Patent ID: 7851088

Claim:
A positive electrode active material for a nonaqueous electrolyte secondary battery having at least a lithium-transition metal composite oxide of a layer structure, wherein: the lithium-transition metal composite oxide is a lithium cobaltate particle, an existence ratio of zirconium and magnesium is respectively 20% or more, wherein the zirconium and magnesium are uniformly dispersed on a surface of the lithium cobaltate particle, at least a part of the zirconium on said surface is present as lithium zirconate, at least a part of the magnesium on said surface is present as magnesium oxide, and the existence ratio is a quotient of a total length of all portions of a first line that exceeds 4% of peak value divided by a length of a second line passing through a point that has a highest concentration of zirconium or magnesium, respectively, that is assigned a peak value of 100%, wherein a concentration of zirconium or magnesium, respectively, per unit area is obtained from a line analysis of the surface of the lithium-transition metal composite oxide by using an electron probe microanalyzer.