All-solid-state secondary battery and method for manufacturing the same

Abstract

To provide an all-solid secondary battery superior in load and high-temperature characteristics, and a manufacturing method thereof.SOLUTION: An all-solid secondary battery according to the present invention comprises a positive electrode, a negative electrode and a solid electrolyte layer. The positive electrode has a mold of a positive electrode mixture containing a positive electrode active material, a conductive assistant, and a sulfide-based solid electrolyte. The positive electrode active material has, on its surface, an Nb-containing oxide layer. Of the positive electrode active material, a particle size distribution has a peak of a first frequency and a peak of a second frequency. The first frequency peak is in a range of 1-8 μm, and the second frequency peak is in a range of 15-35 μm.SELECTED DRAWING: Figure 1

Claims

1. An all-solid-state secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer, The positive electrode has a molded body of a positive electrode mixture comprising a powdered mixture containing a positive electrode active material, a conductive additive, and a sulfide-based solid electrolyte. The positive electrode active material has an Nb-containing oxide layer on its surface. The particle size distribution of the positive electrode active material has a first frequency peak and a second frequency peak. An all-solid-state secondary battery characterized in that the first frequency peak is in the range of 1 to 8 μm, and the second frequency peak is in the range of 15 to 35 μm.

2. The all-solid-state secondary battery according to claim 1, wherein the positive electrode active material is lithium cobalt oxide.

3. The all-solid-state secondary battery according to claim 1 or 2, wherein the ratio of Nb contained in the Nb-containing oxide layer to the entire positive electrode active material, including the Nb-containing oxide layer on the surface of the positive electrode active material, is 0.1% by mass or more and 2.5% by mass or less.

4. The all-solid-state secondary battery according to any one of claims 1 to 3, wherein the content of the positive electrode active material in the positive electrode mixture is 55 to 85% by mass.

5. The all-solid-state secondary battery according to any one of claims 1 to 4, wherein the thickness of the molded body of the positive electrode mixture is 200 μm or more.

6. The all-solid-state secondary battery according to any one of claims 1 to 5, wherein the positive electrode mixture does not contain a resin binder, or contains 0.5% by mass or less thereof.

7. A method for manufacturing an all-solid-state secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer, The process includes preparing a positive electrode mixture consisting of a powder mixture by mixing a positive electrode active material having an Nb-containing oxide layer on its surface, a conductive additive, and a solid electrolyte, and then producing a positive electrode having a molded body of the positive electrode mixture by pressurizing the positive electrode mixture in a powder molding die. As the positive electrode active material, large-sized particles with a most frequent particle size distribution of 15 to 35 μm and small-sized particles with a most frequent particle size distribution of 1 to 8 μm are used. A method for manufacturing an all-solid-state secondary battery, characterized in that a sulfide-based solid electrolyte having an average particle size of 0.1 to 5 μm is used as the solid electrolyte.

8. A method for manufacturing an all-solid-state secondary battery according to claim 7, in which the large-particle size particles and the small-particle size particles are used in a mass ratio of 75:25 to 95:

5.

9. A method for manufacturing an all-solid-state secondary battery according to claim 7 or 8, wherein primary particles are used in at least one of the large-particle size particles and the small-particle size particles.

10. A method for manufacturing an all-solid-state secondary battery according to any one of claims 7 to 9, wherein the ratio of Nb contained in the Nb-containing oxide layer to the entire positive electrode active material, including the Nb-containing oxide layer on the surface of the positive electrode active material, is 0.1% by mass or more and 2.5% by mass or less.

11. A method for manufacturing an all-solid-state secondary battery according to any one of claims 7 to 10, wherein the content of the positive electrode active material in the positive electrode mixture is 55 to 85% by mass.

12. The method for manufacturing an all-solid-state secondary battery according to any one of claims 7 to 11, wherein the preparation of the positive electrode mixture either does not contain a resin binder, or contains one in an amount of 0.5% by mass or less.

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