Solid electrolyte-containing sheet and method for producing same

Abstract

This solid electrolyte-containing sheet comprises a first porous substrate and a second porous substrate. A high-concentration binder region is formed at an interface portion between the first porous substrate and the second porous substrate. The high-concentration binder region contains the binder at a higher concentration than other regions in the first porous substrate and the second porous substrate.

Description

Solid electrolyte-containing sheet and method for manufacturing the same

[0001] The present invention relates to a solid electrolyte-containing sheet and a method for manufacturing the same.

[0002] As a secondary battery such as a lithium-ion battery, one using a solid electrolyte is known. As such a secondary battery, there is one having a configuration in which a solid electrolyte is supported by a sheet-like porous substrate. In this specification, such a sheet is referred to as a "solid electrolyte-containing sheet". The solid electrolyte is usually in powder form. By supporting the solid electrolyte on the porous substrate, the solid electrolyte can be handled as a self-supporting film, making it easier to handle during manufacturing and the like.

[0003] In relation to the above, Japanese Patent Application Laid-Open No. 2020-107449 discloses "a solid electrolyte laminated sheet including a plurality of supports, each of the supports being a self-supporting sheet filled with a solid electrolyte, the self-supporting sheet being a laminate, one outermost layer being a self-supporting sheet filled with a solid electrolyte that is difficult to be oxidized, and the other outermost layer being a self-supporting sheet filled with a solid electrolyte that is difficult to be reduced, the solid electrolyte laminated sheet".

[0004] Incidentally, in the solid electrolyte-containing sheet, the porosity of the porous substrate may preferably be large. Here, the porosity of the porous substrate refers to the porosity of the porous substrate itself, that is, the porosity before being filled with the solid electrolyte. For example, if the porosity of the porous substrate is large, the space for filling the solid electrolyte becomes large. Therefore, in terms of space, the solid electrolyte can be densely filled. As a result, battery characteristics can be improved.

[0005] However, in reality, when the porosity of the porous substrate is large, it becomes difficult to fill the solid electrolyte. This is because when filling the solid electrolyte, the solid electrolyte supplied to the porous substrate flows out and it becomes difficult to be retained in the pores of the porous substrate.

[0006] Therefore, an object of the present invention is to provide a technique capable of densely filling a solid electrolyte into a porous substrate even when the porosity is large.

[0007] In one aspect, the solid electrolyte-containing sheet according to the present invention comprises a first porous substrate filled with a solid electrolyte, and a second porous substrate filled with a solid electrolyte and disposed on the first porous substrate so as to be in contact with the first porous substrate. The first porous substrate and the second porous substrate further contain a binder. A high-concentration binder region is formed at the interface between the first porous substrate and the second porous substrate. The high-concentration binder region is a region in which the binder is contained at a higher concentration than in other regions of the first porous substrate and the second porous substrate.

[0008] Figure 1 is a schematic cross-sectional view showing a solid electrolyte-containing sheet according to an embodiment. Figure 2 is a schematic cross-sectional view showing the state of a solid electrolyte-containing sheet during manufacturing according to a reference example. Figure 3 is a schematic cross-sectional view showing the state of a solid electrolyte-containing sheet during manufacturing according to an embodiment. Figure 4 is a schematic diagram showing a modified example 1. Figure 5 is a schematic cross-sectional view showing a solid electrolyte-containing sheet according to a modified example 2. Figure 6 is a schematic cross-sectional view showing a high-concentration binder region according to a modified example 5. Figure 7 is a schematic diagram showing an example of a binder arrangement method.

[0009] Embodiments of the present invention will be described below with reference to the drawings.

[0010] Figure 1 is a schematic cross-sectional view showing a solid electrolyte-containing sheet 1 according to this embodiment. This solid electrolyte-containing sheet 1 is used as an electrolyte layer in a lithium-ion secondary battery. That is, the solid electrolyte-containing sheet 1 is placed between a positive electrode and a negative electrode (not shown) and used in a lithium-ion secondary battery.

[0011] As shown in Figure 1, the solid electrolyte-containing sheet 1 comprises a first porous substrate 2-1 and a second porous substrate 2-2. The second porous substrate 2-2 is placed on the first porous substrate 2-1 so as to be in contact with the first porous substrate 2-1. The solid electrolyte 4 is filled into each of the first porous substrate 2-1 and the second porous substrate 2-2.

[0012] The first porous substrate 2-1 and the second porous substrate 2-2 further contain a binder. The binder is impregnated into the first porous substrate 2-1 and the second porous substrate 2-2. Here, a high-concentration binder region 3 is formed at the interface between the first porous substrate 2-1 and the second porous substrate 2-2. The high-concentration binder region 3 is a region in which the binder is contained at a higher concentration than in other regions of the first porous substrate 2-1 and the second porous substrate 2-2.

[0013] According to the above configuration, even if the porosity of each porous substrate (2-1 and 2-2) is large, the solid electrolyte 4 can be densely packed. This point will be explained below with reference to an example.

[0014] Figure 2 is a schematic cross-sectional view showing the structure of a solid electrolyte-containing sheet during manufacturing according to a reference example. Figure 2 schematically depicts the structure when filling with solid electrolyte 4. In the reference example, a single porous substrate 2 is used. Unlike this embodiment, a high-concentration binder region 3 is not provided. In this reference example, if the porosity of the porous substrate 2 is large, the supplied solid electrolyte 4 tends to leak out when filling with solid electrolyte 4. As a result, pinholes are likely to occur, making it difficult to densely fill with solid electrolyte 4.

[0015] On the other hand, Figure 3 is a schematic cross-sectional view showing the structure during the manufacturing of the solid electrolyte-containing sheet according to this embodiment. When manufacturing the solid electrolyte-containing sheet 1 according to this embodiment, first, the first porous substrate 2-1 and the second porous substrate 2-2 are bonded together so that a high-concentration binder region 3 is formed. Then, as shown in Figure 3, the solid electrolyte 4 is filled into each porous substrate 2 (2-1 and 2-2). At this time, the high-concentration binder region 3 functions as a wall. Therefore, the supplied solid electrolyte 4 is easily accumulated and difficult to leak out. This suppresses pinholes and allows the solid electrolyte 4 to be densely packed.

[0016] The above is an overview of this embodiment. Next, preferred embodiments and detailed configurations of this embodiment will be described.

[0017] [Porous Substrate] First, the porous substrates 2 (2-1 and 2-2) will be described. The first porous substrate 2-1 and the second porous substrate 2-2 are not particularly limited as long as they can be filled with the solid electrolyte 4. For example, nonwoven fabric can be used as each porous substrate 2. If nonwoven fabric is used, the solid electrolyte-containing sheet 1 can be produced by roll-to-roll, thereby improving productivity. Examples of nonwoven fabrics include PET nonwoven fabric.

[0018] The thickness of each porous substrate 2 is not particularly limited, but is, for example, 1 to 50 μm, preferably 3 to 20 μm.

[0019] Below, the porous substrate 2 (2-1 and 2-2) will be explained further with reference to three modified examples.

[0020] (Modification 1) Figure 4 is a schematic diagram showing Modification 1. Figure 4 schematically shows the configuration of the interface between the first porous substrate 2-1 and the second porous substrate 2-2. In this modification, the first porous substrate 2-1 and the second porous substrate 2-2 are joined together such that parts of them interlock.

[0021] According to this modified example, gaps are less likely to form between the first porous substrate 2-1 and the second porous substrate 2-2, making it difficult for a resistance layer to form. As a result, when the solid electrolyte-containing sheet 1 is used in a secondary battery, good battery characteristics can be obtained.

[0022] To obtain the solid electrolyte-containing sheet according to this modified example, for example, nonwoven fabrics can be used as the first porous substrate 2-1 and the second porous substrate 2-2, respectively. When the nonwoven fabrics are bonded together under pressure, the fibers contained in the nonwoven fabrics interlock at the interface between the first porous substrate 2-1 and the second porous substrate 2-2. As a result, the configuration according to this modified example can be obtained.

[0023] (Variation 2) Next, let's explain Variation 2.

[0024] In this embodiment, the first porous substrate 2-1 and the second porous substrate 2-2 may be formed from the same material, or they may be formed from different materials. However, in the electrolyte layer of a secondary battery, the required properties may differ between the portion near the positive electrode and the portion near the negative electrode. By using different materials for the first porous substrate 2-1 and the second porous substrate 2-2, the properties of the solid electrolyte-containing sheet 1 can be made different on the positive electrode side and the negative electrode side. Therefore, a solid electrolyte-containing sheet 1 having appropriate properties in both the portion near the positive electrode and the portion near the negative electrode can be obtained. Thus, in this modified example, the first porous substrate 2-1 and the second porous substrate 2-2 are formed from different materials.

[0025] Figure 5 is a schematic cross-sectional view showing a solid electrolyte-containing sheet 1 according to Modification 2. Figure 5 shows an example of the solid electrolyte-containing sheet 1 being combined with a positive electrode 5 and a negative electrode 6. That is, Figure 5 shows a cross-section of a secondary battery including the solid electrolyte-containing sheet 1. The solid electrolyte-containing sheet 1 is combined with the positive electrode 5 and the negative electrode 6 such that one of the first porous substrate 2-1 and the second porous substrate 2-2 is in contact with the negative electrode 6 and the other is in contact with the positive electrode 5.

[0026] Here, of the first porous substrate 2-1 and the second porous substrate 2-2, the porous substrate 2 on the negative electrode 6 side is referred to as the "negative electrode side porous substrate," and the porous substrate 2 on the positive electrode 5 side is referred to as the "positive electrode side porous substrate" (the same applies to other variations described below). In the example shown in Figure 5, the first porous substrate 2-1 is the negative electrode side porous substrate, and the second porous substrate 2-2 is the positive electrode side porous substrate.

[0027] In this modified example, the negative electrode porous substrate (first porous substrate 2-1) is made of a material with higher reduction resistance than the positive electrode porous substrate (second porous substrate 2-2). Furthermore, the positive electrode porous substrate (second porous substrate 2-2) is made of a material with higher oxidation resistance than the negative electrode porous substrate (first porous substrate 2-1).

[0028] According to this modified version, stable charge-discharge cycle characteristics can be achieved when used as a secondary battery. In the electrolyte layer used in a secondary battery, high oxidation resistance is required near the positive electrode from the viewpoint of stability during charge and discharge. On the other hand, high reduction resistance is required near the negative electrode 6. According to this modified version, a material with high oxidation resistance is used near the positive electrode 5, and a material with high reduction resistance is used near the negative electrode 6, so the stability of the solid electrolyte-containing sheet 1 during charge and discharge can be increased. As a result, stable charge-discharge cycle characteristics are achieved.

[0029] Furthermore, the relative oxidation resistance of the porous substrates 2 can be determined based on the oxidation potential of each porous substrate 2. Similarly, the relative reduction resistance can also be determined based on the reduction potential of each porous substrate 2.

[0030] Furthermore, in this modified example, the porous substrate on the negative electrode side can be made of polyolefins such as polyethylene and polypropylene. The porous substrate on the positive electrode side can be made of polytetrafluoroethylene, polyimide, polyphenylene oxide, etc.

[0031] (Modification 3) Next, Modification 3 will be described. In this modification, the first porous substrate 2-1 and the second porous substrate 2-2 have different porosities. Here, "porosity" refers to the porosity of the porous substrate itself, as described above, and means the porosity before the solid electrolyte and binder are filled in.

[0032] Specifically, the porous substrate on the negative electrode side has a higher porosity than the porous substrate on the positive electrode side.

[0033] This modified version can suppress short circuits. Specifically, if the porosity of the porous substrate 2 is large, the amount of solid electrolyte that can be packed into it can be increased. Therefore, according to this modified version, the solid electrolyte can be densely packed into the porous substrate on the negative electrode side. This can reduce the resistance (ion conduction resistance) near the negative electrode in the electrolyte layer. If the resistance near the negative electrode in the electrolyte layer is large, unintended lithium may be deposited in the electrolyte layer during charging and discharging. Unintended lithium deposition can cause short circuits. In contrast, according to this modified version, since the porosity of the porous substrate on the negative electrode side is large, the solid electrolyte can be densely packed into the porous substrate on the negative electrode side, the resistance near the negative electrode can be reduced, unintended lithium deposition can be prevented, and short circuits can be suppressed.

[0034] [Solid Electrolyte] Next, we will explain the solid electrolyte 4. The solid electrolyte 4 is not particularly limited and can be any material that functions as an electrolyte in a secondary battery.

[0035] (Modification 4) A preferred embodiment of the solid electrolyte 4 will be described as Modification 4. In this modification, different solid electrolytes 4 are filled in the first porous substrate 2-1 and the second porous substrate 2-2. For convenience of explanation, the solid electrolyte filled in the negative electrode side porous substrate will be referred to as the "negative electrode side solid electrolyte." The solid electrolyte filled in the positive electrode side porous substrate will be referred to as the "positive electrode side solid electrolyte." In this modification, the negative electrode side solid electrolyte has higher reduction resistance than the positive electrode side solid electrolyte, and the positive electrode side solid electrolyte has higher oxidation resistance than the negative electrode side solid electrolyte.

[0036] As explained in Modification Example 2, from the viewpoint of stability during charging and discharging, the electrolyte layer requires high oxidation resistance near the positive electrode and high reduction resistance near the negative electrode. Therefore, by using a material with high reduction resistance as the solid electrolyte on the negative electrode side and a material with high oxidation resistance as the solid electrolyte on the positive electrode side, a solid electrolyte-containing sheet 1 with desirable properties on both the positive and negative electrode sides can be obtained.

[0037] Examples of solid electrolytes with high reduction resistance (negative electrode solid electrolyte) include LiPON and LLZO. On the other hand, examples of solid electrolytes with high oxidation resistance (positive electrode solid electrolyte) include Li ３ PS ４ and Li ７ P ２ S ８ I can be cited as an example.

[0038] Furthermore, the relationship between oxidation resistance and reduction resistance of solid electrolytes can be determined based on oxidation potential and reduction potential, similar to the porous substrates described above.

[0039] [Binder] Next, the binder will be explained. The binder is used to bind the solid electrolyte, the first porous substrate 2-1, and the second porous substrate 2-2 together. The specific material of the binder is not particularly limited. For example, rubber-based binders such as SBR (styrene-butadiene rubber) and polyvinylidene fluoride (PVDF) can be used as binders.

[0040] As described above, the binder is contained in (impregnated) the first porous substrate 2-1 and the second porous substrate 2-2 so as to form a high-concentration binder region 3. The binder may be present throughout the entirety of the first porous substrate 2-1 and the second porous substrate 2-2, or it may be present only at the interface between the first porous substrate 2-1 and the second porous substrate 2-2.

[0041] (Modification Example 5) As a fifth modification example, a preferred example of the high-concentration binder region 3 will be described. FIG. 6 is a schematic cross-sectional view showing the high-concentration binder region 3 according to the fifth modification example. In this modification example, the binder concentration is different between the side of the first porous base material 2-1 and the side of the second porous base material 2-2 in the high-concentration binder region 3. Specifically, as described in the third modification example, the first porous base material 2-1 and the second porous base material 2-2 have different porosity rates. Specifically, the porosity rate of the negative electrode side porous base material (the first porous base material 2-1 in FIG. 6) is larger than the porosity rate of the positive electrode side porous base material (the second porous base material 2-2 in FIG. 6). Here, in this modification example, in the high-concentration binder region 3, the side of the porous base material 2 (the first porous base material 2-1 in FIG. 6) with a large porosity rate has a higher binder concentration than the side of the porous base material (the second porous base material 2-2 in FIG. 6) with a small porosity rate.

[0042] According to this modification example, the solid electrolyte 4 can be filled more densely. In the porous base material 2 with a large porosity rate, originally, the solid electrolyte 4 is likely to flow out and is difficult to be filled. On the other hand, in this modification example, since the binder concentration is high on the side of the porous base material with a large porosity rate, the outflow of the solid electrolyte 4 is effectively suppressed.

[0043] [Manufacturing Method] Next, the manufacturing method of the solid electrolyte-containing sheet according to this embodiment will be described. The manufacturing method of the solid electrolyte-containing sheet 1 according to this embodiment is not particularly limited, but for example, a method as described below can be used.

[0044] First, as one of the first porous base material 2-1 and the second porous base material 2-2, a porous base material 2 having a first surface is prepared. Then, a binder is disposed on the first surface of the prepared porous base material 2. Specifically, the binder is applied to the first surface. Next, the other porous base material is laminated and adhered on the first surface. Thereby, the first porous base material 2-1 and the second porous base material 2-2 can be joined so that the high-concentration binder region 3 is formed.

[0045] Thereafter, each porous substrate is filled with the solid electrolyte 4. At this time, as described above, since the high-concentration binder region 3 functions as a wall, the solid electrolyte 4 is difficult to flow out from each porous substrate 2. The solid electrolyte 4 is densely filled in each porous substrate 2. Thereby, the solid electrolyte-containing sheet 1 according to the present embodiment is obtained.

[0046] In addition, the specific method for disposing (coating) the binder on the porous substrate 2 is not particularly limited. FIG. 7 is a schematic view showing an example of the method for disposing the binder. In the example shown in FIG. 7, first, a substrate 7 such as PET is prepared. A release agent may be applied to the substrate 7. Then, a binder 8 is applied onto the substrate 7. When a release agent is used, the binder 8 is applied on the release agent. Next, one porous substrate 2 (which may be a negative electrode side porous substrate or a positive electrode side porous substrate) is placed on the binder 8 such that the first surface faces the binder 8 side. Then, roll pressing is performed as necessary. Thereby, the binder 8 can be disposed on the first surface of the porous substrate 2. Thereafter, this porous substrate 2 is peeled off from the substrate 7. And it is bonded to the other porous substrate as described above. According to such a method, the binder 8 can be spread uniformly on the first surface. As a result, the adhesive force when bonding the first porous substrate 2-1 and the second porous substrate 2-2 can be improved.

[0047] In addition, the binder 8 may be disposed in advance on the other porous substrate 2 side as well. That is, as the other porous substrate, a porous substrate having a second surface is prepared, and the binder 8 is disposed on the second surface. Then, one porous substrate and the other porous substrate are adhered so that the second surface on which the binder 8 is disposed contacts the first surface. That is, the first porous substrate 2-1 and the second porous substrate 2-2 are bonded together such that the surfaces on which the binders are disposed contact each other. According to such a method, the adhesive force when bonding the first porous substrate 2-1 to the second porous substrate 2-2 can be further improved.

[0048] Furthermore, the method of filling the solid electrolyte 4 is not particularly limited. For example, a slurry containing a solid electrolyte, a binder, and a solvent is prepared. The binder used here may be the same as the binder used when joining the first porous substrate 2-1 and the second porous substrate 2-2, or it may be a different one. The prepared slurry is supplied (coated) to the first porous substrate 2-1 and the second porous substrate 2-2. This allows the solid electrolyte 4 to be filled. As described above, according to this embodiment, the high-concentration binder region 3 functions as a wall, so the solid electrolyte 4 can be densely filled. Also, if the slurry contains a binder, the binder impregnates the entire first porous substrate 2-1 and the second porous substrate 2-2. However, even after the slurry is supplied, the binder concentration is high in the high-concentration binder region 3 where the binder was present before the solid electrolyte was filled, and low in other regions.

[0049] The present invention has been described above using embodiments. It should be noted that the modifications and preferred embodiments described in this embodiment are not independent of each other and can be combined within a non-contradictory range.

[0050] [Note] The following is a summary of typical configurations and their effects included in the present invention.

[0051] (Note 1) A solid electrolyte-containing sheet comprising: a first porous substrate 2-1 filled with a solid electrolyte 4; and a second porous substrate 2-2 filled with a solid electrolyte and disposed on the first porous substrate 2-1 so as to be in contact with the first porous substrate 2-1, wherein the first porous substrate 2-1 and the second porous substrate 2-2 further contain a binder; a high-concentration binder region 3 is formed at the interface between the first porous substrate 2-1 and the second porous substrate 2-2; the high-concentration binder region 3 is a region in which the binder is contained at a higher concentration than in other regions of the first porous substrate 2-1 and the second porous substrate 2-2.

[0052] According to the above configuration, the high-concentration binder region 3 acts as a wall, making it difficult for the solid electrolyte to leak out during filling. As a result, a solid electrolyte-containing sheet with densely packed solid electrolyte can be obtained.

[0053] (Note 2) A solid electrolyte-containing sheet as described in Note 1, wherein the first porous substrate 2-1 and the second porous substrate 2-2 are joined together such that a portion of them interlocks with each other.

[0054] This configuration prevents gaps from forming between the first porous substrate 2-1 and the second porous substrate 2-2. This reduces the resistance in the solid electrolyte-containing sheet 1.

[0055] (Note 3) A solid electrolyte-containing sheet as described in Note 1 or 2, wherein one of the first porous substrate 2-1 and the second porous substrate 2-2 is a negative electrode side porous substrate configured to be in contact with the negative electrode 6, and one of the first porous substrate 2-1 and the second porous substrate 2-2 is a positive electrode side porous substrate configured to be in contact with the positive electrode 5, the negative electrode side porous substrate is made of a material with higher reduction resistance than the positive electrode side porous substrate, and the positive electrode side porous substrate is made of a material with higher oxidation resistance than the negative electrode side porous substrate.

[0056] This configuration allows for improved reduction resistance near the negative electrode and enhanced oxidation resistance near the positive electrode in the solid electrolyte-containing sheet. Therefore, the stability of the solid electrolyte-containing sheet during charging and discharging can be increased.

[0057] (Note 4) A solid electrolyte-containing sheet as described in any of Notes 1 to 3, wherein one of the first porous substrate 2-1 and the second porous substrate 2-2 is a negative electrode side porous substrate configured to be in contact with the negative electrode 6, and the other of the first porous substrate 2-1 and the second porous substrate 2-2 is a positive electrode side porous substrate configured to be in contact with the positive electrode 5, the positive electrode side porous substrate is filled with a positive electrode side solid electrolyte, the negative electrode side porous substrate is filled with a negative electrode side solid electrolyte, the negative electrode side solid electrolyte has higher reduction resistance than the positive electrode side solid electrolyte, and the positive electrode side solid electrolyte has higher oxidation resistance than the negative electrode side solid electrolyte.

[0058] This configuration allows for improved reduction resistance near the negative electrode and enhanced oxidation resistance near the positive electrode in the solid electrolyte-containing sheet. Therefore, the stability of the solid electrolyte-containing sheet during charging and discharging can be increased.

[0059] (Note 5) A solid electrolyte-containing sheet as described in any of Notes 1 to 4, wherein the first porous substrate 2-1 and the second porous substrate 2-2 have different porosities.

[0060] This configuration allows for the optimization of the porosity on both the positive and negative electrode sides of the solid electrolyte-containing sheet.

[0061] (Note 6) A solid electrolyte-containing sheet as described in Note 5, wherein one of the first porous substrate 2-1 and the second porous substrate 2-2 is a negative electrode side porous substrate configured to be in contact with the negative electrode 6, and the other of the first porous substrate 2-1 and the second porous substrate 2-2 is a positive electrode side porous substrate configured to be in contact with the positive electrode 5, and the porosity of the negative electrode side porous substrate is greater than the porosity of the positive electrode side porous substrate.

[0062] This configuration allows for an increase in the density of the solid electrolyte on the negative electrode side of the solid electrolyte-containing sheet, thereby reducing resistance. As a result, unintended lithium deposition can be prevented, and short circuits can be suppressed.

[0063] (Note 7) A solid electrolyte-containing sheet as described in Note 5 or 6, wherein the porosity of the first porous substrate 2-1 and the second porous substrate 2-2 are different, and the concentration of the binder in the high-concentration binder region 3 is greater on the porous substrate side with the higher porosity than on the porous substrate side with the lower porosity.

[0064] With this configuration, the binder concentration is higher on the porous substrate side, which has a larger porosity, thus more reliably preventing leakage during the filling of the solid electrolyte. This allows for a denser filling of the solid electrolyte.

[0065] (Note 8) A solid electrolyte-containing sheet as described in any of Notes 1 to 7, wherein the first porous substrate 2-1 and the second porous substrate 2-2 are each nonwoven fabrics.

[0066] This configuration makes it easier to handle the solid electrolyte-containing sheet as a self-supporting membrane. For example, the solid electrolyte-containing sheet can be handled in a roll-to-roll manner, improving productivity.

[0067] (Note 9) A method for manufacturing a solid electrolyte-containing sheet, comprising the steps of: providing a porous substrate having a first surface; placing a binder on the first surface;, after the step of placing the binder, laminating another porous substrate on the first surface and adhering the other porous substrate to the first porous substrate; and, after the adhering step, filling the first porous substrate and the other porous substrate with a solid electrolyte.

[0068] This method allows the first porous substrate 2-1 and the second porous substrate 2-2 to be bonded together such that a high-concentration binder region is formed. As a result, when the solid electrolyte is filled, the high-concentration binder region acts as a barrier, allowing the solid electrolyte to be densely packed.

[0069] (Note 10) A manufacturing method as described in Note 9, further comprising the steps of: providing a porous substrate having a second surface as another porous substrate; and placing a binder on the second surface, wherein the bonding step includes, after the step of placing the binder on the second surface, bonding the second surface to the first surface, thereby bonding the other porous substrate to one porous substrate.

[0070] According to this method, since the binder is pre-placed not only on one porous substrate but also on other porous substrates, the bonding strength between one porous substrate and the other can be further enhanced.

[0071] (Note 11) A manufacturing method according to Note 9 or 10, wherein the step of applying a binder to the first surface includes the steps of preparing a substrate to which a release agent has been applied, and placing a binder on the first surface by attaching a porous substrate to the release agent.

[0072] This method allows the binder to be spread uniformly across the entire surface of the first layer. As a result, the bonding strength between one porous substrate and the other porous substrate can be improved.

[0073] (Incorporation by Reference) The present invention claims priority under Japanese Patent Application No. 2024-177367 (filing date: October 9, 2024), the disclosures of said application are incorporated herein by reference in their entirety.

Claims

1. A solid electrolyte-containing sheet comprising: a first porous substrate filled with a solid electrolyte; and a second porous substrate filled with a solid electrolyte and disposed on the first porous substrate so as to be in contact with the first porous substrate, wherein the first porous substrate and the second porous substrate further contain a binder, and a high-concentration binder region is formed at the interface between the first porous substrate and the second porous substrate, and the high-concentration binder region is a region in which the binder is contained at a higher concentration than in other regions of the first porous substrate and the second porous substrate.

2. A solid electrolyte-containing sheet according to claim 1, wherein the first porous substrate and the second porous substrate are joined together such that a portion of them interlock with each other.

3. A solid electrolyte-containing sheet according to claim 1 or 2, wherein one of the first porous substrate and the second porous substrate is a negative electrode-side porous substrate configured to be in contact with the negative electrode, the other of the first porous substrate and the second porous substrate is a positive electrode-side porous substrate configured to be in contact with the positive electrode, the negative electrode-side porous substrate is formed of a material with higher reduction resistance than the positive electrode-side porous substrate, and the positive electrode-side porous substrate is formed of a material with higher oxidation resistance than the negative electrode-side porous substrate.

4. A solid electrolyte-containing sheet according to claim 1 or 2, wherein one of the first porous substrate and the second porous substrate is a negative electrode-side porous substrate configured to be in contact with the negative electrode, the other of the first porous substrate and the second porous substrate is a positive electrode-side porous substrate configured to be in contact with the positive electrode, the positive electrode-side porous substrate is filled with a positive electrode-side solid electrolyte, the negative electrode-side porous substrate is filled with a negative electrode-side solid electrolyte, the negative electrode-side solid electrolyte has higher reduction resistance than the positive electrode-side solid electrolyte, and the positive electrode-side solid electrolyte has higher oxidation resistance than the negative electrode-side solid electrolyte.

5. A solid electrolyte-containing sheet according to claim 1 or 2, wherein the first porous substrate and the second porous substrate have different porosities.

6. A solid electrolyte-containing sheet according to claim 5, wherein one of the first porous substrate and the second porous substrate is a negative electrode-side porous substrate configured to be in contact with the negative electrode, and the other of the first porous substrate and the second porous substrate is a positive electrode-side porous substrate configured to be in contact with the positive electrode, and the porosity of the negative electrode-side porous substrate is greater than the porosity of the positive electrode-side porous substrate.

7. A solid electrolyte-containing sheet according to claim 5, wherein the porosity of the first porous substrate and the second porous substrate are different, and the concentration of the binder in the high-concentration binder region is greater on the side of the porous substrate with a higher porosity than on the side of the porous substrate with a lower porosity.

8. A solid electrolyte-containing sheet according to claim 1 or 2, wherein the first porous substrate and the second porous substrate are each a nonwoven fabric.

9. A method for manufacturing a solid electrolyte-containing sheet, comprising the steps of: providing a porous substrate having a first surface; placing a binder on the first surface;, after the step of placing the binder, laminating another porous substrate on the first surface and adhering the other porous substrate to the first porous substrate; and, after the adhering step, filling the first porous substrate and the other porous substrate with a solid electrolyte.

10. A manufacturing method according to claim 9, further comprising the steps of: providing a porous substrate having a second surface as the other porous substrate; and placing a binder on the second surface, wherein the bonding step includes, after the step of placing the binder on the second surface, bonding the second surface to the first surface, thereby bonding the other porous substrate to the first porous substrate.

11. A manufacturing method according to claim 9, wherein the step of placing a binder on the first surface comprises: preparing a substrate coated with a release agent; and placing the binder on the first surface by attaching the first porous substrate onto the release agent.

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