POSITIVE-ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, POSITIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY, AND LITHIUM SECONDARY BATTERY

1 . A positive electrode active material for a lithium secondary battery, containing at least Li, Ni, and an element X, comprising particles including a coating on a surface of a lithium metal composite oxide,

wherein the coating contains the element X,

the element X is one or more elements selected from the group consisting of Al, Ti, Nb, Zr, P, B, Mg, Ba, Si, Sn, and W, and

a formula (1) and a formula (2) are satisfied,

0.20≤X at /Li at   (1)

(X at is an abundance of the element X near a surface of the particle, which is measured by X-ray photoelectron spectroscopy, and Li at is an abundance of Li near the surface of the particle, which is measured by X-ray photoelectron spectroscopy), and

σX≤13.0  (2)

(σX is a standard deviation calculated from the abundances of the element X near the surfaces of a plurality of the particles, which is measured by scanning electron microscope-energy dispersive X-ray spectroscopy).

2 . The positive electrode active material for the lithium secondary battery according to claim 1 ,

wherein no diffraction peak is observed within a range of diffraction angles 2θ=40° to 43° in X-ray diffraction measurement using CuKα rays.

3 . The positive electrode active material for the lithium secondary battery according to claim 1 ,

wherein, in the X-ray diffraction measurement using CuKα rays, two diffraction peaks are present within a range of 2θ=38.5±1°, and, when, between the two diffraction peaks, the diffraction peak on a low angle side is defined as a peak A, and the diffraction peak on a high angle side is defined as a peak B, a formula (3) and a formula (4) are satisfied,

L A /L B ≤1.50  (3)

(L A is a crystallite size obtained from the peak A, and L B is a crystallite size obtained from the peak B), and

0.25≤I A /I B ≤0.60  (4)

(I A is an integrated intensity of the peak A, and I B is an integrated intensity of the peak B).

4 . The positive electrode active material for the lithium secondary battery according to claim 1 ,

wherein, in the X-ray diffraction measurement using CuKα rays, when a diffraction peak present within a range of 2θ=18.5±1° is defined as a peak C, and a diffraction peak present within a range of 2θ=44.5±1° is defined as a peak D, a formula (5) and a formula (6) are satisfied,

1.25≤L C /L D   (5)

(L C is a crystallite size obtained from the peak C, and L D is a crystallite size obtained from the peak D), and

1.1≤I C /I D   (6)

(I C is an integrated intensity of the peak C, and I D is an integrated intensity of the peak D).

5 . A positive electrode for a lithium secondary battery, comprising:

the positive electrode active material for the lithium secondary battery according to claim 1 .

6 . A lithium secondary battery, comprising:

the positive electrode for the lithium secondary battery according to claim 5 .

7 . The positive electrode active material for the lithium secondary battery according to claim 2 ,

wherein, in the X-ray diffraction measurement using CuKα rays, two diffraction peaks are present within a range of 2θ=38.5±1°, and, when, between the two diffraction peaks, the diffraction peak on a low angle side is defined as a peak A, and the diffraction peak on a high angle side is defined as a peak B, a formula (3) and a formula (4) are satisfied,

L A /L B ≤1.50  (3)

(LA is a crystallite size obtained from the peak A, and L B is a crystallite size obtained from the peak B), and

0.25≤IA/IB≤0.60  (4)

(I A is an integrated intensity of the peak A, and I B is an integrated intensity of the peak B).

8 . The positive electrode active material for the lithium secondary battery according to claim 2 ,

wherein, in the X-ray diffraction measurement using CuKα rays, when a diffraction peak present within a range of 2θ=18.5±1° is defined as a peak C, and a diffraction peak present within a range of 2θ=44.5±1° is defined as a peak D, a formula (5) and a formula (6) are satisfied,

1.25≤L C /L D   (5)

(L C is a crystallite size obtained from the peak C, and L D is a crystallite size obtained from the peak D), and

1.1≤I C /I D   (6)

(IC is an integrated intensity of the peak C, and I D is an integrated intensity of the peak D).

9 . A positive electrode for a lithium secondary battery, comprising:

the positive electrode active material for the lithium secondary battery according to claim 2 .

10 . A lithium secondary battery comprising:

the positive electrode for the lithium secondary battery according to claim 9 .

11 . The positive electrode active material for the lithium secondary battery according to claim 3 ,

wherein, in the X-ray diffraction measurement using CuKα rays, when a diffraction peak present within a range of 2θ=18.5±1° is defined as a peak C, and a diffraction peak present within a range of 2θ=44.5±1° is defined as a peak D, a formula (5) and a formula (6) are satisfied,

1.25≤L C /L D   (5)

(LC is a crystallite size obtained from the peak C, and L D is a crystallite size obtained from the peak D), and

1.1≤I C /I D   (6)

(IC is an integrated intensity of the peak C, and I D is an integrated intensity of the peak D).