Positive electrode active material for lithium ion secondary battery

A positive electrode active material for a lithium ion secondary battery, comprising:

• a material represented by LiCo(1−α−β)A(α)B(β)O2, wherein
• element A is selected from the group consisting of Mg, Sc, Ti, Fe, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ru, Rh, Pd, In, Sn, Hf, Ta, W, Re, Cr, Y, Sb, Lu, Au, Pb, Er and combinations thereof, and element B is selected from the group consisting of Na, Al, Si, Ge, Mn, Ca, Te, Hg, Bi, La, Ce, Pr, Nd, Sm, V and combinations thereof;
• a difference between an ionic radius of the element A and an ionic radius of lithium is equal to or less than 20%, and a difference between an ionic radius of the element B and the ionic radius of lithium is equal to or more than 25%;
• a total doping amount (α+β) of the elements A and B satisfies 0.1 mol %≤α+β≤8 mol %, a doping amount α of the element A satisfies 0.05 mol %≤α≤5 mol %, and a doping amount β of the element B satisfies 0.05 mol %≤β≤5 mol %;
• an average valence of the element A is from 1.5 to 3.5, and an average valence of the element B is from 2.0 to 4.0;
• the element A is uniformly distributed in particles of the positive electrode active material;
• and
• the element B has a higher concentration on a surface of the particles than an inside of the particles.