Manufacturing method for all-solid-state battery

Abstract

To provide an all-solid-state battery that suppresses increased bending of an electrode laminate when a battery cell expands by having a laminate film hold down the uppermost surface of the electrode laminate.SOLUTION: A manufacturing method for an all-solid-state battery including an electrode laminate and an outer film for housing the electrode laminate, includes a step for accommodating the electrode laminate in the outer film, a step for sandwiching an area inside the edge portion of the top surface of the outer film so as to face the top surface of the electrode laminate in the laminate direction using a holding member, and a step for sealing the outer film while it is sandwiched by the holding member.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an all-solid-state battery. [Background technology]

[0002] In recent years, research and development into all-solid-state batteries has been underway to contribute to energy efficiency, ensuring that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Since the volume of all-solid-state batteries fluctuates by about 18% from the design value during charging and discharging, a pouch-type laminate is required to absorb the displacement caused by the expansion and contraction of the battery cell.Currently, the electrode stack is wrapped in a laminate film with a cup height that is deeper than the thickness of the electrode stack at EOL SOC 100%, and by setting the excess length, the structure is designed to absorb the displacement (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-71133 Summary of the Invention [Problem to be solved by the invention]

[0005] CAE results confirmed that if the laminate film presses down on the edges of the electrode stack after vacuum sealing, bending of the electrode stack increases when the battery cell expands, increasing the stress generated in the solid electrolyte by 1.7 times (when the insulating frame width is 2.5 mm), which reduces the robustness of the structural design.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing an all-solid-state battery in which a laminate film presses the outermost surface of an electrode laminate, thereby suppressing an increase in bending of the electrode laminate when a battery cell expands, thereby contributing to stabilizing battery performance, improving quality control in the manufacturing process, and ultimately improving energy efficiency. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides the following means. [1] A method for manufacturing an all-solid-state battery including an electrode laminate and an exterior film that houses the electrode laminate, a step of housing the electrode stack in the exterior film; a step of sandwiching an inner region of an edge of the outermost surface of the packaging film with a holding member, the inner region facing the outermost surface of the electrode stack in the stacking direction of the packaging film; and sealing the exterior film in a state where the exterior film is sandwiched between the holding members.

[0008] By arranging the sealing portion of the exterior film in a direction perpendicular to the stacking direction of the electrode laminate and providing a gap between the exterior film and the electrode laminate along the edge of the outermost surface in the stacking direction of the electrode laminate, even if the exterior film presses against the outermost surface of the electrode laminate when covering the electrode laminate with the exterior film, it is possible to prevent the bending of the electrode laminate from increasing when the electrode laminate expands.

[0009] [2] The method for producing an all-solid-state battery according to [1], further comprising, after the step of sealing the exterior film, a step of arranging a buffer material in a region of the exterior film that faces an outermost surface of the electrode stack in the stacking direction and is inside an edge of the outermost surface.

[0010] The insulating layer can prevent the electrode laminate and the exterior film from coming into contact with each other and causing a short circuit between them. Furthermore, by arranging the insulating layer in the vicinity of the gap and the insulating layer, it is possible to prevent the electrode laminate and the exterior film from coming into contact with each other due to expansion and contraction of the electrode laminate. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an all-solid-state battery in which the laminate film presses the outermost surface of the electrode laminate, thereby suppressing an increase in bending of the electrode laminate when the battery cell expands. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing an all-solid-state battery according to one embodiment of the present invention. [Figure 2] 1A to 1C are cross-sectional views showing a method for manufacturing an all-solid-state battery according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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 drawings.

[0014] [All-solid battery] 1 is a cross-sectional view showing an all-solid-state battery according to one embodiment of the present invention. In the drawings used in the following description, characteristic portions may be enlarged for convenience in order to make the characteristics easier to understand, and the dimensional ratios of the components are not limited to those shown.

[0015] 1, the all-solid-state battery 1 of this embodiment includes an electrode laminate 10 and an exterior film 20. The exterior film 20 covers the outer surface 10a of the electrode laminate 10 and houses the electrode laminate 10.

[0016] The electrode stack 10 includes a positive electrode, a negative electrode, and a solid electrolyte layer.

[0017] The exterior film 20 has two sealing portions 21 and 22 arranged in a direction perpendicular to the stacking direction of the electrode laminate 10. That is, the sealing portions 21 and 22 are arranged to face the side surfaces 10b and 10c of the electrode laminate 10 in the stacking direction, respectively. The sealing portions 21 and 22 are preferably folded back to have portions 21A and 22A that extend along the stacking direction of the electrode laminate 10. This makes it possible to prevent peeling force from being applied to the sealing portions 21 and 22 due to expansion and contraction of the electrode laminate 10.

[0018] Along edge portions 11, 12, 13, and 14 of the outermost surface in the stacking direction of the electrode laminate 10 (upper surface 10d of the electrode laminate 10 in the stacking direction and lower surface 10e of the electrode laminate 10 in the stacking direction), gaps 11A, 12A, 13A, and 14A are provided between the outermost surface edge portions 11, 12, 13, and 14 of the electrode laminate 10 in the stacking direction and the exterior film 20. By providing the gaps 11A, 12A, 13A, and 14A, excess lengths 23, 24, 25, and 26 of the exterior film 20 exist along the outermost surface edge portions 11, 12, 13, and 14 of the electrode laminate 10 in the stacking direction.

[0019] 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, i.e., the lengths of the exterior film 20 that are separated from the electrode stack 10, are preferably 1 mm or more and 3 mm or less, and more preferably 1 mm or more and 1.5 mm or less. When the lengths of the excess lengths 23, 24, 25, and 26 are within the above ranges, it is possible to prevent the entire exterior film 20 from being stretched or peeling forces from being applied to the sealing portions 21 and 22 due to expansion and contraction of the electrode stack 10. Furthermore, the length of the exterior film 20 that is 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.

[0020] The all-solid-state battery 1 preferably includes an insulating layer 30 that covers the side surfaces 10b and 10c of the electrode laminate 10 in the stacking direction. Furthermore, the voids 11A, 12A, 13A, and 14A are preferably disposed near the insulating layer 30. In other words, the excess lengths 23, 24, 25, and 26 of the exterior film 20 are preferably disposed near the insulating layer 30. By providing the insulating layer 30, it is possible to prevent the electrode laminate 10 and the exterior film 20 from coming into contact with each other and short-circuiting the electrode laminate 10 and the exterior film 20. Furthermore, by disposing the voids 11A, 12A, 13A, and 14A near the insulating layer 30, it is possible to prevent the electrode laminate 10 and the exterior film 20 from coming into contact with each other due to expansion and contraction of the electrode laminate 10.

[0021] It is preferable that buffer materials 41 and 42 are arranged on the outermost surfaces in the stacking direction of the electrode stack 10 (upper surface 10d in the stacking direction of the electrode stack 10 and lower surface 10e in the stacking direction of the electrode stack 10) 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. By arranging the buffer materials 41 and 42, it is possible to prevent the electrode stack 10 from being damaged when an external force is applied.

[0022] (positive electrode) 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 has the first current collector layer and the first active material layer formed on both main surfaces of the first current collector layer.

[0023] The first current collector layer is preferably made of at least one material with high electrical conductivity. 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), as well as non-metals such as carbon (C). Considering both high conductivity and manufacturing costs, aluminum, nickel, and stainless steel are preferred. Furthermore, aluminum is less likely to react with the positive electrode active material and electrolyte. Therefore, using aluminum for the first current collector layer can reduce the internal resistance of the battery.

[0024] The first current collector layer may have, for example, a foil, plate, mesh, nonwoven fabric, foam, etc. In order to improve adhesion to the first active material layer 32, carbon or the like may be disposed on the surface of the first current collector layer, or the surface may be roughened.

[0025] The first active material layer contains a positive electrode active material that donates and receives lithium ions and electrons. 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 transport electrons, and known positive electrode active materials that can be used for the positive electrode of lithium ion batteries 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 phosphate (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 may be composed of one kind of the above materials alone, or may be composed of two or more kinds.

[0026] The first active material layer contains an electrolyte that transfers lithium ions to and from the positive electrode active material. The electrolyte is not particularly limited as long as it has lithium ion conductivity, and materials commonly used in lithium ion batteries can be used. Examples of the electrolyte include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, polymer-based solid electrolytes such as polyethylene oxide, and gel-based solid electrolytes containing lithium-containing salts and lithium-ion conductive ionic liquids. Among these, sulfide solid electrolyte materials are preferred from the viewpoints of high lithium ion conductivity, good structural formability by pressing, and good interfacial bonding. The electrolyte may be composed of one kind of the above materials alone or two or more kinds of them. The electrolyte contained in the first active material layer may be the same material as the electrolyte contained in the second active material layer or the solid electrolyte layer, or may be a different material.

[0027] The first active material layer may contain a conductive additive to improve the conductivity of the positive electrode. The conductive additive may be any conductive additive generally used in lithium-ion batteries. Examples of the conductive additive include carbon black such as acetylene black and Ketjen black; carbon fiber; vapor-grown carbon fiber; graphite powder; and carbon materials such as carbon nanotubes. The conductive additive may be composed of one or more of the above materials.

[0028] The first active material layer may also contain a binder that functions to bind the positive electrode active materials together and between the positive electrode active material and the first current collector layer.

[0029] In this embodiment, the first active material layer is formed on both main surfaces of the first current collector layer, but this is not limiting and the first active material layer may be formed on only one main surface of the first current collector layer. Furthermore, when the positive electrode is a single-sided coated electrode, a laminated positive electrode in which two positive electrodes are stacked with their current collector surfaces facing each other may be used as a double-sided coated electrode. Furthermore, when the first current collector layer has a three-dimensional porous structure such as a mesh, nonwoven fabric, or foam, the first current collector layer may be provided integrally with the first active material layer.

[0030] The first current collector layers are assembled at one end in the width direction of the all-solid-state battery. The first active material layer is in contact with the solid electrolyte layer and may therefore contain sulfides contained in the solid electrolyte layer.

[0031] (Negative electrode) 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 has the second current collector layer and second active material layers formed on both main surfaces of the second current collector layer and containing a negative electrode active material and an electrolyte.

[0032] The second current collector layer contains at least copper (Cu). Like the first current collector layer, the second current collector layer may contain a material other than copper that has high conductivity. Examples of highly conductive materials other than copper include metals or alloys containing at least one of silver (Ag), palladium (Pd), gold (Au), platinum (Pt), chromium (Cr), and nickel (Ni), or non-metals such as carbon (C). Considering not only high conductivity but also manufacturing costs, nickel or stainless steel is preferred as the material other than copper. Furthermore, stainless steel is less likely to react with the positive electrode active material, negative electrode active material, and electrolyte. Therefore, using stainless steel for the second current collector layer can reduce battery manufacturing costs.

[0033] The second current collector layer may be in the form of, for example, a foil, a plate, a mesh, a nonwoven fabric, a foam, etc. In order to improve adhesion to the second active material layer, carbon or the like may be disposed on the surface of the second current collector layer, or the surface may be roughened.

[0034] The second active material layer contains a negative electrode active material that donates and accepts lithium ions and electrons. The negative electrode active material is not particularly limited as long as it is a material that can reversibly absorb and release lithium ions and transport electrons, and known negative electrode active materials that can be used for the negative electrode of a lithium ion battery can be used. Examples of such materials include carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; alloy-based materials mainly composed of tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, and aluminum alloys; conductive polymers such as polyacene, polyacetylene, and polypyrrole; metallic lithium; lithium titanium composite oxides (e.g., Li4Ti5O 12 These negative electrode active materials may be composed of one kind of the above materials alone, or two or more kinds of them.

[0035] The second active material layer contains an electrolyte that transfers lithium ions to and from the negative electrode active material. The electrolyte is not particularly limited as long as it has lithium ion conductivity, and materials generally used in lithium ion batteries can be used. Examples of the electrolyte include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, polymer-based solid electrolytes such as polyethylene oxide, and gel-based solid electrolytes containing lithium-containing salts and lithium-ion conductive ionic liquids. The electrolyte may be composed of one or more of the above materials. 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 or the solid electrolyte layer.

[0036] The second active material layer may contain a conductive additive, a binder, etc. These materials are not particularly limited, and may be, for example, the same materials as those used in the first active material layer described above.

[0037] In this embodiment, the second active material layer is formed on both main surfaces of the second current collector layer, but this is not limiting and the second active material layer may be formed on only one main surface of the second current collector layer. Furthermore, when the second current collector layer has a three-dimensional porous structure such as a mesh, nonwoven fabric, or foam, the second current collector layer may be provided integrally with the second active material layer.

[0038] (solid electrolyte layer) The solid electrolyte layer is disposed between the first active material layer and the second active material layer.

[0039] The electrolyte is not particularly limited as long as it has lithium ion conductivity and insulating properties, and materials generally used in lithium ion batteries can be used. Examples include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, polymer-based solid electrolytes such as polyethylene oxide, and gel-based electrolytes containing lithium-containing salts and lithium ion-conductive ionic liquids. Among these, sulfide solid electrolyte materials are preferred from the viewpoints of high lithium ion conductivity, structural formability by pressing, and interfacial bonding. The form of the electrolyte material is not particularly limited, but may be, for example, in the form of particles.

[0040] The solid electrolyte layer may contain an adhesive to impart mechanical strength and flexibility.

[0041] The solid electrolyte layer may be in the form of a sheet having a porous substrate and a solid electrolyte supported on the porous substrate. The form of the porous substrate is not particularly limited, and examples thereof include woven fabric, nonwoven fabric, mesh cloth, porous membrane, expanded sheet, and punched sheet. Among these forms, nonwoven fabric is preferred from the viewpoint of handleability, which allows for a higher loading of the solid electrolyte.

[0042] The porous substrate is preferably made of an insulating material, which can improve the insulating properties of the solid electrolyte layer. Examples of insulating materials include resin materials such as nylon, polyester, polyethylene, polypropylene, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinylidene chloride, polyvinyl chloride, polyurethane, vinylon, polybenzimidazole, polyimide, polyphenylene sulfite, polyether ether ketone, cellulose, and acrylic resin; natural fibers such as hemp, wood pulp, and cotton linter; and glass.

[0043] (exterior film) The exterior film 20 is a laminated film having an inner resin layer, a metal layer, and an outer resin layer. Examples of resins that make up the inner and outer resin layers include polyester resins such as polyethylene terephthalate (PET). The metal layer is made of, for example, aluminum foil.

[0044] (insulating layer) The insulating material constituting the insulating layer 30 is not particularly limited, but may be, for example, high-purity alumina.

[0045] (buffer material) The buffer materials 41 and 42 are not particularly limited, but may be made of a material having thermal conductivity and elasticity, for example.

[0046] [Manufacturing method for all-solid-state batteries] 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 including an electrode laminate and an exterior film that houses the electrode laminate, and includes the steps of: housing the electrode laminate in the exterior film (hereinafter referred to as a "first step"); sandwiching, with holding members, a region of the exterior film that faces the outermost surface in the stacking direction of the electrode laminate and is inside the edge of the outermost surface (hereinafter referred to as a "second step"); and sealing the exterior film in a state where the exterior film is sandwiched between the holding members (hereinafter referred to as a "third step").

[0047] The method for manufacturing the all-solid-state battery of this embodiment will be described with reference to FIGS.

[0048] "First step" In the first step, the electrode stack 10 is housed in an exterior film 20.

[0049] "Second step" 2, in the second step, the exterior film 20 faces the outermost surface 10a in the stacking direction of the electrode laminate 10, and the regions inside the edges 11, 12, 13, and 14 of the outermost surface 10a are sandwiched between holding members 101 and 102. This provides a gap between the exterior film 20 and the electrode laminate along the edges 11, 12, 13, and 14 of the outermost surface 10a in the stacking direction of the electrode laminate 10.

[0050] "Third step" In the third step, the exterior film 20 is sealed while being sandwiched between the holding members 101 and 102. When sealing the exterior film 20, two sealing portions 21 and 22 are formed, which are arranged in a direction perpendicular to the stacking direction of the electrode laminate 10. Furthermore, the sealing portions 21 and 22 are folded back to form portions 21A and 22A that extend along the stacking direction of the electrode laminate 10.

[0051] "Fourth step" The method for manufacturing the all-solid-state battery of this embodiment preferably includes, after the step of sealing the exterior film 20 (third step), a step of arranging buffer materials 41, 42 in the exterior film 20 facing the outermost surface 10a in the stacking direction of the electrode laminate 10 and in the region inside the edge portions 11, 12, 13, 14 of the outermost surface 10a.

[0052] Through the above steps, the all-solid-state battery 1 of this embodiment is obtained.

[0053] According to the manufacturing method for the all-solid-state battery of this embodiment, the sealing portions 21, 22 of the exterior film 20 are arranged in a direction perpendicular to the stacking direction of the electrode laminate 10, and a gap is provided between the exterior film 20 and the electrode laminate along the edge of the outermost surface in the stacking direction of the electrode laminate 10. This makes it possible to suppress an increase in bending of the electrode laminate 10 when the electrode laminate 10 expands, even if the exterior film 20 presses the outermost surface of the electrode laminate 10 when covering the electrode laminate 10 with the exterior film 20.

[0054] 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 variations are possible within the scope of the gist of the present invention as set forth in the claims. [Explanation of symbols]

[0055] 1 All-solid-state battery 10 Electrode laminate 11A,12A,13A,14A void 20 Exterior film 23,24,25,26 extra length 30 insulating layer 41,42 Cushioning material

Claims

1. A method for manufacturing an all-solid-state battery including an electrode stack and an exterior film that houses the electrode stack, a step of housing the electrode stack in the exterior film; a step of sandwiching an inner region of an edge of the outermost surface of the packaging film with a holding member, the inner region facing the outermost surface of the electrode stack in the stacking direction of the packaging film; and sealing the exterior film in a state where the exterior film is sandwiched between the holding members.

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

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