Positive electrode structure and method for manufacturing the same

Abstract

To provide a positive electrode structure capable of suppressing a short circuit between current collectors without using a base material for a solid electrolyte layer.SOLUTION: A positive electrode structure 2 according to the present invention comprises a current collector and positive electrode active material layers 22 provided on both surfaces of the current collector. The positive electrode active material layer 22 includes a central part 23 including an active material, and an insulating frame 24 which is arranged on an outer periphery of the central part 23 and has an insulating material having an electric insulation property. The insulating frame 24 covers a surface near an outer edge of the current collector and at least a part of a side end face of the current collector. The side end face of the current collector covered by the insulating frame 24 is covered by the insulating frame 24 of the positive electrode active material layer 22 provided on one surface of the current collector and the insulating frame 24 of the positive electrode active material layer 22 provided on the other surface of the current collector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cathode structure for a secondary battery and a method for manufacturing a cathode structure for a secondary battery. [Background technology]

[0002] In recent years, research and development into secondary batteries that contribute to energy efficiency has been conducted to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. In particular, all-solid-state batteries have many advantages over conventional secondary batteries, such as high energy density and safety, and are expected to be used as power sources for electric vehicles and hybrid electric vehicles, for example.

[0003] An all-solid-state battery has a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer disposed between these active material layers. The solid electrolyte layer also serves as a separator to prevent short-circuiting between the positive electrode and the negative electrode. The positive electrode active material layer and the negative electrode active material layer are each provided with a current collector for connection to an external electrode. Such current collectors may be made of metal foil, such as aluminum foil or copper foil.

[0004] For example, in an all-solid-state battery having a structure in which a solid electrolyte layer and a negative electrode active material layer are respectively disposed on both sides of a positive electrode active material layer, the negative electrode current collectors of the negative electrode active material layers respectively stacked above and below the positive electrode active material layer are bundled together and connected to an electrode. In such a structure, deformation of the metal foil when bundling the negative electrode current collectors may cause the negative electrode current collector to come close to the positive electrode current collector, resulting in a short circuit.

[0005] To address this issue, for example, in an all-solid-state battery having a solid electrolyte layer using a substrate as disclosed in Patent Document 1, the solid electrolyte layer, which is strengthened by the inclusion of the substrate and is thus self-supporting, can be configured to protrude in the same direction as the protruding negative electrode current collector (the direction perpendicular to the stacking direction). In this case, the protruding solid electrolyte layer functions as a canopy, and even if the negative electrode current collector is bent and deformed when bundled, the protruding solid electrolyte layer blocks the negative electrode current collector, preventing it from coming into contact with the positive electrode current collector. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-151100 Summary of the Invention [Problem to be solved by the invention]

[0007] In general, batteries, including all-solid-state batteries, require each component to be made thinner in order to increase the energy density. In the case of a structure in which a substrate is used for the solid electrolyte layer, as in Patent Document 1 mentioned above, the thickness of the substrate can be a barrier to making the solid electrolyte layer thinner. Therefore, in order to make the solid electrolyte layer thinner, development is also underway for all-solid-state batteries that do not use a substrate for the solid electrolyte layer. Even in such all-solid-state batteries, there is a need to develop a structure that can prevent short circuits between current collectors.

[0008] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a positive electrode structure that can suppress short-circuiting of a positive electrode current collector without using a substrate for a solid electrolyte layer, thereby contributing to energy efficiency. [Means for solving the problem]

[0009] In order to achieve the above object, the positive electrode structure according to the invention of claim 1 is a positive electrode structure including a foil-shaped current collector and positive electrode active material layers provided on both sides of the current collector, wherein the positive electrode active material layer has a central portion containing an active material and an insulating frame arranged on the outer periphery of the central portion and having an insulating material with electrical insulation properties, the insulating frame covers the surface of the current collector near the outer edge and at least a part of the side end face of the current collector, and the side end face of the current collector covered by the insulating frame is covered by the insulating frame for the positive electrode active material layer provided on one side of the current collector and the insulating frame for the positive electrode active material layer provided on the other side of the current collector.

[0010] In this positive electrode structure, the positive electrode active material layer has a central portion containing the active material and an insulating frame disposed around the central portion, and the insulating frame covers the surface of the current collector near the outer edge and at least a portion of the side end face of the current collector. Because the insulating frame, which is provided as part of the positive electrode active material layer, also covers the surface of the current collector near the outer edge and at least a portion of the side end face, the insulating frame covers the side end face of the positive electrode current collector on the same side as the protruding direction of the negative electrode current collector, thereby preventing contact between the negative electrode current collector and the positive electrode current collector. Therefore, in an all-solid-state battery using this positive electrode structure, short-circuiting of the positive electrode current collector can be prevented without using a substrate for the solid electrolyte layer.

[0011] Furthermore, the side end face of the current collector covered by the insulating frame of the positive electrode active material layer is covered by an insulating frame provided on one side of the current collector and an insulating frame provided on the other side of the current collector. In this way, the insulating frames provided on both sides of the current collector cover the side end face of the current collector, respectively, so that the side end face of the current collector can be covered efficiently.

[0012] The invention according to claim 2 is characterized in that in the positive electrode structure according to claim 1, the insulating material of the insulating frame is alumina.

[0013] According to this configuration, an insulating frame whose insulating material is alumina can be suitably used.

[0014] The invention according to claim 3 is characterized in that, in the positive electrode structure according to claim 1, the elongation rate of the insulating frame provided on the surface of the current collector is greater than the elongation rate of the current collector.

[0015] According to this configuration, the insulating frame provided on the surface of the current collector has a higher elongation rate than the current collector, so that the side end surface of the current collector can be suitably covered by the insulating frame provided on the surface near the outer edge of the current collector.

[0016] The method for manufacturing a positive electrode structure according to the invention of claim 4 is the method for manufacturing a positive electrode structure according to claim 1, and includes: a first coating step of coating both surfaces of a metal foil sheet that serves as a raw material for a current collector with a slurry of a positive electrode composite containing an active material; a second coating step of coating an area of ​​the metal foil sheet that follows the periphery of the positive electrode composite, at least a portion of which follows the outer edge of the metal foil sheet, with a slurry of an insulating material; and a pressing step of roll-pressing the metal foil sheet coated with the slurry of the positive electrode composite and the slurry of the insulating material at a pressing pressure of 800 to 1200 MPa.

[0017] According to this method for producing a positive electrode structure, a slurry of an insulating material is applied to a region of a metal foil sheet that is along the periphery of the positive electrode composite and at least a portion of which is along the outer edge of the metal foil sheet, followed by roll pressing at a pressure of 800 to 1200 MPa. The insulating material applied to the region along the outer edge of the metal foil sheet is then rolled out by the subsequent roll pressing, and the extended insulating material covers the side edge surfaces of the metal foil sheet. The metal foil sheet is then cut into a desired shape using a rotary die cutter, a trim cutter, or the like, including the side edge surfaces of the metal foil sheet that are covered with the insulating material, thereby obtaining a positive electrode structure in which the surface near the outer edge of the current collector and at least a portion of the side edge surfaces are covered with an insulating frame. Therefore, in an all-solid-state battery using a cathode structure manufactured by this manufacturing method, contact between the anode current collector and the cathode current collector can be suppressed by covering the side end face of the cathode current collector on the same side as the direction in which the anode current collector protrudes with an insulating frame, thereby suppressing short-circuiting of the cathode current collector without using a substrate for the solid electrolyte layer.

[0018] The invention of claim 5 is characterized in that, in the method for manufacturing a positive electrode structure described in claim 4, the slurry of insulating material contains alumina, a styrene butadiene rubber-based or polyvinylidene fluoride-based binder, and butyl butyrate.

[0019] According to this configuration, it is possible to suitably use a slurry of an insulating material containing alumina, a styrene butadiene rubber (SBR)-based or polyvinylidene fluoride (PVDF)-based binder, and butyl butyrate.

[0020] The invention according to claim 6 is characterized in that in the method for manufacturing a positive electrode structure according to claim 4 or 5, the elongation rate of the insulating material slurry in the pressing step is greater than the elongation rate of the metal foil sheet.

[0021] According to this configuration, the side end surfaces of the metal foil sheet can be suitably covered with the insulating material slurry applied to the area along the outer edge of the metal foil sheet.

[0022] A secondary battery according to a seventh aspect of the present invention comprises the positive electrode structure according to the first aspect as a positive electrode.

[0023] According to this configuration, the insulating frame provided as part of the positive electrode active material layer in the positive electrode structure covers the surface near the outer edge of the current collector and at least a portion of the side end face, and this insulating frame covers the side end face of the positive electrode collector on the same side as the direction in which the negative electrode current collector protrudes, thereby preventing contact between the negative electrode current collector and the positive electrode current collector. Therefore, in a secondary battery with this configuration, short-circuiting of the positive electrode current collector can be prevented.

[0024] The invention according to claim 8 is characterized in that the secondary battery according to claim 7 is an all-solid-state battery.

[0025] According to this configuration, in an all-solid-state battery, it is possible to suppress short-circuiting of the positive electrode current collector without using a substrate for the solid electrolyte layer.

[0026] The invention according to claim 9 is characterized in that the secondary battery according to claim 7 or 8 is a lithium metal secondary battery.

[0027] According to this configuration, in a lithium metal secondary battery having a lithium metal layer on the negative electrode, short-circuiting of the positive electrode current collector can be suppressed. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view schematically showing an all-solid-state battery including a positive electrode structure according to one embodiment of the present invention. [Figure 2] 1A to 1C are diagrams illustrating a coating step and a pressing step in a method for manufacturing a positive electrode structure according to an embodiment. [Figure 3] 10A and 10B are diagrams illustrating a cutting step in a manufacturing method of a positive electrode structure according to one embodiment. [Figure 4] 1 is an optical microscope photograph showing an example of a positive electrode structure according to the present invention. [Figure 5] 1 is an optical microscope photograph showing a comparative example of a positive electrode structure. [Figure 6] 1 is an optical microscope photograph showing a comparative example of a positive electrode structure. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of a cathode structure and an all-solid-state battery using the same according to the present invention will be described with reference to the drawings. Note that the drawings used in the following description may be partially enlarged or reduced for ease of explanation, and the size and proportions of each component are not limited to those shown in the drawings.

[0030] [All-solid battery] 1 is a cross-sectional view schematically illustrating an all-solid-state battery 1 including a cathode structure 2 according to an embodiment. The all-solid-state battery 1 is an example of a secondary battery to which the cathode structure 2 according to this embodiment can be applied, and the cathode structure 2 can also be used in secondary batteries that use a liquid electrolyte. As shown in the figure, the all-solid-state battery 1 is an all-solid-state lithium metal battery including a cathode structure 2, solid electrolyte layers 3 laminated on both sides of the cathode structure 2, and anode structures 4 laminated on the surfaces of the solid electrolyte layers 3 opposite to the cathode structure 2, and having a lithium metal layer in the anode. In the following description, the side end face of each part means the end face in a direction perpendicular to the stacking direction of each part.

[0031] [Positive electrode structure] The positive electrode structure 2 has a positive electrode current collector 21 which is a foil-shaped current collector, and a positive electrode active material layer 22 . The positive electrode current collector 21 has a function of collecting current from the positive electrode structure 2. The positive electrode current collector 21 is a foil-shaped member made of an electrically conductive electrode material, and can be formed of, for example, a foil-shaped body made of aluminum (Al), nickel (Ni), stainless steel, or an alloy thereof. In this embodiment, an aluminum foil is used as the positive electrode current collector 21. The positive electrode current collector 21 has a positive electrode protrusion 21A at one of its side ends for connection to a tab lead or a terminal electrode, and the positive electrode protrusion 21A protrudes laterally (in a direction perpendicular to the stacking direction) by a predetermined length.

[0032] The positive electrode active material layer 22 has a central portion 23 containing a positive electrode active material, and an insulating frame 24 provided along the outer periphery of the central portion 23 . The central portion 23 is formed of a positive electrode composite material including a positive electrode active material, a solid electrolyte, a conductive additive, a binder, and the like. The positive 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. Examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), solid solution oxides (LiMnO-LiMO (M=Co, Ni, etc.)), lithium-manganese-nickel-cobalt oxide (LiNiMnCoO), and composite oxides such as olivine-type lithium phosphate oxide (LiFePO). These positive electrode active materials may be used alone or in combination of two or more.

[0033] The solid electrolyte contained in the central portion 23 may be the same as or different from the solid electrolyte contained in the solid electrolyte layer 3 described below. Examples of the conductive additive that can be blended into the central portion 23 include carbon black, acetylene black, ketjen black, and carbon fiber. Examples of binders that can be blended into the central portion 23 include styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene.

[0034] The insulating frame 24 is disposed in close contact with the side end surface of the central portion 23, with approximately the same thickness as the central portion 23, so as to cover the entire side end surface of the central portion 23. The insulating frame 24 is formed using an insulating material having electrical insulation properties and prevents short-circuiting of the central portion 23, which contains the positive electrode active material. Examples of insulating materials that can be used for the insulating frame 24 include ceramic materials such as alumina (Al2O3), and resin materials such as polyolefin resin, vinyl resin, acrylic resin, polyamide resin, fluorine resin, and composite resins of these. In this embodiment, alumina is used as the insulating material because it has high insulation properties, wear resistance, chemical stability, and cost-effectiveness.

[0035] The insulating frame 24 is formed by adding a binder to an insulating material, as described below. The viscosity of the insulating frame 24 is adjusted by adjusting the composition and content of the binder, and the insulating frame 24 is formed to have a predetermined elongation rate. As a result, the insulating frame 24 is configured to cover not only the center portion 23, but also the surface near the outer edge of the positive electrode current collector 21 and the side end face of the positive electrode current collector 21 opposite to the positive electrode protruding portion 21A. Examples of binders that can be mixed with the insulating material include styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene. 1, an insulating frame 24 disposed on one surface (for example, the upper surface in the figure) of the positive electrode current collector 21 and an insulating frame 24 disposed on the other surface (for example, the lower surface in the figure) of the positive electrode current collector 21 both extend toward one end surface of the positive electrode current collector 21 to cover the end surface, thereby forming an end surface covering portion 25. By having this end surface covering portion 25 cover a part of the side end surface of the positive electrode current collector 21, the positive electrode current collector 21 is prevented from coming into contact with another electrode or the like and causing a short circuit.

[0036] [Solid electrolyte layer] As shown in FIG. 1, the solid electrolyte layer 3 is a layer formed between the positive electrode structure 2 and the negative electrode structure 4, and contains a solid electrolyte. Examples of solid electrolytes include sulfide-based solid electrolyte materials, oxide-based solid electrolyte materials, nitride-based solid electrolyte materials, and halide-based solid electrolyte materials. Examples of sulfide-based solid electrolyte materials include LPS-based halogens (Cl, Br, I), Li2S-P2S5, and Li2S-P2S5-LiI. The above description of "Li2S-P2S5" refers to a sulfide-based solid electrolyte material made using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. Examples of oxide-based solid electrolyte materials include NASICON-type oxides, garnet-type oxides, and perovskite-type oxides. Examples of NASICON-type oxides include oxides containing Li, Al, Ti, P, and O (e.g., Li 1.5 Al 0.5 Ti 1.5(PO4)3). Examples of garnet-type oxides include oxides containing Li, La, Zr, and O (e.g., Li7La3Zr2O 12 Examples of perovskite oxides include oxides containing Li, La, Ti, and O (for example, LiLaTiO3).

[0037] The solid electrolyte layer 3 preferably comprises 90 to 97 parts by mass of a solid electrolyte and 3 to 10 parts by mass of a binder. The thickness of the solid electrolyte layer 3 is not particularly limited, as various thicknesses are used depending on the specifications of the cell, but is preferably, for example, 10 μm to 50 μm. The form of the solid electrolyte is not particularly limited, but may be, for example, particulate.

[0038] [Negative electrode structure] The negative electrode structure 4 has a negative electrode current collector 41, which is a foil-shaped current collector, and a negative electrode active material layer 42. The negative electrode active material layer 42 is laminated on each solid electrolyte layer 3. The negative electrode current collector 41 is laminated on each negative electrode active material layer 42, and forms the outermost layer of the all-solid-state battery 1. The negative electrode current collector 41 has a function of collecting current from the negative electrode structure 4. The negative electrode current collector 41 is a foil-shaped member made of an electrically conductive electrode material. Examples of materials that can be used to form the negative electrode current collector 41 include copper (Cu), nickel (Ni), titanium (Ti), cobalt (Co), stainless steel, and alloys thereof. In this embodiment, copper foil is used as the negative electrode current collector 41. The negative electrode current collector 41 has a negative electrode projection 41A that projects laterally at the side end opposite the side on which the positive electrode projection 21A is formed in the positive electrode structure 2 for connection to a tab lead or a terminal electrode.

[0039] In this embodiment, the negative electrode projections 41 of the negative electrode current collectors 41 provided on both sides of the positive electrode structure 2 are joined to a tab lead or a terminal electrode after being bundled together. Therefore, the negative electrode projections 41 may be deformed due to bending or the like when being bundled together and may move to a position close to the positive electrode structure 2. However, as described above, the end of the positive electrode active material layer 22 is covered by the insulating frame 24, and the side end face of the positive electrode current collector 21 on the negative electrode projection 41A side is covered by the end face covering portion 25 of the insulating frame 24. Therefore, there is no risk of a short circuit occurring between the negative electrode structure 4 and the positive electrode structure 2.

[0040] The negative electrode active material layer 42 contains a negative electrode active material. For example, lithium metal, a lithium alloy, or a mixture of these can be used as the negative electrode active material. Examples of elements that can form an alloy with lithium metal include Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, Sn, In, and Zn.

[0041] [Manufacturing method for all-solid-state batteries] Next, a method for manufacturing the all-solid-state battery 1 will be described. The all-solid-state battery 1 of this embodiment is manufactured by a cathode structure manufacturing process for manufacturing a cathode structure 2, a solid electrolyte layer manufacturing process for manufacturing a solid electrolyte layer 3, an anode structure manufacturing process for manufacturing an anode structure 4, and a lamination process for laminating the cathode structure 2, the solid electrolyte 3, and the anode structure 4.

[0042] [Positive electrode structure manufacturing process] First, a method for manufacturing the cathode structure 2 will be described with reference to Fig. 2 and Fig. 3. In Fig. 2 and Fig. 3, the right diagram is a plan view schematically showing a region of the metal foil sheet 210 where the cathode structure 2 is to be manufactured, and the left diagram is a schematic cross-sectional view taken along line AA in the right diagram. First, a first coating step is performed in which a slurry of a positive electrode composite 230 that forms the central portion 23 is coated on both sides of a metal foil sheet 210 that is the raw material for the positive electrode current collector 21, and a second coating step is performed in which a slurry of an insulating material 240 that forms the insulating frame 24 is coated on both sides of the metal foil sheet 210. Fig. 2(a) shows the state of the metal foil sheet 210 after the first coating step and the second coating step have been performed.

[0043] In the first coating step, first, a slurry of the positive electrode composite 230 (positive electrode active material, solid electrolyte, conductive additive, binder, etc.) that constitutes the central portion 23 of the positive electrode active material layer 22 is prepared by adding it to a non-polar solvent. Next, the obtained slurry of the positive electrode composite 230 is applied to predetermined positions on both surfaces of the metal foil sheet 210, and then dried. The predetermined positions to which the slurry is applied will be described later.

[0044] Next, in the second coating step, a slurry is prepared by dispersing alumina powder, a styrene butadiene rubber (SBR)-based or polyvinylidene fluoride (PVDF)-based binder, and butyl butyrate, which are the insulating material 240 constituting the insulating frame 24 of this embodiment, in a solvent. Next, the obtained slurry of insulating material 240 is applied to the areas along the outer periphery of the positive electrode composite 230 on both surfaces of the metal foil sheet 210, and then dried.

[0045] Here, the positions on the metal foil sheet 210 to which the slurries of the positive electrode composite 230 and the insulating material 240 are applied will be described. As shown in FIG. 2( a), the slurry of the positive electrode composite 230 is applied, for example, in a rectangular shape having long and short sides, and the slurry of the insulating material 240 is applied in a rectangular frame shape along the outer periphery of the rectangular positive electrode composite 230. At this time, the slurry of the insulating material 240 is applied in a positional relationship such that one of the short sides of the rectangular frame shape is positioned in an area along the outer edge of the metal foil sheet 210. Therefore, the slurry of the positive electrode composite 230 is applied in a positional relationship such that the short side is positioned inward (away from the outer edge) from the outer edge of the metal foil sheet 210 by the width of the short side of the insulating material 240.

[0046] Next, a pressing step is carried out to pressure-form the metal foil sheet 210 coated with the slurry of the positive electrode composite material 230 and the insulating material 240. The pressure-forming in the pressing step is carried out using a roll press, which is a pressure device. The pressing pressure in the roll press is preferably set in the range of 800 to 1200 MPa. FIG. 2(b) shows the state of the metal foil sheet 210 after the pressing process. The viscosity of the insulating material 240 is adjusted by adjusting the composition and content of the binder, and the insulating material 240 has a predetermined elongation rate higher than that of the metal foil sheet 210. Therefore, the insulating material 240 is deformed by being compressed in the stacking direction by pressing, and each side extends laterally as shown by the dashed lines in FIG. 2(b). Here, one of the short sides of the insulating material 240 is located in a region along the outer edge of the metal foil sheet 210, so the insulating material 240 located in this region along the outer edge extends not only laterally but also in the stacking direction. As a result, an end surface covering portion 25 is formed on a part of the side end surface of the metal foil sheet 210.

[0047] Next, a cutting step is performed in which the pressed metal foil sheet 210 is cut into a predetermined shape. In FIG. 3(a), the cut-out area of ​​the metal foil sheet 210 is indicated by a dashed line. A rotary die cutter or a uniaxial trim cutter is preferably used for cutting. FIG. 3(b) shows the positive electrode structure 2 obtained by the cutting step. As shown in the figure, a positive electrode protrusion 21A is formed on the positive electrode current collector 21 by cutting. Furthermore, the side end surface of the positive electrode current collector 21 opposite to the positive electrode protruding portion 21A is covered by the end surface covering portion 25, resulting in a structure in which the positive electrode current collector 21 is not exposed to the outside. As a result, in the positive electrode structure 2 manufactured by this manufacturing method, part of the side end surface of the positive electrode current collector 21 is covered by the end surface covering portion 25 formed by deformation of the insulating frame 24 and is not exposed to the outside, so that it is possible to prevent the positive electrode current collector from coming into contact with another electrode or the like at the side end surface and causing a short circuit.

[0048] [Solid electrolyte layer manufacturing process] Next, a description will be given of a manufacturing process for the solid electrolyte layer 3. The solid electrolyte layer 3 of this embodiment is produced without using a substrate or the like in order to reduce the thickness, but it is also possible to use a solid electrolyte layer using a substrate or the like. First, the particulate solid electrolyte used in the solid electrolyte layer 3 can be produced by, for example, processing starting materials of the solid electrolyte by a melt quenching method or a mechanical milling method to obtain a mixed material, and then heat-treating the mixed material at a predetermined temperature for a predetermined time, and then pulverizing the mixed material. Next, a slurry of the solid electrolyte layer containing a solid electrolyte, a binder, and a predetermined dispersion medium is prepared, and this is coated on, for example, a PET film whose surface has been treated for release, and dried to prepare a sheet of the solid electrolyte layer 3.

[0049] Next, the manufacturing process of the negative electrode structure 4 will be described. First, the lithium metal material or lithium alloy material constituting the negative electrode active material layer 42 and the metal material constituting the negative electrode current collector 41 are roll-bonded, and then the resulting material is heat-treated and further rolled to obtain a clad material that will be the material for the negative electrode structure 4. Next, the obtained clad material is punched out to a predetermined size to produce the negative electrode structure 4.

[0050] [Lamination process] Next, the lamination step of laminating the positive electrode structure 2, the solid electrolyte 3, and the negative electrode structure 4 will be described. In the lamination process, a laminate is formed by disposing a sheet of the solid electrolyte layer 3 between the cathode structure 2 and the anode structure 4 prepared as described above, and then the laminate is pressed in the lamination direction by press molding to adhere and integrate the layers, thereby obtaining an all-solid-state battery 1. In order to improve the adhesion between the solid electrolyte layer 3 and the cathode structure 2 or the anode structure 4, an active material having ion conductivity or an adhesive material that does not inhibit ion conductivity may be disposed at the bonding interface.

[0051] [Example of positive electrode structure] Next, examples of the positive electrode structure of the present invention will be described. A ternary positive electrode active material made of nickel-cobalt-manganese composite oxide, a solid electrolyte, a binder, and a conductive additive were used to prepare a slurry of a positive electrode composite 230. Next, the obtained slurry was applied to the regions illustrated in FIG. 2 on both sides of an aluminum foil that would become the material for the positive electrode current collector 21, and then the coating was dried. Next, a slurry of insulating material was prepared using alumina as an insulating material, styrene butadiene rubber (SBR) as a binder, and butyl butyrate. The resulting slurry was then applied to the area along the periphery of the positive electrode composite described in Figure 2 and then dried. After drying, the aluminum foil coated with the positive electrode composite and insulating material on both sides was pressed with a roll press at a pressure of 800 MPa, and then punched out to the desired shape and size with a rotary die cutter to form a positive electrode structure.

[0052] Positive electrode structures of Comparative Examples 1 and 2 were fabricated using the same positive electrode composite and insulating material as in the above-described Examples. In Comparative Example 1, the positive electrode structure was cut out with a rotary die cutter after slurry coating without roll pressing. In Comparative Example 2, an insulating material prepared so that its elongation percentage was smaller than that of the Examples was used.

[0053] 4 to 6 are optical microscope photographs showing one end surface of the positive electrode current collector in the positive electrode structures of Example, Comparative Example 1, and Comparative Example 2, respectively. 4, in the positive electrode structure of the example, the end surface covering portion is formed on the side end surface of the positive electrode current collector, and the positive electrode current collector is covered with an insulating material, so that the positive electrode current collector is not exposed to the outside. Therefore, it can be seen that the end surface covering portion can effectively suppress short circuits at the end surface of the positive electrode current collector.

[0054] On the other hand, in Comparative Example 1, the positive electrode current collector was not coated with an insulating material at the side end surface of the positive electrode current collector, and the positive electrode current collector was exposed to the outside. As such, it was confirmed that when pressure was not applied by a roll press, the insulating frame of the positive electrode active material layer did not extend toward the side end surface of the positive electrode current collector, and an end surface coating portion was not formed.

[0055] In Comparative Example 2, it was found that the positive electrode current collector was partially coated with the insulating material on the side end surface, while some parts were uncoated and exposed to the outside. Therefore, it was confirmed that if the elongation of the insulating material is insufficient, the end surface coating portion will also be incomplete, and short circuits at the end surface of the positive electrode current collector cannot be effectively suppressed.

[0056] From the above results, it was found that the present invention can provide a positive electrode structure that can suppress short-circuiting of the positive electrode current collector when used in an all-solid-state battery without using a substrate for the solid electrolyte layer.

[0057] The present invention is not limited to the above-described embodiment, but can be implemented in various forms. [Explanation of symbols]

[0058] 1…All-solid-state battery 2...Positive electrode structure 3...Solid electrolyte layer 4...Negative electrode structure 21...Positive electrode current collector 21A…Positive electrode protrusion 22...Cathode active material layer 23...Central part 24...Insulating frame 25...End face covering part 41...Negative electrode current collector 41A…Negative electrode protrusion 42...Negative electrode active material layer 210...Metal foil sheet 230...Positive electrode mixture 240...Insulating material

Claims

1. A positive electrode structure comprising a foil-shaped current collector and a positive electrode active material layer provided on both sides of the current collector, the positive electrode active material layer has a central portion including an active material and an insulating frame disposed on the outer periphery of the central portion and including an insulating material having electrical insulation properties; the insulating frame covers a surface of the current collector near an outer edge thereof and at least a portion of a side end surface of the current collector; The side end surface of the current collector covered by the insulating frame is covered by the insulating frame of the positive electrode active material layer provided on one surface of the current collector and the insulating frame of the positive electrode active material layer provided on the other surface of the current collector. A positive electrode structure characterized by:

2. 2. The cathode structure of claim 1, wherein the insulating material of the insulating frame is alumina.

3. The positive electrode structure according to claim 1 , wherein the insulating frame provided on the surface of the current collector has a higher elongation than the current collector.

4. A method for producing the cathode structure according to claim 1, comprising: a first coating step of coating both surfaces of a metal foil sheet serving as a raw material for the current collector with a slurry of a positive electrode composite containing the active material; a second coating step of coating the insulating material slurry onto a region of the metal foil sheet along an outer periphery of the positive electrode composite, the region including at least a portion along an outer edge of the metal foil sheet; a pressing step of roll-pressing the metal foil sheet coated with the positive electrode composite slurry and the insulating material slurry at a pressing pressure of 800 to 1200 MPa; A method for manufacturing a positive electrode structure, comprising:

5. The method for manufacturing a cathode structure according to claim 4 , wherein the slurry of the insulating material contains alumina, a styrene-butadiene rubber-based or polyvinylidene fluoride-based binder, and butyl butyrate.

6. The method for manufacturing a cathode structure according to claim 4 or 5, wherein the elongation of the slurry of the insulating material in the pressing step is greater than the elongation of the metal foil sheet.

7. A secondary battery comprising the positive electrode structure according to claim 1 as a positive electrode.

8. The secondary battery according to claim 7 , which is an all-solid-state battery.

9. 9. The secondary battery according to claim 7, which is a lithium metal secondary battery.

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