Solid-state battery

Abstract

To provide a solid-state battery that can prevent the occurrence of an internal short circuit.SOLUTION: The present disclosure provides a solid-state battery having a negative electrode layer, a protective layer, a solid electrolyte layer, and a positive electrode layer in this order, and uses the deposition-dissolution reaction of metal lithium. The negative electrode layer includes a first metal element M1 that can be alloyed with lithium. The protective layer includes a second metal element M2 that can be alloyed with lithium. The first metal element M1 and the second metal element M2 are elements different from each other. In a cross-sectional view in a thickness direction of the solid-state battery, the protective layer has a first projection that projects outward beyond an end face of the negative electrode layer in a direction orthogonal to the thickness direction, and the solid electrolyte layer has a second projection that projects outward beyond an end face of the protective layer in the direction orthogonal to the thickness direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to solid-state batteries. [Background technology]

[0002] Various technologies have been proposed for solid-state batteries (for example, Patent Documents 1 to 3). Methods for improving the energy density of solid-state batteries include the application of lithium-based active materials such as metallic lithium, and anode-free batteries that do not have a negative electrode layer during production. In this regard, a method for forming a protective layer between the negative electrode layer and the solid electrolyte layer has been proposed as a method for improving the cycle characteristics and rate characteristics of solid-state batteries.

[0003] For example, Patent Document 1 describes that in a lithium deposition type secondary battery, a protective layer is provided on at least a part of the main surface of the solid electrolyte layer facing the negative electrode current collector and on at least a part of the side surface of the solid electrolyte layer, and that the protective layer prevents contact between the negative electrode active material layer and the solid electrolyte layer, thereby preventing deterioration of the solid electrolyte layer.

[0004] The protective layer disposed between the negative electrode layer and the solid electrolyte layer may be a protective layer made of a metal such as Sn. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-186164 [Patent Document 2] Japanese Patent Application Publication No. 2023-150044 [Patent Document 3] Japanese Patent Publication No. 2020-158835 Summary of the Invention [Problem to be solved by the invention]

[0006] In solid-state batteries that utilize the deposition-dissolution reaction of metallic lithium, the protective layer may move along the side of the solid electrolyte layer toward the positive electrode layer due to confining pressure or expansion and contraction during charging, resulting in contact with the positive electrode layer and causing a short circuit in the solid-state battery. Also, the negative electrode layer may expand during charging and extend into areas where the protective layer is not formed, causing contact between the solid electrolyte layer and the negative electrode layer, leading to the deposition and extension of Li dendrites within the solid electrolyte layer and causing a short circuit.

[0007] The present disclosure has been made in view of the above problems, and has as its main object to provide a solid-state battery that can suppress the occurrence of internal short circuits. [Means for solving the problem]

[0008] [1] A solid-state battery having an anode layer, a protective layer, a solid electrolyte layer, and a cathode layer in this order, and utilizing a deposition-dissolution reaction of metallic lithium, the negative electrode layer includes a first metal element M1 that can be alloyed with lithium, the protective layer includes a second metal element M2 that can be alloyed with lithium, the first metal element M1 and the second metal element M2 are different elements, In a cross-sectional view in a thickness direction of the solid state battery, the protective layer has a first protruding portion that protrudes outward beyond an end surface of the negative electrode layer in a direction perpendicular to the thickness direction, The solid electrolyte layer has a second protrusion that protrudes outward beyond the end face of the protective layer in a direction perpendicular to the thickness direction.

[0009] [2] a negative electrode current collector on the opposite side of the negative electrode layer from the protective layer, When viewed in a cross section in the thickness direction, the negative electrode current collector has an extension portion that extends outward beyond an end surface of the negative electrode layer in a direction perpendicular to the thickness direction, The solid-state battery according to [1], wherein the extension portion has a bent portion in a region that overlaps with the first protrusion portion of the protective layer in the thickness direction.

[0010] [3] The solid state battery according to [2], wherein the extension portion of the negative electrode current collector and the first protrusion portion of the protective layer are spaced apart from each other.

[0011] [4] In a cross-sectional view in the thickness direction, The solid-state battery according to [2] or [3], wherein α tan θ<β is satisfied, where α is the width of the first protrusion of the protective layer on the side where the extension portion is present, β is the thickness of the negative electrode layer, and θ is the angle of the acute angle side of the bent portion of the extension portion.

[0012] [5] In a cross-sectional view in the thickness direction, The solid-state battery according to any one of [2] to [4], wherein the thickness of the first protrusion on the side where the extension portion is present in the protective layer is thinner than the thickness of an area not having the first protrusion. [Effects of the Invention]

[0013] The present disclosure has an effect of providing a solid-state battery that can suppress the occurrence of internal short circuits. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery according to the present disclosure. [Figure 2] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery according to the present disclosure. [Figure 3] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery according to the present disclosure. [Figure 4] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery according to the present disclosure. [Figure 5] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery according to the present disclosure. [Figure 6] 1 is a schematic cross-sectional view of the solid state batteries obtained in Comparative Examples 1 and 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] The solid-state battery according to the present disclosure will be described in detail below.

[0016] 1A and 1B are schematic cross-sectional views illustrating an example of a solid-state battery according to the present disclosure, with Fig. 1A being a schematic cross-sectional view illustrating the battery before the first charge, and Fig. 1B being a schematic cross-sectional view illustrating the battery after the first charge.

[0017] As shown in FIGS. 1(a) and 1(b), the solid-state battery 10 has a thickness direction D T 1(a) , the solid-state battery 10 includes an anode layer 1, a protective layer 2, a solid electrolyte layer 3, and a cathode layer 4, in this order. The solid-state battery 10 utilizes the deposition-dissolution reaction of metallic lithium. As shown in FIG. 1(a) , in the solid-state battery 10 before the initial charge, the anode layer 1 includes a first metal element M1 that can be alloyed with lithium. The protective layer includes a second metal element M2 that can be alloyed with lithium. Here, the first metal element M1 and the second metal element M2 are different elements. When the solid-state battery 10 shown in FIG. 1(a) is charged, Li-M1 alloying between lithium and the first metal element M1 occurs in the anode layer 1. That is, in the solid-state battery 10 after charge shown in FIG. 1(b) , the anode layer 1 contains a Li-M1 alloy. Furthermore, the anode layer 1 after charge has a metallic Li phase. On the other hand, during discharge, Li dissolves from the Li-M1 alloy or the metallic Li phase.

[0018] Thickness direction D of the solid-state battery 10 T In the cross-sectional view of FIG. 1, the protective layer 2 is T The negative electrode layer 1 has a first protrusion 2E protruding outward from the end surface S1t of the negative electrode layer 1 in a direction perpendicular to the thickness direction, and the solid electrolyte layer 3 has a second protrusion 3E protruding outward from the end surface S2t of the protective layer 2 in a direction perpendicular to the thickness direction. The first protrusion 2E and the second protrusion 3E are each T It protrudes parallel to the direction perpendicular to the

[0019] In a plan view of the solid state battery, the entire outer periphery of the solid electrolyte layer 3 is preferably disposed outside the entire outer periphery of the protective layer 2. Similarly, the entire outer periphery of the protective layer 2 is preferably disposed outside the entire outer periphery of the negative electrode layer 1.

[0020] According to the present disclosure, the solid electrolyte layer has a second protrusion, which prevents the protective layer from wrapping around the side of the solid electrolyte layer to the positive electrode layer due to confining pressure and expansion and contraction during charging and discharging, thereby preventing a short circuit in the solid battery. Furthermore, the protective layer has a first protrusion, which prevents contact between the negative electrode layer and the solid electrolyte layer in areas where the protective layer is not located, even when the negative electrode layer expands during charging. Therefore, it is possible to prevent the precipitation and extension of Li dendrites in the solid electrolyte layer due to contact between the negative electrode layer and the solid electrolyte layer, thereby preventing a short circuit in the solid battery. Furthermore, by providing a protective layer between the negative electrode layer and the solid electrolyte layer, the interface between the negative electrode layer and the solid electrolyte layer can be reliably covered by the protective layer, preventing interfacial peeling and improving cycle characteristics and rate characteristics.

[0021] 1. Negative electrode layer The negative electrode layer in the present disclosure contains a first metal element M1 that can be alloyed with lithium. Examples of the first metal element M1 include Mg, Ag, In, Sn, Si, Ga, Au, and Pt. The negative electrode layer may contain only one type of the first metal element M1, or may contain two or more types. The negative electrode layer may contain an alloy of the first metal element M1 and Li. The negative electrode layer may also contain a metallic Li phase.

[0022] The negative electrode layer usually incorporates Li during charging, forming a Li-M1 alloy. Furthermore, a metallic Li phase forms in the negative electrode layer during charging. Before the first charge and after full discharge, the negative electrode layer may or may not contain Li.

[0023] In a plan view of the solid-state battery, the area of ​​the negative electrode layer is smaller than the area of ​​the solid electrolyte layer and is also smaller than the area of ​​the protective layer. The ratio (A1 / A3) of the area (A1) of the negative electrode layer to the area (A3) of the solid electrolyte layer may be, for example, 0.9 or less, or 0.8 or less. Meanwhile, the ratio (A1 / A3) may be, for example, 0.5 or more, or 0.6 or more. The ratio (A1 / A2) of the area (A1) of the negative electrode layer to the area (A2) of the protective layer may be, for example, smaller than 1.0 and 0.9 or less. Meanwhile, the ratio (A1 / A2) may be, for example, 0.6 or more, or 0.7 or more.

[0024] In a plan view of the solid-state battery, the area of ​​the negative electrode layer and the area of ​​the positive electrode layer may be the same or different. From the viewpoint of suppressing the precipitation of Li dendrites, the area of ​​the negative electrode layer is preferably larger than the area of ​​the positive electrode layer. The ratio (A1 / A4) of the area (A1) of the negative electrode layer 1 to the area (A4) of the positive electrode layer may be, for example, greater than 1.0, 1.1 or more, or 1.2 or more. On the other hand, the ratio (A1 / A4) is, for example, 1.5 or less, 1.4 or less, or 1.3 or less.

[0025] The thickness β of the negative electrode layer may be 0.1 μm or more and 100 μm or less.

[0026] In this specification, the area and thickness of the negative electrode layer refer to the area and thickness of the negative electrode layer in a fully discharged state.

[0027] The negative electrode layer may be a metal foil containing the first metal element M1 or a vapor-deposited layer. Using a metal foil facilitates the manufacture of a solid-state battery. Like metal foils and vapor-deposited layers, the negative electrode layer of the present disclosure may be a layer that does not contain a conductive material (e.g., a carbon material). Similarly, the negative electrode layer of the present disclosure may be a layer that does not contain a binder (e.g., a polymer material).

[0028] 2.Protective layer The protective layer includes a second metal element M2 that can be alloyed with lithium. The second metal element M2 is a metal element different from the first metal element M1. Examples of the second metal element M2 include Sn, In, Mg, Ag, Si, Ga, Zn, Sb, Bi, and Al. The protective layer may include only one type of second metal element, or two or more types. It is particularly preferable that the second metal element M2 includes at least one of In and Sn. The protective layer may include an alloy of the second metal element and Li.

[0029] The protective layer has a first protrusion that protrudes outward beyond the end face of the negative electrode layer in a direction perpendicular to the thickness direction. That is, the area of ​​the protective layer is larger than the area of ​​the negative electrode layer and smaller than the area of ​​the solid electrolyte layer in a plan view. The ratio (A2 / A3) of the area (A2) of the protective layer to the area (A3) of the solid electrolyte layer may be, for example, smaller than 1.0 and 0.9 or less. On the other hand, the ratio (A2 / A3) may be, for example, 0.6 or more, or 0.7 or more.

[0030] The planar shape of the protective layer may be any shape as long as the area of ​​the protective layer is smaller than the area of ​​the solid electrolyte layer.

[0031] The thickness γ of the protective layer may be 0.1 μm or more, or may be 1 μm or less. The thickness γ of the protective layer refers to the thickness of the region of the protective layer that does not have the first protrusion 2E.

[0032] The method for forming the protective layer is not particularly limited, but examples thereof include methods in which one surface of the solid electrolyte layer is used as a film formation surface and the protective layer is formed by vapor deposition, ion plating, sputtering, chemical vapor deposition (CVD), etc. Sputtering is preferred from the viewpoint of being able to form the protective layer uniformly.

[0033] 3.Solid electrolyte layer The solid electrolyte layer in the present disclosure is a layer containing at least a solid electrolyte. The solid electrolyte layer may also contain a binder as needed. The solid electrolyte layer may be in direct contact with a protective layer.

[0034] The solid electrolyte layer has a second protrusion that protrudes outward beyond the end face of the protective layer in a direction perpendicular to the thickness direction, i.e., the area of ​​the solid electrolyte layer is larger than the area of ​​the negative electrode layer and the area of ​​the protective layer in a plan view.

[0035] Examples of solid electrolytes include inorganic solid electrolytes such as halide solid electrolytes, sulfide solid electrolytes, oxide solid electrolytes, and nitride solid electrolytes, and organic solid electrolytes such as polymer electrolytes and gel electrolytes. Among these, sulfide solid electrolytes are particularly preferred because they tend to have good adhesion to the negative electrode even as discharge progresses.

[0036] The sulfide solid electrolyte preferably contains, for example, Li, X (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and a halogen element. The solid electrolyte may be in the form of, for example, particles.

[0037] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-GeS2, Li2S-P2S5-SnS2, Li2S-P2S5-SiS2, Li2S-P2S5-LiI, Li2S-P2S5-LiI-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (where m and n are positive numbers. Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y(where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga, and In.) The above description of "Li2S-P2S5" means a material obtained using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions.

[0038] The solid electrolyte may be glass, glass ceramic, or a crystalline material. Glass can be obtained by amorphous processing of a raw material composition (e.g., a mixture of Li2S and P2S5). Examples of amorphous processing include mechanical milling. Mechanical milling may be dry mechanical milling or wet mechanical milling, with the latter being preferred. This is because it can prevent the raw material composition from adhering to the wall surface of a container or the like. Glass ceramics can be obtained by heat treating glass. Crystalline materials can be obtained, for example, by solid-phase reaction processing of the raw material composition. The solid electrolyte layer may contain one type of solid electrolyte or two or more types. For example, it may contain both an inorganic solid electrolyte and an organic solid electrolyte.

[0039] The solid electrolyte is preferably in the form of particles. 50 On the other hand, the average particle diameter (D 50 ) is, for example, 10 μm or less, and may be 5 μm or less. The Li ion conductivity of the solid electrolyte at 25° C. is, for example, 1×10 -4 S / cm or more, 1×10 -3 It is preferably S / cm or more.

[0040] The content of the solid electrolyte in the solid electrolyte layer is, for example, 70% by weight or more, and may be 90% by weight or more. The solid electrolyte layer may contain a binder as necessary. Examples of the binder include fluorine-based resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), and rubber-based resins such as acrylate butadiene rubber (ABR) and styrene butadiene rubber (SBR). Further, the thickness of the solid electrolyte layer is, for example, 0.1 μm or more. On the other hand, the thickness of the solid electrolyte layer is, for example, 300 μm or less, and may be 100 μm or less.

[0041] 4. Positive electrode layer The positive electrode layer in the present disclosure includes at least a positive electrode active material layer. The positive electrode layer may also contain at least one of a solid electrolyte, a conductive material, and a binder.

[0042] The positive electrode active material is not particularly limited, but is preferably a positive electrode active material capable of intercalating and deintercalating lithium ions. Examples include oxide active materials and sulfur-based active materials. Examples of the oxide active material include rock salt layer-type active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, etc., spinel-type active materials such as LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, etc., and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. Further, as the oxide active material, Li 1+x Mn 2-x-y M y O4 (M is at least one of Al, Mg, Co, Fe, Ni, Zn, 0 < x + y < 2), a LiMn spinel active material represented thereby, lithium titanate, etc. may be used.

[0043] Furthermore, a coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material, since this can suppress the reaction between the oxide active material and the solid electrolyte. Examples of Li-ion conductive oxides include LiNbO3 and Li4Ti5O 12 , Li3PO4. The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coverage of the coating layer on the surface of the oxide active material is, for example, 70% or more, and may be 90% or more.

[0044] The sulfur-based active material is an active material containing at least S element. The sulfur-based active material may or may not contain Li element. Examples of sulfur-based active materials include elemental sulfur, lithium sulfide (Li2S), and lithium polysulfide (Li2Sx, 2≦x≦8).

[0045] The proportion of the positive electrode active material in the positive electrode active material layer is, for example, 20% by weight or more, or alternatively, 30% by weight or more, or 40% by weight or more, while the proportion of the positive electrode active material is, for example, 80% by weight or less, or alternatively, 70% by weight or less, or alternatively, 60% by weight or less.

[0046] Examples of conductive materials include carbon materials. Examples of carbon materials include acetylene black, ketjen black, VGCF, and graphite. The solid electrolyte and binder are the same as those described in "3. Solid Electrolyte Layer." The thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

[0047] The positive electrode layer can be formed by a conventional method. For example, a positive electrode active material and, if necessary, other components are added to a solvent and stirred to prepare a positive electrode slurry. The positive electrode slurry is then applied to one side of a support such as a positive electrode current collector and dried to obtain the positive electrode layer. The support can be appropriately selected from those having self-supporting properties and is not particularly limited, and metal foils such as Cu and Al can be used.

[0048] 5.Negative electrode current collector As shown in FIG. 2(a), a solid-state battery 10 typically has a negative electrode current collector 5 on the side of the negative electrode layer 1 opposite the protective layer 2. Examples of materials for the negative electrode current collector include stainless steel (SUS), copper, nickel, and carbon. Examples of the shape of the negative electrode current collector include foil, mesh, and porous. The thickness of the negative electrode current collector is, for example, 0.1 μm or more, and may be 1 μm or more. If the thickness of the negative electrode current collector is too small, the current collection function may be reduced. On the other hand, the thickness of the negative electrode current collector is, for example, 1 mm or less, and may be 100 μm or less. If the thickness of the negative electrode current collector is too large, the energy density of the solid-state battery may be reduced.

[0049] The shape of the negative electrode current collector in a plan view is not particularly limited, but examples thereof include a circle, an ellipse, a rectangle, and any polygonal shape.

[0050] As shown in FIG. 2(a), the negative electrode current collector 5 may have an extension 5T that extends outward beyond the end surface S1t of the negative electrode layer 1 in a direction perpendicular to the thickness direction in a cross-sectional view in the thickness direction. When a solid-state battery includes multiple power generation units, the extensions of the negative electrode current collectors of each power generation unit are gathered and connected to the negative electrode terminal. In this case, the extensions of the negative electrode current collector are bent. In the present disclosure, as shown in FIG. 2(a), the extension 5T of the negative electrode current collector 5 preferably has a bent portion X in a region that overlaps with the first protrusion 2E of the protective layer 2 in the thickness direction. This is because the negative electrode current collector can be gathered compactly.

[0051] 2(a), it is preferable that the extending portion 5T of the negative electrode current collector 5 and the first protruding portion 2E of the protective layer 2 are spaced apart from each other. This is because this can prevent the precipitation of Li dendrites caused by contact between the negative electrode current collector and the protective layer, and the resulting internal short circuit.

[0052] As shown in Figure 2(b), the thickness direction D T In the cross-sectional view of FIG. 1, when the width of the first protrusion 2E of the protective layer 2 on the side where the extending portion 5T exists is α, the thickness of the negative electrode layer 1 is β, and the angle on the acute side of the bent portion X of the extending portion 5T of the negative electrode current collector 5 is θ, it is preferable that α tan θ < β be satisfied. This is because contact between the negative electrode current collector and the protective layer can be suppressed.

[0053] As shown in Figure 3, the thickness direction D T In the cross-sectional view, the first protruding portion 2E of the protective layer 2 on the side where the extending portion 5T is present may have its end A1 on the negative electrode layer 1 side positioned more inward than its end A2 on the solid electrolyte layer 3 side. This is because contact between the negative electrode current collector and the protective layer can be suppressed, and precipitation of Li dendrites and the resulting internal short circuit can be suppressed.

[0054] 4, the thickness of the first protrusion 2E of the protective layer 2 on the side where the extension 5T is present may be thinner than the thickness of the protective layer 2 in an area not having the first protrusion 2E, because this makes it possible to prevent contact between the negative electrode current collector and the protective layer.

[0055] As shown in FIG. 5, in the solid-state battery 10, an insulating member 7 may be disposed on the end of the first protrusion 2E of the protective layer 2 on the side where the extension 5T is present. This is because contact between the negative electrode current collector and the protective layer can be suppressed. Examples of materials for the insulating member include resin. The resin may be a thermoplastic resin or a cured resin (for example, a cured product of a thermosetting resin or an ultraviolet-curable resin). The insulating member may function as a buffer member that absorbs impact when it comes into contact with the extension.

[0056] 6. Positive electrode current collector As shown in Fig. 2(a), the solid-state battery 10 may have a positive electrode current collector 6 on the side of the positive electrode layer 4 opposite to the solid electrolyte layer 3. Examples of materials for the positive electrode current collector include copper, SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the shape of the positive electrode current collector include foil, mesh, and porous shapes.

[0057] 7. Other configurations The solid-state battery according to the present disclosure may further include a restraining jig that applies a restraining pressure to the positive electrode, the solid electrolyte layer, and the negative electrode in the thickness direction. A known jig can be used as the restraining jig. The restraining pressure is, for example, 0.1 MPa or more, and may be 1 MPa or more. Meanwhile, the restraining pressure is, for example, 50 MPa or less, and may be 20 MPa or less, 15 MPa or less, or 10 MPa or less. The smaller the restraining pressure, the more likely it is that a short circuit will occur. However, providing the protective layer according to the present disclosure can prevent the occurrence of a short circuit.

[0058] 8. Solid state battery In the present disclosure, a solid-state battery refers to a battery containing a solid electrolyte. The solid-state battery may be a semi-solid-state battery that contains a solid electrolyte and a liquid-based material, or an all-solid-state battery that does not contain a liquid-based material.

[0059] When a set of a positive electrode, a solid electrolyte layer, and a negative electrode is considered as a power generation unit, the solid-state battery may have only one power generation unit or may have two or more power generation units. When the solid-state battery has two or more power generation units, the power generation units may be connected in series or in parallel.

[0060] The solid-state battery in the present disclosure is typically a lithium-ion battery. The solid-state battery in the present disclosure may be a primary battery or a secondary battery, but is preferably a secondary battery because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery.

[0061] The use of the battery is not particularly limited, but examples include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, it is preferable to use the battery as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0062] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0063] [Example 1] (Preparation of positive electrode) NCA was used as the positive electrode active material. A sulfide solid electrolyte was used as the solid electrolyte. Using butyl butyrate as a solvent, NCA, solid electrolyte, binder, and conductive material were mixed to a mass composition ratio of NCA:solid electrolyte:binder:conductive material = 84.7:13.4:0.6:1.27 to prepare a positive electrode slurry. The resulting positive electrode slurry was then applied to an aluminum foil positive electrode current collector with a coating gap of 225 μm. The resulting coating was then pre-dried at 60°C for a predetermined time, then fully dried at 165°C for 1 hour, and applied to the positive electrode current collector with a basis weight of 18.7 mg / cm. 2 , design capacity 3.0mAh / cm 2 A positive electrode having a positive electrode layer of the above formula was obtained.

[0064] (Fabrication of solid electrolyte layer) The average particle size (D 50) 2.0 μm sulfide solid electrolyte particles were used. Using butyl butyrate as a solvent, the sulfide solid electrolyte and binder were mixed to a mass composition ratio of sulfide solid electrolyte:binder = 92.6:7.4 to obtain a solid electrolyte slurry. The solid electrolyte slurry was then coated onto a release film with a coating gap of 325 μm. The resulting coating was then pre-dried at room temperature for approximately 3 hours and then fully dried at 165°C for 1 hour. Two coated foils with a diameter of 14.5 mm were punched out from the dried coated foil, and the coated surfaces of the two coated foils were overlapped and pressed at 7 tons. After pressing, the release film was peeled off to obtain a free-standing solid electrolyte layer.

[0065] (Creation of protective layer) A protective layer of Sn was formed on the free-standing solid electrolyte layer by sputtering to a thickness of 0.1 μm. During sputtering, a mask of an appropriate size was applied to the solid electrolyte layer so that the diameter of the protective layer was smaller than the diameter of the solid electrolyte layer (14.5 mm).

[0066] (Preparation of negative electrode) A 1.0 μm thick Mg foil was used as the negative electrode active material. Ni foil was used as the negative electrode current collector. The Mg foil and Ni foil were punched out to a diameter of 13 mm each so that the diameter was smaller than the diameter of the protective layer, and a negative electrode layer made of Mg foil was formed on the Ni foil. This resulted in a negative electrode with a negative electrode layer formed on the negative electrode current collector.

[0067] (Fabrication of solid-state batteries) The fabricated positive electrode was punched out to a diameter of 11.28 mm, and a fabricated free-standing solid electrolyte layer with a diameter of 14.5 mm was placed between the positive and negative electrodes to obtain a laminate. The positive electrode tab was made of Al, and the negative electrode tab was made of Ni. The laminate was vacuum-sealed in an exterior body made of a laminate film with positive and negative terminals attached to it, to obtain a cell. The sealed cell was isostatically pressed at 392 MPa using CIP (cold isostatic pressing) to produce a laminate cell, which is a solid-state battery.

[0068] The stacking surface area of ​​each layer in the resulting solid-state battery was solid electrolyte layer (diameter 14.5 mm) > protective layer > anode layer (diameter 13 mm) > cathode layer (diameter 11.28 mm), with the protective layer having a first protrusion and the solid electrolyte layer having a second protrusion. The solid-state battery obtained had the second protrusion, which prevented the protective layer from wrapping around the cathode layer during restraint and charge / discharge, thereby preventing short circuits. Furthermore, the protective layer had the first protrusion, which prevented contact between the anode layer and the solid electrolyte layer in areas where the protective layer was not located, even when the anode layer expanded during charging, thereby suppressing the precipitation and elongation of Li dendrites.

[0069] [Comparative Example 1] The solid-state battery shown in Figure 6(a) was manufactured in the same manner as in Example 1, except that the area of ​​each layer was set as follows: solid electrolyte layer (diameter 14.5 mm) > protective layer = anode layer = cathode layer (all diameter 11.28 mm). In the obtained solid-state battery, the expansion and creep of the anode layer during charging caused the solid electrolyte layer and anode layer to come into contact, resulting in the precipitation and elongation of Li dendrites in the area where the protective layer was not located, causing a short circuit.

[0070] Comparative Example 2 The solid-state battery shown in Figure 6(b) was manufactured in the same manner as in Example 1, except that the areas of the layers were as follows: solid electrolyte layer (diameter 14.5 mm) > negative electrode layer > positive electrode layer (diameter 11.28 mm) > protective layer. The obtained solid-state battery experienced precipitation and extension of Li dendrites into the solid electrolyte layer from areas where the protective layer was not disposed, resulting in a short circuit.

[0071] [Example 2] A solid-state battery was manufactured in the same manner as in Example 1, except that the areas of the layers were as follows: solid electrolyte layer (diameter 14.5 mm) > protective layer > positive electrode layer (diameter 11.28 mm) > negative electrode layer. In the obtained solid-state battery, Li deposition occurred from the protective layer in the region of the negative electrode layer that did not face the positive electrode layer, resulting in a decrease in cycle performance and rate performance. On the other hand, Li dendrite deposition and extension did not occur in the solid electrolyte layer, so short circuits were suppressed. [Explanation of symbols]

[0072] 1...Anode layer 2...protective layer 3...Solid electrolyte layer 4...Positive electrode layer 5...Negative electrode current collector 6...Positive electrode current collector 10...Solid state battery

Claims

1. A solid-state battery having an anode layer, a protective layer, a solid electrolyte layer, and a cathode layer in this order, and utilizing a deposition-dissolution reaction of metallic lithium, the negative electrode layer includes a first metal element M1 that can be alloyed with lithium, the protective layer includes a second metal element M2 that can be alloyed with lithium, the first metal element M1 and the second metal element M2 are different elements, In a cross-sectional view in a thickness direction of the solid state battery, the protective layer has a first protruding portion that protrudes outward beyond an end surface of the negative electrode layer in a direction perpendicular to the thickness direction, the solid electrolyte layer has a second protrusion that protrudes outward beyond an end face of the protective layer in a direction perpendicular to the thickness direction.

2. a negative electrode current collector on the opposite side of the negative electrode layer from the protective layer, When viewed in a cross section in the thickness direction, the negative electrode current collector has an extension portion that extends outward beyond an end surface of the negative electrode layer in a direction perpendicular to the thickness direction, The solid-state battery according to claim 1 , wherein the extension portion has a bent portion in a region overlapping the first protrusion portion of the protective layer in the thickness direction.

3. The solid state battery according to claim 2 , wherein the extension portion of the negative electrode current collector and the first protrusion portion of the protective layer are spaced apart from each other.

4. In a cross-sectional view in the thickness direction, 3. The solid-state battery according to claim 2, wherein α tan θ < β is satisfied, where α is the width of the first protrusion of the protective layer on the side where the extension portion is present, β is the thickness of the negative electrode layer, and θ is the angle of the acute angle side of the bent portion of the extension portion.

5. In a cross-sectional view in the thickness direction, The solid-state battery according to claim 2 , wherein the thickness of the first protrusion on the side where the extension is present is thinner than the thickness of a region of the protective layer that does not have the first protrusion.

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