Patent ID: 8377594

Claim:
A cathode active material, comprising: cathode active material particles having an average particle diameter D50 of 3 to 20 μm, said cathode active material particles comprising an agglomerated structure of an aggregate of microfine particles which have an average particle diameter D90 of 0.01 to 8 μm, said microfine particles comprising a lithium nickel-manganese-cobalt oxide represented by Formula 1, wherein the lithium nickel-manganese-cobalt oxide has a nickel content of at least 40% among overall transition metals; and polypyrrole coated on a surface of said cathode active material particles: Li x M y O 2 (1) wherein M is Ni 1-a-b Mn a Co b (0.05≦a≦0.4, 0.1≦b≦0.4, 0.4≦(1-a-b)≦0.9), x+y is about 2 and 0.95≦x≦1.15; and wherein a coating amount of polypyrrole coated on an exposed surface of the agglomeration of said cathode active material particles ranges from 0.5 to 10% by weight relative to a total weight of the active material; and a coating thickness ranges from 0.1 to 10 μm.