Solid-state battery

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 technology]

[0002] In recent years, research and development into solid-state batteries has been conducted to contribute to energy efficiency, ensuring more people have access to 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 formed by laminating a positive electrode current collector layer and a positive electrode active material layer containing at least a solid electrolyte, a negative electrode formed by laminating a negative electrode current collector layer and a negative electrode active material layer containing at least a solid electrolyte, and a first solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer. The all-solid-state battery has a structure in which the area of ​​the negative electrode active material layer is larger than the area of ​​the positive electrode active material layer 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 in a direction perpendicular to the lamination direction, and the porosity n1 of the positive electrode active material layer is larger than the area of ​​the negative electrode active material layer in a direction perpendicular to the lamination direction. am is less than 5%.

[0005] Patent Document 1 also describes a method for manufacturing an all-solid-state battery, which includes a step of forming a positive electrode by applying pressure to a positive electrode current collector layer and a positive electrode active material layer in a stacked state, a step of forming a negative electrode by applying pressure to a negative electrode current collector layer and a negative electrode active material layer in a stacked state, and a step of forming a stack unit by applying pressure to a positive electrode, a first solid electrolyte layer, and a negative electrode in a stacked state in this order. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-144855 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the manufacturing method of the all-solid-state battery described in Patent Document 1, when a positive electrode, a first solid electrolyte layer, and a negative electrode are stacked in this order and pressurized, the first solid electrolyte layer may penetrate into 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 pressure is applied in this state, the edge of the positive electrode active material layer is constrained by the first solid electrolyte layer, causing stress concentration and cracks to occur 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 decrease.

[0008] An object of the present invention is to provide a solid-state battery that can suppress the occurrence of cracks in the positive electrode mixture 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 an anode, a solid electrolyte layer, and a cathode are sequentially stacked, the solid electrolyte layer comprising a first solid electrolyte layer disposed on the anode side and a second solid electrolyte layer disposed on the cathode side, the cathode comprising a cathode current collector and a cathode composite layer, at least one end of the cathode composite layer having a slope formed thereon, and the outer periphery of the first solid electrolyte layer being located outside the outer periphery of the cathode composite layer when viewed from above in the stacking direction of the electrode stack.

[0010] (2) The solid-state battery according to (1), wherein, when viewed from above in the stacking direction of the electrode stack, an end of the positive electrode current collector on which the inclined surface is formed is located outside an outer periphery of the positive electrode mixture layer.

[0011] (3) The solid-state battery according to (2), wherein the second solid electrolyte layer is formed on a surface of the positive electrode current collector on which the positive electrode mixture layer is not formed.

[0012] (4) The solid state battery according to any one of (1) to (3), wherein a density of a region of the first solid electrolyte layer facing a region of the positive electrode composite layer where the slope is not formed is higher than a density of a region of the first solid electrolyte layer that does not face a region of the positive electrode composite layer where the slope is not formed.

[0013] (5) The solid state battery according to any one of (1) to (4), wherein a density of a region of the second solid electrolyte layer that does not face a region of the positive electrode composite layer where the slope is not formed is higher than a density of a region of the first solid electrolyte layer that does not face a region of the positive electrode composite layer where the slope is not formed.

[0014] (6) The solid state 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) The solid-state battery according to any one of (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 mixture layer and the solid electrolyte layer during manufacturing. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing a solid-state battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the state of the solid-state battery of FIG. 1 when pressed. [Figure 3] FIG. 10 is a cross-sectional view showing a state during pressing when no inclination is formed at the end of the positive electrode mixture layer on the side from which the positive electrode current collector tab extends. [Figure 4] FIG. 2 is a cross-sectional view showing a modified example of the positive electrode of FIG. [Figure 5] 2 is a cross-sectional view illustrating a region A and a region B of the solid-state battery of FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] [Solid battery] FIG. 1 shows a solid-state battery according to one embodiment of the present invention.

[0020] The solid-state battery 1 includes an electrode stack in which an anode 2, a solid electrolyte layer 4, a cathode 3, a solid electrolyte layer 4, and an anode 2 are sequentially stacked. The solid electrolyte layer 4 includes a first solid electrolyte layer 41 disposed on the anode 2 side and a second solid electrolyte layer 42 disposed on the cathode 3 side. The cathode 3 includes a cathode composite layer 31, a cathode current collector 32, and a cathode composite layer 31 sequentially stacked in the stacking direction of the electrode stack. A cathode current collector tab extends from one end of the cathode current collector 32, for example, toward the back in the figure. The anode 2 includes an anode composite layer 21 and an anode current collector 22 sequentially stacked in the stacking direction of the electrode stack. A cathode current collector tab extends from the end of the anode current collector 22 opposite the end from which the cathode current collector tab extends, for example, toward the front in the figure.

[0021] When viewed from above in the stacking direction of the electrode stack, the solid battery 1 has the outer peripheries of the negative electrode composite layer 21 and the first solid electrolyte layer 41 located outside the outer peripheries of the positive electrode current collector 32 and the second solid electrolyte layer 42. 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. The positive electrode composite layer 31 has slopes formed on both the left and right end portions 31a in the figure. Therefore, when the negative electrode 2, the solid electrolyte layer 4, the positive electrode 3, the solid electrolyte layer 4, and the negative electrode 2 are sequentially stacked and pressed to produce an electrode stack, the first solid electrolyte layer 41 gently fits into the slopes formed on the end portion 31a of the positive electrode composite layer 31 (see FIG. 2 ). At this time, the expansion of positive electrode mixture layer 31 and second solid electrolyte layer 42 is not hindered, which suppresses the occurrence of cracks in positive electrode mixture layer 31 and solid electrolyte layer 4. As a result, a decrease in capacity and durability of 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 may be formed at one end of the positive electrode composite layer 31.

[0023] On the other hand, if the end of the positive electrode mixture layer 31 is not sloped, when the negative electrode 2, the solid electrolyte layer 4, the positive electrode 3, the solid electrolyte layer 4, and the negative electrode 2 are sequentially stacked and pressed (see FIG. 3(a)), the first solid electrolyte layer 41 may enter the ends of the positive electrode mixture 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 FIG. 3(b)). If further pressing is performed at this time, the ends of the positive electrode mixture layer 31 and the second solid electrolyte layer 42 are constrained by the first solid electrolyte layer 41, causing stress to concentrate and resulting in cracks in the positive electrode mixture layer 31 and the solid electrolyte layer 4.

[0024] The angle of the inclination formed at the end of positive electrode composite material layer 31 is not particularly limited, but is, for example, not less than 3° and not more than 60°.

[0025] When solid state battery 1 is viewed from above in the stacking direction of the electrode stack, the end of positive electrode current collector 32 on the side where the slope of positive electrode mixture layer 31 is formed is located outside the outer periphery of positive electrode mixture layer 31. This makes it easier for first solid electrolyte layer 41 to gently fit into the slope formed on end 31a of positive electrode mixture layer 31.

[0026] The area ratio of the region of the positive electrode current collector 32 where the positive electrode composite layer 31 is not formed at (one) end portion on the side where the slope of the positive electrode composite layer 31 is formed to the region of the positive electrode current collector 32 where the positive electrode composite layer 31 is formed is not particularly limited, but is, for example, 1 / 1000 or more and 1 / 5 or less.

[0027] 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 may be located at 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 FIG. 4).

[0028] Positive electrode current collector 32 has second solid electrolyte layer 42 formed on the surface where positive electrode mixture layer 31 is not formed. This prevents solid state battery 1 from short-circuiting.

[0029] Due to the pressure applied when obtaining an electrode laminate by pressing, which will be described later, the density of region A (see FIG. 5) of first solid electrolyte layer 41 facing the region where the slope of positive electrode composite layer 31 is not formed becomes higher than the density of region B (see FIG. 5) of first solid electrolyte layer 41 not facing the region where the slope of positive electrode composite layer 31 is not formed. In addition, the density of region B of second solid electrolyte layer 42 becomes higher than the density of region B of first solid electrolyte layer 41.

[0030] The density of the region A of the first solid electrolyte layer 41 is not particularly limited, but is, for example, 0.5 g / cm 3 More than 6g / cm 3The density of region B of first solid electrolyte layer 41 is not particularly limited, but is, for example, 95% or less of the density of region A of first solid electrolyte layer 41. The thickness of region A of first solid electrolyte layer 41 is not particularly limited, but is, for example, 1 μm or more and 500 μm or less.

[0031] The density of the region A of the second solid electrolyte layer 42 is not particularly limited, but is, for example, 0.5 g / cm 3 More than 6g / cm 3 The density of region B of second solid electrolyte layer 42 is not particularly limited, but is 105% or more of the density of region B of first solid electrolyte layer 41. The thickness of region A of 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 includes an electrode stack in which an anode 2, a solid electrolyte layer 4, and a cathode 3 are sequentially stacked. For example, the solid-state battery 1 may include a plurality of cathodes 3. Alternatively, the solid-state battery 1 may include a single anode 2 and a single solid electrolyte layer 4. In this case, the cathode 3 includes a cathode composite layer 31 and a cathode current collector 32 sequentially stacked in the stacking direction of the electrode stack.

[0033] [Solid-state battery manufacturing method] Next, a method for manufacturing the solid state battery 1 will be described.

[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 for the first solid electrolyte layer 41 disposed on the surface on which the negative electrode composite layer 21 is disposed. The method for disposing the material for the first solid electrolyte layer 41 on the surface on which the negative electrode 2 is disposed with the negative electrode composite layer 21 is not particularly limited, but an example thereof is a method in which the first solid electrolyte layer 41 is transferred 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 applying a slurry obtained by dispersing a solid electrolyte having a median diameter of 1 μm or less in a solvent to a support sheet and then drying the slurry. The pressing pressure is not particularly limited, but is, for example, 10 MPa to 2000 MPa. The pressing temperature is not particularly limited, but is, for example, room temperature to 200°C.

[0035] (Second solid electrolyte layer-positive electrode laminate) A second solid electrolyte layer-cathode laminate is obtained by pressing the cathode 3 with the materials for the second solid electrolyte layer 42 disposed on both sides of the cathode composite layer 31. The method for disposing the materials for the second solid electrolyte layer 42 on both sides of the cathode 3 with the cathode composite layer 31 is not particularly limited, but examples include a method in which the second solid electrolyte layer 42 is transferred onto the cathode 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 having a median diameter of 1 μm or less in a solvent, applying a slurry to a support sheet, and then drying the slurry. The pressing pressure is not particularly limited, but is, for example, 10 MPa to 2000 MPa. The pressing temperature is not particularly limited, but is, for example, room temperature to 1500°C.

[0036] (electrode laminate) The first solid electrolyte layer-negative electrode laminate is pressed in a state in which the surface on which the first solid electrolyte layer 41 of the first solid electrolyte layer-negative electrode laminate is disposed faces the surface on which the second solid electrolyte layer 42 of the second solid electrolyte layer-cathode laminate is disposed. The pressing pressure is not particularly limited as long as it is possible to integrate the solid electrolyte layers 4, but is, for example, 10 MPa or more and 2000 MPa or less. The pressing temperature is also not particularly limited, but is, for example, room temperature or more and 1500°C or less.

[0037] The apparatus used to manufacture the solid state battery 1 is not particularly limited, but examples thereof include a roll press and a plate press.

[0038] The solid-state battery 1 is not particularly limited, but may be, for example, an all-solid-state lithium metal battery. The following describes the case where the solid-state battery 1 is an all-solid-state lithium metal battery.

[0039] Negative electrode mixture layer 21 is a lithium metal layer. Negative electrode current collector 22 is not particularly limited, but may be, for example, copper foil.

[0040] The positive electrode composite layer 31 includes a positive electrode active material and may further include a solid electrolyte, a conductive additive, a binder, and the like. The positive electrode active material is not particularly limited as long as it is capable of absorbing and releasing lithium ions, and examples thereof include lithium nickel cobalt manganese composite oxide. The solid electrolyte is not particularly limited as long as it has lithium ion conductivity, and examples thereof include oxide-based electrolytes and sulfide-based electrolytes. The conductive additive is not particularly limited as long as it has electronic conductivity, and examples thereof include carbon black. The binder is not particularly limited as long as it can improve binding properties, and examples thereof include styrene butadiene rubber.

[0041] The positive electrode current collector 32 is not particularly limited, but may be, for example, 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, and examples thereof 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 binding properties, and examples thereof include styrene butadiene rubber.

[0043] The electrode stack may have an intermediate layer formed between the negative electrode 2 and the solid electrolyte layer 4, the intermediate layer having 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 a lithium metal layer serving as the negative electrode composite layer 21 is not formed at the time of the initial charge. In the anode-free battery, a lithium metal layer serving as the negative electrode composite layer 21 is formed after the initial charge / discharge.

[0044] The intermediate layer contains a metal capable of alloying with lithium and amorphous carbon, and may further contain a binder, etc. The metal capable of alloying with lithium and amorphous carbon are preferably nanoparticles. Examples of metals capable of alloying 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 graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), CNT (carbon nanotube), fullerene, or graphene. The binder is not particularly limited as long as it can improve binding properties, and examples include polyvinylidene fluoride (PVDF).

[0045] The thickness of the intermediate layer is not particularly limited, but is, for example, 1 μm or more and 10 μm or less.

[0046] Although the 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 present invention. For example, the solid state battery 1 may further include an exterior body (e.g., a laminate film) that covers 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 mixture layer 31a End 32 Positive electrode current collector 32a Positive electrode current collecting tab 4 Solid electrolyte layer 41 First solid electrolyte layer 42 Second solid electrolyte layer

Claims

1. an electrode stack in which a negative electrode, a solid electrolyte layer, and a positive electrode are stacked in this order; the solid electrolyte layer includes a first solid electrolyte layer disposed on the negative electrode side and a second solid electrolyte layer disposed on the positive electrode side, the positive electrode includes a positive electrode current collector and a positive electrode mixture layer, and a slope is formed on at least one end of the positive electrode mixture layer; a solid-state battery, wherein, when viewed from above in a stacking direction of the electrode stack, an outer periphery of the first solid electrolyte layer is located outside an outer periphery of the positive electrode mixture layer.

2. 2. The solid state battery according to claim 1, wherein, when viewed from above in a stacking direction of the electrode stack, an end of the positive electrode current collector on which the inclined surface is formed is located outside an outer periphery of the positive electrode mixture layer.

3. The solid-state battery according to claim 2 , wherein the second solid electrolyte layer is formed on a surface of the positive electrode current collector on which the positive electrode mixture layer is not formed.

4. 4. The solid state battery according to claim 1, wherein a density of a region of the first solid electrolyte layer facing a region of the positive electrode mixture layer where the sloped surface is not formed is higher than a density of a region of the first solid electrolyte layer not facing a region of the positive electrode mixture layer where the sloped surface is not formed.

5. 4. The solid state battery according to claim 1, wherein a density of a region of the second solid electrolyte layer that does not face a region of the positive electrode mixture layer where the slope is not formed is higher than a density of a region of the first solid electrolyte layer that does not face a region of the positive electrode mixture layer where the slope is not formed.

6. 4. The solid state battery according to claim 1, wherein, when viewed from above in a stacking direction of the electrode stack, an outer periphery of the first solid electrolyte layer is located outside an outer periphery of the second solid electrolyte layer.

7. The solid-state battery according to claim 1 , which is an all-solid-state lithium metal battery.

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