Patent ID: 7476467

Claim:
A cathode active material for a secondary battery, comprising a lithium manganese-metal composite oxide (A) having a spinel structure and represented by the following general formula 1, and a lithium nickel-manganese-cobalt composite oxide (B) having a layered structure and represented by the following general formula 2: Li 1+x Mn 2−x−y M y O 4 (1) Li 1−a Ni b Mn c Co 1−b−c O 2 (2) wherein, 0<x<0.2; 0<y<0.1; M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Ti, V, Zr and Zn; −0.1≦a≦0.1; 0.3<b<0.5; and 0.3<c<0.5, wherein the content of the lithium manganese-metal composite oxide (A) is in the range of 80% to 95%, based on the total weight of the mixture, and the pH of the cathode active material is in the range of 8.9<pH≦10.2.