Patent Application
20240266498
The present invention relates to an all-solid-state battery.
An all-solid-state battery is provided with a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode. In the all-solid-state battery, the positive electrode and the negative electrode are present while sandwiching the solid electrolyte layer formed by compacting fine particles of solid electrolyte powder therebetween (for example, see Patent Document 1).
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2020-173954
Since solids are brought into contact with each other at the interface between the positive electrode and the solid electrolyte layer and the interface between the negative electrode and the solid electrolyte layer, in order to form favorable interfaces, that is, in order to increase contact areas of the positive electrode and the negative electrode with the solid electrolyte layer, it is necessary to apply high confining pressure to a laminate composed of the positive electrode, the negative electrode and the solid electrolyte layer. However, due to the expansion and contraction of the electrode during charging and discharging, a load is applied to the electrode and the solid electrolyte layer, thereby causing cracks and the like, making the above interface unstable and promoting deterioration of the electrode and the solid electrolyte layer.
Accordingly, in order to stabilize the above-mentioned interface, introduction of a flexible semi-solid electrolyte into the above-mentioned interface has been considered. However, since the semi-solid electrolyte is flexible, it may be released to the outside of the laminate composed of the positive electrode, the negative electrode and the solid electrolyte layer. In that case, the above-mentioned interface becomes unstable and the cycle characteristics of the all-solid-state battery deteriorate, which are problematic.
In order to solve the above problems, the present application has an object of making at least one of the interface between the positive electrode and the solid electrolyte layer and the interface between the negative electrode and the solid electrolyte layer into a stable interface, thereby suppressing the deterioration of the cycle characteristics of the all-solid-state battery. Further, this in turn contributes to energy efficiency.
In order to achieve the above object, the present invention provides the following means.
[1] An all-solid-state battery including: an all-solid-state battery positive electrode in which a positive electrode active material layer is formed on a positive electrode current collector;
In the all-solid battery of the present invention, at least one of the positive electrode active material layer and the negative electrode active material layer is a porous active material layer including a porous current collector and an active material filled in the current collector, an intermediate layer is disposed between the porous active material layer and the solid electrolyte layer, and the intermediate layer includes at least one selected from a gel, a polymer, and a high viscosity electrolyte, so that it is possible to make at least one of the interface between the all-solid-state battery positive electrode and the solid electrolyte layer and the interface between the all-solid-state battery negative electrode and the solid electrolyte layer into a stable interface, and to suppress the deterioration of the cycle characteristics of the all-solid-state battery.
[2] The all-solid-state battery according to [1], wherein the aforementioned porous active material layer has a void on the aforementioned solid electrolyte layer side, and the aforementioned intermediate layer is disposed in the aforementioned void.
Since the porous active material layer has a void on the solid electrolyte layer side, and the intermediate layer is disposed in the void, it is possible to make at least one of the interface between the all-solid-state battery positive electrode and the solid electrolyte layer and the interface between the all-solid-state battery negative electrode and the solid electrolyte layer into a stable interface.
[3] The all-solid-state battery according to [1], wherein the aforementioned negative electrode active material layer contains metallic lithium, a lithium alloy, or silicon.
Even if the negative electrode active material layer contains metallic lithium, a lithium alloy, or silicon, it is possible to make at least one of the interface between the all-solid-state battery positive electrode and the solid electrolyte layer and the interface between the all-solid-state battery negative electrode and the solid electrolyte layer into a stable interface.
According to the present invention, it is possible to make at least one of the interface between the positive electrode and the solid electrolyte layer and the interface between the negative electrode and the solid electrolyte layer into a stable interface, and to suppress the deterioration of the cycle characteristics of the all-solid-state battery.
Hereinafter, embodiments of the present invention will be described in detail.
An all-solid-state battery 1 includes an all-solid-state battery positive electrode (hereinafter sometimes abbreviated as a “positive electrode”) 10, an all-solid-state battery negative electrode (hereinafter sometimes abbreviated as a “negative electrode”) 20, a solid electrolyte layer 30 and an intermediate layer 40. In the all-solid-state battery 1, the positive electrode 10 and the negative electrode 20 are laminated via the solid electrolyte layer 30 and the intermediate layer 40.
The positive electrode 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 formed on one main surface 11a of the positive electrode current collector 11.
The positive electrode active material layer 12 is a porous active material layer that includes a porous current collector 14 and a positive electrode active material filled in the current collector 14.
It is preferable that the positive electrode active material layer 12 has voids 13 on the solid electrolyte layer 30 side. The voids 13 are, for example, a portion where the amount of a positive electrode mixture 60 filled is small or a portion where the positive electrode mixture 60 is not filled in the current collector 14.
The negative electrode 20 includes a negative electrode current collector 21 and negative electrode active material layers 22 formed on both main surfaces 21a of the negative electrode current collector 21.
The intermediate layer 40 is disposed between the positive electrode active material layer 12 and the solid electrolyte layer 30.
The positive electrode current collector 11 is preferably constituted of at least one substance having high electrical conductivity.
Examples of the substance having high electrical conductivity include metals or alloys containing at least any one metal element among silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), chromium (Cr), and nickel (Ni), and nonmetals such as carbon (C). When considering the production cost in addition to the high electrical conductivity, aluminum, nickel, or stainless steel is preferred. Furthermore, aluminum hardly reacts with a positive electrode active material, a negative electrode active material, and a solid electrolyte. Therefore, when aluminum is used for the positive electrode current collector 11, the internal resistance of the all-solid-state battery 1 can be reduced.
Examples of the form of the positive electrode current collector 11 include a foil form, a plate form, a mesh form, a nonwoven fabric form, and a foam form. Further, in order to enhance adhesion to the positive electrode active material layer 12, carbon or the like may be disposed on the surface of the positive electrode current collector 11, or the surface may be roughened.
The positive electrode active material layer 12 includes the porous current collector 14 and a positive electrode active material that is filled in the current collector 14 and allows transfer of lithium ions and electrons thereto and therefrom.
The porous current collector 14 is not particularly limited as long as it can be filled with a positive electrode active material, and examples thereof include a porous body composed of fibrous carbon, a porous body composed of porous carbon, a porous body composed of a transition metal, and a metallic body having a honeycomb structure.
The positive electrode active material is not particularly limited as long as it is a material that can reversibly release and occlude lithium ions and can transport electrons, and any known positive electrode active material applicable to a positive electrode of an all-solid-state lithium ion battery can be used. Examples thereof include complex oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxides (Li2MnO3—LiMO2 (M=Co, Ni, or the like)), lithium-manganese-nickel-cobalt oxides (LiNixMnyCozO2, x+y+z=1) and olivine-type lithium phosphorus 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 be formed of one of the above-described materials alone, or may be formed of two or more types thereof.
The positive electrode active material layer 12 may contain a conductive auxiliary agent from the viewpoint of improving the electrical conductivity of the positive electrode 10. As the conductive auxiliary agent, a conductive auxiliary agent that can generally be used for all-solid-state lithium ion batteries can be used. Examples thereof include carbon black such as acetylene black and Ketjen black; carbon fibers; vapor grown carbon fibers; graphite powder; and carbon materials such as carbon nanotubes. The conductive auxiliary agent may be formed of one of the above-described materials alone, or may be formed of two or more types thereof.
Further, the positive electrode active material layer 12 maycontain a binder having a role of binding the positive electrode active materials to each other and binding the positive electrode active material and the positive electrode current collector 11.
In the present embodiment, the positive electrode active material layer 12 is formed on one main surface 11a of the positive electrode current collector 11, but the present invention is not limited thereto, and the positive electrode active material layer 12 maybe formed on both main surfaces of the positive electrode current collector 11. Further, when the positive electrode active material layer 12 has a three-dimensional porous structure such as a mesh form, a nonwoven fabric form, or a foam form, the positive electrode active material layer 12 maybe provided integrally with the positive electrode current collector 11.
The positive electrode 10 maybe provided with a micron-sized metal pillar formed on the positive electrode current collector 11 and the positive electrode active material layer 12 formed so as to include the metal pillar.
Like the positive electrode current collector 11, the negative electrode current collector 21 is preferably constituted of at least one substance having high electrical conductivity. Examples of the substance having high electrical conductivity include metals or alloys containing at least any one metal element among silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), chromium (Cr), and nickel (Ni), and nonmetals such as carbon (C). When considering the production cost in addition to the high electrical conductivity, copper, nickel, or stainless steel is preferred. Furthermore, stainless steel hardly reacts with a positive electrode active material, a negative electrode active material, and a solid electrolyte. Therefore, when stainless steel is used for the negative electrode current collector 21, the internal resistance of the all-solid-state battery can be reduced.
Examples of the form of the negative electrode current collector 21 include a foil form, a plate form, a mesh form, a nonwoven fabric form, and a foam form. Further, in order to enhance adhesion to the negative electrode active material layer 22, carbon or the like may be disposed on the surface of the negative electrode current collector 21, or the surface may be roughened.
The negative electrode active material layer 22 includes a negative electrode active material that is filled in the current collector 22 and allows transfer of lithium ions and electrons thereto and therefrom. The negative electrode active material is not particularly limited as long as it is a material that can reversibly release and occlude lithium ions and can transport electrons, and any known negative electrode active material applicable to a negative electrode of an all-solid-state lithium ion battery can be used. Examples thereof include carbonaceous materials such as natural graphite, artificial graphite, resinous coal, carbon fibers, activated carbon, hard carbon, and soft carbon; alloy-based materials mainly composed of tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, aluminum alloys, and the like; conductive polymers such as polyacene, polyacetylene, and polypyrrole; metallic lithium, and lithium alloys; and lithium-titanium composite oxides (for example, Li4Ti5O12). These negative electrode active materials may be formed of one of the above-described materials alone, or may be formed of two or more types thereof.
The negative electrode active material layer 22 maycontain a conductive auxiliary agent, a binder, and the like. Although these materials are not particularly limited, for example, the same materials as those used for the positive electrode active material layer 12 described above can be used.
The solid electrolyte layer 30 is disposed between the positive electrode active material layer 12 and the negative electrode active material layer 22.
The solid electrolyte described above is not particularly limited as long as it has lithium ion conductivity and insulating properties, and materials generally used for all-solid-state lithium ion batteries can be used. Examples thereof include inorganic solid electrolytes such as a sulfide solid electrolyte material, an oxide solid electrolyte material, a halide solid electrolyte, and a lithium-containing salt, polymer-based solid electrolytes such as polyethylene oxide, and gel-based solid electrolytes containing a lithium-containing salt or lithium ion conductive ionic liquid. Among these, sulfide solid electrolyte materials are preferred from the viewpoints of high conductivity of lithium ions, and favorable structural formability and interfacial bonding properties by pressing.
Although the form of the solid electrolyte material is not particularly limited, examples thereof include a particulate form.
The solid electrolyte layer 30 maycontain a pressure-sensitive adhesive for imparting mechanical strength and flexibility.
The solid electrolyte layer 30 maybe in a sheet form having a porous base material and a solid electrolyte held by this porous base material. Although the form of the porous base material described above is not particularly limited, examples thereof include a woven fabric, a nonwoven fabric, a mesh cloth, a porous membrane, an expanded sheet, and a punched sheet. Among these forms, a nonwoven fabric is preferred from the viewpoint of handling properties that allow the amount of the solid electrolyte filled to be further increased.
It is preferable that the porous base material described above is formed of an insulating material. As a result, the insulating properties of the solid electrolyte layer 30 can be improved. Examples of the insulating material include resin materials such as nylon, polyester, polyethylene, polypropylene, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymers, polyvinylidene fluoride, polyvinylidene chloride, polyvinyl chloride, polyurethane, vinylon, polybenzimidazole, polyimide, polyphenylene sulfite, polyether ether ketone, cellulose, and acrylic resins; natural fibers such as hemp, wood pulp, and cotton linters; and glass.
The intermediate layer 40 includes at least one selected from a gel, a polymer, and a high viscosity electrolyte.
Examples of the gel include a gel electrolyte containing a gelling material that utilizes a π-π stacking interaction and has a perfluoroalkyl group and a phenylene group, and an electrolytic solution. Examples of the electrolytic solution contained in the gel electrolyte include an electrolytic solution containing dimethyl carbonate and lithium bis(fluorosulfonyl)imide, and having a molar ratio of dimethyl carbonate with respect to lithium bis(fluorosulfonyl)imide of 1.1 or more and 3.0 or less.
As described above, according to the all-solid-state battery 1 of the present embodiment, since the positive electrode active material layer 12 is a porous active material layer that includes a porous current collector and a positive electrode active material filled in the current collector, and the intermediate layer 40 containing at least one selected from a gel, a polymer, and a high viscosity electrolyte is disposed between the positive electrode active material layer 12 and the solid electrolyte layer 30, it is possible to make the interface between the positive electrode 10 and the solid electrolyte layer 30 into a stable interface and to suppress the deterioration of the cycle characteristics of the all-solid-state battery.
In addition, as shown in
It should be noted that in the all-solid-state battery of the present embodiment, the negative electrode active material layer 22 of the negative electrode 20 maybe a porous active material layer including a porous current collector and a negative electrode active material filled in the current collector. When the negative electrode active material layer 22 is a porous active material layer, the intermediate layer 40 is disposed between the negative electrode active material layer 22 and the solid electrolyte layer 30. Further, in the all-solid-state battery of the present embodiment, the positive electrode active material layer 12 and the negative electrode active material layer 22 maybe porous active material layers. When the positive electrode active material layer 12 and the negative electrode active material layer 22 are porous active material layers, the intermediate layer 40 is disposed between the positive electrode active material layer 12 and the solid electrolyte layer 30 and between the negative electrode active material layer 22 and the solid electrolyte layer 30.
A method for forming the voids 13 in the positive electrode active material layer 12 in the positive electrode 10 will be described.
As shown in
While moving the coater 110 along both main surfaces 14a of the current collector 14, the positive electrode mixture 60 is filled into an arbitrary position of the current collector 14. At this time, by pushing out the positive electrode mixture 60 in the coater 110 with the plunger 120, the current collector 14 is filled with the positive electrode mixture 60.
The voids 13 are formed in the positive electrode active material layer 12 by adjusting the position at which the positive electrode mixture 60 is filled in the current collector 14 and the amount of the positive electrode mixture 60 filled in the current collector 14. That is, in the current collector 14, a portion where the amount of the positive electrode mixture 60 filled is small or a portion where the positive electrode mixture 60 is not filled becomes the void 13.
Further, as shown in
While preferred embodiments of the present invention have been described and illustrated above in detail, the present invention is not limited to the above embodiments, and various modifications and changes can be made within the scope of the present invention described in the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-015240 | Feb 2023 | JP | national |
