JP7730651B2 - Manufacturing method of sheet for solid state battery and manufacturing method of laminate used therein - Google Patents

Description

The present invention relates to a method for manufacturing a sheet for a solid-state battery. The present invention also relates to a method for manufacturing a laminate used in the method for manufacturing a sheet for a solid-state battery.

Solid-state batteries do not use flammable organic solvents, which allows for simplified safety devices, leading to superior manufacturing costs and productivity. They also have the advantage of being able to be stacked in series within a cell to achieve higher voltages. The solid electrolyte used in solid-state batteries prevents the movement of ions other than lithium ions, eliminating side reactions caused by the movement of anions, and is expected to lead to improved safety and durability.

Solid electrolyte sheets are used in the manufacture of solid-state batteries. For example, Patent Document 1 describes a method for manufacturing a solid electrolyte sheet equipped with a porous substrate.

Japanese Patent Application Laid-Open No. 2018-129307

One method for manufacturing a solid electrolyte sheet with a porous substrate is to adhere and fill a solid electrolyte material to a porous substrate (see, for example, Patent Document 1). However, further improvements in battery performance are required for solid-state batteries using solid electrolyte sheets obtained by this method.

The present invention therefore aims to provide 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 manufacturing method for the sheet for a solid-state battery.

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, 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) laminating 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 a thickness direction to form the first sheet for a solid battery,
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 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) laminating the third member and the fourth member so that a surface of the third member facing the first porous substrate and a 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 a thickness direction to form the second solid state battery sheet,
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.
[3] A method for producing the first laminate according to [1], 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) 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.
[4] A method for producing the second laminate according to [2], 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 surface of the first member on the side of the first solid electrolyte layer to obtain a third member;
(4e) stacking the second porous substrate on the second solid electrolyte layer side of the second member to obtain a fourth member; and (4f) stacking the third member and the fourth member so that the first porous substrate side of the third member and the second porous substrate side of the fourth member face each other to form a second laminate.

The present invention provides 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 the solid-state battery.

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. 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. FIG. 2B is a schematic process diagram (continuation of FIG. 2A ) showing the method for producing a laminate and a sheet for a solid state battery according to the second embodiment of the present invention. 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. FIG. 3B is a cross-sectional view taken along line AA in FIG. 3A. 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. 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. FIG. 5B is a cross-sectional view taken along line AA of FIG. 5A. 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.

<<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 A-A 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.

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) preparing 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) 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.

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.

According to the first embodiment of the present invention, the laminate manufacturing method includes steps 3a to 3d, making it possible to form a laminate for manufacturing a solid-state battery sheet that can exhibit good battery performance when used in a solid-state battery. The reasons for this effect are presumed to be as follows:

Conventional methods for manufacturing laminates comprising a porous substrate and a solid electrolyte layer include forming a solid electrolyte layer on a porous substrate by applying or immersing the solid electrolyte to the porous substrate to obtain a laminate (see, for example, Patent Document 1). However, applying a solid electrolyte to a porous substrate by applying or immersing the solid electrolyte can result in unevenness 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, these unevenness can result in the formation of through-holes that extend from the surface on which the positive electrode layer is located to the surface on which the negative electrode layer is located. These through-holes may cause short circuits in the battery. The following is a possible 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, which can cause the volume of the solvent to shrink. This volume shrinkage is believed to be significant when applying or immersing the solid electrolyte to a porous substrate.

After extensive research into the above-mentioned issues, the inventors focused on a process of applying a solid electrolyte to a porous substrate by coating or immersion, leading to the present invention. Specifically, the inventors discovered that laminating a preformed solid electrolyte layer on a porous substrate to obtain a laminate can reduce the occurrence of through-holes in the solid electrolyte layer formed on the porous substrate compared to when applying a solid electrolyte to a porous substrate by coating or immersion. Furthermore, pressing the laminate obtained by laminating a preformed solid electrolyte layer on a porous substrate in the thickness direction can reduce the occurrence of through-holes in the solid electrolyte layer filled in the porous substrate. 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 it is presumed that this can result in improved battery performance of the solid battery sheet.

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

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

The term "substrate" in the porous substrate 10 encompasses plate-like, foil-like, sheet-like, membrane-like, mesh-like, and other shapes. When the porous substrate 10 is in sheet form, the porous substrate may be, for example, a fiber sheet. A fiber sheet is a structure formed by molding fibers into a sheet. Examples of fiber sheets include nonwoven fabric, woven fabric, knitted fabric, and paper. When the porous substrate 10 is in membrane form, the porous substrate may be, for example, a microporous membrane.

The term "porous" in the context of the porous substrate 10 refers to a state in which the porous substrate 10 has numerous pores. 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 fill and contact each other when the porous substrate 10 is formed into a sheet for a solid battery, as described below. 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 the first solid electrolyte layer 13 and the second solid electrolyte layer 14 are at least partially filled when the porous substrate 10 is formed into a sheet for a solid battery, as described below. 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 the fibers.

In the embodiments of the present invention, a fiber sheet (nonwoven fabric) is used as the porous substrate 10, as described below. Below, nonwoven fabric will be described as an example of a fiber sheet.

There are various types of nonwoven fabrics, depending on the type of fibers used in their manufacture (fiber length, fiber diameter, fiber material, etc.) and the type of manufacturing method (e.g., web formation method, web fiber bonding method, etc.). There are no particular restrictions on the nonwoven fabric used as the porous substrate 10, as long as it can produce the desired laminate or sheet for a solid-state battery. Examples of nonwoven fabrics include orthogonal 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 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 uniformly adjust the strength ratio in the length direction X and the width direction Y of a cross-laid nonwoven fabric. The basis weight of the cross-type nonwoven fabric may be low or high. An example of a cross-type nonwoven fabric is polyolefin mesh cloth (see JP 2007-259734 A). 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.

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

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

The first member M1 is, for example, sheet-shaped.

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 side of the first support layer 11.

As shown in FIG. 1(b), the first member M1 may further include an electrode layer (cathode layer) 15 disposed 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.

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 solid battery sheet using the laminate 1A, the force applied to the first support layer 11 presses the first solid electrolyte layer 13, 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 solid battery sheet described below as needed. The material, thickness, etc. of the first support layer 11 can be appropriately selected taking into account the role, function, etc. of the first support layer 11. Examples of the first support layer 11 include a metal layer composed of a simple metal, and a resin layer composed 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 the positive electrode current collector used in a general solid-state battery.

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 if 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 that includes 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.

The first solid electrolyte layer 13 contains at least a solid electrolyte and may contain a binder, if 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% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more, based on the mass of the first solid electrolyte layer 13. The upper limit is 100% by mass.

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 solid electrolytes 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. Because sulfide solid electrolytes are soft, they have excellent filling properties into the pores H of the porous substrate 10.

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

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.

When the positive electrode layer 15 is present 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 can be any common method for forming a positive electrode layer, and is not particularly limited. For example, the method for forming the positive electrode layer 15 includes a method that includes 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 it.

The positive electrode layer 15 contains a positive electrode active material and may also 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 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.

<Step 3c>
Step 3c is a step of preparing a second member M2, as shown in FIG.

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 side of the second support layer 12.

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 an optional layer 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, it is preferable that the second support layer 12 function as a negative electrode current collector. This is because the second support layer 12 functions as a negative electrode current collector, allowing a solid battery sheet obtained using the laminate 1A to be used as a solid battery.

The description of the second support layer 12 is omitted here, as it is similar to 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 a negative electrode current collector is copper foil.

The explanation of the second solid electrolyte layer 14 is omitted here, as 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.

The negative electrode layer 16 contains a negative electrode active material and may also 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 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.

The rest of the description of the second member M2 is the same as the description of the first member described above, so it will not be repeated here.

<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).

As shown in FIG. 3, the laminate 1A obtained in step 3d comprises, 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 are omitted.

The stacking order of the porous substrate 10, the first member M1, and the second member M2 is not particularly limited, as long as the porous substrate 10 is positioned 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 simultaneously.

The productivity of laminate 1A formed by laminating pre-prepared porous substrate 10, first member M1, and second member M2 is superior to the productivity of laminate 1A formed by forming one of first solid electrolyte layer 13 and second solid electrolyte layer 14 on one side of porous substrate 10 and then forming the other of first solid electrolyte layer 13 and second solid electrolyte layer 14 on the other side of porous substrate 10. Furthermore, when laminate 1A is formed by laminating pre-prepared porous substrate 10, first member M1, and second member M2, laminate 1A can be manufactured using a roll-to-roll process, as described below.

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. Note that the pressing here refers to a pressing with a lower pressure than the pressing in step 1e of the method for manufacturing 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.

A portion of the first solid electrolyte layer 13 and a portion of the second solid electrolyte layer 14 may fill the pores H of the porous substrate 10 to the extent that they do not come into contact 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 within the porous substrate 10" refers not only to cases where the first solid electrolyte layer 13 and the second solid electrolyte layer 14 do not come into complete contact within the porous substrate 10, but also to cases where they come into slight, unintentional contact.

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 adhesion between the layers. 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 general adhesive layers. For example, the same material and formation method may be used as described in JP 2018-129307 A, and therefore will not be described here.

<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.

Below, we will explain one embodiment of manufacturing laminate 1A using a roll-to-roll method, with reference to Figure 4. Figure 4 is a schematic diagram of the equipment used in this embodiment.

As shown in FIG. 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.

As shown in FIG. 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.

As shown in FIG. 4 , a drying unit 113 that dries the positive electrode mixture applied to one surface of the first support layer 11 by the application unit 112, an application unit 114 that applies the solid electrolyte layer-forming material, and a drying unit 115 that dries the solid electrolyte layer-forming material applied by the application unit 114 may be provided. It is preferable that the first support layer 11 be sequentially processed by the application unit 112, the drying unit 113, the application unit 114, and the drying unit 115 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).

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

As shown in FIG. 4, a pair of press rolls 61, 62 may be provided on the transport path of the laminate 1A. Furthermore, the laminate 1A may be transported while being guided by guide rolls and continuously wound up by a take-up reel 50.

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) The method includes 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.

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.

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 is otherwise similar. 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, a detailed description of steps 4a to 4f will be omitted.

Laminate 1B is preferably manufactured using a roll-to-roll process. This allows laminate 1B to be manufactured continuously, improving the productivity of laminate 1B. Roll-to-roll manufacturing of laminate 1B can be carried out in the same manner as laminate 1A, so a detailed description will be omitted here.

<Method for manufacturing a sheet for a solid-state battery>
Hereinafter, an embodiment of a method for manufacturing 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 illustrating steps 1a to 1e in a method for manufacturing 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 illustrating steps 2a to 2g in a method for manufacturing a sheet for a solid battery according to a second embodiment of the present invention. FIG. 5A is a plan view of solid battery sheets 5A and 5B formed in steps 1e and 2g, and FIG. 5B is a cross-sectional view taken along line A-A 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 manufacture of the sheets for solid batteries 5A and 5B.

As shown in FIGS. 1( a ) to 1 ( e ), the method for producing a sheet for a solid battery 5A according to the first embodiment of the present invention includes the following steps:
(1a) preparing 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) laminating 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) pressing the laminate 1A in the thickness direction to form a sheet for a solid battery 5A,
As shown in FIGS. 5A and 5B , in the solid 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.

The effects obtained by the first embodiment of the present invention are the same as those described in the section on the laminate manufacturing method above, so further description will be omitted here.

<Steps 1a to 1d>
Steps 1a to 1d are the same as steps 3a to 3d in the above-described method for producing a laminate, and therefore will not be described here.

<Step 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.

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 side of the porous substrate 10, and at least a portion of the second solid electrolyte layer 14 fills the pores H from the other side of the porous substrate 10, so that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact within the porous substrate 10. Here, "the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact within the porous substrate 10" means that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 are in 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 are in contact with each other to such an extent that, when the solid battery sheet 5 obtained in step 1e is used in a solid battery, the solid battery operates satisfactorily.

By filling a portion of the first solid electrolyte layer 13 into the pores H from one side of the porous substrate 10 and a portion of the second solid electrolyte layer 14 into the pores H from the other side of the porous substrate 10, it is possible to prevent uneven filling of the solid electrolyte into the porous substrate 10 and the resulting formation of through-holes in the solid electrolyte filled in the porous substrate 10. This improves battery performance.

The remaining portions 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 remaining portions 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 and the other surfaces of the porous substrate 10 while maintaining their layer configurations, 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 remaining portion 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. Note that when the thickness of the second solid electrolyte layer 14 in the second member M2 prepared in step 1c is taken as 1, the thickness of the remaining portion of the second solid electrolyte layer 14 can be the same as the numerical range for the first solid electrolyte layer 13 described above, and therefore is omitted here. Note that the above thickness is the average value of the thicknesses at 10 arbitrarily selected locations.

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. Furthermore, the pressure applied during pressing is preferably such that at least a portion of the first solid electrolyte layer 13 fills the pores H from one side of the porous substrate 10, and at least a portion of the second solid electrolyte layer 14 fills the pores H from the other side of the porous substrate 10, so that the first solid electrolyte layer 13 and the second solid electrolyte layer 14 come into contact within the porous substrate 10.

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, resulting in the formation of a stable sheet. Furthermore, the stronger adhesion between the first solid electrolyte layer 13 and the second solid electrolyte layer 14 and the porous substrate 10 allows 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.

Note that the thickness of the porous substrate 10 may decrease when the laminate 1 is pressed 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.

<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 solid state battery 5A, if necessary.

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

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

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. Solid-state batteries include solid-state batteries that do not contain any liquid or gel-like substances as electrolytes, as well as batteries that contain, for example, 50% by mass or less, 30% by mass or less, or 10% by mass or less of liquid or gel-like substances as electrolytes. Examples of solid-state battery shapes include laminated, cylindrical, and prismatic types.

The solid-state battery comprises 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 solid-state battery sheet 5A, which comprises 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. Furthermore, 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 solid-state battery sheet 5A itself can be used as a solid-state battery.

In an embodiment in which the positive electrode layer 15 and the negative electrode layer 16 are omitted, the solid battery sheet 5A can be used as a solid electrolyte layer, one of the components of the 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 solid battery sheet 5A, 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 solid battery sheet 5A. Similar to the embodiment in which the positive electrode layer 15 and the negative electrode layer 16 are provided, the embodiment in which the positive electrode layer 15 and the negative electrode layer 16 are omitted can also achieve improved battery performance.

<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.

Below, an embodiment of manufacturing a solid state battery sheet 5A using a roll-to-roll method will be described with reference to Figure 6. Figure 6 is a schematic diagram of the apparatus used in this embodiment.

As shown in FIG. 6 , a pair of press rolls 75, 76 are provided on the transport path of the laminate 1A, and the laminate 1A can be pressed with the press rolls 75, 76 to obtain a solid state battery sheet 5A. If necessary, the first support layer 11 and the second support layer 12 may be peeled off from the solid state battery sheet 5A. For example, the solid state battery sheet 5A 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 solid state battery sheet 5A. The peeled first support layer 11 may be continuously wound up by the take-up reel 72, the solid state battery sheet 5A 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.

Second Embodiment
As shown in FIGS. 2A(a) to 2A(e) and 2B(f) to 2B(g), the method for producing the sheet for solid state 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) laminating 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) pressing the laminate 1b in the thickness direction to form a sheet 5B for a solid battery,
As shown in FIGS. 5A and 5B , in the solid 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 the pores H of the first porous substrate 10 a and the second porous substrate 10 b and are in contact with each other.

The effects obtained by the second embodiment of the present invention are similar to those described in the section on the laminate manufacturing method above, so further description will be omitted here.

<Steps 2a to 2f>
Steps 2a to 2f are the same as steps 4a to 4f in the above-described method for producing a laminate, and therefore will not be described here.

<Step 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.

Note that explanations of other solid-state battery sheets, solid-state batteries, and roll-to-roll processes can be similar to those for steps 1a to 1e described above, and therefore will not be repeated here.

The present invention will be explained in more detail below through examples.

・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.

・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 surface side of the first support layer.

・Process 1c
A second member was prepared in the same manner as the first member.

・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).

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

Evaluation: The cross section of the obtained solid battery sheet in the thickness direction was visually observed from a cross-sectional 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 solid battery sheets, it was found that the solid battery sheet of the present invention can effectively suppress the occurrence of through holes in the solid electrolyte layer.

DESCRIPTION OF SYMBOLS 1A, 1B... Laminate 5A, 5B... Sheet for solid battery M1... First member M2... Second member M3... Third member M4... Fourth member 10, 10a, 10b... Porous substrate 11... First support layer 12... Second support layer 13... First solid electrolyte layer 14... Second solid electrolyte layer 15... Cathode layer 16... Negative electrode layer 111, 121... Supply reel 112, 122, 114, 124... Coating section 113, 123, 115, 125... Drying section

Claims (10)

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) laminating 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 a thickness direction to form the first sheet for a solid battery,
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 . 10. The method of claim 1, wherein the first stack comprises an electrode layer between at least one of the first support layer and the first solid electrolyte layer or the second support layer and the second solid electrolyte layer. A method for producing a second sheet for a solid-state battery, 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) laminating the third member and the fourth member so that a surface of the third member facing the first porous substrate and a 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 a thickness direction to form the second solid state battery sheet,
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 of claim 3, wherein the second stack comprises an electrode layer between at least one of the first support layer and the first solid electrolyte layer or the second support layer and the second solid electrolyte layer. 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. 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) 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 , wherein the porous substrate is a nonwoven fabric . 7. The method of claim 6, wherein the first stack comprises an electrode layer between at least one of the first support layer and the first solid electrolyte layer or the second support layer and the second solid electrolyte layer. 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) stacking the second porous substrate on the second solid electrolyte layer side of the second member to obtain a fourth member; and (4f) stacking the third member and the fourth member so that the first porous substrate side of the third member and the second porous substrate side of the fourth member face each other to form a second laminate. 9. The method of claim 8, wherein the second stack comprises an electrode layer between at least one of the first support layer and the first solid electrolyte layer or the second support layer and the second solid electrolyte layer. 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.