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 positive electrode structure for a secondary battery and a method for manufacturing the positive electrode structure for a secondary battery.

Background Art

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

[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, preventing 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, and a metal foil such as an aluminum foil or a copper foil may be used as such a current collector.

[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 laminated above and below the positive electrode active material layer are bundled together and then connected to the electrode. In such a structure, due to deformation of the metal foil when bundling the negative electrode current collectors, the negative electrode current collector may approach the positive electrode current collector and cause a short circuit.

[0005] To address these problems, 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, whose strength is increased by the inclusion of the substrate and which has become self-supporting, can be made to protrude in the same direction as the direction in which the negative electrode current collector protrudes (a direction perpendicular to the stacking direction). In this case, the protruding solid electrolyte layer functions like an overhang, and even if the negative electrode current collector bends and deforms when bundled, the protruding solid electrolyte layer shields it, preventing the negative electrode current collector from coming into contact with the positive electrode current collector. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-151100 [Overview of the project] [Problems that the invention aims to solve]

[0007] In batteries in general, including all-solid-state batteries, increasing energy density requires thinning of each component. As shown in Patent Document 1 above, in structures where a substrate is used for the solid electrolyte layer, the thickness of the substrate can be an obstacle to thinning the solid electrolyte layer. Therefore, in order to thin the batteries, the development of all-solid-state batteries that do not use a substrate for the solid electrolyte layer is also progressing, and even in such all-solid-state batteries, the development of a structure that can suppress short circuits between current collectors is desired.

[0008] This invention was made to solve the above-mentioned problems, and aims to provide a positive electrode structure that can suppress short circuits in the positive electrode current collector without using a substrate in the solid electrolyte layer. This will ultimately contribute to energy efficiency. [Means for solving the problem]

[0009] To achieve the above objective, the positive electrode structure according to claim 1 comprises a foil-shaped current collector and positive electrode active material layers provided on both sides of the current collector, The current collector has a protruding portion that extends outwards for connection with terminal components. Cathode active material layer Each of It consists of a central part containing the active material and an outer periphery of the central part. To surround the whole thing It has an insulating frame having an insulating material that has electrical insulating properties, and the insulating frame Each of This refers to the surface near the outer edge of the current collector and the current collector The opposite side of the protruding part side edge surface and The current collector is covered with a material, and the side end face of the current collector, which is covered with an insulating frame, is characterized in that it is covered by an insulating frame for the positive electrode active material layer provided on one side of the current collector, and an 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 consists of a central part containing the active material and an outer periphery of the central part. To surround the whole thing An insulating frame is positioned on the current collector, and this insulating frame is positioned on the surface near the outer edge of the current collector, and the current collector The opposite side of the protruding part side edge surface and , is covered. In this way, the insulating frame provided as part of the positive electrode active material layer is the surface near the outer edge of the current collector, The opposite side of the protruding part side edge The face Because it is covered, this insulating frame covers the side end face of the positive electrode current collector on the same side as the direction in which the negative electrode current collector protrudes, thereby suppressing 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 circuits of the positive electrode current collector can be suppressed without using a substrate in the solid electrolyte layer.

[0011] Furthermore, the side end faces of the current collector, which are covered by the insulating frame of the positive electrode active material layer, are covered by the insulating frame provided on one side of the current collector and the insulating frame provided on the other side. In this way, the side end faces of the current collector can be efficiently covered by the insulating frames provided on both sides of the current collector.

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

[0013] This configuration allows for the suitability of using an insulating frame in which the insulating material is alumina.

[0014] The invention according to claim 3 is characterized in that, in the positive electrode structure described in 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] With this configuration, the insulating frame provided on the surface of the current collector has a greater elongation rate than the current collector itself, so the insulating frame provided on the surface near the outer edge of the current collector can suitably cover the side end surface of the current collector.

[0016] The method for manufacturing a positive electrode structure according to claim 4 is the method for manufacturing a positive electrode structure according to claim 1, comprising: a first coating step of coating both sides of a metal foil sheet that will be used 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 a region of the metal foil sheet along the outer circumference of the positive electrode composite, at least a portion of which is along 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. A cutting process for cutting out the positive electrode structure of a desired shape from the roll-pressed metal foil sheet, Includes.

[0017] According to this method for manufacturing a positive electrode structure, a slurry of insulating material is applied to a region on a metal foil sheet that is along the outer circumference of the positive electrode composite material, and at least a portion of which is along the outer edge of the metal foil sheet. Then, a roll press is performed at a press pressure of 800 to 1200 MPa. As a result, the insulating material applied to the region along the outer edge of the metal foil sheet is rolled by the subsequent roll press, and the stretched insulating material covers the side edge of the metal foil sheet. Subsequently, a rotary die cutter or trim cutter is used to cut the metal foil sheet into the desired shape, including the side edge of the metal foil sheet that is covered with 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 are covered with an insulating frame. Therefore, in the all-solid-state battery using the positive electrode structure manufactured by this manufacturing method, by covering the side end face of the positive electrode current collector on the same side as the direction in which the negative electrode current collector protrudes with an insulating frame, contact between the negative electrode current collector and the positive electrode current collector can be suppressed. Therefore, short-circuiting of the positive electrode current collector can be suppressed without using a substrate for the solid electrolyte layer.

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

[0019] According to this configuration, a slurry of an insulating substance containing alumina, a styrene-butadiene rubber (SBR)-based or polyvinylidene fluoride (PVDF)-based binder, and butyl butyrate can be suitably used.

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

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

[0022] The secondary battery according to the invention of claim 7 includes the positive electrode structure according to claim 1 as a positive electrode.

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

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

[0025] This configuration makes it possible to suppress short circuits in the positive electrode current collector in an all-solid-state battery without using a substrate in the solid electrolyte layer.

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

[0027] This configuration makes it possible to suppress short circuits in the positive electrode current collector in a lithium metal secondary battery having a lithium metal layer in the negative electrode. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic cross-sectional view showing an all-solid-state battery equipped with a positive electrode structure according to one embodiment of the present invention. [Figure 2] This figure illustrates the coating process and the pressing process in a manufacturing method for a positive electrode structure according to one embodiment. [Figure 3] This is a diagram illustrating the cutting process in a manufacturing method for a positive electrode structure according to one embodiment. [Figure 4] This is an optical microscope image showing an example of the positive electrode structure according to the present invention. [Figure 5] This is an optical microscope image showing a comparative example of a positive electrode structure. [Figure 6] This is an optical microscope image showing a comparative example of a positive electrode structure. [Modes for carrying out the invention]

[0029] Hereinafter, embodiments of the positive electrode structure and the 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 enlarged or reduced in part for the sake of clarity, and the size and proportions of each component are not limited to those shown.

[0030] [All-solid battery] Figure 1 is a schematic cross-sectional view showing an all-solid-state battery 1 equipped with a positive electrode structure 2 according to this embodiment. Note that the all-solid-state battery 1 is an example of a secondary battery to which the positive electrode structure 2 according to this embodiment can be applied, and the positive electrode 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 comprises a positive electrode structure 2, solid electrolyte layers 3 laminated on both sides of the positive electrode structure 2, and negative electrode structures 4 laminated on the side of each solid electrolyte layer 3 opposite to the positive electrode structure 2, and is an all-solid-state lithium metal battery having a lithium metal layer at the negative electrode. In the following explanation, the side end face of each part refers to the end face in a direction perpendicular to the stacking direction of each part.

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

[0032] The positive electrode active material layer 22 has a central portion 23 containing the positive electrode active material and an insulating frame 24 provided along the outer circumference of the central portion 23. The central portion 23 is formed of a positive electrode composite material consisting of a positive electrode active material, a solid electrolyte, a conductive additive, and a binder. The positive electrode active material is not particularly limited as long as it is a material that can reversibly intercept and release lithium ions and perform electron transport, but examples include 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 (LiNi1 / 3Mn1 / 3Co1 / 3O2), and olivine-type lithium phosphate oxide (LiFePO4) and other composite oxides. These positive electrode active materials may be used individually or in combination of two or more types.

[0033] The solid electrolyte contained in the central portion 23 may be the same type as the solid electrolyte contained in the solid electrolyte layer 3 described later, or it may be a different type. Examples of conductive additives that can be incorporated into the central portion 23 include carbon black, acetylene black, Ketjen black, and carbon fiber. Examples of binders that can be incorporated into the central portion 23 include styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene.

[0034] The insulating frame 24 is positioned to closely cover the entire side end surface of the central portion 23, with a thickness approximately the same as the central portion 23. The insulating frame 24 is formed using an electrically insulating material, preventing short circuits in the central portion 23, which contains the positive electrode active material. As the insulating material used for the insulating frame 24, for example, ceramic materials such as alumina (Al2O3), or resin materials such as polyolefin resins, vinyl resins, acrylic resins, polyamide resins, fluororesins, or composite resins thereof can be used. In this embodiment, alumina is used as the insulating material because it has high insulating properties, wear resistance, chemical stability, and cost-effectiveness.

[0035] Furthermore, the insulating frame 24 is formed by incorporating a binder into an insulating material, as will be described later. The viscosity of the insulating frame 24 is adjusted by adjusting the composition and content of the binder, and it is formed to have a predetermined elongation rate. As a result, the insulating frame 24 is configured to cover not only the central 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 projection 21A. Examples of binders that can be incorporated into the above insulating material include styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene. As shown in Figure 1, both the insulating frame 24 positioned on one side of the positive electrode current collector 21 (for example, the upper side in the figure) and the insulating frame 24 positioned on the other side of the positive electrode current collector 21 (for example, the lower side in the figure) extend toward one end face of the positive electrode current collector 21 to cover the end face, forming an end face covering portion 25. By covering a portion of the side end face of the positive electrode current collector 21 with this end face covering portion 25, it is suppressed that the positive electrode current collector 21 comes into contact with other electrodes or the like and short-circuits.

[0036] [Solid electrolyte layer] As shown in Figure 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 (for example, Li 1.5 Al 0.5 Ti 1.5Examples of garnet-type oxides include (PO4)3). For example, oxides containing Li, La, Zr, and O (e.g., Li7La3Zr2O) 12 Examples include perovskite-type oxides, such as those containing Li, La, Ti, and O (e.g., LiLaTiO3).

[0037] The solid electrolyte layer 3 preferably consists of 90 to 97 parts by mass of solid electrolyte and 3 to 10 parts by mass of binder. The thickness of the solid electrolyte layer 3 is not particularly limited as various forms are used depending on the specifications of the cell, but it is preferably 10 μm to 50 μm. There are no particular restrictions on the form of the solid electrolyte, but it can be particulate, for example.

[0038] [Negative electrode structure] The negative electrode structure 4 comprises 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 top of the solid electrolyte layer 3. The negative electrode current collector 41 is laminated on top of the negative electrode active material layer 42, forming the outermost layer of the all-solid-state battery 1. The negative electrode current collector 41 has the function of collecting current from the negative electrode structure 4. The negative electrode current collector 41 is a foil-shaped member made of a conductive electrode material. The materials that make up the negative electrode current collector 41 include copper (Cu), nickel (Ni), titanium (Ti), cobalt (Co), stainless steel, or 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 protrudes laterally at the side end opposite to the side where the positive electrode projection 21A is formed in the positive electrode structure 2, for connection with a tab lead or terminal electrode.

[0039] In this embodiment, the negative electrode protrusions 41 of the negative electrode current collectors 41, each provided on both sides of the positive electrode structure 2, are bundled together and then joined to the tab leads or terminal electrodes. As a result, the negative electrode protrusions 41, which may be deformed due to bending or other factors during bundling, may move to a position close to the positive electrode structure 2. However, as described above, the ends of the positive electrode active material layer 22 are covered by the insulating frame 24, and the side end face of the positive electrode current collector 21 on the negative electrode protrusion 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. As the negative electrode active material, for example, lithium metal or lithium alloy can be used alone, or a mixture thereof can be used. Examples of elements that can form alloys with lithium metal include Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, Sn, In, Zn, etc.

[0041] [Manufacturing method for all-solid-state batteries] Next, we will explain the manufacturing method of the all-solid-state battery 1. The all-solid-state battery 1 of this embodiment is manufactured by a positive electrode structure manufacturing step for manufacturing a positive electrode structure 2, a solid electrolyte layer manufacturing step for manufacturing a solid electrolyte layer 3, a negative electrode structure manufacturing step for manufacturing a negative electrode structure 4, and a lamination step for laminating the positive electrode structure 2, the solid electrolyte 3, and the negative electrode structure 4.

[0042] [Positive electrode structure manufacturing process] First, the manufacturing method of the positive electrode structure 2 will be explained with reference to Figures 2 and 3. In Figures 2 and 3, the right figure is a schematic plan view showing the manufacturing area of ​​the positive electrode structure 2 on the metal foil sheet 210, and the left figure is a schematic cross-sectional view along line AA in the right figure. First, a first coating step is performed on both sides of the metal foil sheet 210, which will be the raw material for the positive electrode current collector 21, in which a slurry of the positive electrode composite material 230 that constitutes the central part 23 is applied, and a second coating step is performed in which a slurry of the insulating material 240 that constitutes the insulating frame 24 is applied. Figure 2(a) shows the state of the metal foil sheet 210 after the first and second coating steps have been performed.

[0043] In the first coating step, first, a slurry of the positive electrode mixture 230 (positive electrode active material, solid electrolyte, conductive additive, binder, etc.) that constitutes the central part 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 mixture 230 is applied to predetermined positions on both surfaces of the metal foil sheet 210 and then dried. The predetermined positions for applying the slurry will be described later.

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

[0045] Here, we will describe the positions on the metal foil sheet 210 to which the slurry of the positive electrode mixture 230 and the insulating material 240 is applied. As shown in Figure 2(a), the slurry of the positive electrode mixture 230 is applied in a rectangular shape having, for example, a long side and a short side, and the slurry of the insulating material 240 is applied in a rectangular frame shape along the outer circumference of the rectangular positive electrode mixture 230. At this time, the slurry of the insulating material 240 is applied in such a positional relationship that one of the short sides of the rectangular frame shape is located in a region along the outer edge of the metal foil sheet 210. Therefore, the slurry of the positive electrode mixture 230 is applied in such a position that the short side of the insulating material 240 is located inward (away from the outer edge) by the width of the short side of the insulating material 240 from the outer edge of the metal foil sheet 210.

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

[0047] Next, a cutting process is performed to cut the pressed metal foil sheet 210 into a predetermined shape. Figure 3(a) shows the cutting area of ​​the metal foil sheet 210 with a dashed line. A rotary die cutter or a uniaxial trim cutter is preferably used for cutting. Figure 3(b) shows the positive electrode structure 2 obtained by the cutting process. As shown in the figure, a positive electrode projection 21A is formed on the positive electrode current collector 21 by cutting. Furthermore, the side end face of the positive electrode current collector 21 opposite to the positive electrode projection 21A is covered by the end face covering portion 25, resulting in a structure where 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, a portion of the side end face of the positive electrode current collector 21 is covered by the end face covering portion 25 formed by the deformation of the insulating frame 24, and is not exposed to the outside, thus suppressing short circuits caused by the positive electrode current collector coming into contact with other electrodes at its side end face.

[0048] [Solid electrolyte layer manufacturing process] Next, the manufacturing process of the solid electrolyte layer 3 will be described. In this embodiment, the solid electrolyte layer 3 is made without using a substrate or the like in order to make it thin, but it is also possible to use a solid electrolyte layer that uses a substrate or the like. First, the particulate solid electrolyte used in the solid electrolyte layer 3 can be produced, for example, by processing the starting material of the solid electrolyte by a melt-quenching method or a mechanical milling method to obtain a mixed material, which is then heat-treated at a predetermined temperature and time, and then pulverized. Next, a slurry of a solid electrolyte layer containing a solid electrolyte, a binder, and a predetermined dispersion medium is prepared. This slurry is then coated onto, for example, a PET film whose surface has been treated for mold release, and dried to produce a sheet of the solid electrolyte layer 3.

[0049] Next, we will explain the manufacturing process for the negative electrode structure 4. 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 rolled and joined together, and then the resulting material is heat-treated and further rolled to obtain a clad material that will be used for the negative electrode structure 4. Next, the negative electrode structure 4 is fabricated by punching out the obtained clad material to a predetermined size.

[0050] [Lamination process] Next, we will explain the lamination process for stacking the positive electrode structure 2, the solid electrolyte 3, and the negative electrode structure 4. In the lamination process, a laminate is formed by placing a sheet of solid electrolyte layer 3 between the positive electrode structure 2 and the negative electrode structure 4, which were manufactured as described above. Then, the laminate is pressed in the lamination direction by press molding to bring it into close contact and integrate it, thereby obtaining an all-solid-state battery 1. Furthermore, in order to improve the adhesion between the solid electrolyte layer 3 and the positive electrode structure 2 or negative electrode structure 4, an ion-conductive active material or an adhesive material that does not inhibit ion conductivity may be placed at the bonding interface.

[0051] [Examples of positive electrode structures] Next, an embodiment of the positive electrode structure of the present invention will be described. A slurry of positive electrode composite material 230 was prepared using a ternary positive electrode active material consisting of nickel-cobalt-manganese composite oxide, a solid electrolyte, a binder, and a conductive additive. Next, the obtained slurry was coated onto the areas on both sides of the aluminum foil, which would be the material for the positive electrode current collector 21, as shown in Figure 2, and then dried. Next, an insulating slurry was prepared using alumina as an insulating material, styrene-butadiene rubber (SBR) as a binder, and butyl butyrate. Then, the obtained slurry was coated onto the region along the outer circumference of the positive electrode composite material as described in Figure 2, and then dried. After drying, the aluminum foil coated on both sides with the positive electrode composite material and insulating material was pressed with a roll press at a press pressure of 800 MPa, and then punched out into the desired shape and size using a rotary die cutter to form the positive electrode structure.

[0052] The cathode structures of Comparative Examples 1 and 2 were fabricated using the same cathode composite material and insulating material as in the above-described examples. In Comparative Example 1, the cathode structure was cut out using a rotary die cutter after slurry coating, without using a roll press. In Comparative Example 2, an insulating material was prepared so that its elongation rate was lower than that of the examples.

[0053] Figures 4 to 6 are optical microscope images showing one end face of the positive electrode current collector in the positive electrode structures of Example, Comparative Example 1, and Comparative Example 2, respectively. As shown in Figure 4, in the positive electrode structure of the embodiment, an end-face covering is formed on the side end face of the positive electrode current collector, and it can be confirmed that the positive electrode current collector is not exposed to the outside because it is covered with an insulating material. Therefore, it can be seen that short circuits at the end face of the positive electrode current collector can be effectively suppressed by the end-face covering.

[0054] On the other hand, in Comparative Example 1, the positive electrode current collector is not covered with insulating material at its side end face, leaving it exposed to the outside. Thus, it was confirmed that when pressure is not applied by a roll press, the insulating frame of the positive electrode active material layer does not extend toward the side end face of the positive electrode current collector, and no end face covering is formed.

[0055] Furthermore, in Comparative Example 2, it can be seen that at the side end face of the positive electrode current collector, while the positive electrode current collector is partially covered with insulating material, there are also parts that are not covered and are exposed to the outside. Therefore, it was confirmed that if the elongation rate of the insulating material is insufficient, the end face covering will also be incomplete, and short circuits at the end face of the positive electrode current collector cannot be effectively suppressed.

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

[0057] Furthermore, the present invention is not limited to the embodiments described above and 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...Insulation 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 composite material 240...Insulating material

Claims

1. A positive electrode structure comprising a foil-shaped current collector and positive electrode active material layers provided on both sides of the current collector, The current collector has a protruding portion that extends outwards for connection with terminal components, Each of the positive electrode active material layers comprises a central portion containing the active material and an insulating frame having an electrically insulating insulating material that surrounds the entire outer periphery of the central portion. Each of the insulating frames covers the surface near the outer edge of the current collector and the side end face of the current collector opposite to the protruding portion. The side end face 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 side of the current collector and the insulating frame of the positive electrode active material layer provided on the other side of the current collector. A positive electrode structure characterized by the following features.

2. The positive electrode structure according to claim 1, wherein the insulating material of the insulating frame is alumina.

3. The positive electrode structure according to claim 1, wherein 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.

4. A method for manufacturing a positive electrode structure according to claim 1, A first coating step involves coating both sides of a metal foil sheet, which is the raw material for the current collector, with a slurry of a positive electrode composite containing the active material. A second coating step involves applying the slurry of the insulating material to a region of the metal foil sheet along the outer circumference of the positive electrode composite, where at least a portion of the region is along the outer edge of the metal foil sheet. A pressing step in which the metal foil sheet coated with the slurry of the positive electrode composite material and the slurry of the insulating material is roll-pressed at a pressing pressure of 800 to 1200 MPa, A cutting process for cutting out the positive electrode structure of a desired shape from the roll-pressed metal foil sheet, A method for manufacturing a positive electrode structure, including [the specified element].

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

7. A secondary battery comprising the positive electrode structure described in claim 1 as the positive electrode.

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

9. A secondary battery according to claim 7 or 8, which is a lithium metal secondary battery.

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