Positive electrode active material containing lithium composite oxide and lithium composite oxyfluoride, and battery including positive electrode containing positive electrode active material

1. A positive electrode active material comprising:

a lithium composite oxide; and

a lithium composite oxyfluoride covering at least part of the lithium composite oxide, wherein

the lithium composite oxyfluoride is represented by a composition formula Li α Me2 β O γ F δ , where Me2 represents at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ru, and W; 1.0≤α≤2.1; 0.8≤β≤1.3; 1.5≤γ≤2.9; and 0.1≤δ≤1.5, and

a crystal structure of the lithium composite oxyfluoride belongs to space group FM-3M,

wherein a mass ratio of the lithium composite oxyfluoride to the lithium composite oxide is 0.001 or more and 0.1 or less.

2. The positive electrode active material according to claim 1 ,

wherein the mass ratio is 0.01 or more and 0.05 or less.

3. The positive electrode active material according to claim 1 ,

wherein the lithium composite oxide is represented by a composition formula Li x Me1 y A z O 2 , where Me1 represents at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ru, and W; A represents at least one selected from the group consisting of B, P, Si, S, and N; 0.5≤x≤1.34; 0.5≤y≤1.0; 0≤z≤0.5; and 1.5≤x+y+z≥2.0.

4. The positive electrode active material according to claim 1 ,

wherein 1.0≤α≤2.0, β=1.0, 1.5≤γ≤2.0, and 0.5≤δ≤1.0.

5. The positive electrode active material according to claim 1 ,

wherein Me2 includes at least one selected from the group consisting of Mn, Co, Ni, Fe, Cu, V, Ti, Cr, and Zn as an essential component.

6. The positive electrode active material according to claim 1 ,

wherein Me2 includes at least one selected from the group consisting of Mn and Ni as an essential component.

7. The positive electrode active material according to claim 1 ,

wherein the mass proportion of the lithium composite oxide in the positive electrode active material is 50% or more.

8. The positive electrode active material according to claim 1 ,

wherein the positive electrode active material is a mixture of a plurality of first particles containing the lithium composite oxide and a plurality of second particles containing the lithium composite oxyfluoride, and

at least one of the plurality of first particles is in direct contact with at least one of the plurality of second particles.

9. A battery comprising:

a positive electrode containing the positive electrode active material according to claim 1 ;

a negative electrode; and

an electrolyte.

10. The battery according to claim 9 ,

wherein the positive electrode includes a positive electrode active material layer containing the positive electrode active material as a main component.

11. The battery according to claim 9 ,

wherein the negative electrode includes:

a negative electrode active material into and from which lithium ion is reversibly occluded and released; or

a material on which lithium metal is reversibly precipitated and dissolved, and the electrolyte is a nonaqueous electrolyte solution.

12. The battery according to claim 9 ,

wherein the negative electrode includes:

a negative electrode active material into and from which lithium ion is reversibly occluded and released; or

a material on which lithium metal is reversibly precipitated and dissolved, and the electrolyte is a solid electrolyte.