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

A lithium metal composite oxide powder, which comprises primary particles and secondary particles that are aggregates of the primary particles, and has an α-NaFeO2 type crystal structure,

• wherein a half width (A) of a diffraction peak in a range of 2θ=18.7±1° in a powder X-ray diffraction measurement for the lithium metal composite oxide powder using a CuKα ray is 0.135° or more and 0.165° or less,
• wherein a c-axis lattice constant of the α-NaFeO2 type crystal structure is 14.178 Å or more and 14.235 Å or less,
• wherein the powder X-ray diffraction measurement is performed using the CuKα ray under a condition of a diffraction angle of 2θ=10° to 90°, a sampling width of 0.02°, and a scan speed of 4°/min, and
• wherein the lithium metal composite oxide powder satisfies composition formula (I)
• Li[Lix(Ni(1−y−z−w)COyMnzMw)1−x]O2 (I),
• wherein −0.1≤x≤0.2, 0≤y≤0.4, 0≤z≤0.4, 0≤w≤0.1, y+z+w≤0.3, and M is one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Zn, B, Al, Ga, Ti, Zr, Ge, Fe, Cu, Cr, V, W, Mo, Sc, Y, Nb, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, In, and Sn.