Patent ID: 7727673

Claim:
A cathode active material comprising: a core active material composed of one or more complex oxide particles having an average composition represented by Li (1+x) Co (1−y) M y O (2−z) where M is magnesium and aluminum, where x, y and z range from −0.10≦x≦0.10, 0<y<0.50 and −0.10≦z≦0.20 respectively; a coating layer arranged on at least a part of the score active material, the coating layer made of a compound including lithium, and coating elements nickel and manganese, and oxygen; wherein a composition ratio between nickel and manganese ranges from less than 100:0 to 30:70 at a molar ratio of nickel:manganese, and a surface layer arranged on at least a part of the coating layer, the surface layer made of an oxide including at least one surface element selected from the group consisting of titanium, silicon, magnesium and zirconium.