Patent ID: 8497039

Claim:
A cathode active material for lithium secondary batteries, wherein the cathode active material is lithium transition metal oxide having a layered crystal structure, wherein the transition metal is a blended transition metal of Ni and Mn, and an average oxidation number of transition metals except lithium is more than +3, and specific conditions represented by the following Formulae (1) and (2) are satisfied: m (Ni)≧ m (Mn) (1) 0.4< m (Ni 2+ )/ m (Mn 4+ )<1 (2) wherein m(Ni) and m(Mn) represent a molar number of nickel and manganese, respectively, and m(Ni 2+ )/m(Mn 4+ ) is a molar ratio of Ni 2+ to Mn 4+ .