Positive electrode active material for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery

A positive electrode active material for a non-aqueous electrolyte secondary battery, the positive electrode active material including a lithium-transition metal composite oxide having a spinel structure and represented by the general formula Li1+αNi0.5-x Mn1.5-y-zGeyMx+zO4, wherein 0≤α<0.2, 0≤x<0.2, 0<y<0.45, 0≤z<0.2, and M represents at least one or more elements selected from the group consisting of Mg, Al, Sc, Ti, Cr, V, Fe, and Co, wherein

• when, on a cross section of a secondary particle of the lithium-transition metal composite oxide, a thickness portion from a center to a ⅓ radius is defined as a central portion, and a thickness portion from a surface to the ⅓ radius is defined to as a surface portion, in the secondary particle of the lithium-transition metal composite oxide, Gesurf is higher than Gebulk, where Gesurf represents a number of moles of Ge based on a total number of moles of metal elements excluding Li being 2 in the surface portion, and Gebulk represents a number of moles of Ge based on a total number of moles of metal elements excluding Li being 2 in the central portion, and
• a ratio of the Gesurf to the Gebulk (Gesurf/Gebulk) satisfies a relation of 1.5<Gesurf/Gebulk<5.0.