Method for producing all-solid-state battery

Abstract

This method for producing an all-solid-state battery comprises a step for transferring, on a solid electrolyte layer, a negative electrode layer or a negative electrode intermediate layer through roll-pressing in a first direction defined as the advancing direction. The solid electrolyte layer is formed so as to cover an end surface of the positive electrode layer at the terminal end portion thereof in the first direction. The solid electrolyte layer has an inclined part that is shaped such that the upper surface thereof becomes higher along the first direction. The inclined part is provided at least at the terminal end portion of the solid electrolyte layer in the first direction.

Description

Manufacturing method for all-solid-state batteries

[0001] The present invention relates to a method for manufacturing an all-solid-state battery.

[0002] An all-solid-state battery is a secondary battery that uses a solid electrolyte. Known all-solid-state batteries have a configuration in which the end of a positive electrode layer is covered with a solid electrolyte layer. For example, Patent Document 1 (JP 2021-086687 A) describes an all-solid-state battery having a specific configuration, in which the solid electrolyte layer includes an electrolyte base and an electrode side contact portion that extends from the end of the electrolyte base and contacts a side surface of a first electrode layer.

[0003] Incidentally, during the manufacture of an all-solid-state battery, transfer using a roll press may be performed to form an anode layer on a solid electrolyte layer. Specifically, a solid electrolyte layer is first formed on a cathode layer. Then, the anode layer is transferred onto the solid electrolyte layer by roll press. Here, if a configuration is adopted in which the solid electrolyte layer covers the end of the cathode layer, the cathode layer is not present under the solid electrolyte layer at the end of the roll press. Therefore, it becomes difficult to apply a load to the anode layer at the end. In other words, load loss is likely to occur. As a result, transfer failure of the anode layer may occur.

[0004] In addition, when manufacturing an all-solid-state battery, a layer called anode intermediate layer or the like may be transferred onto the solid electrolyte by roll pressing instead of the anode layer. Transfer failure due to load loss may also occur during transfer of the anode intermediate layer.

[0005] Therefore, an object of the present invention is to provide a technique capable of preventing transfer defects when transferring a negative electrode layer or a negative electrode intermediate layer by roll pressing.

[0006] FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery according to a first embodiment. FIG. 2 is a plan view showing a partial configuration of the all-solid-state battery. FIG. 3A is a schematic cross-sectional view showing a step of forming a positive electrode layer (step S1). FIG. 3B is a schematic cross-sectional view showing a step of forming a solid electrolyte layer (step S2). FIG. 3C is a schematic cross-sectional view showing a step of transferring an anode layer (step S3). FIG. 4 is a schematic cross-sectional view showing an all-solid-state battery according to a reference example. FIG. 5 is a schematic cross-sectional view showing an all-solid-state battery according to another reference example. FIG. 6 is a schematic cross-sectional view showing the shape of a solid electrolyte layer in an all-solid-state battery according to a modified example of the first embodiment. FIG. 7 is a cross-sectional view for explaining the inclination angle. FIG. 8 is a cross-sectional view showing a modified example of the first embodiment. FIG. 9 is a plan view showing an all-solid-state battery according to a second embodiment. FIG. 10 is a view showing the AA' cross section of FIG. 9.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0008] (1) First Embodiment (Configuration of All-Solid-State Battery) Fig. 1 is a schematic cross-sectional view showing an all-solid-state battery 1 according to a first embodiment. The all-solid-state battery 1 has a positive electrode current collector foil 2, a positive electrode layer 3, a solid electrolyte layer 4, a negative electrode layer 5, and a negative electrode current collector foil 6. The positive electrode layer 3 is provided on the positive electrode current collector foil 2. The solid electrolyte layer 4 is provided on the positive electrode layer 3. The negative electrode layer 5 is provided on the solid electrolyte layer 4. The negative electrode current collector foil 6 is provided on the negative electrode layer 5.

[0009] In the example shown in FIG. 1 , a positive electrode layer 3, a solid electrolyte layer 4, a negative electrode layer 5, and a negative electrode current collector foil 6 are provided on the upper and lower sides of the positive electrode current collector foil 2, respectively. If a configuration in which the solid electrolyte layer 4 is sandwiched between the positive electrode layer 3 and the negative electrode layer 5 is defined as one unit, the configuration shown in FIG. 1 illustrates a configuration in which two units are stacked via the positive electrode current collector foil 2. However, the all-solid-state battery 1 may include a single unit. That is, the positive electrode layer 3, the solid electrolyte layer 4, the negative electrode layer 5, and the negative electrode current collector foil 6 may be provided on only one side of the positive electrode current collector foil 2. Alternatively, the all-solid-state battery 1 may include three or more units. That is, another unit may be stacked on the outside of the negative electrode current collector foil 6.

[0010] 1 , a first direction is defined as a direction perpendicular to the stacking direction. As will be described in detail later, during the manufacture of the all-solid-state battery 1, the anode layer 5 is formed on the solid electrolyte layer 4 by transfer using a roll press. The first direction is the direction in which the roll press, which is performed to transfer the anode layer 5, advances.

[0011] The solid electrolyte layer 4 covers the end face of the positive electrode layer 3 at its starting end and end end in the first direction. Specifically, when viewed along the stacking direction, the end face of the solid electrolyte layer 4 in the first direction is located outside the end face of the positive electrode layer 3. The solid electrolyte layer 4 covers the end face of the positive electrode layer 3 so as to contact the end face of the positive electrode layer 3.

[0012] The solid electrolyte layer 4 has an inclined portion 7. The inclined portion 7 is a portion having a shape such that the upper surface thereof becomes higher along the first direction. That is, the height of the upper surface of the inclined portion 7 increases from the starting end side toward the terminal end side in the first direction. The inclined portion 7 is provided at least at the terminal end side in the first direction. Note that in the example shown in FIG. 1 , the inclined portion 7 is provided not only at the terminal end side but also at the starting end side in the first direction.

[0013] Fig. 2 is a plan view showing a partial configuration of the all-solid-state battery 1. Fig. 2 shows the shapes of the positive electrode current collector foil 2, the positive electrode layer 3, and the solid electrolyte layer 4. As shown in Fig. 2, in this embodiment, the positive electrode current collector foil 2, the positive electrode layer 3, and the solid electrolyte layer 4 are all rectangular. Although not shown, the negative electrode layer 5 and the negative electrode current collector foil 6 are also rectangular. However, the planar shape of the all-solid-state battery 1 is not limited to a rectangular shape, and other shapes may be used.

[0014] (Manufacturing Method of All-Solid-State Battery) Next, a manufacturing method of the all-solid-state battery 1 according to this embodiment will be described. The manufacturing method according to this embodiment includes a step of forming a positive electrode layer (step S1), a step of forming a solid electrolyte layer (step S2), a step of transferring a negative electrode layer (step S3), and a step of forming a negative electrode current collector foil 6 (step S4). Each step will be described below.

[0015] (Step S1) Formation of Positive Electrode Layer First, the positive electrode layer is formed. FIG. 3A is a schematic cross-sectional view showing the step of forming the positive electrode layer (Step S1). The positive electrode layer 3 is formed on the positive electrode current collector foil 2. The positive electrode layer 3 can be formed, for example, by applying a slurry containing the constituent materials thereof and drying it. Alternatively, the positive electrode layer 3 may be formed by transfer printing.

[0016] (Step S2) Formation of Solid Electrolyte Layer Next, a solid electrolyte layer 4 having an inclined portion 7 is formed. FIG. 3B is a schematic cross-sectional view showing the step of forming a solid electrolyte layer (step S2). As shown in FIG. 3B, the solid electrolyte layer 4 is formed on the positive electrode layer 3. Like the positive electrode layer 3, the solid electrolyte layer 4 can also be formed by coating or transferring a slurry.

[0017] (Step S3) Transfer of Negative Electrode Layer Next, the negative electrode layer 5 is transferred using a roll press. FIG. 3C is a schematic cross-sectional view showing this step. The roll press is performed so that the roll 8 moves along the first direction. At this time, the inclined portion 7 is provided, so that loss of load is prevented. This point will be specifically described with reference to a reference example.

[0018] 4 is a schematic cross-sectional view showing an all-solid-state battery according to a reference example. In this reference example, at the end portion of the solid electrolyte layer 4 in the first direction, the height of its upper surface is lowered along the first direction. That is, a slope opposite to that of the sloped portion 7 in the present embodiment is formed. When such a configuration is adopted, load loss occurs at the end portion in the first direction during roll pressing, making transfer defects of the anode layer 5 more likely to occur. In contrast, in the present embodiment, the sloped portion 7 is provided at the end portion in the first direction. At the sloped portion 7, the height of the upper surface increases as the roll advances, so load loss does not occur. This makes it possible to suppress transfer defects.

[0019] In this embodiment, as a preferred example, the inclined portion 7 is also provided at the starting end in the first direction (see FIG. 3C , etc.). Meanwhile, FIG. 5 is a schematic cross-sectional view showing an all-solid-state battery according to another reference example. In this reference example, the solid electrolyte layer 4 bulges at the starting end in the first direction. As a result, a portion of the starting end is inclined so that its height decreases along the first direction. Even when such a configuration is adopted, load loss may occur at the inclined portion, resulting in transfer defects. In contrast, if the inclined portion 7 is also provided at the starting end in the first direction, load loss at the starting end is also prevented. This more reliably prevents transfer defects.

[0020] (Step S4) Formation of Negative Electrode Current Collector Foil After the formation of the negative electrode layer 5, the negative electrode current collector foil 6 is formed on the negative electrode layer 5. Thereafter, necessary steps such as connecting a tab are carried out. In this way, the all-solid-state battery 1 is obtained.

[0021] As described above, according to this embodiment, since the inclined portion 7 is provided, no loss of load occurs when the negative electrode layer 5 is transferred by roll pressing. This makes it possible to suppress transfer defects of the negative electrode layer 5.

[0022] (Others) In the present embodiment, the case where the anode layer 5 is transferred onto the solid electrolyte layer 4 by roll pressing has been described as an example. However, an anode intermediate layer may be used instead of the anode layer 5. The anode intermediate layer is a layer provided on the solid electrolyte layer 4 in a deposition-type all-solid-state battery. A deposition-type all-solid-state battery is an all-solid-state battery configured such that metallic lithium is deposited as an anode active material between the solid electrolyte layer 4 and the anode current collector foil 6 during charging. In such a deposition-type all-solid-state battery, if the deposited metallic lithium comes into direct contact with the solid electrolyte layer 4, the solid electrolyte layer 4 may be damaged. Therefore, an anode intermediate layer may be used to protect the solid electrolyte layer 4. The metallic lithium as the anode active material is deposited between the anode intermediate layer and the anode current collector foil 6 and does not come into contact with the solid electrolyte layer 4. This protects the solid electrolyte layer 4. When producing an all-solid-state battery having such an anode intermediate layer, the anode intermediate layer may be transferred onto the solid electrolyte layer 4 by roll pressing instead of the anode layer. When transferring the negative electrode intermediate layer, transfer defects due to loss of load may occur. However, according to this embodiment, the provision of the inclined portion 7 makes it possible to prevent transfer defects when transferring the negative electrode intermediate layer.

[0023] In this embodiment, as a preferred example, a case where the inclined portion 7 is provided at the starting end and the ending end in the first direction as shown in Fig. 1 has been described. However, it is sufficient that the inclined portion 7 is provided at least at the ending end in the first direction. In other words, the inclined portion 7 does not have to be provided at the starting end. Alternatively, the inclined portion 7 may be provided in a portion other than the starting end.

[0024] 6 is a schematic cross-sectional view showing a configuration of an all-solid-state battery 1 according to a modified example of this embodiment during manufacturing. In the example shown in Fig. 6, the entire area of ​​the solid electrolyte layer 4 is the inclined portion 7. Even when such a configuration is adopted, load loss is prevented, and therefore transfer defects of the anode layer 5 are prevented.

[0025] In a preferred embodiment, when viewed along the stacking direction, the area occupied by the inclined portion 7 is 10 to 100% of the entire area of ​​the solid electrolyte layer 4. If the inclined portion 7 is provided in such a range, transfer defects of the negative electrode layer or the negative electrode intermediate layer can be more reliably prevented.

[0026] In a preferred embodiment, the inclination angle of the inclined portion 7 is 2 to 60°. FIG. 7 is a cross-sectional view illustrating the inclination angle. As shown in FIG. 7, the inclination angle θ refers to the angle of the upper surface of the inclined portion 7 with respect to a flat surface (a surface parallel to the positive electrode layer 3 and the positive electrode current collector foil 2). If the inclination angle is 2° or more, load loss is sufficiently prevented. If the inclination angle is 60° or less, a load is easily applied uniformly to the negative electrode layer 5 during roll pressing, making it less likely that the negative electrode layer 5 will "twist." The inclination angle of the inclined portion 7 is preferably 20 to 40°.

[0027] The inclination angle of the inclined portion 7 does not have to be constant. FIG. 8 is a cross-sectional view showing a modified example of this embodiment. In this modified example, the inclined portion 7 has multiple regions (regions 7-1 and 7-2) with different inclination angles. As in this modified example, multiple regions with different inclination angles may be formed. In the example shown in FIG. 8, region 7-1 and region 7-2 are continuous. However, the multiple regions may be separated.

[0028] In a preferred embodiment, the inclination angle of the region on the terminal end side in the first direction among the plurality of regions (7-1, 7-2) is larger than the inclination angle of the region on the starting end side. With this configuration, even if the roll speed during roll pressing is increased, load loss is less likely to occur, and transfer defects of the negative electrode layer 5 can be more reliably prevented.

[0029] As described above, in step S2, the solid electrolyte layer 4 having the inclined portion 7 is formed. The method for forming the inclined portion 7 is not particularly limited. For example, the inclined portion 7 can be formed by performing at least one roll press. That is, after the solid electrolyte layer 4 is placed on the positive electrode layer 3, roll press is performed with the first direction as the moving direction. If the rolls are moved at a certain speed during roll press, load loss occurs at the end portion in the first direction. Due to load loss, the end portion of the solid electrolyte layer 4 is less likely to be compressed than other portions. As a result, the thickness of the end portion of the solid electrolyte layer 4 increases along the first direction. This allows the inclined portion 7 to be formed at the end portion.

[0030] In a preferred embodiment, at least one additional roll press (hereinafter referred to as additional roll press) is performed after the step (step S3) of transferring the negative electrode layer 5 (or the negative electrode intermediate layer). By performing the additional roll press, the negative electrode layer 5 (or the negative electrode intermediate layer) can be more firmly bonded to the solid electrolyte layer 4. The additional roll press may be performed before disposing the negative electrode current collector foil 6 on the negative electrode layer 5, or may be performed before disposing the negative electrode current collector foil 6. Alternatively, the additional roll press may be a roll press performed to dispose the negative electrode current collector foil 6.

[0031] (2) Second Embodiment Next, a second embodiment will be described. Note that detailed description of the same points as in the first embodiment will be omitted.

[0032] FIG. 9 is a plan view showing the all-solid-state battery 1 according to this embodiment. FIG. 10 is a view showing the AA' cross section of FIG. 9. In this embodiment, a second direction is defined as a direction perpendicular to both the stacking direction and the first direction. Supports 9 are disposed on both sides of the positive electrode layer 3 in the second direction. The supports 9 are disposed on the positive electrode current collector foil 2. The supports 9 are formed before the step of forming the solid electrolyte layer 4 (step S2). The supports 9 extend along the first direction. In the second direction, the ends of the solid electrolyte layer 4 are located outside the ends of the positive electrode layer 3 and are supported by the supports 9.

[0033] According to this embodiment, the solid electrolyte layer 4 is supported by the support 9 at both ends in the second direction. Therefore, load loss during roll pressing is suppressed at both ends in the second direction as well. As a result, the anode layer 5 (or the anode intermediate layer) can be firmly bonded to the solid electrolyte layer 4.

[0034] Note that, for example, an insulating material can be used as the support 9. For example, the support 9 can be formed from an insulating polymer, an ion-conductive polymer, an insulating inorganic material, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or the like.

[0035] (3) Constituent Materials, etc. Next, constituent materials, etc. of each part included in the all-solid-state battery 1 described in the above-described embodiment will be described.

[0036] There are no particular limitations on the positive electrode current collector foil 2 as long as it can be used in the all-solid-state battery 1. For example, aluminum foil or the like can be used as the positive electrode current collector foil 2. The thickness of the positive electrode current collector foil 2 is, for example, 5 to 50 μm, and preferably 8 to 20 μm.

[0037] The constituent material of the solid electrolyte layer 4 is not particularly limited. Preferably, the solid electrolyte layer 4 includes a solid electrolyte and a binder. Examples of the solid electrolyte include a sulfide solid electrolyte. Examples of the sulfide solid electrolyte include Li ２ S-P ２ S ５ Li-based compounds and the like can be mentioned. ２ S-P ２ S ５ Examples of the Li-based compounds include ２ S and P ２ S ５ In addition, compounds containing lithium halide can be used. For example, the sulfide solid electrolyte can be Li ２ S-P ２ S ５ System LiCl, Li ２ S-P ２ S ５ The system LiBr and Li ２ S-P ２ S ５The content of the solid electrolyte in the solid electrolyte layer 4 is, for example, 90 mass % or more.

[0038] Examples of the binder contained in the solid electrolyte layer 4 include a fluorine-based binder such as polyvinylidene fluoride (PVDF) and styrene butadiene rubber (SBR). The content of the binder in the solid electrolyte layer 4 is, for example, 2 to 10 mass %.

[0039] The thickness of the solid electrolyte layer 4 is, for example, 5 to 100 μm.

[0040] The positive electrode layer 3 includes a positive electrode active material. The positive electrode active material is not particularly limited, but may include, for example, an NMC-based positive electrode active material. The positive electrode layer 3 may further include an auxiliary agent and a binder. For example, carbon materials include carbon black such as acetylene black, graphite, and carbon nanotubes. For example, binders include fluorine-based binders such as polyvinylidene fluoride (PVDF), and styrene butadiene rubber (SBR).

[0041] The thickness of the positive electrode layer is, for example, 10 to 500 μm, preferably 50 to 200 μm.

[0042] There is no particular limitation on the material of the negative electrode current collector foil 6. For example, SUS and copper foils can be used as the negative electrode current collector foil 6.

[0043] The negative electrode layer 5 is a layer containing a negative electrode active material. The negative electrode active material is not particularly limited. The negative electrode layer 5 may be configured to absorb lithium (or precipitate lithium) during charging and release lithium ions during discharging. For example, the negative electrode layer 5 may be formed from a material containing a resin binder and a negative electrode active material dispersed in the resin binder. Examples of the negative electrode active material that can be used include lithium metal, silicon materials, tin materials, compounds containing silicon or tin (oxides, nitrides, alloys with other metals), and carbon materials (graphite, etc.). The thickness of the negative electrode layer 5 is, for example, 1 to 50 μm, preferably 10 to 30 μm.

[0044] The negative electrode intermediate layer only needs to have the function of protecting the solid electrolyte layer 4 from metallic lithium that deposits on the negative electrode side during charging. The negative electrode intermediate layer can be realized, for example, by a layer containing carbon particles such as carbon black, metal particles (silver particles), and a binder (for example, a resin binder). The thickness of the negative electrode intermediate layer is, for example, 1 to 50 μm, preferably 10 to 30 μm.

[0045] [Additional Notes] Representative configurations included in this embodiment are summarized below as additional notes.

[0046] (Supplementary Note 1) A method for manufacturing an all-solid-state battery, comprising: a step of forming a positive electrode layer (step S1); a step of forming a solid electrolyte layer (4) on the positive electrode layer (3) (step S2); and a step of transferring an anode layer (5) or an anode intermediate layer onto the solid electrolyte layer (4) by roll pressing with a first direction as a traveling direction (step S3), wherein the solid electrolyte layer (4) is formed so as to cover an end face of the positive electrode layer (3) at an end portion in the first direction, and the solid electrolyte layer (4) has an inclined portion (7) having a shape such that an upper surface rises along the first direction, and the inclined portion (7) is provided at least at an end portion of the solid electrolyte layer in the first direction.

[0047] According to this method, since the inclined portion 7 is provided at the end portion in the first direction, load loss is unlikely to occur during roll pressing, and as a result, transfer defects of the negative electrode layer or the negative electrode intermediate layer can be prevented.

[0048] (Supplementary Note 2) The manufacturing method according to Supplementary Note 1, wherein the step of forming the solid electrolyte layer includes the step of forming the inclined portion by performing roll pressing with the first direction as a traveling direction.

[0049] This method allows for the creation of a sloped portion.

[0050] (Supplementary Note 3) The manufacturing method according to Supplementary Note 1 or 2, wherein an area occupied by the inclined portion is 10 to 100% of an entire area of ​​the solid electrolyte layer when viewed along the stacking direction.

[0051] According to this method, the loss of load during roll pressing can be more reliably suppressed, and transfer defects of the negative electrode layer or the negative electrode intermediate layer can be more reliably prevented.

[0052] (Supplementary Note 4) The manufacturing method according to any one of Supplementary Notes 1 to 3, wherein the inclination angle of the inclined portion is 2 to 60°.

[0053] According to this method, since the inclination angle is 2° or more, load loss during roll pressing is more reliably suppressed, and transfer defects of the negative electrode layer or negative electrode intermediate layer are more reliably prevented. Furthermore, since the inclination angle is 60° or less, the load is applied uniformly to the negative electrode layer or negative electrode intermediate layer at the inclined portion. Therefore, the occurrence of "twist" due to uneven application of the load is prevented.

[0054] (Supplementary Note 5) The manufacturing method according to any one of Supplementary Notes 1 to 4, wherein the inclined portion has a plurality of regions with different inclination angles.

[0055] (Appendix 6) The manufacturing method according to any one of appendices 1 to 5, further comprising the step of performing roll pressing at least once after the step of transferring the negative electrode layer or the negative electrode intermediate layer.

[0056] According to this method, the negative electrode layer or the negative electrode intermediate layer can be more firmly adhered to the solid electrolyte layer.

[0057] (Supplementary Note 7) The manufacturing method according to any one of Supplementary Notes 1 to 6, wherein a direction perpendicular to both the stacking direction and the first direction is defined as a second direction, and the manufacturing method further includes a step of arranging supports on both sides of the positive electrode layer in the second direction, and an end of the solid electrolyte layer is located outside an end of the positive electrode layer in the second direction and is supported by the supports.

[0058] According to this method, the load loss is prevented even at both ends in the second direction, and therefore transfer defects of the negative electrode layer or the negative electrode intermediate layer are more reliably prevented.

Claims

1. A method for manufacturing an all-solid-state battery, comprising: a step of forming a positive electrode layer; a step of forming a solid electrolyte layer on the positive electrode layer; and a step of transferring an anode layer or an anode intermediate layer onto the solid electrolyte layer by roll pressing with a first direction as a traveling direction, wherein the solid electrolyte layer is formed so as to cover an end face of the positive electrode layer at an end portion in the first direction, and the solid electrolyte layer has an inclined portion having a shape such that an upper surface becomes higher along the first direction, and the inclined portion is provided at least at an end portion of the solid electrolyte layer in the first direction.

2. A manufacturing method according to claim 1, wherein the step of forming the solid electrolyte layer includes a step of forming the inclined portion by performing roll pressing with the first direction as a progression direction.

3. A manufacturing method according to claim 1 or 2, wherein the area occupied by the inclined portion when viewed along the stacking direction is 10 to 100% of the area of ​​the entire solid electrolyte layer.

4. A manufacturing method according to claim 1 or 2, wherein the inclination angle of the inclined portion is 2 to 60 degrees.

5. A manufacturing method according to claim 1 or 2, wherein the inclined portion has a plurality of regions with different inclination angles.

6. The manufacturing method according to claim 1 or 2, further comprising the step of performing roll pressing at least once after the step of transferring the negative electrode layer or the negative electrode intermediate layer.

7. A manufacturing method according to claim 1 or 2, wherein a direction perpendicular to both the stacking direction and the first direction is defined as a second direction, and the manufacturing method further comprises a step of arranging supports on both sides of the positive electrode layer in the second direction, and an end of the solid electrolyte layer is located outside the end of the positive electrode layer in the second direction and is supported by the supports.

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