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

A lithium metal composite oxide powder having a layered crystal structure, the powder 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 one or more elements selected from the group consisting of B, Si, S, and P,
• a ratio of a content of the element M to a total amount of Ni and the element X in the lithium metal composite oxide powder is 0.01 mol % or more and 5 mol % or less,
• a ratio of a content of Ni to the total amount of Ni and the element X, which is indicated by Ni/(Ni+X), in the lithium metal composite oxide powder is 0.4 or more in terms of a mole ratio, and
• the following (1), (2), and (3) are satisfied,
• (1) a mole ratio between element concentrations of Li and the element M that is indicated by Li/element M continuously increases from a particle surface to a particle center of the lithium metal composite oxide powder,
• (2) a mole ratio between element concentrations of O and the element M that is indicated by O/element M continuously increases from the particle surface to the particle center of the lithium metal composite oxide powder, and
• (3) a mole ratio between the element concentrations of the element M and O that is indicated by element M/O inside the particle of the lithium metal composite oxide powder is 0.05 or less.