. Then, this mixed solution was put into a petri dish made of polytetrafluoroethylene, allowed to stand at room temperature for 1 hour, and then vacuum dried (170 ° C., 2 hours). As a result, a sheet (A2) with an electrolyte was obtained in which glass fibers were contained as a dispersed phase in the matrix phase composed of the solid electrolyte Li ₇ P ₂ S _{8 I and the glass fibers did not protrude on both sides of the sheet.} The mass ratio of the glass fiber and the solid electrolyte in the sheet with electrolyte (A2) was 10:90.

Then, the sheet with an electrolyte (A2) was press-processed in the same manner as in Example 1 to obtain an electrolyte sheet having a thickness of 20 μm. Then, in the same manner as in Example 1, a graph (not shown) showing the Si profile in the thickness direction of the electrolyte sheet is created, and the average value of the gray values in the horizontal direction is 51 or more (that is, the location where the Si element is present). When the ratio of the area where the pixel determined to be (20% or more) to the cross-sectional thickness was determined, it was 100% (see Table 1).
Further, in the same manner as in Example 1, a powder drop test, a bending test and a conductivity measurement were performed, and the results are also shown in Table 1.

Comparative Example 1
Under an argon atmosphere, the Li ₂ S powder and the P ₂ S ₅ powder are weighed so as to have a molar ratio of 3: 1, and these powders, ethyl propionate, and zirconia balls are placed in a centrifuge tube and added. The shaking treatment was performed to obtain a slurry (suspension) containing a solid electrolyte precursor. Then, the zirconia balls were taken out from the centrifuge tube, dried under reduced pressure at 170 ° C. and desolubilized to obtain a solid electrolyte powder. The obtained solid electrolyte was confirmed by XRD to contain a peak due to the crystalline phase of _{Li 3} PS _4. The lithium ion conductivity of this solid electrolyte was 1.5 × 10 ^-4 S / cm (room temperature).
Next, in order to prepare a solid electrolyte-containing slurry, the solid electrolyte powder was ground with a pestle and a pestle until the average particle size was 10 μm or less. Then, the obtained solid electrolyte particles were dispersed in dehydrated heptane under an argon atmosphere to obtain a solid electrolyte-containing slurry. The mass ratio of the solid electrolyte particles and the dehydrated heptane in this solid electrolyte-containing slurry is 1: 1.

Then, using a four-sided film applicator manufactured by Allgood Co., Ltd., the solid electrolyte-containing slurry was applied to the nonwoven fabric (N1) having a size of 30 mm × 90 mm by the following operation.
The nonwoven fabric (N1) was placed on a fluororesin plate, and the gap between the nonwoven fabric (N1) and the applicator roll was set to 200 μm, and the solid electrolyte-containing slurry was applied to the one-sided surface of the nonwoven fabric (N1). After air-drying, the solid electrolyte-containing slurry was applied to the other surface of the nonwoven fabric (N1) under the same conditions and air-dried. Next, the obtained solid electrolyte-coated sheet was placed on a hot plate at 100 ° C. and desolubilized to obtain a sheet with an electrolyte (B1). The volume ratio of the non-woven fabric (N1) to the solid electrolyte in the sheet with electrolyte (B1) was 12:88. The mass ratio of the glass fiber and the solid electrolyte was 9:91.

Then, the sheet with an electrolyte (B1) was press-processed in the same manner as in Example 1 to obtain an electrolyte sheet having a thickness of 88 μm. Then, in order to observe the cross section of the obtained electrolyte sheet, the image of FIG. 5 was obtained with a scanning electron microscope in the same manner as in the electrolyte sheet of Example 1. Then, by the energy dispersive X-ray analysis method, mapping analysis on the Si element contained in the glass fiber constituting the nonwoven fabric (N1) was performed. The analysis target is the portion surrounded by the dotted line in FIG. 5 (horizontal: about 142 μm, vertical: about 88 μm). The image surrounded by the dotted line was cut out and shown in FIG. 6 as a Si element map. In FIG. 6, the black portion is a portion having a Si element. Next, in the same manner as in Example 1, the region where the average value of the gray values in the horizontal direction is 51 or more (that is, the number of pixels determined to be the presence of the Si element is 20% or more) is the cross section. When the ratio to the thickness was calculated, it was 50% (see Table 1).
Further, in the same manner as in Example 1, a powder drop test, a bending test and a conductivity measurement were performed, and the results are also shown in Table 1.

As is clear from Table 1, in Comparative Example 1, since the abundance ratio of the inorganic fibers in the electrolyte sheet was less than 60%, the desorption (powder drop) of the solid electrolyte was remarkable and the appearance was poor, and in the bending test. Desorption (powder drop) of the solid electrolyte was also confirmed. On the other hand, Examples 1 and 2 are examples of the electrolyte sheet of the present invention, and there was no desorption (powder drop) of the solid electrolyte, and no cracks or cracks were confirmed in the bending test.

The present invention is not limited to Examples 1 and 2 described above, and the electrolyte sheet may be obtained by improving individual steps.
For example, in Example 2, Li 2 _S powder, after obtaining a slurry containing P ₂ S ₅ powder and LiI powders, although mixed with a dispersion of glass fibers, glass fibers, during the preparation of the slurry may be produced the mixture was added, from the beginning, a glass fiber, Li 2 _S powder, used with P ₂ S ₅ powder and LiI powders, the mixture may be produced.

The electrolyte sheet of the present invention includes personal computers, home appliances such as cameras, power storage devices, portable electronic devices or communication devices such as mobile phones, electric tools such as power tools, electric bicycles, passenger cars such as electric vehicles, and wind power generation. It is suitable for forming an electrolyte layer for a lithium ion battery, which constitutes a stationary storage battery of a solar cell device, a watch, glasses, a wearable terminal, a drone, a flying object, a robot structure, etc., which make the best use of safety.

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

In an electrolyte sheet containing a plurality of inorganic fibers and a solid electrolyte,
An electrolyte sheet characterized in that the proportion of the inorganic fibers present is 60% or more in a cross section in the thickness direction cut perpendicular to the surface stretching direction of the electrolyte sheet.
The electrolyte sheet according to claim 1, wherein the content ratio of the solid electrolyte is 60 to 95% by mass when the total amount of the inorganic fibers and the solid electrolyte is 100% by mass.
The electrolyte sheet according to claim 1 or 2, wherein the inorganic fiber contains glass fiber.
The electrolyte sheet according to any one of claims 1 to 3, wherein the solid electrolyte contains a compound containing a lithium element, a phosphorus element and a sulfur element.
The electrolyte sheet according to any one of claims 1 to 3, wherein the solid electrolyte contains a compound containing a lithium element, a phosphorus element, a sulfur element and a halogen element.
The electrolyte sheet according to any one of claims 1 to 5, wherein the solid electrolyte has amorphous properties.
The electrolyte sheet according to any one of claims 1 to 5, wherein the solid electrolyte has crystallinity.
The electrolyte sheet according to any one of claims 1 to 7, wherein the inorganic fiber contains a fiber having a fiber diameter of 50 μm or less.
The electrolyte sheet according to any one of claims 1 to 8, wherein the ratio of voids is 20% or less when the cross section of the electrolyte sheet is viewed.
A product containing an electrolyte sheet, wherein the electrolyte sheet according to any one of claims 1 to 9 is housed in a package.
A lithium ion battery comprising the electrolyte sheet according to any one of claims 1 to 9.
A solid electrolyte-coated fiber comprising a fiber portion made of fibers and a solid electrolyte-coated layer containing a solid electrolyte and covering at least a part of the surface of the fiber portion.