Manufacturing method of sheet for solid state battery and manufacturing method of laminate used therein

Abstract

To provide a method for manufacturing a solid-state battery sheet capable of achieving excellent battery performance when used in a solid-state battery, and a method for manufacturing a laminate to be used in the method for manufacturing a solid-state battery sheet.SOLUTION: A method for manufacturing a solid-state battery sheet includes a step of preparing a first member M1 having a first support layer 11 and a first solid electrolyte layer 13, a step of preparing a second member M2 having a second support layer 12 and a second solid electrolyte layer 14, a step of obtaining a first laminate body 1A from the first member M1 and the second member M2 so that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 face each other via a porous base material 10, and a step of pressing the laminate 1A in the thickness direction to form a solid-state battery sheet 5A. In the solid-state battery sheet 5A, at least a part of the first solid electrolyte layer 13 and at least a part of the second solid electrolyte layer 14 are filled in pores H of the porous base material 10 and are in contact with each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a sheet for a solid state battery, and also to a method for producing a laminate used in the method for producing a sheet for a solid state battery. [Background technology]

[0002] Because solid-state batteries do not use flammable organic solvents, they can simplify safety devices, are superior in manufacturing cost and productivity, and can be stacked in series within the cell to achieve high voltage. In the solid electrolyte used in solid-state batteries, only lithium ions move, so side reactions caused by the movement of anions do not occur, and this is expected to lead to improved safety and durability.

[0003] A solid electrolyte sheet is used in the manufacture of solid-state batteries. For example, Patent Document 1 describes a method for manufacturing a solid electrolyte sheet having a porous substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-129307 Summary of the Invention [Problem to be solved by the invention]

[0005] As a method for manufacturing a solid electrolyte sheet having a porous substrate, there is a method in which a solid electrolyte material is attached to a porous substrate and filled (for example, Patent Document 1). However, further improvement in battery performance is required for a solid battery using a solid electrolyte sheet obtained by this method.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing a sheet for a solid battery that can exhibit good battery performance when used in a solid battery, and a method for manufacturing a laminate used in the method for manufacturing the sheet for a solid battery. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides the following method. [1] A method for producing a first sheet for a solid-state battery, The method comprises the steps of: (1a) providing a porous substrate; (1b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (1c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; (1d) stacking the first member and the second member with the porous substrate interposed between them so that the first solid electrolyte layer and the second solid electrolyte layer face each other to obtain a first laminate; and (1e) pressing the first laminate in the thickness direction to form the first sheet for a solid-state battery; Including, the method, wherein in the first sheet for a solid battery, at least a portion of the first solid electrolyte layer and at least a portion of the second solid electrolyte layer fill the pores of the porous substrate and are in contact with each other. [2] A method for producing a second sheet for a solid-state battery, The method comprises the steps of: (2a) providing a first porous substrate and a second porous substrate; (2b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (2c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; (2d) laminating the first porous substrate on the surface of the first member that faces the first solid electrolyte layer to obtain a third member; (2e) laminating the second porous substrate on the second solid electrolyte layer side of the second member to obtain a fourth member; (2f) stacking the third member and the fourth member so that the surface of the third member facing the first porous substrate and the surface of the fourth member facing the second porous substrate face each other to obtain a second laminate; and (2g) pressing the second laminate in the thickness direction to form the second solid-state battery sheet; Including, the method, wherein in the second sheet for a solid battery, at least a portion of the first solid electrolyte layer and at least a portion of the second solid electrolyte layer are filled in and in contact with the pores of the first porous substrate and the second porous substrate. [3] A method for producing the first laminate according to [1] above, comprising the following steps: (3a) providing a porous substrate; (3b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (3c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; and (3d) A step of stacking the first member and the second member with the porous substrate interposed between them so that the first solid electrolyte layer and the second solid electrolyte layer face each other to obtain a first laminate. The method comprising: [4] A method for producing the second laminate according to [2] above, comprising the following steps: (4a) providing a first porous substrate and a second porous substrate; (4b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (4c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; (4d) laminating the first porous substrate on the first solid electrolyte layer side of the first member to obtain a third member; (4e) laminating the second porous substrate on the second solid electrolyte layer side of the second member to obtain a fourth member; and (4f) A step of stacking the third member and the fourth member so that the surface of the third member facing the first porous substrate and the surface of the fourth member facing the second porous substrate face each other to form a second laminate. The method comprising: [Effects of the Invention]

[0008] According to the present invention, there are provided a method for manufacturing a sheet for a solid state battery that can exhibit good battery performance when used in a solid state battery, and a method for manufacturing a laminate used in the method for manufacturing the sheet for a solid state battery. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic process diagram showing a method for producing a laminate and a sheet for a solid state battery according to a first embodiment of the present invention. [Figure 2A] FIG. 2A is a schematic process diagram showing a method for producing a laminate and a sheet for a solid state battery according to a second embodiment of the present invention. [Figure 2B] FIG. 2B is a schematic process diagram (continuation of FIG. 2A) showing a method for producing a laminate and a sheet for a solid state battery according to a second embodiment of the present invention. [Figure 3A] FIG. 3A is a plan view of a laminate formed by the laminate manufacturing method according to the first and second embodiments of the present invention. [Figure 3B] FIG. 3B is a cross-sectional view taken along line AA in FIG. 3A. [Figure 4] FIG. 4 is a schematic diagram of an apparatus used in the method for producing a laminate according to the first embodiment of the present invention. [Figure 5A] FIG. 5A is a plan view of a sheet for a solid state battery formed by the method for manufacturing a sheet for a solid state battery according to the first and second embodiments of the present invention. [Figure 5B] FIG. 5B is a cross-sectional view taken along line AA in FIG. 5A. [Figure 6] FIG. 6 is a schematic diagram of an apparatus used in the method for producing a sheet for a solid state battery according to the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] <<Laminate manufacturing method>> Hereinafter, an embodiment of a method for producing a laminate according to the present invention will be described with reference to Figs. 1 to 3. Figs. 1(a) to 1(d) are schematic process diagrams showing steps 3a to 3d in a method for producing a laminate according to a first embodiment of the present invention. Figs. 2A(a) to 2A(e) and 2B(f) are schematic process diagrams showing steps 4a to 4f in a method for producing a laminate according to a second embodiment of the present invention. Fig. 3A is a plan view of laminates 1A and 1B obtained in steps 3d and 4f, and Fig. 3B is a cross-sectional view taken along line AA in Fig. 3A. In each drawing, X indicates the length direction, Y indicates the width direction Y, and Z indicates the thickness direction. The length direction X, width direction Y, and thickness direction Z are perpendicular to one another. The length direction X corresponds to the machine direction (MD) during the production of laminates 1A and 1B.

[0011] First Embodiment As shown in FIGS. 1(a) to 1(d), the method for producing the laminate 1A according to the first embodiment of the present invention includes the following steps: (3a) providing a porous substrate 10; (3b) preparing a first member M1 including a first support layer 11 and a first solid electrolyte layer 13 provided on one surface of the first support layer 11; (3c) preparing a second member (M2) including a second support layer (12) and a second solid electrolyte layer (14) provided on one surface of the second support layer (12); and (3d) A step of stacking the first member M1 and the second member M2 with the porous substrate 10 interposed between them so that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 face each other to obtain a laminate 1A. Includes.

[0012] The order in which steps 3a, 3b, and 3c are performed is not particularly limited. Step 3d is performed after steps 3a, 3b, and 3c.

[0013] According to the first embodiment of the present invention, the method for producing a laminate includes steps 3a to 3d, and therefore, it is possible to form a laminate for producing a sheet for a solid state battery that can exhibit good battery performance when used in a solid state battery. The reason for this effect is presumed to be as follows.

[0014] Conventionally, a method for manufacturing a laminate comprising a porous substrate and a solid electrolyte layer includes a method of forming a solid electrolyte layer on a porous substrate by applying or immersing a solid electrolyte to the porous substrate to obtain a laminate (see, for example, Patent Document 1). However, when applying a solid electrolyte to a porous substrate by applying or immersing, unevenness may occur on the surface of the solid electrolyte layer in the resulting laminate. When observing a cross section of the solid electrolyte layer in the thickness direction, this unevenness may result in the formation of through-holes that extend from the surface on which the positive electrode layer is disposed to the surface on which the negative electrode layer is disposed. Such through-holes may cause short circuits in the battery. The following is presumed to be the cause of the formation of such through-holes. First, when forming a solid electrolyte layer, a slurry containing a solid electrolyte and a solvent is dried to remove the solvent, and the volume of the solvent may shrink. This volume shrinkage is presumed to be significant when applying or immersing a solid electrolyte to a porous substrate.

[0015] Therefore, the present inventors have conducted extensive research into the above-mentioned problems and have focused on a process of attaching a solid electrolyte to a porous substrate by coating or immersion, thereby arriving at the present invention. Specifically, the present inventors have newly discovered that by laminating a preformed solid electrolyte layer on a porous substrate to obtain a laminate, the occurrence of through-holes in the solid electrolyte layer formed on the porous substrate can be reduced compared to when a solid electrolyte is attached to a porous substrate by coating or immersion. Furthermore, by pressing the laminate obtained by laminating a preformed solid electrolyte layer on a porous substrate in the thickness direction, the occurrence of through-holes in the solid electrolyte layer filled in the porous substrate can be reduced. Therefore, according to the first embodiment of the present invention, it is possible to reduce the occurrence of voids in the solid electrolyte layer formed on the porous substrate and the occurrence of through-holes in the solid electrolyte layer filled in the porous substrate. This reduces the occurrence of short circuits when a solid battery sheet obtained using the laminate is used in a solid battery, and as a result, it is presumed that the battery performance of the solid battery sheet can be improved.

[0016] <Process 3a> Step 3a is a step of preparing a porous substrate 10 as shown in FIG. 1(a).

[0017] The porous substrate 10 is preferably a substrate that can provide the solid electrolyte layer with self-supporting properties and strength. The porous substrate 10 may have a single-layer structure or a multi-layer structure.

[0018] The "substrate" in the porous substrate 10 includes a plate, foil, sheet, membrane, mesh, and the like. When the porous substrate 10 is in a sheet form, the porous substrate may be, for example, a fiber sheet. A fiber sheet is a structure in which fibers are formed into a sheet form. Examples of fiber sheets include nonwoven fabrics, woven fabrics, knitted fabrics, and paper. When the porous substrate 10 is in a membrane form, the porous substrate may be, for example, a microporous membrane.

[0019] The term "porous" in the porous substrate 10 refers to a state in which a large number of pores are present. The porous substrate 10 may be composed of a plurality of fibrous materials, as long as it has pores H that allow the first solid electrolyte layer 13 and the second solid electrolyte layer 14 to be filled and contact each other when a sheet for a solid battery, described later, is formed. That is, as shown in FIG. 1(a), the porous substrate 10 has pores H inside or on its surface that extend from one side to the other side of the porous substrate 10. The size of the pores H may be such that at least a portion of the first solid electrolyte layer 13 and the second solid electrolyte layer 14 are filled in the pores H when a sheet for a solid battery, described later, is formed. The pores H in the porous substrate 10 may be, for example, micropores, mesopores, or macropores. The pores H may be interconnected. Furthermore, when the porous substrate 10 is a fiber sheet, the term "porous" refers to a state in which voids are present in the gaps between fibers.

[0020] In the embodiment of the present invention, as will be described later, a fiber sheet (nonwoven fabric) is used as the porous substrate 10. Hereinafter, a nonwoven fabric will be described as an example of a fiber sheet.

[0021] There are various types of nonwoven fabrics depending on the type of fiber used in the production of the nonwoven fabric (fiber length, fiber diameter, fiber material, etc.), the type of production method (for example, web formation method, web fiber bonding method, etc.), etc. The nonwoven fabric used as the porous substrate 10 is not particularly limited as long as it can produce a desired laminate or sheet for a solid state battery. Examples of nonwoven fabrics include cross-fiber nonwoven fabrics, long-fiber nonwoven fabrics, short-fiber nonwoven fabrics, wet-laid nonwoven fabrics, dry-laid nonwoven fabrics, air-laid nonwoven fabrics, carded nonwoven fabrics, parallel-laid nonwoven fabrics, cross-laid nonwoven fabrics, random nonwoven fabrics, spunbonded nonwoven fabrics, meltblown nonwoven fabrics, flash-spun nonwoven fabrics, chemically bonded nonwoven fabrics, hydroentangled nonwoven fabrics, needle-punched nonwoven fabrics, stitch-bonded nonwoven fabrics, thermally bonded nonwoven fabrics, burst fiber nonwoven fabrics, tow-opened nonwoven fabrics, split fiber nonwoven fabrics, composite nonwoven fabrics, laminated nonwoven fabrics, coated nonwoven fabrics, and laminated nonwoven fabrics. Of these, cross-laid nonwoven fabrics are preferred. Cross-laid nonwoven fabrics are preferred because they allow for easy adjustment of the strength ratio in the length direction X and the width direction Y, the basis weight (basis weight), and the like. It is preferable to adjust the strength ratio in the length direction X and the width direction Y of cross-laid nonwoven fabrics uniformly. The basis weight of the cross-type nonwoven fabric may be low or high. An example of the cross-type nonwoven fabric is polyolefin mesh cloth (see JP 2007-259734 A). Note that the specific basis weight (basis weight) of the nonwoven fabric can be the same as that described in, for example, JP 2018-129307 A, and therefore will not be described here.

[0022] The material, porosity, air permeability, thickness, etc. constituting the porous substrate 10 can be the same as those of porous substrates used in general sheets for solid state batteries. For example, the porous substrate can be the same as the porous substrate described in JP 2018-129307 A, and therefore description thereof will be omitted here.

[0023] <Process 3b> Step 3b is a step of preparing a first member M1, as shown in FIG. 1(b).

[0024] The first member M1 is, for example, in the form of a sheet.

[0025] As shown in FIG. 1(b), the first member M1 includes a first support layer 11 and a first solid electrolyte layer 13 provided on one surface of the first support layer 11.

[0026] As shown in FIG. 1(b), the first member M1 may further include an electrode layer (cathode layer) 15 provided between the first support layer 11 and the first solid electrolyte layer 13. The cathode layer 15 is an optional layer and can be omitted. The present invention also encompasses embodiments in which the cathode layer 15 is omitted. The present invention also encompasses embodiments in which one or both of the cathode layer 15 and the anode layer 16 described below are provided, or in which neither are provided. When the cathode layer 15 is provided between the first support layer 11 and the first solid electrolyte layer 13, the first support layer 11 preferably functions as a cathode current collector. This is because the first support layer 11 functions as a cathode current collector, allowing a solid battery sheet obtained using the laminate 1A to be used as a solid battery.

[0027] When forming the laminate 1A, the first support layer 11 supports the first solid electrolyte layer 13 and the positive electrode layer 15. When forming a sheet for a solid battery using the laminate 1A, the first support layer 11 presses the first solid electrolyte layer 13 by a force applied to the first support layer 11, causing at least a portion of the first solid electrolyte layer 13 to fill the pores H of the porous substrate 10. The first support layer 11 may also be used as a positive electrode current collector as described above, or may be peeled off from the sheet for a solid battery described below as necessary. The material, thickness, etc. of the first support layer 11 can be appropriately selected taking into consideration the role, function, etc. of the first support layer 11. Examples of the first support layer 11 include a metal layer made of a simple metal, and a resin layer made of a resin such as a thermoplastic resin or a thermosetting resin. When the first support layer 11 functions as a positive electrode current collector, the material, thickness, etc. of the first support layer can be the same as, for example, the material, thickness, etc. of a positive electrode current collector used in a general solid state battery.

[0028] The first solid electrolyte layer 13 is formed on the surface of the positive electrode layer 15 (or on the surface of the first support layer 11 when the positive electrode layer 15 is omitted). The method for forming the first solid electrolyte layer 13 can be any general method for forming a solid electrolyte layer, and is not particularly limited. For example, the method for forming the first solid electrolyte layer 13 may include a method including a step of dissolving a solid electrolyte in a solvent, applying the solution to the surface of the positive electrode layer 15 or the surface of the first support layer 11, and drying the solution.

[0029] The first solid electrolyte layer 13 contains at least a solid electrolyte and may contain a binder as necessary. The first solid electrolyte layer 13 may contain one type of solid electrolyte or two or more types of solid electrolytes. The "solid electrolyte" is in powder or granular form. The content of the solid electrolyte in the first solid electrolyte layer 13 is not particularly limited, but is, for example, 50 mass % or more, preferably 70 mass % or more, and more preferably 90 mass % or more, based on the mass of the first solid electrolyte layer 13. The upper limit is 100 mass %.

[0030] The solid electrolyte can be appropriately selected from solid electrolytes commonly used in solid-state batteries (e.g., all-solid-state lithium-ion batteries). Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. In the present invention, it is preferable to use a sulfide solid electrolyte. The sulfide solid electrolyte is soft and therefore has excellent filling properties into the pores H of the porous substrate 10.

[0031] Examples of sulfide solid electrolytes include general sulfide solid electrolytes, such as solid electrolytes containing lithium, phosphorus, and sulfur. From the viewpoint of further improving lithium ion conductivity, the sulfide solid electrolyte is preferably made of a material having an argyrodite crystal structure. Other detailed descriptions of sulfide solid electrolytes are similar to those described in, for example, Japanese Patent No. 6595153, WO2019 / 009228, and JP2018-067552A, and therefore will not be repeated here.

[0032] The thickness of the first solid electrolyte layer 13 can be adjusted appropriately taking into consideration the ability of the solid electrolyte to fill the pores H of the porous substrate 10, the amount of solid electrolyte to be filled into the pores H of the porous substrate 10, etc. The thickness of the first solid electrolyte layer 13 is adjusted so that when a portion of the first solid electrolyte layer 13 fills the pores H of the porous substrate 10, the remainder of the first solid electrolyte layer 13 (the portion of the first solid electrolyte layer 13 that does not fill the pores H of the porous substrate 10) maintains its layer shape. The thickness of the first solid electrolyte layer 13 is, for example, 0.1 μm or more and 1000 μm or less.

[0033] When the positive electrode layer 15 is provided between the first support layer 11 and the first solid electrolyte layer 13, the positive electrode layer 15 is formed on the first support layer 11. The method for forming the positive electrode layer 15 is not particularly limited and may be a general method for forming a positive electrode layer. For example, the method for forming the positive electrode layer 15 may include a method including a step of applying a positive electrode mixture containing a positive electrode active material to the surface of the first support layer 11 and drying the applied mixture.

[0034] The positive electrode layer 15 contains a positive electrode active material and may contain a solid electrolyte, a conductive additive, a binder, etc. as necessary. The positive electrode layer 15 may contain one type of positive electrode active material, or may contain two or more types of positive electrode active materials. The positive electrode active material can be appropriately selected from positive electrode active materials commonly used in solid-state batteries (e.g., all-solid-state lithium-ion batteries). Examples of positive electrode active materials include metal oxides and metal sulfides. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0035] <Process 3c> Step 3c is a step of preparing a second member M2, as shown in FIG. 1(c).

[0036] As shown in FIG. 1( c ), the second member M2 includes a second support layer 12 and a second solid electrolyte layer 14 provided on one surface of the second support layer 12 .

[0037] As shown in FIG. 1(c), the second member M2 may further include an electrode layer (negative electrode layer) 16 provided between the second support layer 12 and the second solid electrolyte layer 14. The negative electrode layer 16 is a layer that is provided as needed and can be omitted. The present invention also encompasses embodiments in which the negative electrode layer 16 is omitted. When the negative electrode layer 16 is provided between the second support layer 12 and the second solid electrolyte layer 14, the second support layer 12 preferably functions as a negative electrode current collector. This is because the second support layer 12 functions as a negative electrode current collector, and thus a solid battery sheet obtained using the laminate 1A can be used as a solid battery.

[0038] The description of the second support layer 12 is omitted here because it is the same as that of the first support layer 11. The material constituting the second support layer 12, the thickness of the second support layer 12, etc. may be the same as or different from those of the first support layer 11. When the second support layer 12 functions as a negative electrode current collector, the material, thickness, etc. of the second support layer 12 can be the same as, for example, the material, thickness, etc. of a negative electrode current collector used in a general solid-state battery. An example of the negative electrode current collector is copper foil.

[0039] The description of the second solid electrolyte layer 14 is omitted here because it is similar to that of the first solid electrolyte layer 13. The material constituting the second solid electrolyte layer 14, the thickness of the second solid electrolyte layer 14, etc. may be the same as or different from those of the first solid electrolyte layer 13.

[0040] The negative electrode layer 16 contains a negative electrode active material and may contain a solid electrolyte, a conductive additive, a binder, etc. as necessary. The negative electrode layer 16 may contain one type of negative electrode active material, or may contain two or more types of negative electrode active materials. The negative electrode active material can be appropriately selected from negative electrode active materials commonly used in all-solid-state lithium-ion batteries. Examples of negative electrode active materials include carbon materials, metal materials, and silicon-based materials.

[0041] Other details of the second member M2 are the same as those of the first member described above, and therefore will not be described here.

[0042] <Process 3d> Step 3d is a step of obtaining a laminate 1A by stacking the first member M1 and the second member M2 with the porous substrate 10 interposed between them so that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 face each other, as shown in FIG. 1(d).

[0043] As shown in Fig. 3, the laminate 1A obtained in step 3d includes, in order, a first support layer 11, a positive electrode layer 15, a first solid electrolyte layer 13, a porous substrate 10, a second solid electrolyte layer 14, a negative electrode layer 16, and a second support layer 12. The positive electrode layer 15 and the negative electrode layer 16 are layers that are provided as needed and can be omitted. The present invention also encompasses embodiments in which the positive electrode layer 15 and / or the negative electrode layer 16 is omitted.

[0044] The stacking order of the porous substrate 10, the first member M1, and the second member M2 is not particularly limited as long as they are stacked so that the porous substrate 10 is located between the first solid electrolyte layer 13 and the second solid electrolyte layer 14. For example, the porous substrate 10 may be stacked on the second member M2 and then the first member M1 may be stacked thereon, the porous substrate 10 may be stacked on the first member M1 and then the second member M2 may be stacked thereon, or the first member M1 and the second member M2 may be stacked on the porous substrate 10 at the same time.

[0045] The productivity of the laminate 1A when the laminate 1A is formed by laminating a porous substrate 10, a first member M1, and a second member M2 that have been prepared in advance is superior to the productivity of the laminate 1A when the laminate 1A is formed by forming one of the first solid electrolyte layer 13 and the second solid electrolyte layer 14 on one surface of the porous substrate 10, and then forming the other of the first solid electrolyte layer 13 and the second solid electrolyte layer 14 on the other surface of the porous substrate 10. Furthermore, when the laminate 1A is formed by laminating a porous substrate 10, a first member M1, and a second member M2 that have been prepared in advance, the laminate 1A can be manufactured by a roll-to-roll method, as described below.

[0046] In step 3d, the laminate 1A may be pressed in the thickness direction as needed. The pressing can be performed, for example, by a roll press. The pressing here refers to pressing with a lower pressure than the pressing in step 1e of the method for producing a sheet for a solid battery, which will be described later. Specifically, the pressure is preferably such that a portion of the first solid electrolyte layer 13 filled in the pores H of the porous substrate 10 and a portion of the second solid electrolyte layer 14 filled in the pores H of the porous substrate 10 do not come into contact with each other within the porous substrate 10.

[0047] The pores H of the porous substrate 10 may be filled with a portion of the first solid electrolyte layer 13 and a portion of the second solid electrolyte layer 14 to the extent that they do not come into contact with each other within the porous substrate 10. Here, "to the extent that they (a portion of the first solid electrolyte layer 13 and a portion of the second solid electrolyte layer 14) do not come into contact with each other within the porous substrate 10" refers not only to a case where the first solid electrolyte layer 13 and the second solid electrolyte layer 14 do not come into complete contact with each other within the porous substrate 10, but also to a case where they come into slight contact with each other unintentionally.

[0048] The laminate 1A may optionally include an adhesive layer between the porous substrate 10 and the first solid electrolyte layer 13 and / or between the porous substrate 10 and the second solid electrolyte layer 14 to improve interlayer adhesion. The adhesive layer may be formed on at least one surface of the porous substrate 10, or may be formed on the surface of the first solid electrolyte layer 13 opposite the first support layer 11 and / or the surface of the second solid electrolyte layer 14 opposite the second support layer 12 in step 3b and / or step 3c described above. The material and formation method of the adhesive layer may be the same as those of a general adhesive layer. For example, the same material and formation method may be used as those described in JP 2018-129307 A, and therefore will not be described here.

[0049] <Roll-to-roll method> The laminate 1A is preferably produced by a roll-to-roll process, which allows the laminate 1A to be produced continuously and improves the productivity of the laminate 1A.

[0050] An embodiment of manufacturing the laminate 1A by a roll-to-roll method will be described below with reference to Fig. 4. Fig. 4 is a schematic diagram of an apparatus used in this embodiment.

[0051] 4, the porous substrate 10 may be transported by being continuously supplied from a supply reel 101 and continuously wound up by a take-up reel 50. During transport, the porous substrate 10 may be guided by a guide roll. The supply reel 101 may be rotatably supported, and the porous substrate 10 may be wound around the supply reel 101.

[0052] 4, the first support layer 11 may be transported by being continuously supplied from a supply reel 111 and continuously wound up by a take-up reel 50. During transport, the first support layer 11 may be guided by a guide roll. The supply reel 111 may be rotatably supported, and the first support layer 11 may be wound around the supply reel 111.

[0053] 4, a drying section 113 that dries the positive electrode mixture applied to one surface of the first support layer 11 by the application section 112, an application section 114 that applies a solid electrolyte layer-forming material, and a drying section 115 that dries the solid electrolyte layer-forming material applied by the application section 114 may be provided. The first support layer 11 is preferably subjected to treatments in the application section 112, the drying section 113, the application section 114, and the drying section 115 in sequence to form the first member M1. The solid electrolyte layer-forming material is, for example, a slurry containing a solid content (e.g., a solid electrolyte) and a solvent (e.g., an organic solvent).

[0054] 4, a drying section 123 that dries the negative electrode mixture applied to one surface of the second support layer 12 by the application section 122, an application section 124 that applies a solid electrolyte layer-forming material, and a drying section 125 that dries the solid electrolyte layer-forming material applied by the application section 124 may be provided. The second support layer 12 is preferably subjected to treatments in the application section 122, the drying section 123, the application section 124, and the drying section 125 in sequence, thereby forming a second member M2. Note that the second member M2 can be formed by a roll-to-roll process in the same manner as the first member M1 described above.

[0055] 4, a pair of press rolls 61, 62 may be provided on the transport path of the laminate 1A. The laminate 1A may be transported while being guided by guide rolls and continuously wound up by a take-up reel 50.

[0056] Second Embodiment As shown in FIGS. 2A(a) to 2A(e) and 2B(f), the method for producing the laminate 1B according to the second embodiment of the present invention includes the following steps: (4a) preparing a first porous substrate 10a and a second porous substrate 10b; (4b) preparing a first member M1 including a first support layer 11 and a first solid electrolyte layer 13 provided on one surface of the first support layer 11; (4c) preparing a second member M2 including a second support layer 12 and a second solid electrolyte layer 14 provided on one surface of the second support layer 12; (4d) a step of laminating a first porous substrate 10a on the surface of the first member M1 facing the first solid electrolyte layer 13 to obtain a third member M3; (4e) a step of laminating a second porous substrate 10b on the surface of the second member M2 facing the second solid electrolyte layer 14 to obtain a fourth member M4; (4f) A step of stacking the third member M3 and the fourth member M4 so that the surface of the third member M3 facing the first porous substrate 10a and the surface of the fourth member M4 facing the second porous substrate 10b to form the laminate 1B. Includes.

[0057] The order in which steps 4a, 4b, and 4c are performed is not particularly limited. Step 4d is performed after steps 4a and 4b, step 4e is performed after steps 4a and 4c, and step 4f is performed after steps 4d and 4e. The effects obtained by the second embodiment are similar to those of the first embodiment, which includes steps 3a to 3d, and therefore will not be described here.

[0058] The first embodiment, which includes steps 3a to 3d, uses one porous substrate 10, whereas the second embodiment, which includes steps 4a to 4f, uses two porous substrates 10a and 10b, but can be similar in other respects. Specifically, step 4a can be similar to step 3a, step 4b to step 3b, step 4c to step 3c, and steps 4d, 4e, and 4f to step 3d. Therefore, detailed description of steps 4a to 4f will be omitted.

[0059] The laminate 1B is preferably produced by a roll-to-roll method. The roll-to-roll method allows the laminate 1B to be produced continuously, thereby improving the productivity of the laminate 1B. The roll-to-roll method for producing the laminate 1B can be carried out in the same manner as for the laminate 1A, and therefore detailed description thereof will be omitted here.

[0060] <Method for manufacturing a sheet for a solid-state battery> Hereinafter, an embodiment of a method for producing a sheet for a solid battery according to the present invention will be described with reference to FIGS. 1, 2, and 5. FIGS. 1(a) to 1(e) are schematic process diagrams showing steps 1a to 1e in the method for producing a sheet for a solid battery according to a first embodiment of the present invention. FIGS. 2A(a) to 2A(e) and 2B(f) to 2B(g) are schematic process diagrams showing steps 2a to 2g in the method for producing a sheet for a solid battery according to a second embodiment of the present invention. FIG. 5A is a plan view of sheets for a solid battery 5A and 5B formed in steps 1e and 2g, and FIG. 5B is a cross-sectional view taken along line AA in FIG. 5A. In each drawing, X indicates the length direction, Y indicates the width direction Y, and Z indicates the thickness direction. The length direction X, width direction Y, and thickness direction Z are perpendicular to one another. The length direction X corresponds to the machine direction (MD) during the production of sheets for a solid battery 5A and 5B.

[0061] As shown in FIGS. 1(a) to 1(e), the method for producing a sheet for a solid state battery 5A according to the first embodiment of the present invention includes the following steps: (1a) providing a porous substrate 10; (1b) preparing a first member M1 including a first support layer 11 and a first solid electrolyte layer 13 provided on one surface of the first support layer 11; (1c) preparing a second member M2 including a second support layer 12 and a second solid electrolyte layer 14 provided on one surface of the second support layer 12; (1d) a step of stacking the first member M1 and the second member M2 with the porous substrate 10 interposed therebetween so that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 face each other to obtain a laminate 1A; and (1e) A step of pressing the laminate 1A in the thickness direction to form a sheet 5A for a solid-state battery Including, As shown in FIGS. 5A and 5B, in the solid state battery sheet 5A, at least a portion of the first solid electrolyte layer 13 and at least a portion of the second solid electrolyte layer 14 fill the pores H of the porous substrate 10 and are in contact with each other.

[0062] The effects obtained by the first embodiment of the present invention are the same as those described in the section on the method for manufacturing the laminate, and therefore will not be described here.

[0063] <Process 1a~Process 1d> Steps 1a to 1d are the same as steps 3a to 3d in the above-described method for producing a laminate, and therefore a description thereof will be omitted here.

[0064] <Process 1e> Step 1e is a step of pressing the laminate 1A in the thickness direction Z to form a sheet 5A for a solid state battery.

[0065] In step 1e, the laminate 1A is pressed in the thickness direction Z, whereby at least a portion of the first solid electrolyte layer 13 fills the pores H from one surface of the porous substrate 10, and at least a portion of the second solid electrolyte layer 14 fills the pores H from the other surface of the porous substrate 10, so that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact with each other within the porous substrate 10. Here, "the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact with each other within the porous substrate 10" means that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact with each other through the pores H of the porous substrate 10. However, it is preferable that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact with each other to such an extent that, when the sheet for solid battery 5 obtained in step 1e is used in a solid-state battery, the solid-state battery operates satisfactorily.

[0066] A portion of the first solid electrolyte layer 13 fills the pores H from one surface of the porous substrate 10, and a portion of the second solid electrolyte layer 14 fills the pores H from the other surface of the porous substrate 10, thereby preventing the solid electrolyte from filling the porous substrate 10 unevenly and the resulting formation of through-holes in the solid electrolyte filled in the porous substrate 10. This improves battery performance.

[0067] The remainder of the first solid electrolyte layer 13 (the portion of the first solid electrolyte layer 13 that did not fill the pores H of the porous substrate 10) and the remainder of the second solid electrolyte layer 14 (the portion of the second solid electrolyte layer 14 that did not fill the pores H of the porous substrate 10) remain on one side and the other side of the porous substrate 10 while maintaining their layer shapes, respectively, thereby preventing exposure of the porous substrate 10. This improves contact between the first solid electrolyte layer 13 and the positive electrode layer 15 and between the second solid electrolyte layer 14 and the negative electrode layer 16, thereby improving battery performance. In the first embodiment, when the thickness of the first solid electrolyte layer 13 in the first member M1 prepared in step 1b is defined as 1, the thickness of the remainder of the first solid electrolyte layer 13 in the solid battery sheet 5A obtained in step 1e may be, for example, 0.1 or more, 0.2 or more, 0.3 or more, or 0.5 or more. When the thickness of the second solid electrolyte layer 14 in the second member M2 prepared in step 1c is defined as 1, the thickness of the remaining portion of the second solid electrolyte layer 14 is omitted here because it can be set to the same numerical range as that of the first solid electrolyte layer 13. The thickness is the average value of the thicknesses at 10 arbitrarily selected locations.

[0068] The pressing method in step 1e is not particularly limited as long as it can press the laminate 1A in the thickness direction, and examples thereof include roll pressing. The pressure during pressing is preferably such that at least a portion of the first solid electrolyte layer 13 fills the pores H from one surface of the porous substrate 10, and at least a portion of the second solid electrolyte layer 14 fills the pores H from the other surface of the porous substrate 10, and the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact with each other within the porous substrate 10.

[0069] The pressing method in step 1e may be a method in which the laminate 1A is pressed while being heated, if necessary. Examples include HIP (Hot Isostatic Press), WiP (Warm Isostatic Press), and heated roll pressing. By pressing the laminate 1A while being heated in step 1e, the first solid electrolyte layer 13 and the second solid electrolyte layer 14 are more firmly adhered to the porous substrate 10, thereby forming a stable sheet. Furthermore, the first solid electrolyte layer 13 and the second solid electrolyte layer 14 are more firmly adhered to the porous substrate 10, thereby enabling the first support layer 11 and the second support layer 12 to be easily peeled from the solid battery sheet 5A. The heating temperature is not particularly limited, but is preferably 30°C or higher, more preferably 50°C or higher, and particularly preferably 70°C or higher. Meanwhile, the heating temperature is preferably 200°C or lower, more preferably 150°C or lower, and particularly preferably 100°C or lower.

[0070] The thickness of the porous substrate 10 may be reduced by pressing the laminate 1 in the thickness direction Z. Therefore, the thickness of the porous substrate 10 after pressing may be smaller than the thickness of the porous substrate 10 before pressing.

[0071] <Process 1f> The first embodiment of the present invention may include a step of peeling off the first support layer 11 and the second support layer 12 from the sheet for a solid state battery 5A, if necessary.

[0072] The first support layer 11 and the second support layer 12 can be peeled off, for example, by pressing the sheet for a solid battery 5A or by bending the sheet for a solid battery 5A.

[0073] The sheet 5A for a solid state battery can be used to manufacture a solid state battery. When the sheet 5A for a solid state battery is used to manufacture a solid state battery, the sheet 5A for a solid state battery may be cut into a desired shape. Note that such cutting may be performed at a stage prior to the sheet 5A for a solid state battery (for example, at the stage of manufacturing the laminate 1A, the sheet 5A for a solid state battery, etc.).

[0074] The solid-state battery is preferably a lithium solid-state battery. The lithium solid-state battery may be a primary battery or a secondary battery, but is preferably a lithium secondary battery. The solid-state battery includes not only a solid-state battery that does not contain any liquid or gel substance as an electrolyte, but also a battery that contains, for example, 50% by mass or less, 30% by mass or less, or 10% by mass or less of a liquid or gel substance as an electrolyte. Examples of the shape of the solid-state battery include a laminate type, a cylindrical type, and a prismatic type.

[0075] The solid-state battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer. The sheet 5A for a solid-state battery including the positive electrode layer and the negative electrode layer can be used as the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, which are components of a solid-state battery. When the first support layer 11 functions as a positive electrode current collector and the second support layer 12 functions as a negative electrode current collector, the sheet 5A for a solid-state battery itself can be used as a solid-state battery.

[0076] In an embodiment in which the positive electrode layer 15 and the negative electrode layer 16 are omitted, the sheet 5A for a solid battery can be used as a solid electrolyte layer, one of the components of a solid battery. The positive electrode layer of the solid battery can be formed on the surface S1 of the first solid electrolyte layer 13 of the sheet 5A for a solid battery, and the negative electrode layer of the solid battery can be formed on the surface S2 of the second solid electrolyte layer 14 of the sheet 5A for a solid battery. The embodiment in which the positive electrode layer 15 and the negative electrode layer 16 are omitted can also achieve improved battery performance, similar to the embodiment in which the positive electrode layer 15 and the negative electrode layer 16 are provided.

[0077] <Roll-to-roll method> The sheet for a solid state battery 5A is preferably produced by a roll-to-roll method, which allows the sheet for a solid state battery 5A to be produced continuously and improves the productivity of the sheet for a solid state battery 5A.

[0078] An embodiment in which a sheet 5A for a solid state battery is produced by a roll-to-roll method will be described below with reference to Fig. 6. Fig. 6 is a schematic diagram of an apparatus used in this embodiment.

[0079] As shown in FIG. 6 , a pair of press rolls 75 and 76 are provided on the transport path of the laminate 1A, and the laminate 1A is pressed by the press rolls 75 and 76 to obtain a sheet 5A for a solid battery. If necessary, the first support layer 11 and the second support layer 12 may be peeled off from the sheet 5A for a solid battery. For example, the sheet 5A for a solid battery may be transported while being guided by guide rolls 81, 82, and 83, thereby peeling off the first support layer 11 and the second support layer 12 from the sheet 5A for a solid battery. The peeled first support layer 11 may be continuously wound up by the take-up reel 72, the sheet 5A for a solid battery may be continuously wound up by the take-up reel 73, and the peeled second support layer 12 may be continuously wound up by the take-up reel 74.

[0080] Second Embodiment As shown in FIGS. 2A(a) to 2A(e) and 2B(f) to 2B(g), the method for producing a sheet for a solid battery 5B according to the second embodiment of the present invention includes the following steps: (2a) preparing a first porous substrate 10a and a second porous substrate 10b; (2b) preparing a first member M1 including a first support layer 11 and a first solid electrolyte layer 13 provided on one surface of the first support layer 11; (2c) preparing a second member M2 including a second support layer 12 and a second solid electrolyte layer 14 provided on one surface of the second support layer 12; (2d) a step of laminating a first porous substrate 10a on the surface of the first member M1 facing the first solid electrolyte layer 13 to obtain a third member M3; (2e) a step of laminating a second porous substrate 10b on the surface of the second member M2 facing the second solid electrolyte layer 14 to obtain a fourth member M4; (2f) a step of stacking the third member M3 and the fourth member M4 so that the surface of the third member M3 facing the first porous substrate 10a and the surface of the fourth member M4 facing the second porous substrate 10b to obtain a laminate 1B; and (2g) Step of pressing the laminate 1b in the thickness direction to form a sheet 5B for a solid state battery Including, As shown in FIGS. 5A and 5B, in the solid state battery sheet 5B, at least a portion of the first solid electrolyte layer 13 and at least a portion of the second solid electrolyte layer 14 fill in and contact with the pores H of the first porous substrate 10a and the second porous substrate 10b.

[0081] The effects obtained by the second embodiment of the present invention are the same as those described in the section on the method for manufacturing the laminated body, and therefore will not be described here.

[0082] <Process 2a~Process 2f> Steps 2a to 2f are the same as steps 4a to 4f in the above-described method for producing a laminate, and therefore a description thereof will be omitted here.

[0083] <Process 2g> Step 2g is the same as step 1e in the method for producing a sheet for a solid state battery described above, and therefore the description thereof will be omitted here.

[0084] The other explanations about the solid-state battery sheet, the solid-state battery, and the roll-to-roll method can be the same as those in the above-mentioned steps 1a to 1e, and therefore will not be repeated here. [Example]

[0085] The present invention will be described in more detail below with reference to examples.

[0086] ·Process 1a As a porous substrate, a polyolefin nonwoven fabric (thickness: 30 μm, material: polyethylene and polypropylene, basis weight: 5 g / m 2 ) was prepared.

[0087] ·Process 1b A first member was prepared, which included a first support layer (SUS foil, thickness: 10 μm) and a first solid electrolyte layer (composition: solid electrolyte / binder=99 / 1 (mass ratio), thickness: 35 μm) provided on one side of the first support layer.

[0088] ·Process 1c The second member was prepared in the same manner as the first member.

[0089] ·Process 1d The first member and the second member were laminated with the porous substrate interposed between them so that the first solid electrolyte layer and the second solid electrolyte layer faced each other, thereby obtaining a laminate (thickness: 120 μm).

[0090] ·Process 1e The resulting laminate was roll-pressed to obtain a sheet for a solid state battery (thickness: 45 μm).

[0091] ·evaluation The cross section of the obtained sheet for a solid battery in the thickness direction was visually observed from a cross section image obtained by SEM (scanning electron microscope). As a result, at least a part of the first solid electrolyte layer and at least a part of the second solid electrolyte layer filled the pores of the porous substrate and were in contact with each other. Furthermore, when compared with conventional sheets for a solid battery, it was found that the sheet for a solid battery of the present invention can effectively suppress the generation of through holes in the solid electrolyte layer. [Explanation of symbols]

[0092] 1A, 1B...Laminate 5A,5B...Solid battery sheet M1: First member M2: Second member M3: Third member M4...Fourth member 10,10a,10b...Porous base material 11. First support layer 12. Second Support Layer 13. First solid electrolyte layer 14...Second solid electrolyte layer 15. Positive electrode layer 16. Negative electrode layer 111,121···Supply reel 112, 122, 114, 124... Application section 113,123,115,125...Drying section

Claims

1. A method for producing a first solid-state battery sheet, comprising: The method comprises the steps of: (1a) providing a porous substrate; (1b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (1c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; (1d) stacking the first member and the second member so that the first solid electrolyte layer and the second solid electrolyte layer face each other via the porous substrate to obtain a first laminate; and (1e) A step of pressing the first laminate in the thickness direction to form the first sheet for a solid-state battery. Including, In the first sheet for a solid battery, at least a portion of the first solid electrolyte layer and at least a portion of the second solid electrolyte layer are filled in and in contact with the pores of the porous substrate; The method, wherein the porous substrate is a nonwoven fabric.

2. The method described in claim 1, wherein the first laminate has an electrode layer at least between the first support layer and the first solid electrolyte layer, or between the second support layer and the second solid electrolyte layer.

3. A method for producing a second solid-state battery sheet, comprising: The method comprises the steps of: (2a) providing a first porous substrate and a second porous substrate; (2b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (2c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; (2d) laminating the first porous substrate on the surface of the first member on the side of the first solid electrolyte layer to obtain a third member; (2e) laminating the second porous substrate on the second solid electrolyte layer side of the second member to obtain a fourth member; (2f) stacking the third member and the fourth member so that the surface of the third member facing the first porous substrate and the surface of the fourth member facing the second porous substrate to obtain a second laminate; and (2g) pressing the second laminate in the thickness direction to form the second solid-state battery sheet; Including, the method, wherein in the second solid battery sheet, at least a portion of the first solid electrolyte layer and at least a portion of the second solid electrolyte layer are filled in and in contact with the pores of the first porous substrate and the second porous substrate.

4. The method described in claim 3, wherein the second laminate has an electrode layer at least between the first support layer and the first solid electrolyte layer, or between the second support layer and the second solid electrolyte layer.

5. The method according to any one of claims 1 to 4, wherein the first solid electrolyte layer and the second solid electrolyte layer each contain a sulfide solid electrolyte.

6. 10. A method for producing the first laminate of claim 1, comprising the steps of: (3a) providing a porous substrate; (3b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (3c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; and (3d) A step of stacking the first member and the second member so that the first solid electrolyte layer and the second solid electrolyte layer face each other via the porous substrate to obtain a first laminate. Including, The method, wherein the porous substrate is a nonwoven fabric.

7. The method described in claim 6, wherein the first laminate has an electrode layer at least between the first support layer and the first solid electrolyte layer or between the second support layer and the second solid electrolyte layer.

8. 4. A method for producing the second laminate of claim 3, comprising the steps of: (4a) providing a first porous substrate and a second porous substrate; (4b) preparing a first member including a first support layer and a first solid electrolyte layer provided on one surface of the first support layer; (4c) preparing a second member including a second support layer and a second solid electrolyte layer provided on one surface of the second support layer; (4d) laminating the first porous substrate on the surface of the first member on the side of the first solid electrolyte layer to obtain a third member; (4e) laminating the second porous substrate on the second solid electrolyte layer side of the second member to obtain a fourth member; and (4f) A step of stacking the third member and the fourth member so that the surface of the third member facing the first porous substrate and the surface of the fourth member facing the second porous substrate to form a second laminate. The method comprising:

9. The method described in claim 8, wherein the second laminate has an electrode layer at least between the first support layer and the first solid electrolyte layer, or between the second support layer and the second solid electrolyte layer.

10. The method according to any one of claims 6 to 9, wherein the first solid electrolyte layer and the second solid electrolyte layer each contain a sulfide solid electrolyte.

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