Patent ID: 8911902

Claim:
A positive electrode active material for a secondary lithium battery comprising lithium nickel complex oxide material having a surface portion and a core portion, in which lithium ions are distributed in a concentration gradient decreasing from the surface portion to the core portion of the lithium nickel complex oxide material; wherein the surface portion of the positive active electrode material comprises a lithium nickel complex oxide represented by Formula 2 below, and a core portion of the positive active electrode material comprises a lithium nickel complex oxide represented by Formula 3 below: Li a [Ni x Co y Mn z ]O 2 <Formula 2> wherein in Formula 2, 1.1≦a≦1.2, 0.5≦x≦0.6, 0.2≦y≦0.3, 0.2≦z≦0.3, and x+y+z=1; and Li a [Ni x Co y Mn z ]O 2 <Formula 3> wherein in Formula 3, 0.8≦a≦0.9 0.5≦x≦0.6, 0.2≦y≦0.3, 0.2≦z≦0.3 and x+y+z=1, and wherein, in the lithium nickel complex oxide, a mole ratio of lithium to nickel of the surface portion of the lithium nickel complex oxide is from 1.22 to 1.5 times a mole ratio of lithium to nickel of the core portion of the lithium nickel complex oxide.