| abstract |
A positive electrode active material for a magnesium secondary battery, and a positive electrode for a magnesium secondary battery and a magnesium secondary battery in which the positive electrode active material is used are provided. The positive electrode active material consists of a magnesium composite oxide which is represented by Formula (1): Mg x M1 y M2 z O 2 and which has a rock salt-type crystal structure of space group Fm-3m. In Formula (1), M1 is Ni, Co, or Mn, M2 is different from M1 and is at least one element selected from the group consisting of Ni, Co, Mn, Ti, V, Cr, Fe, Cu, Nb, W, Mo, and Ru, 0<x≤1, 0<y<2, 0<z<1; and 1.5≤x+y+z≤2.0. |