Method for manufacturing solid electrolyte-containing sheet

Abstract

This method for manufacturing a solid electrolyte-containing sheet comprises: a first step of applying a slurry containing a solid electrolyte and a dispersion medium onto a substrate to form an initial coating film; a second step of disposing a porous sheet on the initial coating film; a third step of applying an additional slurry onto the porous sheet to form a precursor sheet; and a fourth step of drying the precursor sheet to obtain the solid electrolyte-containing sheet. In the second step, the porous sheet is disposed on the initial coating film in a state of containing the dispersion medium.

Description

Method for manufacturing a solid electrolyte-containing sheet

[0001] The present invention relates to a method for producing a solid electrolyte-containing sheet.

[0002] Secondary batteries using solid electrolytes are known. In producing such secondary batteries, a solid electrolyte-containing sheet may be used. A solid electrolyte-containing sheet is a sheet in which a solid electrolyte is supported by a support such as a porous sheet. By supporting the solid electrolyte by the support, the solid electrolyte can be handled as a free-standing membrane.

[0003] In relation to the above, Japanese Patent No. 7286703 discloses "a method for manufacturing a solid electrolyte sheet filled with a solid electrolyte, comprising: a first step of applying a slurry containing a solid electrolyte onto a substrate; a second step of forming a solid electrolyte layer by drying the slurry on the substrate; a third step of stacking a sheet-like three-dimensional structure on an upper surface of the solid electrolyte layer; a fourth step of applying a slurry containing a solid electrolyte to the inside and upper part of the three-dimensional structure; and a fifth step of drying the slurry inside and upper part of the three-dimensional structure to obtain a solid electrolyte sheet filled with a solid electrolyte."

[0004] In a solid electrolyte-containing sheet using a porous sheet as a support, it is preferable that the porous sheet is filled with the solid electrolyte at a high filling rate in order to prevent short circuits and obtain good charge / discharge characteristics.

[0005] Therefore, an object of the present invention is to provide a method for producing a solid electrolyte-containing sheet, which allows a porous sheet to be filled with a solid electrolyte at a high filling rate.

[0006] In one aspect, a method for producing a solid electrolyte-containing sheet according to the present invention includes a first step of applying a slurry containing a solid electrolyte and a dispersion medium onto a substrate to form an initial coating film, a second step of arranging a porous sheet on the initial coating film, a third step of applying additional slurry onto the porous sheet to produce a precursor sheet, and a fourth step of drying the precursor sheet to produce a solid electrolyte-containing sheet. In the second step, the porous sheet is arranged on the initial coating film that contains the dispersion medium.

[0007] FIG. 1 is a schematic cross-sectional view showing a solid electrolyte-containing sheet. FIG. 2 is a process cross-sectional view showing a manufacturing method according to an embodiment. FIG. 3A is a schematic cross-sectional view showing a manufacturing method according to Reference Example 1. FIG. 3B is a schematic cross-sectional view showing a manufacturing method according to Reference Example 2. FIG. 3C is a schematic cross-sectional view showing a method according to Reference Example 3. FIG. 4 is a schematic cross-sectional view showing a manufacturing method according to Modification Example 1. FIG. 5 is a schematic cross-sectional view showing a manufacturing method according to Modification Example 2.

[0008] Hereinafter, a method for manufacturing a solid electrolyte-containing sheet according to an embodiment of the present invention will be described with reference to the drawings. (Solid electrolyte-containing sheet) First, a solid electrolyte-containing sheet 1 manufactured by the manufacturing method according to this embodiment will be described. The solid electrolyte-containing sheet 1 according to this embodiment is a sheet for a secondary battery. The solid electrolyte-containing sheet 1 is combined with a positive electrode layer and a negative electrode layer and used as a secondary battery.

[0009] 1 is a schematic cross-sectional view showing a solid electrolyte-containing sheet 1. The solid electrolyte-containing sheet 1 has a porous sheet 2 and a solid electrolyte 3. The solid electrolyte 3 itself is a powder. The solid electrolyte 3 is arranged on both sides of the porous sheet 2 so as to form layers. The solid electrolyte 3 also fills the pores of the porous sheet 2.

[0010] In other words, the solid electrolyte-containing sheet 1 has a composite layer A and a pair of single layers B. The composite layer A is a layer having a porous sheet 2 filled with a solid electrolyte 3. The pair of single layers B are layers provided so as to sandwich the composite layer A, and are layers containing the solid electrolyte 3 but not the porous sheet 2. The porous sheet 2 is covered by the pair of single layers B and is not exposed.

[0011] According to the above-described configuration, the porous sheet 2 functions as a support, and the solid electrolyte can be handled as a free-standing film. Normally, the solid electrolyte 3 is hard and brittle, and does not have the form of a free-standing film by itself. In contrast, by combining the porous sheet 2, the solid electrolyte can be handled as a free-standing film. As a result, the solid electrolyte can be easily handled during the manufacture of the secondary battery, etc.

[0012] The porous sheet 2 may be any material as long as it has the function of supporting the solid electrolyte. For example, a nonwoven fabric may be used as the porous sheet 2. For example, a nonwoven fabric made of PET may be used as the porous sheet 2.

[0013] The thickness of the porous sheet 2 (ie, the thickness of the composite layer A) is not particularly limited, but is, for example, 1 to 50 μm, and preferably 3 to 20 μm.

[0014] On the other hand, the thickness of each of the individual layers B is, for example, 1 to 100 μm, preferably 3 to 30 μm.

[0015] The solid electrolyte 3 may be any solid electrolyte that can be used as an electrolyte for a lithium ion secondary battery. As the solid electrolyte, sulfides and oxides can be used. As the sulfide solid, for example, an LPS system (e.g., Argyrodite (Li ６ P.S. ５ Cl), and LGPS systems (e.g., Li １０ GeP ２ S １２) materials. (Method for manufacturing a solid electrolyte-containing sheet) Next, a method for manufacturing a solid electrolyte-containing sheet according to this embodiment will be described. In the above-mentioned solid electrolyte-containing sheet 1, it is desirable that the porous sheet 2 is filled with the solid electrolyte 3 at a high filling rate in order to obtain good battery characteristics. Furthermore, since the porous sheet 2 does not normally have the function of an electrolyte (ionic conductivity), it is preferable that it is not in contact with the electrode layer. Therefore, it is preferable that the porous sheet 2 is not exposed in the solid electrolyte-containing sheet 1. If the porous sheet 2 is exposed, the battery capacity may decrease.

[0016] Therefore, in this embodiment, a manufacturing method is devised so that a high filling rate is achieved and the porous sheet 2 is not exposed.

[0017] 2A to 2C are cross-sectional views illustrating the steps of the manufacturing method according to this embodiment, which includes first to fourth steps.

[0018] Generally speaking, in the first step, a slurry containing a solid electrolyte and a dispersion medium is prepared. Then, the prepared slurry is applied onto a substrate 4. In this way, an initial coating film 5-1 is formed.

[0019] Subsequently, in the second step, the porous sheet 2 is placed on the initial coating film 5-1. At this time, the porous sheet 2 is placed on the initial coating film 5-1 while the initial coating film 5-1 contains a dispersion medium. That is, the porous sheet 2 is placed on the initial coating film 5-1 in a wet state. Since the initial coating film 5-1 is in a wet state, the initial coating film 5-1 penetrates into a part of the porous sheet 2.

[0020] Subsequently, in the third step, additional slurry is applied onto the porous sheet 2 to form an additional coating film 5-2. This results in a precursor sheet 8. The obtained precursor sheet 8 has a configuration in which coating films 5 (initial coating film 5-1 and additional coating film 5-2) formed from the slurry are provided on both sides of the porous sheet 2. The slurry also permeates into the porous sheet 2, filling the pores.

[0021] Subsequently, in the fourth step, the precursor sheet 8 is dried. That is, the dispersion medium is removed. As a result, a solid electrolyte-containing sheet 1 is obtained. In this specification, "drying" refers to removing the dispersion medium to the extent that the coating film 5 has substantially no fluidity. The obtained solid electrolyte-containing sheet 1 is then peeled off from the substrate 4 as necessary and used for manufacturing a secondary battery.

[0022] The above is an outline of the manufacturing method according to this embodiment. According to this method, the solid electrolyte can be filled into the porous sheet 2 at a high filling rate. This will be described below with reference to a reference example.

[0023] Fig. 3A is a schematic diagram showing a manufacturing method according to Reference Example 1. In this Reference Example, as shown in Fig. 3A(a), first, a porous sheet 2 is placed on a substrate 4. Next, as shown in Fig. 3A(b), a slurry is applied to the porous sheet 2 to form a coating film 5. Then, as shown in Fig. 3A(c), the coating film 5 is dried. In this way, a solid electrolyte-containing sheet 1 is obtained.

[0024] In the method according to Reference Example 1, the slurry is supplied only to one surface (upper surface) of the porous sheet 2. Therefore, the slurry may not penetrate to the vicinity of the other surface (lower surface). As a result, a filling defect X may occur, making it difficult to obtain a high filling rate. In addition, the porous sheet 2 is easily exposed. In contrast, according to the present embodiment, the slurry is supplied to both surfaces of the porous sheet 2, so the slurry easily penetrates the entire porous sheet 2. Therefore, the solid electrolyte can be filled at a high filling rate. In addition, the porous sheet 2 is less likely to be exposed.

[0025] FIG. 3B is a schematic cross-sectional view showing a manufacturing method according to Reference Example 2. In this Reference Example, first, as shown in FIG. 3B(a), a slurry is applied to a substrate 4 to form an initial coating film 5-1. Then, as shown in FIG. 3B(b), the initial coating film 5-1 is dried. Then, as shown in FIG. 3B(c), a porous sheet 2 is placed on the initial coating film 5-1. Then, as shown in FIG. 3B(d), additional slurry is applied to the porous sheet 2 to form an additional coating film 5-2. This results in a precursor sheet 8. Then, as shown in FIG. 3B(e), the precursor sheet 8 is dried. This results in a solid electrolyte-containing sheet 1.

[0026] According to the method of Reference Example 2, the porous sheet 2 is placed after the initial coating film 5-1 has dried. That is, the porous sheet 2 is placed on the initial coating film 5-1, which is substantially free of a dispersion medium. Because it does not contain a dispersion medium, the initial coating film 5-1 has almost no fluidity. Therefore, the slurry (initial coating film 5-1) is unlikely to penetrate into the pores of the porous sheet 2. Furthermore, when additional slurry is applied, as in Reference Example 1, the slurry may not penetrate to the vicinity of the underside of the porous sheet 2. As a result, it becomes difficult to fill the solid electrolyte near the initial coating film 5-1 (see filling defect X in the figure). As a result, it becomes difficult to obtain a high filling rate.

[0027] In contrast, according to the present embodiment, the porous sheet 2 is placed on the initial coating film 5-1 that contains a dispersion medium. At the time the porous sheet 2 is placed, the initial coating film 5-1 has a certain degree of fluidity. Therefore, the initial coating film 5-1 easily penetrates into the porous sheet 2. As a result, a high filling rate can be achieved.

[0028] As described above, according to this embodiment, a higher filling rate can be achieved compared to the methods of Reference Examples 1 and 2, and exposure of the porous sheet 2 can be prevented.

[0029] In addition, according to the method according to this embodiment, the solid electrolyte-containing sheet 1 can be obtained in a short process. This point will be explained in comparison with Reference Example 3.

[0030] FIG. 3C is a schematic cross-sectional view showing a method according to Reference Example 3. In this Reference Example, first, as shown in FIG. 3C(a), a porous sheet 2 is placed on a substrate 4. Next, as shown in FIG. 3C(b), a slurry is applied to the porous sheet 2 to form an initial coating film 5-1. Next, as shown in FIG. 3C(c), the initial coating film 5-1 is dried. Next, as shown in FIG. 3C(d), the porous sheet 2 is inverted. Next, as shown in FIG. 3C(e), additional slurry is applied to the porous sheet 2 to form an additional coating film 5-2. This results in a precursor sheet 8. Next, as shown in FIG. 3C(f), the precursor sheet 8 is dried to obtain a solid electrolyte-containing sheet 1.

[0031] In the method according to Reference Example 3, the drying step is performed twice. Also, a step of inverting the porous sheet 2 is included. That is, the porous sheet 2 needs to be peeled off from the substrate 4, inverted, and then placed again on the substrate 4. In contrast, according to the method according to the present embodiment, the drying step is performed only once. Also, the step of inverting the porous sheet 2 is not required. Therefore, the solid electrolyte-containing sheet 1 can be produced in a short process, improving productivity.

[0032] The first embodiment has been generally described above with reference to the Reference Example. Next, details of each step in this embodiment will be described. (First Step) In the first step (see FIG. 2), as described above, a slurry containing a solid electrolyte and a dispersion medium is used. The slurry may contain other components (e.g., a resin binder component, etc.). The content of the solid components (components excluding the dispersion medium) in the slurry may be an amount sufficient to obtain the fluidity required to form a coating film. For example, the content of the solid components in the slurry is, for example, 30 to 95% by mass, preferably 50 to 90% by mass.

[0033] The dispersion medium may be any liquid component that can be removed by drying. For example, mesitylene or the like can be used as the dispersion medium.

[0034] The method for applying the slurry is not particularly limited, and for example, an applicator, a die coater, or the like can be used.

[0035] There are no particular limitations on the thickness of the initial coating film 5-1 formed in the first step, and the thickness of the initial coating film 5-1 is, for example, 1 to 200 μm, preferably 3 to 100 μm.

[0036] The amount of slurry applied in the first step is preferably greater than the amount of additional slurry applied in the third step. This allows the thickness of the pair of single layers B (see FIG. 1) to be uniform. Specifically, when the porous sheet 2 is placed on the initial coating film 5-1 in the second step, the initial coating film 5-1 fills more than half of the area of ​​the porous sheet 2 in the thickness direction. Therefore, if the amount of additional slurry applied in the third step is equal to or greater than the amount of slurry applied in the first step, the thickness of the single layer B formed by the additional slurry may be excessively thick. On the other hand, if the amount of additional slurry applied in the third step is small, in other words, if the amount of slurry applied in the first step is greater than the amount of additional slurry applied in the third step, the thickness of the pair of single layers B is more likely to be uniform.

[0037] The amount of slurry applied in the first step (mass per unit area) is, for example, 130% or more, and preferably 150 to 500%, when the amount of additional slurry applied in the third step (mass per unit area) is taken as 100%. (Second Step) Next, the second step will be described in detail. As described above, in the second step, the porous sheet 2 is disposed in a state in which the initial coating film 5-1 contains a dispersion medium.

[0038] The amount of dispersion medium in the initial coating film 5-1 at the start of the second step may be an amount that allows the initial coating film 5-1 to have sufficient fluidity, i.e., the dispersion medium may remain until the start of the second step in an amount that allows the initial coating film 5-1 to have fluidity such that a portion of the initial coating film 5-1 penetrates into the porous sheet 2.

[0039] Specifically, when the amount of dispersion medium at the time of coating the slurry in the first step (hereinafter sometimes referred to as the "initial amount") is taken as 100% by mass, the amount of dispersion medium contained in the initial coating film 5-1 at the start of the second step is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 85% by mass or more. If the dispersion medium is contained in such an amount, the initial coating film 5-1 will easily penetrate into the porous sheet 2.

[0040] As shown in FIG. 2, in the second step, it is preferable to arrange the porous sheet 2 so that the upper surface of the porous sheet 2 is exposed from the initial coating film 5-1.

[0041] In the second step, the porous sheet 2 is preferably arranged so as not to come into contact with the substrate 4 .

[0042] For example, the porous sheet 2 is simply placed on the initial coating film 5-1 without applying pressure or the like. This allows the porous sheet 2 to be positioned so that the upper surface of the porous sheet 2 is exposed from the initial coating film 5-1 and so that the porous sheet 2 does not come into contact with the substrate 4. By positioning the porous sheet 2 in this manner, exposure of the porous sheet 2 can be more reliably prevented. (Third Step) Next, the third step will be described in detail. In the third step, as described above, an additional slurry is applied to the porous sheet 2 to form the additional coating film 5-2. The composition of the additional slurry can be the same as the composition of the slurry used in the first step. As in the first step, the method for applying the additional slurry is not particularly limited, and an applicator, a die coater, or the like can be used. The additional slurry is applied so that the surface of the porous sheet 2 is not exposed.

[0043] In this embodiment, it is preferable that the dispersion medium in the initial coating film 5-1 remains at least until the start of the third step. That is, as shown in FIG. 2, it is preferable that the initial coating film 5-1 is in a wet state at the start of the third step. This method makes it difficult for a boundary to form inside the porous sheet 2 between the slurry applied in the first step and the additional slurry applied in the third step. This allows the slurry to be uniformly impregnated into the porous sheet 2, making it easier to uniformly fill the solid electrolyte.

[0044] Specifically, when the initial amount of the dispersion medium is taken as 100% by mass, the amount of the dispersion medium in the initial coating film 5-1 at the start of the third step is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more. If the dispersion medium remains in such an amount, the solid electrolyte can be uniformly filled.

[0045] In order to allow the dispersion medium to remain in the initial coating film 5-1 until the start of the third step, it is sufficient to avoid "active drying" before the third step. By avoiding active drying, the initial coating film 5-1 can be kept wet until the start of the third step.

[0046] In this specification, the term "active drying" is used to distinguish it from "natural drying" and is intended to mean placing an object to be dried in an environment in which the evaporation rate of the dispersion medium is faster than in the processes before and after. For example, "active drying" can be a process in which an object to be dried is dried in an oven. Alternatively, "active drying" can be a process in which an object to be dried is dried by blowing air.

[0047] From another perspective, in this embodiment, it is preferable that the dispersion medium removal rate after the end of the third step is greater than the dispersion medium removal rate between the end of the first step and the start of the third step. By adopting such a method, a certain amount of dispersion medium remains in the initial coating film 5-1 at the start of the third step, making it easier to uniformly fill the porous sheet 2 with the solid electrolyte. In this specification, the "dispersion medium removal rate between the end of the first step and the start of the third step" refers to the amount of dispersion medium removed from the first step to the start of the third step, assuming that the initial amount of dispersion medium is 100% by mass. Furthermore, the "dispersion medium removal rate after the end of the third step" refers to the amount of dispersion medium removed after the end of the third step, assuming that the amount of dispersion medium in the precursor sheet 8 at the end of the third step is 100% by mass. (Fourth Step) Next, the fourth step will be described in detail. In the fourth step, the precursor sheet 8 is dried as described above. That is, the dispersion medium is removed to the extent that the coating film 5 loses its fluidity. In this way, the solid electrolyte-containing sheet 1 is obtained.

[0048] Drying may be natural drying or active drying. Preferably, the precursor sheet 8 is dried by active drying. The temperature during active drying is not particularly limited. For example, active drying can be performed at 20 to 100°C.

[0049] The drying removes most of the dispersion medium. If the amount of dispersion medium in the precursor sheet 8 at the end of the third step is taken as 100% by mass, the amount of dispersion medium removed after the end of the third step is, for example, 70% by mass or more, preferably 80% by mass or more, and more preferably 95% by mass or more. (Variation 1) Next, Variation 1 of this embodiment will be described. FIG. 4 is a schematic cross-sectional view showing a manufacturing method according to Variation 1. In this variation, "active drying" is performed in the fourth step. The time from the end of the third step to the start of the active drying in the fourth step is longer than the time from the end of the second step to the start of the third step. Other points are the same as those of the previously described embodiment.

[0050] When active drying is performed in the fourth step, as in this modification, it is preferable to ensure a certain amount of time between the end of the third step and the start of active drying. If active drying is performed immediately after the end of the third step, the slurry will not easily penetrate into the porous sheet 2. In contrast, according to this modification, time is ensured between the end of the third step and the start of active drying for the slurry to penetrate into the porous sheet 2. This makes it easier for the solid electrolyte to fill the porous sheet 2. In other words, the filling rate is likely to be increased. (Modification 2) Next, Modification 2 will be described. Figure 5 is a schematic cross-sectional view showing a manufacturing method according to this modification. In this modification, unlike the examples shown in Figures 2 and 4, active drying is performed between the second step and the third step. In other words, at the start of the third step, the initial coating film 5-1 contains almost no dispersion medium. Other points are similar to the previously described embodiments and modifications.

[0051] As in this modified example, active drying may be performed between the second and third steps. Even if active drying is performed between the second and third steps, if the initial coating film 5-1 is wet at the start of the second step, the initial coating film 5-1 will easily penetrate into the porous sheet 2, thereby achieving a high filling rate. In addition, active drying between the second and third steps makes it easier to manage the film thickness of the initial coating film 5-1. Therefore, this modified example also has advantageous effects from a different perspective than the examples shown in Figures 2 and 4.

[0052] In this modification, the amount of the dispersion medium in the initial coating film 5-1 at the start of the third step is, for example, less than 50% by mass, preferably 30% by mass or less, and more preferably 10% by mass or less, where the initial amount is taken as 100% by mass. Such an amount makes it easy to control the film thickness of the initial coating film 5-1.

[0053] The present invention has been described above with reference to the embodiments. The main configurations and effects of the present invention are summarized below as appendices. (Appendix 1) A method for producing a solid electrolyte-containing sheet includes a first step of applying a slurry containing a solid electrolyte and a dispersion medium onto a substrate to form an initial coating film (5-1), a second step of arranging a porous sheet on the initial coating film (5-1), a third step of applying additional slurry onto the porous sheet (2) to produce a precursor sheet (8), and a fourth step of drying the precursor sheet (8) to produce a solid electrolyte-containing sheet (1), wherein in the second step, the porous sheet (2) is arranged on the initial coating film (5-1) that still contains the dispersion medium.

[0054] According to this method, it is possible to fill the porous sheet 2 with the solid electrolyte at a high filling rate. (Appendix 2) The manufacturing method according to Appendix 1, wherein the dispersion medium in the initial coating film 5-1 remains at least until the start of the third step.

[0055] According to this method, the slurry supplied in the first step and the slurry supplied in the third step are more likely to be uniformly mixed in the porous sheet 2. As a result, boundaries are less likely to occur inside the porous sheet 2, and the solid electrolyte can be uniformly filled. (Appendix 3) A manufacturing method according to Appendix 2, wherein the fourth step includes a step of drying the precursor sheet 6 by active drying, and the time from the end of the second step to the start of the third step is shorter than the time from the end of the third step to the start of the active drying in the fourth step.

[0056] According to this method, since the time between the second step and the third step is short, a sufficient amount of dispersion medium can be contained in the initial coating film 5-1 at the start of the third step. On the other hand, since the time between the end of the third step and the start of active drying in the fourth step is long, there is sufficient time for the coating film to penetrate into the porous sheet 2. (Appendix 4) A manufacturing method according to any one of Appendices 1 to 3, in which the removal rate of the dispersion medium after the end of the third step is greater than the removal rate of the dispersion medium from the end of the first step to the start of the third step.

[0057] According to this method, a sufficient amount of the dispersion medium is contained in the initial coating film 5-1 at the start of the third step. This makes it easier for the additional coating film 5-2 to mix with the initial coating film 5-1. This makes it less likely for a boundary to form between the initial coating film 5-1 and the additional coating film 5-2 in the porous sheet 2, allowing the solid electrolyte to be uniformly filled. (Appendix 5) The manufacturing method described in Appendix 1 further includes a step of removing the dispersion medium contained in the initial coating film 5-1 by active drying between the second step and the third step.

[0058] According to such a method, the initial coating film 5-1 loses its fluidity by being actively dried, making it easier to control the film thickness of the initial coating film 5-1. (Appendix 6) A manufacturing method according to any one of Appendices 1 to 5, wherein the second step includes a step of arranging the porous sheet 2 so that the upper surface of the porous sheet 2 is exposed from the initial coating film 5-1. (Appendix 7) A manufacturing method according to any one of Appendices 1 to 6, wherein the second step includes a step of arranging the porous sheet 2 so that the porous sheet 2 does not come into contact with the substrate 4.

[0059] According to this method, it is possible to more reliably prevent exposure of the porous sheet 2. (Appendix 8) The manufacturing method according to any one of Appendices 1 to 7, wherein the amount of the slurry applied in the first step is greater than the amount of the additional slurry applied in the third step.

[0060] This method makes it possible to make uniform the thickness of the single layer B present on both sides of the porous sheet 2. (Incorporation by Reference) This invention claims priority to Japanese Patent Application No. 2024-117250 (filing date: July 22, 2024), the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A method for producing a solid electrolyte-containing sheet, comprising: a first step of applying a slurry containing a solid electrolyte and a dispersion medium onto a substrate to form an initial coating; a second step of arranging a porous sheet on the initial coating; a third step of applying additional slurry onto the porous sheet to produce a precursor sheet; and a fourth step of drying the precursor sheet to produce a solid electrolyte-containing sheet, wherein in the second step, the porous sheet is arranged on the initial coating that still contains the dispersion medium.

2. The manufacturing method according to claim 1, wherein the dispersion medium in the initial coating film remains at least until the start of the third step.

3. A manufacturing method according to claim 2, wherein the fourth step includes a step of drying the precursor sheet by active drying, and the time between the end of the second step and the start of the third step is shorter than the time between the end of the third step and the start of the active drying in the fourth step.

4. A manufacturing method according to claim 1 or 2, wherein the removal rate of the dispersion medium after the end of the third step is greater than the removal rate of the dispersion medium from the end of the first step to the start of the third step.

5. The manufacturing method according to claim 1, further comprising a step between the second step and the third step of removing the dispersion medium contained in the initial coating film by active drying.

6. A manufacturing method according to claim 1 or 2, wherein the second step includes a step of positioning the porous sheet so that the upper surface of the porous sheet is exposed from the initial coating film.

7. A manufacturing method according to claim 1 or 2, wherein the second step includes a step of positioning the porous sheet so that the porous sheet does not come into contact with the substrate.

8. The manufacturing method according to claim 1 or 2, wherein the amount of the slurry applied in the first step is greater than the amount of the additional slurry applied in the third step.

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