Method for manufacturing all-solid-state battery

Abstract

Provided is a method for manufacturing an all-solid-state battery, which suppresses an increase in bending of an electrode laminate when a battery cell expands by pressing the outermost surface of the electrode laminate with a laminated film. This method for manufacturing an all-solid-state battery is a method for manufacturing an all-solid-state battery provided with an electrode laminate and an exterior film that accommodates the electrode laminate. The method comprises: a step for accommodating the electrode laminate in the exterior film; a step for sandwiching, by means of a holding member, a region of the exterior film, said region facing the outermost surface in the lamination direction of the electrode laminate and being located inside the edge of the outermost surface; and a step for sealing the exterior film in a state in which the exterior film is sandwiched by the holding member.

Description

[0001] Cross-references between related applications

[0002] This application claims priority based on Japanese Patent Application No. 2024-057644 filed on March 29, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a method for manufacturing an all-solid-state battery. Background Art

[0004] In recent years, research and development of all-solid-state batteries, which contribute to energy efficiency, has been conducted to ensure that more people have access to appropriate, reliable, sustainable, and advanced energy.

[0005] All-solid-state batteries experience volume fluctuations during charge and discharge, necessitating pouch-type lamination to absorb displacement caused by expansion and contraction of the battery cells. Currently, one structure involves surrounding the electrode stack with a laminate film formed to a cup depth greater than the thickness of the electrode stack at 100% end-of-life (EOL) SOC, with excess length to absorb this displacement (see, for example, Japanese Patent Application Laid-Open No. 2011-71133). Summary of the Invention

[0006] It has been confirmed that if the laminate film presses the ends of the electrode stack after vacuum sealing, the electrode stack bends more during battery cell expansion and the stress generated in the solid electrolyte increases, resulting in a decrease in the robustness of the structural design.

[0007] The present invention provides a method for manufacturing an all-solid-state battery that suppresses the increased bending of the electrode stack caused by a laminating film pressing against the outermost surface of the electrode stack during expansion of the battery cell. This method contributes to stabilizing battery performance, improving quality control during the manufacturing process, and increasing energy efficiency.

[0008] The solution of the present invention provides the following method.

[0009] [1] A method for manufacturing an all-solid-state battery, the all-solid-state battery comprising an electrode stack and an exterior film for housing the electrode stack, wherein:

[0010] The manufacturing method of the all-solid-state battery has the following characteristics:

[0011] The step of housing the electrode stack in the outer film;

[0012] a step of sandwiching a region of the exterior film that faces the outermost surface of the electrode stack in the stacking direction and is located inside an edge of the outermost surface with a holding member; and

[0013] a step of sealing the exterior film while the exterior film is sandwiched between the holding members.

[0014] By arranging the sealing portion of the outer packaging film in a direction perpendicular to the stacking direction of the electrode stack and providing a gap between the outer packaging film and the electrode stack along the edge of the outermost surface in the stacking direction of the electrode stack, even when the electrode stack is covered with the outer packaging film, the outer packaging film presses the outermost surface of the electrode stack, thereby suppressing the increase in the bending of the electrode stack when the electrode stack expands.

[0015] [2] The method for manufacturing an all-solid-state battery according to [1], wherein:

[0016] The method for manufacturing an all-solid-state battery includes, after the step of sealing the exterior film, the step of disposing a buffer material in a region of the exterior film that faces the outermost surface of the electrode stack in the stacking direction and is located inside an edge of the outermost surface.

[0017] The provision of an insulating layer can prevent the electrode stack from coming into contact with the outer film, thereby preventing a short circuit between the electrode stack and the outer film. Furthermore, by arranging the aforementioned gap near the insulating layer, even if the outer film and the insulating layer come into contact due to expansion or contraction of the electrode stack, a short circuit between the electrode stack and the outer film can be prevented.

[0018] According to the aspect of the present invention, it is possible to provide an all-solid-state battery that suppresses the laminate film from pressing the outermost surface of the electrode stack and thereby suppressing an increase in the bending of the electrode stack during expansion of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a cross-sectional view showing an all-solid-state battery according to one embodiment of the present invention.

[0020] Figure 2 This is a cross-sectional view illustrating a method for manufacturing an all-solid-state battery according to one embodiment of the present invention. DETAILED DESCRIPTION

[0021] Hereinafter, a method for manufacturing an all-solid-state battery according to one embodiment of the present invention will be described with reference to the accompanying drawings.

[0022] All-solid-state batteries

[0023] Figure 1 This is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention. It should be noted that the drawings used in the following description may show enlarged portions of features for ease of understanding, and the dimensional ratios of the various components are not limited to those shown.

[0024] like Figure 1As shown, the all-solid-state battery 1 of this embodiment includes an electrode stack 10 and an exterior film 20 . The exterior film 20 covers the outer surface 10 a of the electrode stack 10 and houses the electrode stack 10 .

[0025] The electrode stack 10 includes a positive electrode, a negative electrode, and a solid electrolyte layer.

[0026] The exterior film 20 has two sealing portions 21 and 22 arranged in a direction perpendicular to the stacking direction of the electrode stack 10. Specifically, the sealing portions 21 and 22 are arranged so as to face the side surfaces 10b and 10c of the electrode stack 10 in the stacking direction, respectively. The sealing portions 21 and 22 are preferably folded back to have portions 21A and 22A extending in the stacking direction of the electrode stack 10. This can suppress the forces that could cause the sealing portions 21 and 22 to peel due to expansion and contraction of the electrode stack 10.

[0027] Along the edges 11, 12, 13, and 14 of the outermost surface of the electrode stack 10 in the stacking direction (the upper surface 10d of the electrode stack 10 in the stacking direction and the lower surface 10e of the electrode stack 10 in the stacking direction), gaps 11A, 12A, 13A, and 14A are formed between these outermost edges 11, 12, 13, and 14 of the electrode stack 10 in the stacking direction and the exterior film 20. The provision of gaps 11A, 12A, 13A, and 14A results in excess lengths 23, 24, 25, and 26 of the exterior film 20 being present along the outermost edges 11, 12, 13, and 14 of the electrode stack 10 in the stacking direction.

[0028] The excess lengths 23, 24, 25, and 26 of the exterior film 20 refer to portions of the exterior film 20 that are not in contact with the electrode stack 10 and are separated from the electrode stack 10. The lengths of the excess lengths 23, 24, 25, and 26, that is, the lengths of the exterior film 20 separated from the electrode stack 10, are preferably from 1 mm to 3 mm, and more preferably from 1 mm to 1.5 mm. When the lengths of the excess lengths 23, 24, 25, and 26 are within the above ranges, it is possible to suppress the overall extension of the exterior film 20 due to expansion and contraction of the electrode stack 10 or the application of peeling forces to the sealing portions 21 and 22. In addition, the length of the exterior film 20 separated from the electrode stack 10 is the maximum length of the gaps 11A, 12A, 13A, and 14A in the thickness direction of the all-solid-state battery 1.

[0029] The all-solid-state battery 1 preferably includes an insulating layer 30 that covers the side surfaces 10b and 10c in the stacking direction of the electrode stack 10. Furthermore, the gaps 11A, 12A, 13A, and 14A are preferably arranged near the insulating layer 30. In other words, the excess lengths 23, 24, 25, and 26 of the exterior film 20 are preferably arranged near the insulating layer 30. Providing the insulating layer 30 can prevent the electrode stack 10 and the exterior film 20 from coming into contact and short-circuiting the electrode stack 10 and the exterior film 20. Furthermore, by arranging the gaps 11A, 12A, 13A, and 14A near the insulating layer 30, even if the exterior film 20 and the insulating layer 30 come into contact due to expansion or contraction of the electrode stack 10, short-circuiting the electrode stack 10 and the exterior film 20 can be prevented.

[0030] Preferably, cushioning members 41 and 42 are disposed on the outermost surfaces of the electrode stack 10 in the stacking direction (the upper surface 10d and the lower surface 10e of the electrode stack 10 in the stacking direction) inside the gaps 11A, 12A, 13A, and 14A, in other words, inside the excess lengths 23, 24, 25, and 26 of the exterior film 20. The provision of cushioning members 41 and 42 can prevent damage to the electrode stack 10 when external force is applied.

[0031] (positive electrode)

[0032] The positive electrode is formed by laminating a first current collector layer and a first active material layer containing at least a positive electrode active material. In this embodiment, the positive electrode includes a first current collector layer and first active material layers formed on both main surfaces of the first current collector layer.

[0033] The first current collector layer is preferably composed of at least one substance having high electrical conductivity.

[0034] Examples of highly conductive materials include metals or alloys containing at least one of silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), chromium (Cr), and nickel (Ni), or non-metallic materials such as carbon (C). Considering both high conductivity and manufacturing cost, aluminum, nickel, or stainless steel are preferred. Furthermore, aluminum is less likely to react with the positive electrode active material and the electrolyte. Therefore, using aluminum in the first current collector layer can reduce the internal resistance of the battery.

[0035] The first current collector layer may be shaped like a foil, a plate, a mesh, a nonwoven fabric, or a foam. In order to improve adhesion to the first active material layer 32, the surface of the first current collector layer may be provided with carbon or roughened.

[0036] The first active material layer contains a positive electrode active material that accepts electrons from lithium ions. The positive electrode active material is not particularly limited as long as it is a material that can reversibly release and absorb lithium ions and can transport electrons. A known positive electrode active material that can be applied to the positive electrode of a lithium ion battery can be used. For example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxide (Li2MnO3-LiMO2 (M=Co, Ni, etc.)), lithium-manganese-nickel-cobalt oxide (LiNi x Mn y Co z O2, x+y+z=1), composite oxides such as olivine-type lithium phosphorus oxide (LiFePO4); conductive polymers such as polyaniline and polypyrrole; sulfides such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, and Li-Mo-S compounds; mixtures of sulfur and carbon; etc. The positive electrode active material can be composed of one of the above materials alone or of two or more.

[0037] The first active material layer includes an electrolyte that transfers lithium ions with the positive electrode active material. As an electrolyte, there is no particular limitation as long as it is an electrolyte with lithium ion conductivity, and materials commonly used in lithium ion batteries can be used. As electrolytes, for example, sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, inorganic solid electrolytes such as lithium salts, solid electrolytes of polymer systems such as polyethylene oxide, and gel-based solid electrolytes containing lithium salts and lithium ion conductive ionic liquids can be cited. Among them, from the perspective of higher lithium ion conductivity and pressure-based structural formability and good interface bonding, sulfide solid electrolyte materials are preferred.

[0038] The electrolyte may be composed of one of the above materials alone or of two or more. The electrolyte contained in the first active material layer may be the same material as or different from the electrolyte contained in the second active material layer and the solid electrolyte layer.

[0039] The first active material layer may also contain a conductive additive to improve the conductivity of the positive electrode. Any conductive additive commonly used in lithium-ion batteries can be used. Examples include carbon blacks such as acetylene black and Ketjen Black; carbon fibers; vapor-grown carbon fibers; graphite powder; and carbon nanotubes. The conductive additive may be composed of one of the above materials alone or a combination of two or more.

[0040] Furthermore, the first active material layer may contain a binder that has a function of binding the positive electrode active materials to each other and to the first current collector layer.

[0041] In this embodiment, the first active material layer is formed on both main surfaces of the first current collector layer, but this is not limited to this. The first active material layer may also be formed on only one main surface of the first current collector layer. In addition, when the positive electrode is a single-sided coated electrode, a stacked positive electrode formed by stacking the current collector surfaces of two positive electrodes in a manner that matches each other may be used as a double-sided coated electrode. In addition, when the first current collector layer has a three-dimensional porous structure such as a mesh, non-woven fabric, or foam, the first current collector layer may also be provided integrally with the first active material layer.

[0042] The first current collector layer is assembled at one end portion in the width direction of the all-solid-state battery.

[0043] The first active material layer is in contact with the solid electrolyte layer and therefore may contain sulfides contained in the solid electrolyte layer.

[0044] (negative electrode)

[0045] The negative electrode is formed by laminating a second current collector layer and a second active material layer containing at least a negative electrode active material. In this embodiment, the negative electrode includes the second current collector layer and the second active material layer formed on both main surfaces of the second current collector layer and containing a negative electrode active material and an electrolyte.

[0046] The second current collector layer contains at least copper (Cu). Like the first current collector layer, the second current collector layer may also contain substances other than copper with higher conductivity. Examples of substances other than copper with higher conductivity include metals or alloys containing at least one metal element of silver (Ag), palladium (Pd), gold (Au), platinum (Pt), chromium (Cr), and nickel (Ni), or non-metals such as carbon (C). When considering manufacturing costs in addition to high conductivity, nickel or stainless steel is preferred as the substance other than copper. In addition, stainless steel is difficult to react with the positive electrode active material, the negative electrode active material, and the electrolyte. Therefore, when stainless steel is used in the second current collector layer, the manufacturing cost of the battery can be reduced.

[0047] The second current collector layer may be shaped like a foil, a plate, a mesh, a nonwoven fabric, or a foam. In order to improve adhesion to the second active material layer, the surface of the second current collector layer may be provided with carbon or roughened.

[0048] The second active material layer contains a negative electrode active material that accepts electrons with lithium ions. As the negative electrode active material, there is no particular limitation as long as it is a material that can reversibly release and absorb lithium ions and can transport electrons. A known negative electrode active material that can be applied to the negative electrode of a lithium ion battery can be used. For example, carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; alloy materials based on tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, and aluminum alloys; conductive polymers such as polyacetylene, polyacetylene, and polypyrrole; metallic lithium; lithium-titanium composite oxides (such as Li4Ti5O 12 ) and other lithium alloys. These negative electrode active materials may be composed of one of the above materials alone or of two or more.

[0049] The second active material layer includes an electrolyte that transfers lithium ions to and from the negative electrode active material. As an electrolyte, there is no particular limitation as long as it is an electrolyte with lithium ion conductivity, and materials commonly used in lithium ion batteries can be used. As electrolytes, for example, sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, inorganic solid electrolytes containing lithium salts, solid electrolytes of polymer systems such as polyethylene oxide, and gel-based solid electrolytes containing lithium salts and lithium ion conductive ionic liquids can be cited. The electrolyte can be composed of one of the above materials alone, or it can be composed of two or more.

[0050] The electrolyte contained in the second active material layer may be the same as or different from the electrolyte contained in the first active material layer and the solid electrolyte layer.

[0051] The second active material layer may also contain a conductive additive, a binder, etc. These materials are not particularly limited, but for example, the same materials as those used for the first active material layer described above can be used.

[0052] In this embodiment, the second active material layer is formed on both main surfaces of the second current collector layer, but the present invention is not limited thereto. The second active material layer may be formed on only one main surface of the second current collector layer. In addition, when the second current collector layer has a three-dimensional porous structure such as a mesh, non-woven fabric, or foam, the second current collector layer may be provided integrally with the second active material layer.

[0053] (Solid electrolyte layer)

[0054] The solid electrolyte layer is disposed between the first active material layer and the second active material layer.

[0055] As electrolyte, as long as it is an electrolyte with lithium ion conductivity and insulation, there is no particular limitation, and materials commonly used in lithium ion batteries can be used. For example, sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, inorganic solid electrolytes such as lithium salts, solid electrolytes of polymer systems such as polyethylene oxide, and gel electrolytes containing lithium salts and lithium ion conductive ionic liquids can be cited. Among them, from the viewpoint of the higher conductive properties of lithium ions and the structural formability and good interface bonding properties based on pressure, sulfide solid electrolyte materials are preferably used.

[0056] The form of the electrolyte material is not particularly limited, but an example thereof may be a particle form.

[0057] The solid electrolyte layer may contain a binder for imparting mechanical strength and flexibility.

[0058] The solid electrolyte layer can also be a sheet having a porous substrate and a solid electrolyte retained on the porous substrate. As the form of the above-mentioned porous substrate, there is no particular limitation, but for example, woven fabrics, non-woven fabrics, meshes, porous membranes, expansion sheets, punching sheets, etc. can be cited. Among these forms, from the viewpoint of making the handling of the filling amount of the solid electrolyte higher, non-woven fabrics are preferably used.

[0059] The porous substrate is preferably made of an insulating material. This improves the insulation properties of the solid electrolyte layer. Examples of insulating materials include nylon, polyester, polyethylene, polypropylene, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinylidene chloride, polyvinyl chloride, polyurethane, vinylon, polybenzimidazole, polyimide, polyphenylene sulfide, polyetheretherketone, cellulose, acrylic resin and other resin materials; natural fibers such as hemp, wood pulp, cotton linter, and glass.

[0060] (Exterior film)

[0061] The exterior film 20 is a laminated film comprising an inner resin layer, a metal layer, and an outer resin layer. Examples of the resins constituting the inner and outer resin layers include polyester resins such as polyethylene terephthalate (PET). The metal layer is formed, for example, from aluminum foil.

[0062] (Insulation layer)

[0063] The insulating material constituting the insulating layer 30 is not particularly limited, and examples thereof include high-purity alumina.

[0064] (Buffer)

[0065] The cushioning materials 41 and 42 are not particularly limited, and examples thereof include cushioning materials made of a material having thermal conductivity and elasticity.

[0066] [Manufacturing method of all-solid-state batteries]

[0067] A method for manufacturing an all-solid-state battery according to one embodiment of the present invention is a method for manufacturing an all-solid-state battery comprising an electrode stack and an exterior film for housing the electrode stack, the method comprising: housing the electrode stack in the exterior film (hereinafter referred to as the “first step”); sandwiching a region of the exterior film that is opposed to the outermost surface of the electrode stack in the stacking direction and located inward of an edge of the outermost surface using a retaining member (hereinafter referred to as the “second step”); and sealing the exterior film while the exterior film is sandwiched by the retaining member (hereinafter referred to as the “third step”).

[0068] Reference Figure 1 as well as Figure 2 A method for manufacturing the all-solid-state battery according to this embodiment will be described.

[0069] "First process"

[0070] In the first step, the electrode stack 10 is housed in the exterior film 20 .

[0071] "Second Process"

[0072] In the second step, Figure 2 As shown, the region of the exterior film 20 that faces the outermost surface 10a in the stacking direction of the electrode stack 10 and is located inside the edges 11, 12, 13, and 14 of the outermost surface 10a is sandwiched between the retaining members 101 and 102. Thus, a gap is provided between the exterior film 20 and the electrode stack along the edges 11, 12, 13, and 14 of the outermost surface 10a in the stacking direction of the electrode stack 10.

[0073] "Third Process"

[0074] In the third step, the exterior film 20 is sealed while being sandwiched between the holding members 101 and 102. When the exterior film 20 is sealed, two sealed portions 21 and 22 are formed, arranged in a direction perpendicular to the stacking direction of the electrode stack 10. Furthermore, the sealed portions 21 and 22 are folded back to form portions 21A and 22A extending in the stacking direction of the electrode stack 10.

[0075] "Fourth Process"

[0076] The method for manufacturing an all-solid-state battery of the present embodiment preferably includes, after the step of sealing the exterior film 20 (the third step), a step of disposing buffer members 41 and 42 in regions of the exterior film 20 that are opposed to the outermost surface 10 a in the stacking direction of the electrode stack 10 and that are located inside the edges 11, 12, 13, and 14 of the outermost surface 10 a.

[0077] Through the above steps, the all-solid-state battery 1 of this embodiment is obtained.

[0078] According to the method for manufacturing an all-solid-state battery of the present embodiment, the sealing portions 21 and 22 of the exterior film 20 are arranged in a direction orthogonal to the stacking direction of the electrode stack 10, and a gap is provided between the exterior film 20 and the electrode stack along the edge of the outermost surface of the electrode stack 10 in the stacking direction. Thus, even when the electrode stack 10 is covered with the exterior film 20, the exterior film 20 presses on the outermost surface of the electrode stack 10, and thus, an increase in the bending of the electrode stack 10 when the electrode stack 10 expands can be suppressed.

[0079] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. A method for manufacturing an all-solid-state battery, the all-solid-state battery comprising an electrode stack and an exterior film housing the electrode stack, wherein: The manufacturing method of the all-solid-state battery has the following characteristics: The step of housing the electrode stack in the outer film; a step of sandwiching a region of the exterior film that faces the outermost surface of the electrode stack in the stacking direction and is located inside an edge of the outermost surface with a holding member; and a step of sealing the exterior film while the exterior film is sandwiched between the holding members.

2. The method for manufacturing an all-solid-state battery according to claim 1, wherein: The method for manufacturing an all-solid-state battery includes, after the step of sealing the exterior film, the step of disposing a buffer material in a region of the exterior film that faces the outermost surface of the electrode stack in the stacking direction and is located inside an edge of the outermost surface.

Images