All-solid-state batteries

Abstract

To provide an all-solid battery capable of suppressing corrosion caused by hydrogen sulfide at a negative electrode when hydrogen sulfide is generated inside a battery cell.SOLUTION: An all-solid battery 1 includes a positive electrode 10 in which a first current collector layer 11 and a first active material layer 12 are stacked, a negative electrode 20 in which a second current collector layer 21 containing at least copper and a second active material layer 22 are stacked, a solid electrolyte layer 30 disposed between the first active material layer 12 and the second active material layer 22, and a first tab lead and a second tab lead 50 joined to the second current collector layer 21. At least one of the positive electrode 10, the negative electrode 20, and the solid electrolyte layer 30 contains sulfide. The all-solid battery 1 also includes a removable insulating cover 60 that covers the second tab lead 50.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to all-solid-state batteries.

Background Art

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable, and advanced energy, research and development have been conducted on all-solid-state batteries that contribute to energy efficiency.

[0003] Conventionally, the lead tab foil of an aluminum electrolytic capacitor has sometimes suffered from corrosion disconnection because it is exposed to deterioration of the electrolytic solution and halogens such as chlorine that leak from the capacitor members during long-term use of the capacitor.

[0004] As a method for suppressing the corrosion disconnection of the lead tab foil as described above, for example, it is known to use an aluminum foil for an electrode and a lead tab for connecting this electrode to an external terminal, and to bond an adhesive or adhesive resin sheet to this lead tab (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, in solid-state battery technology, if hydrogen sulfide is generated inside the battery cell, the copper that makes up the current collector layer of the negative electrode may corrode. In that case, the tab lead connected to the negative electrode may corrode and become brittle, and may break due to vibration or other factors. If the tab lead breaks while the charge level is high, the charge level cannot be reduced at the negative electrode where the tab lead has broken, which presents a problem as it becomes impossible to safely remove the battery cell.

[0007] This invention aims to solve the above-mentioned problems by suppressing corrosion caused by hydrogen sulfide at the negative electrode when hydrogen sulfide is generated inside the battery cell. This will ultimately contribute to energy efficiency. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides the following means. [1] A positive electrode having a first current collector layer and a first active material layer stacked together, A negative electrode comprising a second current collector layer containing at least copper and a second active material layer stacked together, A solid electrolyte layer disposed between the first active material layer and the second active material layer, The device comprises a first tab lead and a second tab lead joined to the second current collector layer, At least one of the positive electrode, the negative electrode, and the solid electrolyte layer contains a sulfide, A solid-state battery having a removable insulating cover that covers the second tab lead.

[0009] By covering the second tab lead and having a removable insulating cover, even if hydrogen sulfide is generated from at least one of the positive electrode, negative electrode, and solid electrolyte layer inside the battery cell, corrosion of the second tab lead by hydrogen sulfide generated from the solid electrolyte layer can be suppressed, and corrosion of the second current collector layer by hydrogen sulfide can be suppressed.

[0010] [2] The all-solid-state battery according to [1], wherein the second current collector layer and the first tab lead are joined by welding, and the second current collector layer and the second tab lead are joined by fastening means.

[0011] The second current collector layer and the first tab lead are joined by welding, allowing for a strong connection between them. The connection structure between the second current collector layer and the second tab lead can be simplified by joining them with fastening means.

[0012] [3] The first tab lead is a tab lead for charging and discharging, The all-solid-state battery according to [1] or [2], wherein the second tab lead is a tab lead for residual discharge.

[0013] The first tab lead is a charge / discharge tab lead, allowing the negative electrode to be charged and discharged through it. The second tab lead is a residual discharge tab lead, allowing the residual current of the negative electrode to be released to the outside through it, thereby reducing the charge level of the negative electrode. This allows the battery cell to be safely removed. [Effects of the Invention]

[0014] According to the present invention, when hydrogen sulfide is generated inside a battery cell, corrosion caused by hydrogen sulfide at the negative electrode can be suppressed. [Brief explanation of the drawing]

[0015] [Figure 1] This is a plan view showing an example of the structure of the negative electrode constituting an all-solid-state battery according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view along line A-A' in Figure 1, showing an example of an all-solid-state battery according to an embodiment of the present invention. [Figure 3] This is a cross-sectional view along line B-B' in Figure 1, showing an example of an all-solid-state battery according to an embodiment of the present invention. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0017] [Configuration of All-Solid-State Battery] FIG. 1 is a plan view showing an example of the structure of a negative electrode constituting an all-solid-state battery according to an embodiment of the present invention. FIG. 2 shows an example of an all-solid-state battery according to an embodiment of the present invention and is a cross-sectional view taken along line A-A' of FIG. FIG. 3 shows an example of an all-solid-state battery according to an embodiment of the present invention and is a cross-sectional view taken along line B-B' of FIG. In addition, the drawings used in the following description may show, for the sake of clarity of the features, the characteristic parts enlarged for convenience, and the dimensional ratios and the like of each component are not limited to those shown in the drawings.

[0018] The all-solid-state battery 1 includes a positive electrode 10, a negative electrode 20, a solid electrolyte layer 30 disposed between the positive electrode 10 and the negative electrode 20 and containing a solid electrolyte, a first tab lead 40 and a second tab lead 50 joined to the negative electrode 20, and an insulating cover 60 covering the second tab lead 50. Further, the all-solid-state battery 1 may include a third tab lead 70 joined to the positive electrode 10 and an exterior film 90 covering the laminate 80 composed of the positive electrode 10, the negative electrode 20, and the solid electrolyte layer 30 from the outside.

[0019] The positive electrode 10 and the negative electrode 20 are alternately laminated via the solid electrolyte layer 30. Charging and discharging of the all-solid-state battery 1 are performed by the transfer of lithium ions between the positive electrode 10 and the negative electrode 20 via the solid electrolyte layer 30.

[0020] (Positive Electrode) The positive electrode 10 is formed by laminating a first current collector layer 11 and a first active material layer 12 containing at least a solid electrolyte. In the present embodiment, the positive electrode 10 has a first current collector layer 11 and positive electrode active material layers 12A and 12B formed on both main surfaces of the first current collector layer 11 and containing a positive electrode active material and a solid electrolyte.< /

[0021] The first current collector layer 11 is preferably composed of at least one substance having a high conductivity. Examples of highly conductive materials include metals or alloys containing at least one metallic element from silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), chromium (Cr), and nickel (Ni), or nonmetals such as carbon (C). Considering both high conductivity and manufacturing cost, aluminum, nickel, or stainless steel are preferred. Furthermore, aluminum is less reactive with the positive electrode active material, negative electrode active material, and solid electrolyte. Therefore, using aluminum in the first current collector layer 11 can reduce the internal resistance of the all-solid-state battery.

[0022] Examples of the shape of the first current collector layer 11 include foil-like, plate-like, mesh-like, non-woven fabric-like, and foam-like forms. Furthermore, in order to improve adhesion with the positive electrode active material layers 12A and 12B, carbon or the like may be placed on the surface of the first current collector layer 11, or the surface may be roughened.

[0023] The first active material layer 12 (positive electrode active material layers 12A, 12B) contains a positive electrode active material that exchanges lithium ions and electrons. The positive electrode active material is not particularly limited as long as it is a material that can reversibly release and absorb lithium ions and perform electron transport, and known positive electrode active materials applicable to the positive electrode of an all-solid-state lithium-ion battery can be used. For example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxide (Li2MnO3-LiMO2 (M=Co, Ni, etc.)), lithium-manganese-nickel-cobalt oxide (LiNi x Mn y Co z Examples include composite oxides such as O2 (x+y+z=1), olivine-type lithium phosphate oxide (LiFePO4); conductive polymers such as polyaniline and polypyrrole; sulfides such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, and Li-Mo-S compounds; and mixtures of sulfur and carbon. The positive electrode active material may consist of one of the above materials alone or of two or more materials.

[0024] The first active material layer 12 contains a solid electrolyte that exchanges lithium ions with the positive electrode active material. The solid electrolyte is not particularly limited as long as it has lithium ion conductivity; generally, materials used in all-solid-state lithium-ion batteries can be used. Examples include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts; polymer-based solid electrolytes such as polyethylene oxide; and gel-based solid electrolytes containing lithium-containing salts or lithium-ion-conductive ionic liquids. Of these, sulfide solid electrolyte materials are preferred from the viewpoint of high lithium ion conductivity, good structural moldability by pressing, and good interfacial bonding properties. The solid electrolyte may be composed of one of the above materials alone, or of two or more materials. The solid electrolyte contained in the positive electrode active material layers 12A and 12B may be the same material as the solid electrolyte contained in the negative electrode active material layers 22A and 22B, or the solid electrolyte layer 30, or it may be a different material.

[0025] The first active material layer 12 may contain a conductive additive from the viewpoint of improving the conductivity of the positive electrode 10. As the conductive additive, conductive additives that can be used in all-solid-state lithium-ion batteries can be used. Examples include carbon black such as acetylene black and kecheng black; carbon fiber; vapor-phase carbon fiber; graphite powder; and carbon nanotubes. The conductive additive may consist of one of the above materials alone or of two or more materials.

[0026] Furthermore, the first active material layer 12 may also contain a binder that serves to bind the positive electrode active materials together and the positive electrode active materials together with the first current collector layer 11.

[0027] In this embodiment, the positive electrode active material layers 12A and 12B are formed on both main surfaces of the first current collector layer 11. However, the embodiment is not limited to this, and either the positive electrode active material layer 12A or 12B may be formed on one main surface of the first current collector layer 11. Furthermore, if the positive electrode 10 is a single-sided coated electrode, a laminated positive electrode formed by stacking two positive electrodes so that their current collector surfaces are aligned may be used as a double-sided coated electrode. In addition, if the first current collector layer 11 has a three-dimensional porous structure such as a mesh, nonwoven fabric, or foam, the first current collector layer 11 may be provided integrally with the positive electrode active material layers 12A and 12B.

[0028] The first current collector layer 11 is assembled at one end in the width direction of the all-solid-state battery 1. Since the first active material layer 12 is in contact with the solid electrolyte layer 30, it may contain sulfides contained in the solid electrolyte layer 30.

[0029] (Negative electrode) The negative electrode 20 is formed by laminating a second current collector layer 21 and a second active material layer 22 containing at least a solid electrolyte. In this embodiment, the negative electrode 20 has a second current collector layer 21 and negative electrode active material layers 22A and 22B formed on both main surfaces of the second current collector layer 21, which contain negative electrode active material and a solid electrolyte.

[0030] The second current collector layer 21 contains at least copper (Cu). The second current collector layer 21 may also contain a substance other than copper with high conductivity, similar to the first current collector layer 11. Examples of substances other than copper with high conductivity include metals or alloys containing at least one metallic element from silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), chromium (Cr), and nickel (Ni), or nonmetals such as carbon (C). Considering both high conductivity and manufacturing cost, nickel or stainless steel are preferred as the substance other than copper. Furthermore, stainless steel does not react easily with the positive electrode active material, negative electrode active material, and solid electrolyte. Therefore, using stainless steel in the second current collector layer 21 can reduce the internal resistance of the all-solid-state battery.

[0031] Examples of the shape of the second current collector layer 21 include foil-like, plate-like, mesh-like, nonwoven fabric-like, and foam-like forms. Furthermore, in order to improve adhesion with the second active material layer 22, carbon or the like may be placed on the surface of the second current collector layer 21, or the surface may be roughened.

[0032] The second active material layer 22 (negative electrode active material layers 22A, 22B) contains a negative electrode active material that exchanges lithium ions and electrons. The negative electrode active material is not particularly limited as long as it is a material that can reversibly release and absorb lithium ions and perform electron transport, and known negative electrode active materials applicable to the negative electrode of an all-solid-state lithium-ion battery can be used. For example, carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; alloy materials mainly composed of tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, and aluminum alloys; conductive polymers such as polyacene, polyacetylene, and polypyrrole; metallic lithium; lithium titanium composite oxide (e.g., Li4Ti5O 12 Examples include the above. These negative electrode active materials may consist of one of the above materials alone, or of two or more materials.

[0033] The second active material layer 22 contains a solid electrolyte that exchanges lithium ions with the negative electrode active material. The solid electrolyte is not particularly limited as long as it has lithium ion conductivity; generally, materials used in all-solid-state lithium-ion batteries can be used. Examples include inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts; polymer-based solid electrolytes such as polyethylene oxide; and gel-based solid electrolytes containing lithium-containing salts or lithium-ion-conductive ionic liquids. The solid electrolyte may be composed of one of the above materials alone, or of two or more materials. The solid electrolyte contained in the negative electrode active material layers 22A and 22B may be the same as or different from the solid electrolyte contained in the positive electrode active material layers 12A and 12B and the solid electrolyte layer 30.

[0034] The second active material layer 22 may contain conductive additives and binders. There are no particular restrictions on these materials, but for example, materials similar to those used in the positive electrode active material layers 12A and 12B described above can be used.

[0035] In this embodiment, the negative electrode active material layers 22A and 22B are formed on both main surfaces of the second current collector layer 21. However, the embodiment is not limited to this, and either the negative electrode active material layer 22A or 22B may be formed on one main surface of the second current collector layer 21. For example, if the negative electrode 20 is formed in the bottommost layer in the stacking direction of the laminate described later, there is no opposing positive electrode 10 below the negative electrode 20 located in the bottommost layer. Therefore, in the negative electrode 20 located in the bottommost layer, the negative electrode active material layer 22A may be formed only on one upper surface in the stacking direction. Furthermore, if the second current collector layer 21 is a three-dimensional porous structure such as a mesh, nonwoven fabric, or foam, the second current collector layer 21 may be provided integrally with the negative electrode active material layers 22A and 22B.

[0036] The second current collector layer 21 is assembled at the other end in the width direction of the all-solid-state battery 1 (the end opposite to the side where the first current collector layer 11 is assembled). Since the second active material layer 22 is in contact with the solid electrolyte layer 30, it may contain sulfides contained in the solid electrolyte layer 30.

[0037] (Solid electrolyte layer) The solid electrolyte layer 30 is positioned between the first active material layer 12 and the second active material layer 22. Furthermore, in the direction perpendicular to the stacking direction, the area of ​​the solid electrolyte layer 30 is larger than the area of ​​the first active material layer 12 in the positive electrode 10. This suppresses lithium electrodeposition at the outer periphery of the electrode.

[0038] The above-mentioned solid electrolyte is not particularly limited as long as it has lithium-ion conductivity and insulating properties, and materials generally used in all-solid-state lithium-ion batteries can be used. For example, inorganic solid electrolytes such as sulfide solid electrolyte materials, oxide solid electrolyte materials, halide solid electrolytes, and lithium-containing salts, as well as polymer-based solid electrolytes such as polyethylene oxide, and gel-based solid electrolytes containing lithium-containing salts or lithium-ion conductive ionic liquids can be used. Of these, sulfide solid electrolyte materials are preferred from the viewpoint of high lithium-ion conductivity and good structural moldability and interfacial bonding properties when pressed. There are no particular restrictions on the form of the solid electrolyte material, but for example, it can be in the form of particulate matter.

[0039] The solid electrolyte layer 30 may contain an adhesive to provide mechanical strength and flexibility.

[0040] The solid electrolyte layer 30 may be in the form of a sheet having a porous substrate and a solid electrolyte held in the porous substrate. There are no particular restrictions on the form of the porous substrate, but examples include woven fabric, nonwoven fabric, mesh cloth, porous membrane, expanded sheet, punched sheet, etc. Of these forms, nonwoven fabric is preferred from the viewpoint of handling, which allows for a higher amount of solid electrolyte filling.

[0041] The porous substrate described above is preferably made of an insulating material. This improves the insulating properties of the solid electrolyte layer 30. Examples of insulating materials include resin materials such as nylon, polyester, polyethylene, polypropylene, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinylidene chloride, polyvinyl chloride, polyurethane, vinylon, polybenzimidazole, polyimide, polyphenylene sulfite, polyetheretherketone, cellulose, and acrylic resins; natural fibers such as hemp, wood pulp, and cotton linters; and glass.

[0042] (First tab lead) The first tab lead 40 is joined to the second current collector layer 21. More specifically, the first tab lead 40 is joined to the end of the second current collector layer 21, which is assembled at the other end in the width direction of the all-solid-state battery 1. The second current collector layer 21 and the first tab lead 40 are joined by a weld 100. The first tab lead 40 is a charge / discharge tab lead. That is, the all-solid-state battery 1 is charged and discharged through the first tab lead 40.

[0043] (Second tab read) The second tab lead 50 is joined to the second current collector layer 21. More specifically, the second tab lead 50 is joined at its end to the second current collector layer 21, which is assembled at the other end in the width direction of the all-solid-state battery 1. The second current collector layer 21 and the second tab lead 50 are joined by fastening means 110. The second tab lead 50 is a residual discharge tab lead. That is, the all-solid-state battery 1 releases its remaining capacity through the second tab lead 50.

[0044] Examples of fastening means for joining the second current collector layer 21 and the second tab lead 50 include rivets. The thickness of the second tab lead 50 may be thinner than the thickness of the second current collector layer 21. The width of the second tab lead 50 may be smaller than the width of the second current collector layer 21. The electronic conductivity of the second tab lead 50 is not particularly limited as long as residual discharge of the negative electrode 20 is possible, and may be lower than the electronic conductivity of the second current collector layer 21. The direction in which the second tab lead 50 extends from the laminate 80 may be parallel to the first tab lead 40, or it may extend from a different surface in the laminate 80 from which the first tab lead 40 extends, and may not be parallel to the first tab lead 40.

[0045] (Insulating cover) The insulating cover 60 covers the second tab lead 50 from the outside and is removable. That is, the insulating cover 60 is removed when releasing residual capacitance from the negative electrode 20. The insulating cover 60 is heat-sealed to the second tab lead 50 or bonded via adhesive or bonding agent. The insulating cover 60 is formed from, for example, a resin sheet. The resin constituting the resin sheet is not particularly limited as long as it has heat resistance, electrolyte resistance (e.g., alcohol resistance), and low permeability to moisture, oil, halogens, etc., but examples include polypropylene resin, polyester resin, polycarbonate resin, polyamide resin, polyacetal resin, polyvinyl chloride resin, polyvinylidene fluoride resin, vinyl resins such as polyvinylidene chloride, ethylene-propylene copolymer, polysulfone resin, polyethersulfone resin, polycarbonate resin, polyimide resin, polyphenylene sulfide resin, etc.

[0046] (Third tab read) The third tab lead 70 is joined to the first current collector layer 11. More specifically, the third tab lead 70 is joined at one end of the first current collector layer 11, which is assembled at one end in the width direction of the all-solid-state battery 1. The first current collector layer 11 and the third tab lead 70 are joined by a weld 100. The third tab lead 70 is a charge / discharge tab lead. That is, the all-solid-state battery 1 is charged and discharged via the third tab lead 70.

[0047] (Exterior film) The outer film 90 is a laminated film having an inner resin layer, a metal layer, and an outer resin layer. Examples of resins constituting the inner and outer resin layers include polyester resins such as polyethylene terephthalate (PET). The metal layer is made of, for example, aluminum foil.

[0048] As described above, according to this embodiment, the all-solid-state battery 1 is equipped with a second tab lead 50 joined to the second current collector layer 21, and has a removable insulating cover 60 that covers the second tab lead 50. Therefore, even if hydrogen sulfide is generated inside the all-solid-state battery 1 from at least one of the positive electrode 10, negative electrode 20, and solid electrolyte layer 30, corrosion of the second tab lead 50 by hydrogen sulfide can be suppressed, and corrosion of the second current collector layer 21 by hydrogen sulfide can be suppressed. The second tab lead 50 is used to release the capacity remaining in the negative electrode 20 to the outside of the all-solid-state battery 1, so corrosion can be suppressed by covering it with the insulating cover 60 when not in use. Furthermore, since the second tab lead 50 is used only to release the remaining capacity of the negative electrode 20, it may have high resistance, and may be joined to the second current collector layer 21 by fastening means 110 as described above.

[0049] Furthermore, the second tab lead 50 can also be used for chemical conversion charging and discharging of all-solid-state batteries. For example, in all-solid-state batteries, it is preferable to perform charging and discharging, including chemical conversion, while maintaining a constrained state. Therefore, it is preferable to be able to perform chemical conversion processing in the form of an all-solid-state battery. For example, in an all-solid-state battery in which multiple battery cells are connected in series, by using the second tab lead 50, it becomes possible to perform chemical conversion charging and discharging individually for each battery cell, thereby improving the yield. Also, when chemical conversion processing is performed on an all-solid-state battery in which 10 battery cells are connected in series as is, charging and discharging at 30V is required, so it is not possible to control a small voltage range. In addition, since it is the sum of the voltages of the 10 battery cells, the same control is performed whether the voltage of each battery cell is different or not, so the quality of the battery cannot be guaranteed. Therefore, by using the second tab lead 50, chemical conversion charging and discharging can be performed individually for each battery cell, which makes it possible to control a small voltage range and improve the quality of the battery.

[0050] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0051] 1 All-solid-state battery 10 positive electrode 11. First current collector layer 12 First active material layer 12A Cathode active material layer 12B Positive electrode active material layer 20 negative electrode 21. Second current collector layer 22 Second active material layer 22A negative electrode active material layer 22B Negative electrode active material layer 30 Solid electrolyte layer 40 First Tabread 50 Second Tabread 60 Insulating cover 70 Third Tabread 80-layer structure 90 Exterior film

Claims

1. A positive electrode in which a first current collector layer and a first active material layer are stacked, A negative electrode comprising a second current collector layer containing at least copper and a second active material layer stacked together, A solid electrolyte layer disposed between the first active material layer and the second active material layer, It comprises a first tab lead and a second tab lead joined to the second current collector layer, At least one of the positive electrode, the negative electrode, and the solid electrolyte layer contains a sulfide, The second tab lead has a removable insulating cover, A solid-state battery in which the insulating cover is heat-sealed to the second tab lead or bonded to the second tab lead via an adhesive or bonding agent.

2. The second current collector layer and the first tab lead are joined by welding. The all-solid-state battery according to claim 1, wherein the second current collector layer and the second tab lead are joined by fastening means.

3. The first tab lead is a tab lead for charging and discharging, The all-solid-state battery according to claim 1 or 2, wherein the second tab lead is a tab lead for residual discharge.

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