solid-state batteries

Abstract

To provide a solid-state battery capable of suppressing the occurrence of a crack in a positive electrode mixture layer and a solid electrolyte layer during production.SOLUTION: A solid-state battery 1 includes an electrode laminate in which a negative electrode 2, a solid electrolyte layer 4, and a positive electrode 3 are sequentially laminated. The solid electrolyte layer 4 includes: a first solid electrolyte layer 41 disposed on the negative electrode 2 side; and a second solid electrolyte layer 42 disposed on the positive electrode 3 side. The positive electrode 3 includes: a positive electrode current collector 32; and a positive electrode mixture layer 31, and an inclined surface is formed on at least one end part 31a of the positive electrode mixture layer 31. In the solid-state battery 1, an outer peripheral part of the first solid electrolyte layer 41 exists on the outer side of the outer peripheral part of the positive electrode mixture layer 31 when viewed from above in a stacking direction of the electrode laminate.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to a solid-state battery. 【Background Art】 【0002】 In recent years, research and development have been carried out on solid-state batteries that contribute to energy efficiency in order to enable more people to access affordable, reliable, sustainable, and advanced energy. 【0003】 As a solid-state battery, an all-solid-state battery in which a solid electrolyte layer is disposed between a positive electrode and a negative electrode is known. 【0004】 Patent Document 1 describes an all-solid-state battery including a positive electrode in which a positive electrode current collector layer and a positive electrode active material layer containing at least a solid electrolyte are laminated, a negative electrode in which a negative electrode current collector layer and a negative electrode active material layer containing at least a solid electrolyte are laminated, and a first solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. Here, in the all-solid-state battery, in a direction perpendicular to the lamination direction, the area of the negative electrode active material layer is larger than the area of the positive electrode active material layer, and in a direction perpendicular to the lamination direction, the area of the first solid electrolyte layer is larger than the area of the positive electrode active material layer, and the porosity n1 of the positive electrode active material layer am is 5% or less. 【0005】 Further, Patent Document 1 describes a method for manufacturing an all-solid-state battery, including a step of forming a positive electrode by pressing a positive electrode current collector layer and a positive electrode active material layer in a laminated state, a step of forming a negative electrode by pressing a negative electrode current collector layer and a negative electrode active material layer in a laminated state, and a step of forming a laminate unit by pressing a positive electrode, a first solid electrolyte layer, and a negative electrode in this order in a laminated state. 【Prior Art Documents】 【Patent Documents】 【0006】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2022-144855 【Summary of the Invention】 [Problems that the invention aims to solve] 【0007】 However, in the method for manufacturing an all-solid-state battery described in Patent Document 1, when the positive electrode, the first solid electrolyte layer, and the negative electrode are stacked in this order and pressurized, the first solid electrolyte layer may penetrate the edge of the positive electrode active material layer, causing the first solid electrolyte layer to come into close contact with the positive electrode current collector tab. If further pressurization is applied at this time, the edge of the positive electrode active material layer is constrained by the first solid electrolyte layer, causing stress concentration and resulting in cracks in the positive electrode active material layer and the first solid electrolyte layer. As a result, the capacity and durability of the all-solid-state battery may decrease. 【0008】 The present invention aims to provide a solid-state battery capable of suppressing the occurrence of cracks in the positive electrode composite layer and the solid electrolyte layer during manufacturing. [Means for solving the problem] 【0009】 (1) A solid-state battery comprising an electrode stack in which a negative electrode, a solid electrolyte layer, and a positive electrode are sequentially stacked, wherein the solid electrolyte layer comprises a first solid electrolyte layer located on the negative electrode side and a second solid electrolyte layer located on the positive electrode side, and the positive electrode comprises a positive electrode current collector and a positive electrode composite layer, wherein a bevel is formed on at least one end of the positive electrode composite layer, and when viewed from above in the stacking direction of the electrode stack, the outer periphery of the first solid electrolyte layer is located outside the outer periphery of the positive electrode composite layer. 【0010】 (2) The solid battery according to (1), wherein, when viewed from above in the stacking direction of the electrode stack, the end of the positive electrode current collector on the side where the slope is formed is located outside the outer circumference of the positive electrode composite layer. 【0011】 (3) The solid battery according to (2), wherein the positive electrode current collector has the second solid electrolyte layer formed on a surface on which the positive electrode composite layer is not formed. 【0012】 (4) The solid battery according to any one of (1) to (3), wherein the density of the region of the first solid electrolyte layer opposite to the region of the positive electrode composite layer where the slope is not formed is higher than the density of the region of the first solid electrolyte layer that does not oppose the region of the positive electrode composite layer where the slope is not formed. 【0013】 (5) The solid battery according to any one of (1) to (4), wherein the density of the region of the second solid electrolyte layer that does not face the region of the positive electrode composite layer in which the slope is not formed is higher than the density of the region of the first solid electrolyte layer that does not face the region of the positive electrode composite layer in which the slope is not formed. 【0014】 (6) The solid battery according to any one of (1) to (5), wherein, when viewed from above in the stacking direction of the electrode stack, the outer periphery of the first solid electrolyte layer is located outside the outer periphery of the second solid electrolyte layer. 【0015】 (7) A solid-state battery as described in any one of items (1) to (6), which is an all-solid-state lithium metal battery. [Effects of the Invention] 【0016】 According to the present invention, it is possible to provide a solid-state battery that can suppress the occurrence of cracks in the positive electrode composite layer and the solid electrolyte layer during manufacturing. [Brief explanation of the drawing] 【0017】 [Figure 1] This is a cross-sectional view showing a solid-state battery according to the present invention. [Figure 2] Figure 1 is a cross-sectional view showing the state of the solid battery during pressing. [Figure 3] This is a cross-sectional view showing the state during pressing when no slope is formed at the end of the positive electrode composite layer on the side where the positive electrode current collector tab extends. [Figure 4] This is a cross-sectional view showing a modified example of the positive electrode in Figure 1. [Figure 5] This is a cross-sectional view illustrating regions A and B of the solid-state battery in Figure 1. 【Best Mode for Carrying Out the Invention】 【0018】 Hereinafter, embodiments of the present invention will be described with reference to the drawings. 【0019】 [Solid State Battery] FIG. 1 shows a solid state battery according to an embodiment of the present invention. 【0020】 The solid state battery 1 includes an electrode laminate in which a negative electrode 2, a solid electrolyte layer 4, a positive electrode 3, the solid electrolyte layer 4, and the negative electrode 2 are sequentially laminated. Here, the solid electrolyte layer 4 includes a first solid electrolyte layer 41 disposed on the side of the negative electrode 2 and a second solid electrolyte layer 42 disposed on the side of the positive electrode 3. Further, the positive electrode 3 includes a positive electrode composite layer 31, a positive electrode current collector 32, and the positive electrode composite layer 31 sequentially laminated in the stacking direction of the electrode laminate, and a positive electrode current collecting tab extends from one end of the positive electrode current collector 32, for example, in the depth direction in the figure. Furthermore, the negative electrode 2 includes a negative electrode composite layer 21 and a negative electrode current collector 22 sequentially laminated in the stacking direction of the electrode laminate, and a negative electrode current collecting tab extends from the end of the negative electrode current collector 22 on the side opposite to the side where the positive electrode current collecting tab extends, for example, in the front direction in the figure. 【0021】 When viewed from above in the stacking direction of the electrode stack, the outer periphery of the negative electrode composite layer 21 and the first solid electrolyte layer 41 of the solid battery 1 is located outside the outer periphery of the positive electrode current collector 32 and the second solid electrolyte layer 42. At this time, the outer periphery of the negative electrode composite layer 21 is located at approximately the same position as the outer periphery of the first solid electrolyte layer 41, and the outer periphery of the positive electrode current collector 32 is located at approximately the same position as the outer periphery of the second solid electrolyte layer 42. In addition, the positive electrode composite layer 31 has bevels formed on both the left and right ends 31a in the figure. Therefore, when manufacturing the electrode stack by pressing the negative electrode 2, solid electrolyte layer 4, positive electrode 3, solid electrolyte layer 4, and negative electrode 2 in a sequential stacked state, the first solid electrolyte layer 41 gently fits into the bevels formed on the ends 31a of the positive electrode composite layer 31 (see Figure 2). In this case, the elongation of the positive electrode composite layer 31 and the second solid electrolyte layer 42 is not hindered, and the occurrence of cracks in the positive electrode composite layer 31 and the solid electrolyte layer 4 is suppressed. As a result, the decrease in capacity and durability of the solid battery 1 is suppressed. 【0022】 The inclination only needs to be formed at at least one end of the positive electrode composite layer 31, and may be formed at all ends of the positive electrode composite layer 31, or at just one end of the positive electrode composite layer 31. 【0023】 On the other hand, if a slope is not formed at the end of the positive electrode composite layer 31, when the negative electrode 2, solid electrolyte layer 4, positive electrode 3, solid electrolyte layer 4, and negative electrode 2 are pressed in a sequentially stacked state (see Figure 3(a)), the first solid electrolyte layer 41 may enter the edges of the positive electrode composite layer 31 and the second solid electrolyte layer 42, causing the first solid electrolyte layer 41 to come into close contact with the positive electrode current collector tab 32a (see Figure 3(b)). When this occurs, further pressing will cause stress to concentrate as the edges of the positive electrode composite layer 31 and the second solid electrolyte layer 42 are constrained by the first solid electrolyte layer 41, resulting in cracks in the positive electrode composite layer 31 and the solid electrolyte layer 4. 【0024】 The angle of inclination formed at the edge of the positive electrode composite layer 31 is not particularly limited, but is, for example, 3° or more and 60° or less. 【0025】 When viewed from above in the stacking direction of the electrode stack, the end of the positive electrode current collector 32 on the side where the slope of the positive electrode composite layer 31 is formed is located outside the outer circumference of the positive electrode composite layer 31. This makes it easier for the first solid electrolyte layer 41 to gently fit into the slope formed on the end 31a of the positive electrode composite layer 31. 【0026】 The area ratio of the region on the side (one end) where the slope of the positive electrode composite layer 31 is formed to the region where the positive electrode composite layer 31 is formed of the positive electrode current collector 32 is not particularly limited, but is, for example, 1 / 1000 or more and 1 / 5 or less. 【0027】 Furthermore, when viewing the solid-state battery 1 from above in the stacking direction of the electrode stack, the end of the positive electrode current collector 32 on the side where the slope of the positive electrode composite layer 31 is formed may be located in approximately the same position as the end of the positive electrode composite layer 31 on the side where the slope of the positive electrode composite layer 31 is formed (see Figure 4). 【0028】 The positive electrode current collector 32 has a second solid electrolyte layer 42 formed on the surface where the positive electrode composite layer 31 is not formed. This suppresses short circuits in the solid-state battery 1. 【0029】 Due to the pressure applied when pressing to obtain the electrode laminate, as described later, the density of region A (see Figure 5) of the first solid electrolyte layer 41 opposite to the region where the slope of the positive electrode composite layer 31 is not formed becomes higher than the density of region B (see Figure 5) of the first solid electrolyte layer 41 that does not oppose the region where the slope of the positive electrode composite layer 31 is not formed. Also, the density of region B of the second solid electrolyte layer 42 becomes higher than the density of region B of the first solid electrolyte layer 41. 【0030】 The density of region A of the first solid electrolyte layer 41 is not particularly limited, but for example, 0.5 g / cm³ 3 More than 6g / cm 3The following applies: The density of region B of the first solid electrolyte layer 41 is not particularly limited, but for example, it is 95% or less of the density of region A of the first solid electrolyte layer 41. The thickness of region A of the first solid electrolyte layer 41 is not particularly limited, but for example, it is 1 μm or more and 500 μm or less. 【0031】 The density of region A in the second solid electrolyte layer 42 is not particularly limited, but for example, 0.5 g / cm³ 3 More than 6g / cm 3 The following applies: The density of region B of the second solid electrolyte layer 42 is not particularly limited, but is 105% or more of the density of region B of the first solid electrolyte layer 41. The thickness of region A of the second solid electrolyte layer 42 is not particularly limited, but is, for example, 1 μm or more and 500 μm or less. 【0032】 The solid-state battery 1 is not particularly limited as long as it comprises an electrode stack in which a negative electrode 2, a solid electrolyte layer 4, and a positive electrode 3 are sequentially stacked. For example, the solid-state battery 1 may comprise multiple positive electrodes 3. Alternatively, the solid-state battery 1 may comprise a single negative electrode 2 and a single solid electrolyte layer 4. In this case, the positive electrode 3 consists of a positive electrode composite layer 31 and a positive electrode current collector 32 sequentially stacked in the stacking direction of the electrode stack. 【0033】 [Manufacturing method for solid-state batteries] Next, we will explain the manufacturing method of the solid-state battery 1. 【0034】 (First solid electrolyte layer - negative electrode laminate) A first solid electrolyte layer-negative electrode laminate is obtained by pressing the negative electrode 2 with the material constituting the first solid electrolyte layer 41 placed on the side of the negative electrode 2 where the negative electrode composite layer 21 is located. The method for placing the material constituting the first solid electrolyte layer 41 on the side of the negative electrode 2 where the negative electrode composite layer 21 is located is not particularly limited, but one example is to transfer the first solid electrolyte layer 41 onto the negative electrode composite layer 21 using a first solid electrolyte layer transfer sheet. The first solid electrolyte layer transfer sheet can be obtained, for example, by dispersing a solid electrolyte with a median diameter of 1 μm or less in a solvent, applying a slurry obtained from this slurry to a support sheet, and then drying it. The pressing pressure is not particularly limited, but for example, it is between 10 MPa and 2000 MPa. The pressing temperature is not particularly limited, but for example, it is between room temperature and 200°C. 【0035】 (Second solid electrolyte layer - cathode laminate) A second solid electrolyte layer-positive electrode laminate is obtained by pressing the positive electrode 3 with the materials constituting the second solid electrolyte layer 42 placed on both sides of the positive electrode composite layer 31. The method for placing the materials constituting the second solid electrolyte layer 42 on both sides of the positive electrode 3 with the positive electrode composite layer 31 is not particularly limited, but one example is to transfer the second solid electrolyte layer 42 onto the positive electrode composite layer 31 using a second solid electrolyte layer transfer sheet. The second solid electrolyte layer transfer sheet can be obtained, for example, by dispersing a solid electrolyte with a median diameter of 1 μm or less in a solvent, applying the resulting slurry to a support sheet, and then drying it. The pressing pressure is not particularly limited, but for example, it is between 10 MPa and 2000 MPa. The pressing temperature is not particularly limited, but for example, it is between room temperature and 1500°C. 【0036】 (Electrode stack) An electrode laminate is obtained by pressing the first solid electrolyte layer-negative electrode laminate with the side on which the first solid electrolyte layer 41 is located facing the side on which the second solid electrolyte layer-positive electrode laminate is located. The pressing pressure is not particularly limited as long as it is possible to integrate the solid electrolyte layers 4, but for example, it is between 10 MPa and 2000 MPa. The pressing temperature is not particularly limited, but for example, it is between room temperature and 1500°C. 【0037】 The equipment used to manufacture the solid battery 1 is not particularly limited, but examples include a roll press and a flat plate press. 【0038】 The solid-state battery 1 is not particularly limited, but an example is an all-solid-state lithium metal battery. The following description will focus on the case where the solid-state battery 1 is an all-solid-state lithium metal battery. 【0039】 The negative electrode composite layer 21 is a lithium metal layer. The negative electrode current collector 22 is not particularly limited, but an example is copper foil. 【0040】 The positive electrode composite layer 31 contains a positive electrode active material and may further contain a solid electrolyte, a conductive additive, a binder, etc. The positive electrode active material is not particularly limited as long as it is capable of intercalating and releasing lithium ions, but examples include lithium nickel cobalt manganese composite oxide. The solid electrolyte is not particularly limited as long as it has lithium ion conductivity, but examples include oxide-based electrolytes and sulfide-based electrolytes. The conductive additive is not particularly limited as long as it has electronic conductivity, but examples include carbon black. The binder is not particularly limited as long as it can improve the binding properties, but examples include styrene butadiene rubber. 【0041】 The positive electrode current collector 32 is not particularly limited, but an example is aluminum foil. 【0042】 The first solid electrolyte layer 41 and the second solid electrolyte layer 42 contain a solid electrolyte and may further contain a binder or the like. The solid electrolyte is not particularly limited as long as it has lithium ion conductivity, but examples include inorganic solid electrolytes such as oxide-based electrolytes and sulfide-based electrolytes. The solid electrolytes constituting the first solid electrolyte layer 41 and the second solid electrolyte layer 42 may be the same or different. The binder is not particularly limited as long as it can improve the binding properties, but examples include styrene-butadiene rubber. 【0043】 Furthermore, the electrode stack may have an intermediate layer formed between the negative electrode 2 and the solid electrolyte layer 4, which has the function of uniformly depositing lithium metal. This stabilizes the interface between the intermediate layer and the first solid electrolyte layer 41. In this case, the solid battery 1 may be an anode-free battery in which the lithium metal layer as the negative electrode composite layer 21 is not formed at the time of the first charge. In an anode-free battery, the lithium metal layer as the negative electrode composite layer 21 is formed after the first charge and discharge. 【0044】 The intermediate layer contains a metal that can alloy with lithium and amorphous carbon, and may further contain a binder. The metal that can alloy with lithium and amorphous carbon are preferably nanoparticles. Examples of metals that can alloy with lithium include tin (Sn), silicon (Si), zinc (Zn), magnesium (Mg), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), aluminum (Al), bismuth (Bi), and antimony (Sb). Examples of amorphous carbon include carbon blacks such as acetylene black, furnace black, and Ketjen black, as well as coke and activated carbon. The amorphous carbon may be easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), CNT (carbon nanotube), fullerene, or graphene. The binder is not particularly limited as long as it can improve binding properties, but an example is polyvinylidene fluoride (PVDF). 【0045】 The thickness of the intermediate layer is not particularly limited, but for example, it is between 1 μm and 10 μm. 【0046】 Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the above embodiments may be modified as appropriate within the scope of the spirit of the present invention. For example, the solid battery 1 may further include an outer casing (for example, a laminate film) that surrounds the electrode stack. [Explanation of Symbols] 【0047】 1 solid state battery 2 negative electrode 21 Negative electrode composite layer 22 Negative electrode current collector 3 Positive electrode 31. Positive electrode composite layer 31a End 32 Positive electrode current collector 32a Positive electrode current collector tab 4 Solid electrolyte layer 41 First solid electrolyte layer 42 Second solid electrolyte layer

Claims

[Claim 1] The electrode laminate comprises a negative electrode, a solid electrolyte layer, and a positive electrode, which are stacked sequentially. The solid electrolyte layer comprises a first solid electrolyte layer located on the negative electrode side and a second solid electrolyte layer located on the positive electrode side. The positive electrode comprises a positive electrode current collector and a positive electrode composite layer, and a slope is formed at at least one end of the positive electrode composite layer. When viewed from above in the stacking direction of the electrode stack, the outer periphery of the first solid electrolyte layer is located outside the outer periphery of the positive electrode composite layer. A solid-state battery in which the density of the region of the first solid electrolyte layer opposite to the region of the positive electrode composite layer where the slope is not formed is higher than the density of the region of the first solid electrolyte layer that does not oppose the region of the positive electrode composite layer where the slope is not formed. [Claim 2] The electrode laminate comprises a negative electrode, a solid electrolyte layer, and a positive electrode, which are stacked sequentially. The solid electrolyte layer comprises a first solid electrolyte layer located on the negative electrode side and a second solid electrolyte layer located on the positive electrode side. The positive electrode comprises a positive electrode current collector and a positive electrode composite layer, and a slope is formed at at least one end of the positive electrode composite layer. When viewed from above in the stacking direction of the electrode stack, the outer periphery of the first solid electrolyte layer is located outside the outer periphery of the positive electrode composite layer. A solid-state battery in which the density of the region of the positive electrode composite material layer in the second solid electrolyte layer that does not face the region where the slope is not formed is higher than the density of the region of the positive electrode composite material layer in the first solid electrolyte layer that does not face the region where the slope is not formed. [Claim 3] The electrode laminate comprises a negative electrode, a solid electrolyte layer, and a positive electrode, which are stacked sequentially. The solid electrolyte layer comprises a first solid electrolyte layer located on the negative electrode side and a second solid electrolyte layer located on the positive electrode side. The positive electrode comprises a positive electrode current collector and a positive electrode composite layer, and a slope is formed at at least one end of the positive electrode composite layer. When viewed from above in the stacking direction of the electrode stack, the outer periphery of the first solid electrolyte layer is located outside the outer periphery of the positive electrode composite layer. A solid-state battery in which, when viewed from above in the stacking direction of the electrode stack, the outer periphery of the first solid electrolyte layer is located outside the outer periphery of the second solid electrolyte layer. [Claim 4] The solid battery according to any one of claims 1 to 3, wherein, when viewed from above in the stacking direction of the electrode stack, the end of the positive electrode current collector on the side where the slope is formed is located outside the outer periphery of the positive electrode composite layer. [Claim 5] The solid battery according to claim 4, wherein the positive electrode current collector has the second solid electrolyte layer formed on a surface where the positive electrode composite layer is not formed. [Claim 6] The solid battery according to any one of claims 1 to 3, which is an all-solid-state lithium metal battery.

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