| abstract |
An electrode active material includes particles of a lithium-containing composite oxide represented by the general compositional formula: Li 1+x MO 2 , where −0.15≦x≦0.15, and M represents an element group of three or more elements including at least Ni, Co and Mn, wherein the ratios of Ni, Co and Mn to the total elements constituting M satisfy 45≦a≦90, 5≦b≦30, 5≦c≦30 and 10≦b+c≦55, where the ratios of Ni, Co and Mn are represented by a, b and c, respectively, in units of mol %, the average valence A of Ni in the whole particles is 2.2 to 3.2, the valence B of Ni on the surface of the particles has the relationship: B<A, the average valence C of Co in the whole particles is 2.5 to 3.2, the valence D of Co on the surface of the particles has the relationship: D<C, and the average valence of Mn in the whole particles is 3.5 to 4.2. |