Solid-state battery

Abstract

The problem to be solved by the present invention is to provide a solid-state battery comprising: an electrode laminate in which a negative electrode, a solid electrolyte layer, and a positive electrode are laminated in this order; the solid electrolyte layer is provided with a first solid electrolyte layer disposed on the negative electrode side, the positive electrode is provided with a positive electrode current collector and a positive electrode mixture layer, the positive electrode current collector sheet extends from one end of the positive electrode current collector, and the positive electrode current collector sheet extends from the other end of the positive electrode current collector in a plan view from the lamination direction of the electrode laminate. The outer peripheral portion of the first solid electrolyte layer is located on the outer side of the outer peripheral portion of the positive electrode mixture layer, and the positive electrode collector sheet has a low-friction region formed on the surface of the side facing the first solid electrolyte layer, the low-friction region having a lower friction coefficient than the positive electrode collector.

Description

Technical Field

[0001] The present invention relates to a solid battery. Background Art

[0002] In recent years, research and development of solid-state batteries that contribute to improving energy efficiency have been carried out to ensure that more people have access to affordable, reliable, sustainable, and advanced energy.

[0003] As a solid-state battery, an all-solid-state battery having a solid electrolyte layer disposed between a positive electrode and a negative electrode is known.

[0004] Patent Document 1 describes an all-solid-state battery comprising: a positive electrode, a positive electrode current collector layer and a positive electrode active material layer containing at least a solid electrolyte; a negative electrode, 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. In this all-solid-state battery, in a direction perpendicular to the stacking direction, the area of ​​the negative electrode active material layer is greater than the area of ​​the positive electrode active material layer, and in a direction perpendicular to the stacking direction, the area of ​​the first solid electrolyte layer is greater than the area of ​​the positive electrode active material layer. The porosity n1 of the positive electrode active material layer is 1. am Less than 5%.

[0005] In addition, patent document 1 describes a method for manufacturing an all-solid-state battery, which includes the following steps: pressurizing a positive electrode collector layer and a positive electrode active material layer while they are stacked to form a positive electrode; pressurizing a negative electrode collector layer and a negative electrode active material layer while they are stacked to form a negative electrode; and pressurizing a positive electrode, a first solid electrolyte layer, and a negative electrode while they are stacked in sequence to form a stack unit.

[0006] [Prior Art Literature]

[0007] (Patent Document)

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-144855 Summary of the Invention

[0009] [Problems to be solved by the invention]

[0010] However, in the manufacturing method of the all-solid-state battery described in Patent Document 1, when the positive electrode, first solid electrolyte layer, and negative electrode are stacked in this order and pressurized, the first solid electrolyte layer sometimes enters the end of the positive electrode active material layer, causing the first solid electrolyte layer to adhere tightly to the positive electrode current collector. In this case, if further pressure is applied, the end of the positive electrode active material layer is constrained by the first solid electrolyte layer, resulting in stress concentration and cracks in the positive electrode active material layer and the first solid electrolyte layer. As a result, the capacity of the all-solid-state battery is reduced, or the durability is reduced.

[0011] An object of the present invention is to provide a solid battery capable of suppressing cracks in a positive electrode composite material layer and a solid electrolyte layer during manufacture.

[0012] [Technical means to solve the problem]

[0013] (1) A solid battery comprising: an electrode stack having a negative electrode, a solid electrolyte layer, and a positive electrode stacked in sequence; and the solid electrolyte layer comprising a first solid electrolyte layer disposed on the negative electrode side, the positive electrode comprising a positive electrode collector and a positive electrode composite material layer, the positive electrode collector sheet extending from one end of the positive electrode collector, the outer peripheral portion of the first solid electrolyte layer being located further outside the outer peripheral portion of the positive electrode composite material layer when viewed from above in the stacking direction of the electrode stack, and the positive electrode collector sheet having a low friction region having a lower friction coefficient than that of the positive electrode collector formed on the surface of the positive electrode collector sheet on the side opposite to the first solid electrolyte layer.

[0014] (2) The solid battery according to (1), wherein the low-friction region contains a solid lubricant.

[0015] (3) The solid battery according to (1), wherein the low friction region includes a metal having a higher hardness than a material constituting the positive electrode current collector.

[0016] (4) The solid battery according to any one of (1) to (3), wherein the solid electrolyte layer further includes a second solid electrolyte layer disposed on the positive electrode side.

[0017] (5) The solid battery according to (4), wherein the outer peripheral portion of the first solid electrolyte layer is located outside the outer peripheral portion of the second solid electrolyte layer when viewed in plan from the stacking direction of the electrode stack.

[0018] (6) The solid state battery according to any one of (1) to (5), wherein the solid state battery is an all-solid state lithium metal battery.

[0019] (Effects of the Invention)

[0020] According to the present invention, it is possible to provide a solid battery capable of suppressing the occurrence of cracks in the positive electrode composite material layer and the solid electrolyte layer during production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a cross-sectional view showing a solid state battery according to one embodiment of the present invention.

[0022] Figure 2 It is a drawing Figure 1 Cross-sectional view of a solid-state battery during pressing.

[0023] Figure 3 It is shown in Figure 1 A cross-sectional view of the solid battery during pressing when the low-friction region A does not exist. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0025] [Solid-state battery]

[0026] Figure 1 A solid-state battery according to one embodiment of the present invention is shown.

[0027] Solid-state battery 1 includes an electrode stack comprising a negative electrode 2, a solid electrolyte layer 4, a positive electrode 3, a solid electrolyte layer 4, and a negative electrode 2 stacked in this order. Here, 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. A portion of first solid electrolyte layer 41 extends into the ends of positive electrode composite material layer 31 and second solid electrolyte layer 42. Furthermore, positive electrode 3 comprises a positive electrode composite material layer 31, a positive electrode current collector 32, and a positive electrode composite material layer 31 stacked in this order in the stacking direction of the electrode stack. A positive electrode current collector tab 32a extends from one end of the positive electrode current collector 32. Furthermore, negative electrode 2 comprises a negative electrode composite material layer 21 and a negative electrode current collector 22 stacked in this order in the stacking direction of the electrode stack. A negative electrode current collector tab extends from the end of the negative electrode current collector 22 on the side opposite to the side from which the positive electrode current collector tab 32a extends.

[0028] When the solid battery 1 is viewed from above in the stacking direction of the electrode stack, the outer peripheries of the negative electrode composite material layer 21 and the first solid electrolyte layer 41 exist outside the outer peripheries of the positive electrode composite material layer 31 and the second solid electrolyte layer 42. At this time, the outer periphery of the negative electrode composite material layer 21 exists at approximately the same position as the outer periphery of the first solid electrolyte layer 41, and the outer periphery of the positive electrode composite material layer 31 exists at approximately the same position as the outer periphery of the second solid electrolyte layer 42. In addition, the positive electrode current collector sheet 32a has a low friction region A having a lower friction coefficient than the positive electrode current collector 32 formed in the region facing the first solid electrolyte layer 41. Therefore, when the electrode stack is manufactured by pressing in a state where the negative electrode 2, the solid electrolyte layer 4, the positive electrode 3, the solid electrolyte layer 4 and the negative electrode 2 are stacked in sequence, even if the first solid electrolyte layer 41 enters the end portions of the positive electrode composite material layer 31 and the second solid electrolyte layer 42 (refer to Figure 2 (a)), the first solid electrolyte layer 41 is also not in close contact with the positive electrode current collector 32a (refer to Figure 2 (b)). At this point, even if further pressing is performed, the ends of the positive electrode composite material layer 31 and the second solid electrolyte layer 42 are not constrained by the first solid electrolyte layer 41, so stress is not concentrated, and the formation of cracks in the positive electrode composite material layer 31 and the solid electrolyte layer 4 is suppressed. As a result, a decrease in the capacity and durability of the solid battery 1 is suppressed.

[0029] Furthermore, the low-friction region A only needs to be formed on the surface of the positive electrode current collector sheet 32a facing the first solid electrolyte layer 41. It can be formed on the entire surface of the positive electrode current collector sheet 32a facing the first solid electrolyte layer 41, or it can be formed on a portion of the surface of the positive electrode current collector sheet 32a facing the first solid electrolyte layer 41. Furthermore, the low-friction region A may or may not be in contact with the positive electrode composite material layer 31.

[0030] On the other hand, if the low friction region A is not formed on the surface of the positive electrode current collector 32a on the side facing the first solid electrolyte layer 41, 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 laminated in this order and pressed (see Figure 3 (a)), sometimes the first solid electrolyte layer 41 enters the end of the positive electrode composite material layer 31 and the second solid electrolyte layer 42, and the first solid electrolyte layer 41 is in close contact with the positive electrode collector 32a (refer to Figure 3 (b)). At this time, if further pressing is performed, the ends of the positive electrode material layer 31 and the second solid electrolyte layer 42 are constrained by the first solid electrolyte layer 41, so stress concentrates, causing cracks in the positive electrode material layer 31 and the solid electrolyte layer 4.

[0031] The material constituting the low-friction region A is not particularly limited, and examples thereof include solid lubricants. Examples of solid lubricants include polytetrafluoroethylene (PTFE). The method for forming the low-friction region A composed of PTFE on the surface of the positive electrode current collector sheet 32 ​​a is not particularly limited, and examples thereof include powder coating.

[0032] Examples of materials other than those mentioned above that constitute the low-friction region A include metals having a higher hardness than the material constituting the positive electrode current collector 32. For example, when the positive electrode current collector 32 is made of aluminum, examples of metals having a higher hardness than aluminum include stainless steel. The method for forming the low-friction region A made of stainless steel on the surface of the positive electrode current collector sheet 32a is not particularly limited, and examples thereof include rolling, sputtering, vapor deposition, and plating.

[0033] The surface roughness Ra (arithmetic mean height) of the low friction region A is not particularly limited, but is, for example, 0.2 μm or less.

[0034] The density of the region of the first solid electrolyte layer 41 facing the second solid electrolyte layer 42 is not particularly limited, but is, for example, 0.5 g / cm 3 Above and 6 g / cm 3 The thickness of the region of the first solid electrolyte layer 41 facing the second solid electrolyte layer 42 is not particularly limited, and is, for example, 1 μm or more and 500 μm or less.

[0035] The density of the second solid electrolyte layer 42 is not particularly limited, but is, for example, 0.5 g / cm 3 Above and 6 g / cm 3 The thickness of the second solid electrolyte layer 42 is not particularly limited, and is, for example, 1 μm or more and 500 μm or less.

[0036] Furthermore, the solid-state battery 1 is not particularly limited as long as it includes an electrode stack in which the negative electrode 2, the solid electrolyte layer 4, and the positive electrode 3 are stacked in this order. For example, the solid-state battery 1 may include multiple positive electrodes 3. Alternatively, the solid-state battery 1 may include a single negative electrode 2 and a single solid electrolyte layer 4. In this case, the positive electrode 3 includes a positive electrode composite material layer 31 and a positive electrode current collector 32 stacked in this order in the stacking direction of the electrode stack. Furthermore, the solid electrolyte layer 4 may not include the second solid electrolyte layer 42.

[0037] [Method for manufacturing solid-state batteries]

[0038] Next, a method for manufacturing the solid state battery 1 will be described.

[0039] (First solid electrolyte layer-negative electrode stack)

[0040] The material constituting the first solid electrolyte layer 41 is arranged on the surface of the negative electrode 2 on the side where the negative electrode composite material layer 21 is arranged, and the material is pressed to obtain a first solid electrolyte layer-negative electrode laminate. There is no particular limitation on the method for configuring the material constituting the first solid electrolyte layer 41 on the surface of the negative electrode 2 on the side where the negative electrode composite material layer 21 is arranged. For example, there can be cited a method of transferring the first solid electrolyte layer 41 onto the negative electrode composite material layer 21 using a first solid electrolyte layer transfer sheet. For example, a slurry obtained by dispersing a solid electrolyte having a median particle size of less than 1 μm in a solvent is applied to a support sheet and then dried to obtain a first solid electrolyte layer transfer sheet. There is no particular limitation on the pressing pressure, and for example, it is greater than 10 MPa and less than 2000 MPa. There is no particular limitation on the pressing temperature, and for example, it is greater than room temperature and less than 1500°C.

[0041] (Second solid electrolyte layer-positive electrode stack)

[0042] The second solid electrolyte layer-positive electrode laminate is obtained by pressing in a state where the material constituting the second solid electrolyte layer 42 is arranged on the surfaces of both sides of the positive electrode 3 where the positive electrode composite material layer 31 is arranged. There is no particular limitation on the method for configuring the material constituting the second solid electrolyte layer 42 on the surfaces of both sides of the positive electrode 3 where the positive electrode composite material layer 31 is arranged. For example, a method of transferring the second solid electrolyte layer 42 onto the positive electrode composite material layer 31 using a second solid electrolyte layer transfer sheet can be cited. For example, a slurry obtained by dispersing a solid electrolyte having a median particle size of less than 1 μm in a solvent is applied to a support sheet and then dried to obtain a second solid electrolyte layer transfer sheet. The pressing pressure is not particularly limited, for example, it is greater than 10 MPa and less than 2000 MPa. The pressing temperature is not particularly limited, for example, it is greater than room temperature and less than 1500°C.

[0043] (Electrode stack)

[0044] The first solid electrolyte layer-negative electrode stack is arranged so that the surface on which the first solid electrolyte layer 41 is disposed faces the surface on which the second solid electrolyte layer 42 is disposed, and the electrode stack is formed. The pressing pressure is not particularly limited, provided that the solid electrolyte layer 4 is integrated, 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.

[0045] The apparatus used when producing the solid battery 1 is not particularly limited, and examples thereof include a roller press apparatus and a flat plate press apparatus.

[0046] The solid battery 1 is not particularly limited, and an example thereof includes an all-solid-state lithium metal battery. Hereinafter, a case where the solid battery 1 is an all-solid-state lithium metal battery will be described.

[0047] The negative electrode mixture layer 21 is a lithium metal layer. The negative electrode current collector 22 is not particularly limited, and examples thereof include copper foil.

[0048] The positive electrode composite material layer 31 contains a positive electrode active material and may further contain a solid electrolyte, a conductive additive, a binder, and the like. As the positive electrode active material, there is no particular limitation as long as it can absorb and release lithium ions, and examples thereof include lithium nickel cobalt manganese composite oxides. As the solid electrolyte, there is no particular limitation as long as it has lithium ion conductivity, and examples thereof include oxide-based electrolytes and sulfide-based electrolytes. As the conductive additive, there is no particular limitation as long as it has electronic conductivity, and examples thereof include carbon black. As the binder, there is no particular limitation as long as it can improve the bonding properties, and examples thereof include styrene butadiene rubber.

[0049] The positive electrode current collector 32 is not particularly limited, and an example thereof may be aluminum foil.

[0050] The first solid electrolyte layer 41 and the second solid electrolyte layer 42 include a solid electrolyte and may further include a binder. 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. In addition, 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 adhesion, and an example thereof includes styrene butadiene rubber.

[0051] Alternatively, the electrode stack may include an intermediate layer between the negative electrode 2 and the solid electrolyte layer 4 that allows for uniform lithium metal deposition. 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-less battery that does not form a lithium metal layer as the negative electrode composite material layer 21 during initial charge. In an anode-less battery, a lithium metal layer as the negative electrode composite material layer 21 is formed after the initial charge and discharge.

[0052] The intermediate layer includes a metal capable of alloying with lithium and amorphous carbon, and may further include a binder. The metal capable of alloying with lithium and the 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, coke, and activated carbon. Amorphous carbon may be easily graphitized carbon (soft carbon), or difficult to graphitize carbon (hard carbon), carbon nanotubes (CNTs), fullerenes, and graphene. The binder is not particularly limited as long as it can improve adhesion, and examples include polyvinylidene fluoride (PVDF).

[0053] The thickness of the intermediate layer is not particularly limited, and is, for example, 1 μm or more and 10 μm or less.

[0054] While the embodiments of the present invention have been described above, the present invention is not limited to the aforementioned embodiments and may be modified as appropriate within the scope of the present invention. For example, the solid-state battery 1 may further include a package (e.g., a laminate film) that packages the electrode stack.

[0055] Reference numerals

[0056] 1: Solid-state battery

[0057] 2: Negative electrode

[0058] 21: Negative electrode composite material layer

[0059] 22: Negative electrode collector

[0060] 3: Positive electrode

[0061] 31: Positive electrode composite material layer

[0062] 32: Positive electrode collector

[0063] 32a: Positive electrode collector

[0064] 4: Solid electrolyte layer

[0065] 41: First solid electrolyte layer

[0066] 42: Second solid electrolyte layer

[0067] A: Low friction area

Claims

1. A solid battery comprising: An electrode stack, comprising a negative electrode, a solid electrolyte layer, and a positive electrode stacked in this order; and The solid electrolyte layer includes a first solid electrolyte layer disposed on the negative electrode side. The positive electrode comprises a positive electrode current collector and a positive electrode composite material layer, wherein the positive electrode current collector sheet extends from one end of the positive electrode current collector. 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 material layer. The positive electrode current collector sheet has a low friction region having a lower friction coefficient than that of the positive electrode current collector formed on a surface thereof facing the first solid electrolyte layer.

2. The solid state battery according to claim 1, wherein The aforementioned low friction region contains a solid lubricant.

3. The solid battery according to claim 1, wherein The low friction region includes a metal having a higher hardness than a material constituting the positive electrode current collector.

4. The solid state battery according to any one of claims 1 to 3, wherein The solid electrolyte layer further includes a second solid electrolyte layer disposed on the positive electrode side.

5. The solid state battery according to claim 4, wherein When viewed in plan from the stacking direction of the electrode stack, the outer peripheral portion of the first solid electrolyte layer is located outside the outer peripheral portion of the second solid electrolyte layer.

6. The solid state battery according to any one of claims 1 to 3, wherein The solid battery is an all-solid-state lithium metal battery.

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