Manufacturing method for all-solid-state battery

Abstract

To provide a manufacturing method for an all-solid-state battery that suppresses the destruction of an electrode current collector caused by contamination existing between an outer film and the electrode current collector and embedded in the electrode current collector when the surface of the electrode current collector is covered with the outer film.SOLUTION: A manufacturing method for an all-solid-state battery has a heating step for heating at least a portion of an outer film facing the outermost surface in the stacking direction of an electrode laminate, and a housing step for housing the electrode laminate in the outer film.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Welding is used to join tab leads to electrode current collectors of electrode laminates included in all-solid-state batteries. Joining by welding generates spatter (metallic foreign matter), which may remain on the surface of the electrode current collector as contamination. Furthermore, when the tab lead is cut, chips are generated, which may remain on the surface of the tab lead as contamination. If the surface of the electrode current collector is covered with an exterior film while contamination is present on its surface, the exterior film exerts a force that presses the contamination against the surface of the electrode current collector. This can cause the contamination to become embedded in the electrode current collector, resulting in the destruction of the electrode current collector.

[0003] A known example of a laminated battery that reduces the occurrence of defects during manufacturing due to the presence of contamination between an exterior film and an electrode current collector is one that includes an electrode body and a laminated case that houses the electrode body, where the laminated case has a multilayer structure including a sealant layer, a gas barrier layer, an outer layer, and an intermediate layer located between the sealant layer and the gas barrier layer, where the gas barrier layer is an aluminum layer, and the intermediate layer contains 5% by mass to 50% by mass of polyrotaxane (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-125487 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the laminate battery of Patent Document 1, although corrosion due to a short circuit between the aluminum layer and the negative electrode is suppressed by utilizing the high elasticity of the intermediate layer containing a specific amount of polyrotaxane, when the surface of the electrode current collector is covered with an exterior film, it is not possible to suppress the electrode current collector from being destroyed due to the embedding of contamination in the electrode current collector.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a manufacturing method for an all-solid-state battery that, when covering the surface of an electrode current collector with an exterior film, prevents contamination present between the exterior film and the electrode current collector from being embedded in the electrode current collector and destroying the electrode current collector, thereby contributing to stabilizing battery performance and improving quality control in the manufacturing process, and ultimately to improving quality control. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides the following means. [1] a heating step of heating at least a portion of the exterior film facing the outermost surface of the electrode laminate in the lamination direction; and a housing step of housing the electrode stack in the exterior film.

[0008] Before the exterior film and the electrode laminate come into contact, at least the portion of the exterior film that faces the outermost surface of the electrode laminate in the lamination direction is softened by heating, which makes it easier for the exterior film to absorb contamination even if contamination is present between the exterior film and the electrode current collector.

[0009] [2] The method for producing an all-solid-state battery according to [1], wherein the temperature at which the portion is heated in the heating step exceeds the glass transition point of the resin constituting the portion.

[0010] By heating the part to a temperature exceeding the glass transition point of the resin that constitutes the part, it is possible to prevent the electrode stack from being damaged by heating the exterior film.

[0011] [3] The exterior film has a sealant resin layer, a metal layer, and an outer resin layer, The method for producing an all-solid-state battery according to [1] or [2], wherein the sealant resin layer, the metal layer, and the outer resin layer are laminated in this order.

[0012] By using an exterior film having a sealant resin layer, a metal layer, and an outer resin layer, and softening the sealant resin layer by heating, even if contamination exists between the exterior film and the electrode current collector, the sealant resin layer becomes more likely to absorb the contamination.

[0013] [4] The exterior film has a sealant resin layer, an insulating resin layer, a metal layer, and an outer resin layer, The method for producing an all-solid-state battery according to [1] or [2], wherein the sealant resin layer, the insulating resin layer, the metal layer, and the outer resin layer are laminated in this order.

[0014] By using an exterior film having a sealant resin layer, an insulating resin layer, a metal layer, and an outer resin layer, the insulating resin layer can suppress short-circuiting between the metal layer and the electrode laminate when the electrode laminate is housed in the exterior film. Furthermore, the exterior film having the insulating resin layer has durability against high load restraint during cycling.

[0015] [5] The method for producing an all-solid-state battery according to [3] or [4], wherein the sealant resin constituting the sealant resin layer has a glass transition point of less than 45°C.

[0016] The sealant resin constituting the sealant resin layer has a glass transition point of less than 45° C., so that the sealant resin layer is sufficiently softened in the heating step.

[0017] [6] The method for producing an all-solid-state battery according to [4], wherein the insulating resin constituting the insulating resin layer has a glass transition point that exceeds the glass transition point of the sealant layer and a melting point that is 230°C or higher.

[0018] The insulating resin constituting the insulating resin layer has a glass transition point that exceeds the glass transition point of the sealant layer and a melting point of 230°C or higher, which prevents the insulating resin layer from softening during the heating process and also prevents short circuits between the metal layer and the electrode laminate. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a method for manufacturing an all-solid-state battery that, when covering the surface of an electrode current collector with an exterior film, prevents contamination present between the exterior film and the electrode current collector from being embedded in the electrode current collector and destroying the electrode current collector. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a cross-sectional view showing an exterior film used in the method for producing an all-solid-state battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an exterior film used in the method for producing an all-solid-state battery according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for convenience in order to make the characteristics easier to understand, and the dimensional ratios of each component are not limited to those shown in the drawings.

[0022] [Manufacturing method for all-solid-state batteries] The method for manufacturing an all-solid-state battery of this embodiment includes a heating step of heating at least a portion of an exterior film that faces the outermost surface of the electrode stack in the stacking direction, and an accommodating step of accommodating the electrode stack in the exterior film.

[0023] "Electrode laminate" The electrode stack in this embodiment includes a positive electrode, a negative electrode, and an electrolyte layer.

[0024] (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.

[0025] 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.

[0026] The first 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 first active material layer, carbon or the like may be disposed on the surface of the first current collector layer, or the surface may be roughened.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The first active material layer may be formed on both main surfaces of the first current collector layer, or on only one main surface of the first current collector layer. When the positive electrode is a single-sided coated electrode, a laminated positive electrode formed by stacking two positive electrodes with their current collector surfaces facing each other may be used as a double-sided coated electrode. 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.

[0032] 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 electrolyte layer and may contain sulfides contained in the electrolyte layer.

[0033] (Negative electrode) The negative electrode has at least a second active material layer containing a negative electrode active material.

[0034] The second current collector layer may contain, for example, 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 manufacturing costs in addition to high conductivity, 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The second active material layer may be formed on both main surfaces of the second current collector layer, or on only one main surface of the second current collector layer. 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.

[0040] (electrolyte layer) The electrolyte layer is disposed between the first active material layer and the second active material layer.

[0041] 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.

[0042] The electrolyte layer may contain an adhesive to impart mechanical strength and flexibility.

[0043] The 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 solid electrolyte.

[0044] The porous substrate is preferably made of an insulating material, which can improve the insulation of the 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.

[0045] "Heating process" In the heating step, at least a portion of an exterior film that covers the surface of the electrode laminate and houses the electrode laminate, facing the outermost surface in the stacking direction of the electrode laminate, is heated. Even if contamination is present on the outermost surface of the electrode laminate, the heating softens at least the portion of the exterior film facing the outermost surface in the stacking direction of the electrode laminate. Therefore, when a force is applied from the exterior film pressing the contamination against the outermost surface of the electrode current collector, the contamination is prevented from being embedded in the exterior film, which would otherwise cause damage to the electrode current collector.

[0046] In the heating step, the temperature to which the above-mentioned portion is heated is preferably, for example, 45°C or higher and lower than 80°C. If the temperature to which the above-mentioned portion is heated exceeds the glass transition point of the resin constituting the above-mentioned portion, the above-mentioned portion will soften, and when the exterior film exerts a force pressing the contamination against the outermost surface of the electrode current collector, the contamination will be embedded in the exterior film. The temperature to which the above-mentioned portion is heated may be 45°C or higher, or 60°C or higher. When the exterior film used is one according to the first or second embodiment described below, the portion to be heated in the heating step is the sealant resin layer.

[0047] Exterior film The exterior film used in the method for producing an all-solid-state battery according to this embodiment will be described.

[0048] (First embodiment) FIG. 1 is a cross-sectional view showing a first embodiment of an exterior film used in the method for producing an all-solid-state battery according to the present embodiment. As shown in FIG. 1 , the exterior film 1 has a sealant resin layer 2, a metal layer 3, and an outer resin layer 4. The sealant resin layer 2, the metal layer 3, and the outer resin layer 4 are laminated in this order. The sealant resin layer 2 and the metal layer 3 are laminated via a first adhesive layer 5. The metal layer 3 and the outer resin layer 4 are laminated via a second adhesive layer 6. The sealant resin layer 2 is the portion facing the outermost surface in the lamination direction of the electrode laminate. Therefore, in the method for producing an all-solid-state battery of this embodiment, at least the sealant resin layer 2 is heated to soften it.

[0049] The sealant resin constituting the sealant resin layer 2 preferably has a glass transition point of, for example, less than 45° C. The sealant resin constituting the sealant resin layer 2 preferably has a melting point of, for example, 130° C. or higher. By setting the glass transition point and melting point of the sealant resin within the above ranges and heating at a temperature above the glass transition point and below the melting point, the sealant resin layer 2 can be sufficiently softened.

[0050] As the sealant resin, for example, one having a Rockwell hardness of less than 85 is preferred.

[0051] Examples of the sealant resin include modified polypropylene and polyethylene.

[0052] The thickness of the sealant resin layer 2 is preferably 10 μm or more and 80 μm or less, and more preferably 10 μm or more and 40 μm or less. When the thickness of the sealant resin layer 2 is equal to or more than the lower limit, the diameter (particle size) of the contaminants is 10 μm or more, and therefore the contaminants can be absorbed within the sealant resin layer 2. When the thickness of the sealant resin layer 2 is equal to or less than the upper limit, the sealant resin layer 2 can be prevented from becoming thick.

[0053] Examples of the metal that constitutes the metal layer 3 include aluminum.

[0054] The thickness of the metal layer 3 is preferably 20 μm or more and 120 μm or less, and more preferably 40 μm or more and 80 μm or less.

[0055] Examples of resins that form the outer resin layer 4 include polyesters such as polyethylene terephthalate.

[0056] Examples of adhesives that form the first adhesive layer 5 and the second adhesive layer 6 include epoxy resins and urethane resins.

[0057] The thickness of the first adhesive layer 5 and the second adhesive layer 6 is preferably 1 μm or more and 3 μm or less.

[0058] (Second embodiment) FIG. 2 is a cross-sectional view showing a second embodiment of an exterior film used in the method for producing an all-solid-state battery of this embodiment. As shown in FIG. 2 , the exterior film 10 has a sealant resin layer 11, an insulating resin layer 12, a metal layer 13, and an outer resin layer 14. The sealant resin layer 11, the insulating resin layer 12, the metal layer 13, and the outer resin layer 14 are laminated in this order. The sealant resin layer 11 and the insulating resin layer 12 are laminated via a first adhesive layer 15. The insulating resin layer 12 and the metal layer 13 are laminated via a second adhesive layer 16. The metal layer 13 and the outer resin layer 14 are laminated via a third adhesive layer 17. The sealant resin layer 11 is the portion facing the outermost surface of the exterior film 10 in the lamination direction. Therefore, in the method for producing an all-solid-state battery of this embodiment, at least the sealant resin layer 11 is heated to soften it.

[0059] The sealant resin constituting the sealant resin layer 11 is the same as the sealant resin constituting the sealant resin layer 2 described above.

[0060] The thickness of the sealant resin layer 11 is the same as that of the sealant resin layer 2 described above.

[0061] The resin constituting the insulating resin layer 12 preferably has a glass transition point that exceeds the glass transition point of the sealant layer and a melting point of 230° C. or higher. By setting the glass transition point and melting point of the resin constituting the insulating resin layer 12 within the above ranges, softening of the insulating resin layer 12 by heating the above-mentioned portion is suppressed.

[0062] Examples of resins that can be used to form the insulating resin layer 12 include polyethylene terephthalate, reinforced polypropylene containing fibers such as glass fibers, reinforced polyester containing fibers such as glass fibers, polyimide, and polybenzimidazole.

[0063] The thickness of the insulating resin layer 12 is adjusted appropriately depending on the resin that constitutes the insulating resin layer 12 .

[0064] The metal constituting the metal layer 13 is the same as the metal constituting the metal layer 3 described above.

[0065] The thickness of the metal layer 13 is the same as that of the metal layer 3 described above.

[0066] The resin constituting the outer resin layer 14 is the same as the resin constituting the outer resin layer 4 described above.

[0067] The thickness of the outer resin layer 14 is the same as that of the outer resin layer 4 described above.

[0068] The adhesives constituting the first adhesive layer 15, the second adhesive layer 16, and the third adhesive layer 17 are the same as the adhesives constituting the first adhesive layer 5 and the second adhesive layer 6. The adhesives constituting the first adhesive layer 15, the adhesives constituting the second adhesive layer 16, and the adhesives constituting the third adhesive layer 17 may all be different, two may be the same, or all may be the same.

[0069] The thicknesses of the first adhesive layer 15, the second adhesive layer 16 and the third adhesive layer 17 are similar to the thicknesses of the first adhesive layer 5 and the second adhesive layer 6 described above.

[0070] "Containment process" In the housing step, the electrode stack is housed in an exterior film in which at least a portion facing the outermost surface of the electrode stack in the stacking direction has been heated in the heating step. That is, in the housing step, the electrode stack is covered and surrounded with an exterior film so that at least the heated portion is in contact with the outermost surface of the electrode stack in the stacking direction.

[0071] Through the above steps, an all-solid-state battery including an electrode stack and an exterior film that houses the electrode stack is obtained.

[0072] According to the method for manufacturing an all-solid-state battery of this embodiment, at least a portion of the exterior film that faces the outermost surface in the stacking direction of the electrode laminate is softened by heating before the exterior film and the electrode laminate are brought into contact with each other. This makes it possible for the exterior film to more easily absorb contamination even when contamination is present between the exterior film and the electrode current collector.

[0073] 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]

[0074] 1,10 Outer film 2,11 Sealant resin layer 3,13 Metal layer 4,14 Outer resin layer 5,15 First adhesive layer 6,16 Second adhesive layer 12 Insulating resin layer 17 Third adhesive layer

Claims

1. a heating step of heating at least a portion of the exterior film facing the outermost surface of the electrode laminate in the lamination direction; and a housing step of housing the electrode stack in the exterior film.

2. The method for producing an all-solid-state battery according to claim 1 , wherein the temperature at which the portion is heated in the heating step exceeds a glass transition point of a resin constituting the portion.

3. the exterior film has a sealant resin layer, a metal layer, and an outer resin layer, The method for manufacturing an all-solid-state battery according to claim 1 , wherein the sealant resin layer, the metal layer, and the outer resin layer are laminated in this order.

4. the exterior film has a sealant resin layer, an insulating resin layer, a metal layer, and an outer resin layer, The method for manufacturing an all-solid-state battery according to claim 1 , wherein the sealant resin layer, the insulating resin layer, the metal layer, and the outer resin layer are laminated in this order.

5. The method for producing an all-solid-state battery according to claim 3 or 4, wherein the sealant resin constituting the sealant resin layer has a glass transition point of less than 45°C.

6. 5. The method for producing an all-solid-state battery according to claim 4, wherein the insulating resin constituting the insulating resin layer has a glass transition point that is higher than the glass transition point of the sealant layer and a melting point that is 230°C or higher.

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