Battery sheet manufacturing method and all-solid-state battery manufacturing method

Abstract

To provide a battery sheet manufacturing method and an all-solid-state battery manufacturing method that enable the production of thin-film solid electrolyte layers with good control.SOLUTION: A manufacturing method of a battery sheet according to an embodiment includes a lamination step of laminating a first electrode primary sheet and a solid electrolyte primary sheet to manufacture a battery primary sheet, and a stretching step of stretching the battery primary sheet to simultaneously stretch the first electrode primary sheet and the solid electrolyte primary sheet.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] With the remarkable development of electronics technology, portable electronic devices are becoming smaller, lighter, thinner, and more multifunctional. There is also a strong demand for batteries, which serve as the power source for electronic devices, to be smaller, lighter, thinner, more reliable, and safer. All-solid-state batteries, which use solid electrolytes, are attracting attention because they are safer than lithium-ion secondary batteries, which use liquid electrolytes.

[0003] An all-solid-state battery is manufactured by preparing a positive electrode sheet, a negative electrode sheet, and a solid electrolyte sheet, and then compressing them. For example, Patent Documents 1 to 3 disclose methods for manufacturing any of the positive electrode sheet, negative electrode sheet, and solid electrolyte sheet. Patent Documents 1 to 3 also disclose the use of polytetrafluoroethylene (PTFE) as a binder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-99315 [Patent Document 2] Special Publication No. 2022-514039 [Patent Document 3] Japanese Patent Publication No. 2022-121547 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for all-solid-state batteries with large electric capacity and low internal resistance. Along with the development of such all-solid-state batteries, solid electrolyte sheets are being made thinner. Solid electrolyte sheets are obtained by stretching a primary solid electrolyte sheet. When a solid electrolyte sheet is made thinner, deformation, cracks, etc. may occur when the solid electrolyte sheet is peeled off from the stretching jig. If the solid electrolyte sheet is deformed, the thickness of the solid electrolyte layer of the all-solid-state battery becomes non-uniform, and the all-solid-state battery may not exhibit the desired performance. Furthermore, if a crack occurs in the solid electrolyte sheet, the positive electrode and the negative electrode may short-circuit, causing the all-solid-state battery to malfunction.

[0006] The present disclosure has been made in view of the above problems, and aims to provide a method for manufacturing a battery sheet and a method for manufacturing an all-solid-state battery that can produce a thin-film solid electrolyte layer with good control. [Means for solving the problem]

[0007] In order to solve the above problems, the following means are provided.

[0008] The method for manufacturing a battery sheet according to a first aspect includes a lamination step and a stretching step. In the lamination step, a first electrode primary sheet and a solid electrolyte primary sheet are laminated to produce a battery primary sheet. In the stretching step, the battery primary sheet is stretched, and the first electrode primary sheet and the solid electrolyte primary sheet are stretched simultaneously. [Effects of the Invention]

[0009] The battery sheet manufacturing method and all-solid-state battery manufacturing method according to the above aspects can produce a thin-film solid electrolyte layer with good control. [Brief explanation of the drawings]

[0010] [Figure 1] 3A to 3C are schematic diagrams illustrating a lamination step in the manufacturing method of the battery sheet according to the embodiment. [Figure 2] 3A to 3C are schematic diagrams illustrating a stretching step in the manufacturing method of the battery sheet according to the present embodiment. [Figure 3] 1A to 1C are schematic diagrams for explaining a method for manufacturing an all-solid-state battery according to an embodiment of the present invention. [Figure 4] FIG. 1 is a cross-sectional view of an all-solid-state battery according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present disclosure is not limited thereto. Appropriate modifications may be made within the scope of the present disclosure.

[0012] The method for manufacturing the battery sheet according to the first embodiment includes a lamination step and a stretching step.

[0013] In the lamination step, a battery primary sheet 10 is produced. The battery primary sheet 10 has a first electrode primary sheet 1, a second electrode primary sheet 2, and a solid electrolyte primary sheet 3. In the lamination step, for example, the first electrode primary sheet 1, the second electrode primary sheet 2, and the solid electrolyte primary sheet 3 are laminated in the following order: first electrode primary sheet 1, solid electrolyte primary sheet 3, second electrode primary sheet 2.

[0014] First, a first electrode primary sheet 1, a solid electrolyte primary sheet 3, and a second electrode primary sheet 2 are fabricated. The primary sheets are sheets for fabricating each layer of the all-solid-state battery. Hereinafter, the first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2 may be collectively referred to as primary sheets. The thickness of each primary sheet is thicker than the thickness of the layer corresponding to each primary sheet in the all-solid-state battery.

[0015] The first electrode primary sheet 1 is, for example, a sheet-shaped mixture containing a positive electrode active material and a binder. The first electrode primary sheet 1 may contain, in addition to the positive electrode active material and the binder, for example, a solid electrolyte, a conductive additive, etc.

[0016] The positive electrode active material is not particularly limited as long as it can reversibly absorb and release, and insert and extract (intercalate and deintercalate) lithium ions, and any positive electrode active material used in known all-solid-state batteries can be used. Examples of the positive electrode active material include lithium-containing metal oxides and lithium-containing metal phosphates.

[0017] Examples of lithium-containing metal oxides include LiMO2 and LiM2O4 (wherein M includes one or more of Co, Ni, Mn, Al, Fe, and P). For example, lithium-containing metal oxides include LiCoO2, LiNiO2, and LiNi O.8 Co 0.15 Al 0.05 O2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiMn2O4, LiMn 1.9 Co 0.1 O4. The lithium-containing metal phosphate is, for example, an olivine-type oxide represented by the general formula LiMPO4. The lithium-containing metal phosphate is, for example, LiFePO4.

[0018] The positive electrode active material may also be lithium-free. Examples of such positive electrode active materials include non-lithium-containing metal oxides (MnO2, V2O5, etc.), non-lithium-containing metal sulfides (MoS2, etc.), and non-lithium-containing fluorides (FeF3, VF3, etc.). When using a lithium-free positive electrode active material, the negative electrode is doped with lithium ions in advance, or a lithium-ion-containing negative electrode is used.

[0019] Examples of the binder include polyvinylidene fluoride (PVDF) or a copolymer thereof, polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), polyethersulfone (PES), polyacrylic acid (PA) and a copolymer thereof, metal ion crosslinked polyacrylic acid (PA) and a copolymer thereof, maleic anhydride-grafted polypropylene (PP), maleic anhydride-grafted polyethylene (PE), and mixtures thereof.

[0020] Polytetrafluoroethylene (PTFE) is particularly preferred as the binder. PTFE has the property of fibrillating when subjected to shearing force. The fibrillated PTFE is well entangled with the positive electrode active material, allowing for a reduction in the amount of binder used. PTFE can be produced by emulsion polymerization. The primary particle diameter of PTFE is, for example, 10 nm to 100 nm. PTFE is formed by agglomeration of primary particles to form secondary particles. The size of the secondary particles is, for example, 50 μm to 1000 μm.

[0021] The solid electrolyte is the same as that used in the solid electrolyte primary sheet described below.

[0022] The conductive additive is a fine particle having electrical conductivity. Examples of the conductive additive include carbon powder, carbon nanotubes, carbon materials, metal fine powder, a mixture of carbon materials and metal fine powder, and conductive oxides. Examples of the carbon powder include carbon black such as acetylene black and ketjen black. The carbon nanotubes may be single-walled or multi-walled. Examples of the carbon material include vapor grown carbon fiber (VGCF), graphite, graphene, etc. Examples of the metal fine powder include powder of copper, nickel, stainless steel, iron, etc. The conductive additive is preferably a substance containing carbon.

[0023] The second electrode primary sheet 2 is, for example, a sheet-shaped mixture containing a negative electrode active material and a binder. The second electrode primary sheet 2 may contain, in addition to the negative electrode active material and the binder, for example, a solid electrolyte, a conductive additive, etc. Here, an example has been shown in which the first electrode primary sheet 1 contains a positive electrode active material and the second electrode primary sheet 2 contains a negative electrode active material, but the first electrode primary sheet 1 may also contain a negative electrode active material and the second electrode primary sheet 2 may also contain a positive electrode active material.

[0024] The negative electrode active material may be any compound capable of absorbing and releasing ions, and active materials used in known batteries can be used. Examples of the negative electrode active material include carbon materials, metals or alloys capable of reacting with lithium or sodium, composite materials of these metals or alloys with carbon materials, oxides, sulfur-modified polyacrylonitrile, metallic lithium, metallic sodium, etc. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fiber (MCF), cokes, glassy carbon, organic compound sintered bodies, and hard carbon. Examples of metals or alloys capable of reacting with lithium or sodium include Si, SiO x , Sn, and aluminum. The oxides are lithium titanate (Li4Ti5O 12 ), SnO2, etc.

[0025] The solid electrolyte, conductive additive, and binder contained in the second electrode primary sheet 2 may be the same as those contained in the first electrode primary sheet 1.

[0026] The solid electrolyte primary sheet 3 is, for example, a sheet-like mixture containing a solid electrolyte and a binder.

[0027] The solid electrolyte is, for example, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a complex hydride-based solid electrolyte, or a halide-based solid electrolyte. The solid electrolyte is preferably, for example, a sulfide-based solid electrolyte or a halide-based solid electrolyte.

[0028] Examples of sulfide-based solid electrolytes include Li2S-SiS2, Li2S-P2S5, Li2S-GeS2, Li2S-B2S3, Li2S-Ga2S3, Li2S-Al2S3, Li2S-GeS2-P2S5, Li2S-Al2S3-P2S5, Li2S-P2S3, Li2S-P2S3-P2S5, LiX-Li2S-P2S5, LiX-Li2S-SiS2, and LiX-Li2S-B2S3. Examples of halide-based solid electrolytes include Li2ZrCl6, Li2ZrSO4Cl4, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, and Li3(Al, Ga, In)X6. X is a halogen element, and is at least one element selected from the group consisting of F, Cl, Br, and I.

[0029] Sulfide-based solid electrolytes and halide-based solid electrolytes may react with water and deteriorate in performance, so it is preferable to carry out the entire manufacturing process of all-solid-state batteries in a moisture-reduced, rare gas atmosphere such as argon, or a low-humidity atmosphere with a dew point of, for example, −70° C. or lower.

[0030] The particle size of the solid electrolyte may be appropriately selected taking into consideration constraints such as the thickness of the solid electrolyte layer. The particle size of the solid electrolyte is, for example, preferably 10 nm or more and 100 μm or less, more preferably 30 nm or more and 20 μm or less, and even more preferably 50 nm or more and 10 μm or less. If the particle size of the solid electrolyte is larger than the thickness of the solid electrolyte layer, the film thickness of the solid electrolyte layer will be non-uniform. The particle size of the solid electrolyte is preferably smaller than the thickness of the solid electrolyte layer.

[0031] The binder contained in the solid electrolyte primary sheet 3 is the same as that contained in the first electrode primary sheet 1, and is preferably, for example, PTFE. The amount of binder in the solid electrolyte sheet is preferably 0.01 wt% or more and 5 wt% or less, and more preferably 0.1 wt% or more and 2 wt% or less, relative to the solid electrolyte.

[0032] The first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2 can be produced by mixing the materials that make up these primary sheets and forming them into sheets.

[0033] When mixing the materials that make up the primary sheet, it is preferable to apply shear force to the materials. For example, if the binder is PTFE, applying shear force to the PTFE causes the PTFE to fibrillate into a fibrous form. The fibrillated PTFE becomes well entangled with other materials, strengthening the binding force between the materials.

[0034] For example, when the amount of material is small, the material may be placed in a mortar made of agate or the like, and a shear force may be applied to the material by pressing a pestle against the material in the mortar and rotating it.

[0035] Furthermore, for example, when there is a large amount of material, shear force may be applied to the material by mixing using a crusher, V-type mixer, Turbula type mixer, Henschel mixer, kneader, or the like.

[0036] Further shear force may be applied to the material by repeatedly stretching and folding the mixed material. The material may be stretched by stretching the mixture placed on a flat plate with a rod, or by passing the mixture between two roll mills.

[0037] The mixture can be formed into a sheet by the above-mentioned stretching operation, or, if a very thick primary sheet is to be made, the mixture can be pressed into a mold and then formed into a sheet.

[0038] The thickness of each primary sheet can be freely designed. The thickness of each primary sheet is, for example, 100 μm or more. For example, the thickness of the first electrode primary sheet 1 and the second electrode primary sheet 2 is thicker than the thickness of the solid electrolyte primary sheet 3. The thickness of the first electrode primary sheet 1 and the second electrode primary sheet 2 is designed so that the mass ratio of the positive electrode active material or the negative electrode active material per unit area in the positive electrode or the negative electrode in the all-solid-state battery is a predetermined value.

[0039] A small amount of liquid may be used to assist in the mixing and stretching during the preparation of the primary sheet. The liquid is not particularly limited. For example, saturated hydrocarbons such as hexane, aromatic hydrocarbons such as toluene and xylene, alcohols such as methanol, ethanol, propanol, and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran, dioxane, and diethyl ether, amides such as N,N-dimethylformamide, N-methylpyrrolidone (NMP), and N,N-dimethylacetamide, halogenated hydrocarbons such as ethylene chloride and chlorobenzene, siloxane-based liquids such as dimethylsilicone, methylphenylsilicone, and cyclosiloxane, and fluorine-based liquids such as hydrofluoroethers can be used for the mixing and stretching of the primary sheet. The liquid may be selected appropriately taking into account the properties of the solid electrolyte species.

[0040] Next, the first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2 are laminated in this order. For example, the solid electrolyte primary sheet 3 is placed on the first electrode primary sheet 1, and the second electrode primary sheet 2 is placed on the solid electrolyte primary sheet 3, and pressure is applied to them. By applying pressure to the laminate, the first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2 are brought into close contact with each other, and a battery primary sheet 10 is obtained.

[0041] Next, the stretching step is carried out. Fig. 2 is a schematic diagram for explaining the stretching step. In the stretching step, the battery primary sheet 10 is stretched. By stretching the battery primary sheet 10, the first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2 are stretched simultaneously.

[0042] The stretched battery primary sheet 10 becomes a battery sheet 20. The stretched first electrode primary sheet 1 becomes a first electrode sheet 11. The stretched solid electrolyte primary sheet 3 becomes a solid electrolyte sheet 13. The stretched second electrode primary sheet 2 becomes a second electrode sheet 12. The mass ratios per unit area of ​​the first electrode primary sheet 1, solid electrolyte primary sheet 3, and second electrode primary sheet 2 in the battery primary sheet 10 are approximately the same as the mass ratios per unit area of ​​the first electrode sheet 11, solid electrolyte sheet 13, and second electrode sheet 12 in the battery sheet 20.

[0043] The primary battery sheet 10 is stretched, for example, until the mass per unit area of ​​the positive electrode active material in the first electrode sheet 11 reaches a designed value. The primary battery sheet 10 may also be stretched, for example, until the mass per unit area of ​​the negative electrode active material in the second electrode sheet 12 reaches a designed value.

[0044] The stretching ratio of the battery primary sheet 10 is preferably 2 times or more, and more preferably 4 times or more. The stretching ratio of the battery primary sheet 10 is preferably 100 times or less, and more preferably 10 times or less. If the stretching ratio is low, the thickness of the battery primary sheet 10 before stretching will also be thin, making it difficult to produce a thin battery primary sheet 10. Furthermore, if the stretching ratio is high, stable stretching will be difficult, increasing the risk of unevenness. The stretching ratio is calculated by dividing the thickness of the battery primary sheet 10 before stretching by the thickness of the battery sheet 20 after stretching. For example, if the thickness of the battery primary sheet 10 before stretching is 200 μm and the thickness of the battery sheet 20 after stretching is 100 μm, the stretching ratio is 2.

[0045] The stretching method in the stretching step is not particularly limited. For example, as shown in FIG. 2, the battery primary sheet 10 may be placed on a flat plate 4 and stretched using a stretching roller 5. The flat plate 4 may have a guide for determining the thickness of the stretched product. The stretching roller 5 may also have a guide ring for determining the thickness of the stretched product. The battery primary sheet 10 may be cut into small pieces every time it reaches a certain thickness. By repeating the cutting into small pieces and stretching, the stretch ratio of the battery primary sheet 10 can be increased even in a small space.

[0046] Alternatively, for example, the primary battery sheet 10 may be stretched by passing it between two stretching rollers that are spaced apart by a fixed gap. The primary battery sheet 10 is preferably stretched multiple times. For example, the primary battery sheet 10 can be stretched in stages by narrowing the gap between the two stretching rollers each time the primary battery sheet 10 passes between the two stretching rollers. The stretching ratio in each stretching is preferably 2 times or less. Avoiding rapid stretching can improve the uniformity of the thickness of the battery sheet 20.

[0047] Alternatively, multiple pairs of two stretching rollers may be provided, and the primary battery sheet 10 may be stretched in multiple stages. For example, the gap between the stretching rollers may be narrower in the pair of stretching rollers arranged in the later stage of stretching. Also, for example, the rotation speed of the stretching rollers may be faster in the pair of stretching rollers arranged in the later stage of stretching.

[0048] The thickness of the solid electrolyte sheet 13 after stretching in the stretching step is, for example, 30 μm or less. By stretching the solid electrolyte primary sheet 3 as part of the battery primary sheet 10, the thickness of the solid electrolyte sheet 13 can be reduced without deformation or breakage.

[0049] The battery sheet 20 according to this embodiment is obtained by simultaneously stretching the first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2. Because the solid electrolyte sheet 13 is held by the first electrode sheet 11 and the second electrode sheet 12, the solid electrolyte sheet 13 is less likely to deform or crack. Therefore, according to the manufacturing method of the battery sheet 20 according to this embodiment, the thickness of the solid electrolyte sheet 13 can be made thin. An all-solid-state battery with a thin solid electrolyte has a large capacity per unit volume and a small internal resistance.

[0050] If the solid electrolyte sheet 13 is produced independently, it is difficult to peel the solid electrolyte sheet 13 from the flat plate 4 and the stretching rollers 5 that come into contact with the sheet during stretching without causing deformation or cracking. In contrast, in the method for producing the battery sheet 20 according to this embodiment, the solid electrolyte sheet 13 is molded as part of the battery sheet 20 rather than being molded separately, making deformation and cracking less likely to occur.

[0051] Furthermore, the manufacturing method of the battery sheet 20 according to this embodiment can reduce the number of steps because it is not necessary to individually stretch the first electrode sheet 11, the solid electrolyte sheet 13, and the second electrode sheet 12. Furthermore, by collectively stretching the first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2, it is possible to improve the adhesion between the first electrode sheet 11, the solid electrolyte sheet 13, and the second electrode sheet 12.

[0052] So far, an example of a manufacturing method for the battery sheet 20 according to this embodiment has been described, but the present disclosure is not limited to this example. For example, when metallic lithium, a lithium alloy, or the like is used as the negative electrode, the second electrode primary sheet 2 may be omitted. That is, in the lamination step, the first electrode primary sheet 1 and the solid electrolyte primary sheet 3 may be laminated, and in the stretching step, the first electrode primary sheet 1 and the solid electrolyte primary sheet 3 may be stretched simultaneously.

[0053] Next, an all-solid-state battery is fabricated using the fabricated battery sheet 20. For example, current collectors are bonded to the first and second surfaces of the battery sheet 20. If a liquid is used to stretch the battery sheet 20, the current collectors and the battery sheet 20 are bonded after the liquid has been sufficiently dried.

[0054] For example, a battery sheet 20 is placed on one side of a first current collector so that the first current collector and the first electrode sheet 11 are in contact with each other. Next, a second current collector is placed on one side of the battery sheet 20 so that the second current collector and the second electrode sheet 12 are in contact with each other. Next, these laminates are compressed to obtain an all-solid-state battery.

[0055] The method for compressing the laminate is not particularly limited. For example, compression can be performed using a sheet press, a roll press, or the like. Sheet presses include die presses using a metal die or the like, cold isostatic presses, hot isostatic presses, and the like. Die presses are suitable for efficiently producing small items. Cold isostatic presses and hot isostatic presses are suitable for items with large areas or when compressing large quantities. When battery sheets are produced in single sheets, it is suitable to use a sheet press, and cold isostatic presses and hot isostatic presses may be further performed after the sheet press.

[0056] Alternatively, the laminate may be compressed by roll pressing. FIG. 3 is a schematic diagram illustrating a compression step, which is part of the method for producing an all-solid-state battery according to this embodiment. Roll pressing is a method in which a film to be compressed is sandwiched between compression rolls 15 and compressed by rotating the compression rolls 15. For example, as shown in FIG. 3, the battery sheet 20 is sandwiched between current collectors 30 and passed between two compression rolls 15, thereby roll-pressing the battery sheet 20. Roll pressing can be performed using an apparatus similar to that used in the stretching step. Roll pressing can apply a uniform high pressure to the laminate and also enables roll-to-roll production, resulting in high productivity.

[0057] Pressing can be performed at room temperature or in a heated atmosphere. When PTFE is used as a binder, heating makes the PTFE more easily deformable, thereby increasing the packing density of the solid electrolyte sheet. However, if the temperature is too high, the solid electrolyte sheet may be altered, so it is preferable to adjust the temperature appropriately according to the material.

[0058] The current collector 30 may be a conductive foil or mesh. For example, metal foil, expanded metal, punched metal, graphite sheet, carbon cloth, etc. can be used for the current collector 30. When a bipolar all-solid-state battery is produced, it is preferable that the current collector 30 be a metal foil.

[0059] The material of the current collector 30 can be appropriately selected taking into consideration the materials of the solid electrolyte and active material. For example, aluminum, copper, nickel, titanium, and stainless steel can be used for the current collector 30. The thickness of the current collector 30 is preferably 3 μm to 100 μm, and more preferably 7 μm to 20 μm. If the thickness of the current collector 30 is 3 μm or less, it becomes easily damaged, and if the thickness of the current collector 30 is 100 μm or more, the energy density of the all-solid-state battery will be low.

[0060] Furthermore, to improve the adhesion between the current collector 30 and the first electrode sheet 11 or the second electrode sheet 12, it is possible to form irregularities on one surface of the current collector 30 or to form an adhesion layer. The irregularities can be formed by blasting, etching, or the like. The adhesion layer preferably contains, for example, an organic substance. For example, polyvinylidene fluoride (PVDF), acrylic resin, cellulose-based resin, silicone resin, various rubbers, etc. can be used for the adhesion layer. The thickness of the adhesion layer is preferably thin to ensure electrical contact between the current collector 30 and the first electrode sheet 11 or the second electrode sheet 12. The adhesion layer may contain the above-mentioned conductive additive.

[0061] FIG. 4 is a cross-sectional view of a bipolar all-solid-state battery 100. The bipolar all-solid-state battery 100 has current collectors 30 and battery units 21 alternately stacked. The battery units 21 are formed by cutting a battery sheet 20 into small pieces. The battery units 21 have a first electrode, a solid electrolyte layer, and a second electrode. The first electrode is formed by cutting a first electrode sheet 11 into small pieces. The solid electrolyte layer is formed by cutting a solid electrolyte sheet 13 into small pieces. The second electrode is formed by cutting a second electrode sheet 12 into small pieces.

[0062] A bipolar all-solid-state battery 100 is obtained by alternately stacking current collectors 30 and battery sheets 20, compressing them, and cutting them into small pieces. The battery sheet 20 is made up of a first electrode sheet 11, a solid electrolyte sheet 13, and a second electrode sheet 12 that are integrated, making it easy to control the positions of the sheets when stacking them. If the first electrode sheet 11, the solid electrolyte sheet 13, and the second electrode sheet 12 were not integrated, it would be necessary to control the positions of each sheet, complicating the manufacturing process.

[0063] The above describes the embodiments of the present disclosure in detail with reference to the drawings. However, each configuration and combination thereof in each embodiment is an example, and addition, omission, substitution, and other modifications of the configuration are possible within the scope that does not deviate from the spirit of the present disclosure. [Example]

[0064] "Example 1" (Preparation of solid electrolyte primary sheet 3) 32 parts by mass of Li2SO4 (lithium sulfate) powder, 68 parts by mass of ZrCl4 (zirconium chloride) powder, and zirconia balls as media were placed in a zirconia container and the lid was closed. This container was placed in a planetary ball mill and rotated. Li2SO4 and ZrCl4 underwent a mechanochemical reaction to form Li2ZrSO4Cl4. Li2ZrSO4Cl4 is a powder substance with partial crystallinity and is a solid electrolyte with Li-ion conductivity. The Li2ZrSO4Cl4 powder was sieved to remove coarse particles, yielding a solid electrolyte.

[0065] Next, a solid electrolyte primary sheet 3 was produced using this solid electrolyte. 100 parts by mass of Li2ZrSO4Cl4 and 0.75 parts by mass of PTFE were weighed, placed in an agate mortar, and mixed using an agate pestle. The average secondary particle diameter of PTFE was 500 μm. The PTFE was fibrillated by mixing, resulting in a mass of solid electrolyte and PTFE. Next, the mass was placed on a flat plate 4 and stretched using a stretching roller 5 to form a plate. The plate-shaped composite was folded and stretched multiple times. Finally, the mixture was stretched using a stretching roller 5 on a flat plate 4 equipped with a 120 μm guide to produce a solid electrolyte primary sheet 3 with a thickness of 120 μm.

[0066] (Preparation of first electrode primary sheet 1) A first electrode primary sheet 1 was produced using lithium cobalt oxide (LCO) as the positive electrode active material, the above Li2ZrSO4Cl4 as the solid electrolyte particles, graphite as the conductive additive, and PTFE with an average secondary particle size of 500 μm as the binder.

[0067] 60 parts by mass of LCO, 40 parts by mass of Li2ZrSO4Cl4, 4 parts by mass of graphite, and 0.4 parts by mass of PTFE were weighed and mixed in an agate mortar using an agate pestle. The PTFE was fibrillated by mixing, resulting in a mass consisting of the positive electrode active material, solid electrolyte, conductive additive, and binder. The mass was placed on a flat plate 4 and stretched using a stretching roller 5 to form a plate. The stretched mixture was folded and stretched multiple times. Finally, the mixture was stretched using a stretching roller 5 on a flat plate 4 equipped with a 300 μm guide to produce a first electrode primary sheet 1 with a thickness of 300 μm.

[0068] (Preparation of second electrode primary sheet 2) A second electrode primary sheet 2 was produced using lithium titanate (LTO) as the negative electrode active material, the above Li2ZrSO4Cl4 as the solid electrolyte particles, graphite as the conductive additive, and PTFE with an average secondary particle size of 500 μm as the binder.

[0069] 60 parts by mass of LTO, 40 parts by mass of Li2ZrSO4Cl4, 4 parts by mass of graphite, and 0.4 parts by mass of PTFE were weighed and mixed in an agate mortar using an agate pestle. The PTFE was fibrillated by mixing, resulting in a mass consisting of the negative electrode active material, solid electrolyte, conductive additive, and binder. The mass was placed on a flat plate 4 and stretched using a stretching roller 5 to form a plate. The stretched mixture was folded and stretched multiple times. Finally, the mixture was stretched using a stretching roller 5 on a flat plate 4 equipped with a 350 μm guide to produce a second electrode primary sheet 2 with a thickness of 350 μm.

[0070] (Lamination process) A first electrode primary sheet 1, a solid electrolyte primary sheet 3, and a second electrode primary sheet 2 were laminated in this order on a flat plate 4. A stretching roller 5 was placed so as to be in contact with the second electrode primary sheet 2, and pressure was applied to the laminate while the stretching roller 5 was rotating. The first electrode primary sheet 1, the solid electrolyte primary sheet 3, and the second electrode primary sheet 2 were adhered together by the pressure, and a battery primary sheet 10 was obtained. The sheet thickness of the battery primary sheet 10 was 770 μm.

[0071] (Stretching process) The battery primary sheet 10 was cut into small pieces. One of the small pieces of the battery primary sheet 10 was placed on a flat plate 4 and stretched using a stretching roller 5. The battery primary sheet 10 was stretched until the thickness of the stretched product reached 360 μm, thereby producing a battery sheet 20. The stretching ratio of the battery sheet 20 was 2.14 times (770 μm ÷ 360 μm). The battery sheet 20 was peeled off from the flat plate 4. No defects such as tearing or deformation occurred in the battery sheet 20 during the peeling.

[0072] (Fabrication of all-solid-state batteries) Two 15 μm thick aluminum foils on which a conductive adhesive layer made of acetylene black and PVDF was formed were prepared as current collectors 30. One current collector 30 was placed on a first surface of a battery sheet 20, and the other current collector 30 was placed on a second surface of the battery sheet 20. Then, as shown in FIG. 3 , a roll press was prepared, and the battery sheet sandwiched between the two current collectors 30 was placed between compression rolls 15 of the roll press and compressed. The current collectors 30 and the battery sheet 20 were in close contact with each other, and an all-solid-state battery was obtained.

[0073] The fabricated all-solid-state battery was cut and the cross section was observed under a digital microscope. A solid electrolyte layer was confirmed between the positive and negative electrodes. The interface between the positive electrode and the solid electrolyte layer and the interface between the negative electrode and the solid electrolyte layer were almost parallel, and the thickness of the solid electrolyte layer was 30 μm.

[0074] "Example 2" Example 2 differs from Example 1 in that the thickness of the solid electrolyte primary sheet 3 was 240 μm, the thickness of the first electrode primary sheet 1 was 600 μm, and the thickness of the second electrode primary sheet 2 was 700 μm. The battery primary sheet 10 of Example 2 was stretched to form a battery sheet 20 with a thickness of 360 μm. The stretch ratio of the battery sheet 20 was 4.28 (1540 μm ÷ 360 μm).

[0075] In Example 2 as well, when the battery sheet 20 was peeled off from the flat plate 4, no defects such as tearing or deformation occurred in the battery sheet 20. Furthermore, similar to Example 1, when the cross section was observed, a solid electrolyte layer with a uniform thickness was confirmed.

[0076] "Example 3" Example 3 differs from Example 1 in that a bipolar all-solid-state battery was fabricated. Battery sheets 20 and current collectors 30 were prepared using the same procedure as in Example 1. Four battery sheets 20 and five current collectors 30 were prepared. The layers were stacked in the following order: current collector, battery sheet, current collector, battery sheet, current collector, battery sheet, current collector, battery sheet, current collector, and current collector, and then compressed to obtain a bipolar battery cell.

[0077] The bipolar all-solid-state battery of Example 3 operated normally. Furthermore, cross-sectional observation confirmed that each battery sheet had a solid electrolyte layer with a uniform thickness.

[0078] "Comparative Example 1" A solid electrolyte primary sheet 3 was produced under the same conditions as those used in Example 1. The produced solid electrolyte primary sheet 3 was cut into small pieces, and one of the pieces was placed on a flat plate 4 and stretched to a thickness of 55 μm using a stretching roller 5 to produce a solid electrolyte sheet 13. Cracks were observed in the stretched solid electrolyte sheet 13. Furthermore, when an attempt was made to peel the solid electrolyte sheet 13 from the flat plate 4, deformation occurred in the solid electrolyte sheet 13. Furthermore, when the peeled solid electrolyte sheet 13 was placed on a flat surface, a portion of it rose, and a flat sheet could not be obtained. [Explanation of symbols]

[0079] 1. First electrode primary sheet 2 Second electrode primary sheet 3. Primary solid electrolyte sheet 4 flat plate 5 Stretching roller 10 Primary battery sheet 11 First electrode sheet 12 Second electrode sheet 13 Solid electrolyte sheet 15 Compression Roll 20 Battery Sheet 21 Battery unit 30 Current collector 100 solid state battery

Claims

1. a lamination step of laminating a first electrode primary sheet and a solid electrolyte primary sheet to prepare a battery primary sheet; stretching the battery primary sheet to simultaneously stretch the first electrode primary sheet and the solid electrolyte primary sheet.

2. the laminating step includes a step of further laminating a second electrode primary sheet on the side of the solid electrolyte primary sheet opposite to the first electrode primary sheet, The method for manufacturing a battery sheet according to claim 1 , wherein the stretching step stretches the first electrode primary sheet, the solid electrolyte primary sheet, and the second electrode primary sheet simultaneously.

3. The method for producing a battery sheet according to claim 1 , wherein the primary solid electrolyte sheet has a thickness of 100 μm or more.

4. The method for producing a battery sheet according to claim 1 , wherein in the stretching step, the primary battery sheet is stretched at a stretching ratio of 2 or more.

5. 2. The method for producing a battery sheet according to claim 1, wherein the thickness of the solid electrolyte sheet after the primary solid electrolyte sheet is stretched in the stretching step is 30 μm or less.

6. The method for manufacturing a battery sheet according to claim 1 , wherein the primary solid electrolyte sheet comprises polytetrafluoroethylene.

7. The method for manufacturing a battery sheet according to claim 1 , wherein the first electrode primary sheet comprises polytetrafluoroethylene.

8. The method for manufacturing a battery sheet according to claim 1 , wherein the primary solid electrolyte sheet contains a halide-based solid electrolyte.

9. A method for producing an all-solid-state battery, comprising laminating current collectors on each of a first surface and a second surface of a battery sheet produced by the method for producing a battery sheet according to claim 1 .

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