Lithium metal composite oxide powder and positive electrode active material for lithium secondary battery

1. A lithium metal composite oxide powder having a layered structure, comprising:

at least Li, Ni, an element X, and an element M,

wherein the element X is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, and V,

the element M is B,

M/(Ni+X) that is a content ratio of the element M to a total amount of Ni and the element X that are contained in the lithium metal composite oxide powder is 0.01 mol % or more and 5 mol % or less,

Ni/(Ni+X) that is a content ratio of Ni to the total amount of Ni and the element X that are contained in the lithium metal composite oxide powder satisfies 0.40 or more in terms of a mole ratio, and

a ratio of the element M eluted into N-methyl-2-pyrrolidone measured under the following measurement conditions is 0.09 or less, and

wherein measurement conditions are as follows:

1 g of the lithium metal composite oxide powder is weighed and immersed in N-methyl-2-pyrrolidone weighed to 3.5 g, thereby preparing a measurement sample, the measurement sample is put into a closed container and left at room temperature of 25° C. for 96 hours,

after that, the measurement sample is centrifuged at 3000 rpm for 10 minutes,

after the centrifugation, 100 μL of a supernatant is collected, and a content ratio of the element M that is contained in 100 μL of the supernatant is measured,

the ratio of the element M eluted into N-methyl-2-pyrrolidone is calculated by the following equation, and

the ratio of element M eluted into N-methyl-2-pyrrolidone=(amount of element M eluted into N-methyl-2-pyrrolidone)/(amount of element M in lithium metal composite oxide powder before immersed in N-methyl-2-pyrrolidone).

2. The lithium metal composite oxide powder according to claim 1 ,

wherein a BET specific surface area is more than 0.30 m 2 /g and less than 0.80 m 2 /g.

3. The lithium metal composite oxide powder according to claim 1 ,

wherein D 50 that is a 50% cumulative diameter obtained from a particle size distribution measurement value is 4.1 μm or more and 10.0 μm or less.

4. The lithium metal composite oxide powder according to claim 1 ,

wherein, in powder X-ray diffraction measurement using a CuKα ray, a crystallite size in a peak within a range of 2θ=18.7±1° is more than 840 Å.

5. The lithium metal composite oxide powder according to claim 1 ,

wherein the ratio of the element M eluted into N-methyl-2-pyrrolidone is more than 0.001 and 0.04 or less.

6. A positive electrode active material for a lithium secondary battery, comprising:

the lithium metal composite oxide powder according to claim 1 .

7. A positive electrode comprising:

the positive electrode active material for a lithium secondary battery according to claim 6 .

8. A positive electrode for a lithium secondary battery comprising a positive electrode active material,

wherein the positive electrode active material comprises the lithium metal composite oxide powder according to claim 1 , and

wherein a ratio (XA) occupied by Li 55 eV that is calculated by the following equation (A) from a spectrum obtained by measuring a surface of the positive electrode for a lithium secondary battery by XPS is 30% or more,

XA =Li 55 eV /(Li 54 eV +Li 55 eV )×100  (A)

in the equation (A), Li 54 eV is a peak area of a peak at 54 eV that appears at the time of waveform separation of the spectrum obtained by measuring the surface of the positive electrode for a lithium secondary battery by XPS, and Li 55 eV means a peak area of a peak at 55 eV.

9. A lithium secondary battery comprising:

the positive electrode for a lithium secondary battery according to claim 7 .

10. A lithium secondary battery comprising:

the positive electrode for a lithium secondary battery according to claim 8 .