Patent ID: 8192711

Claim:
A process for producing a surface modified lithium-containing composite oxide for a cathode active material for a lithium ion secondary battery, wherein a lithium titanium composite oxide is contained in a surface layer of particles of a lithium-containing composite oxide represented by the formula: Li p N x M y O z F a , where N is at least one element selected from the group consisting of Co, Mn and Ni, M is at least one element selected from the group consisting of Al, Sn, alkaline earth metal elements and transition metal elements other than Co, Mn and Ni, 0.9≦p≦1.3, 0.9≦x≦2.0, 0≦y≦0.1, 1.9≦z≦4.2, and 0≦a≦0.05, which comprises impregnating a solution comprising a lithium source and a titanium source dissolved therein into a powder of the lithium-containing composite oxide, and subjecting obtained lithium titanium-impregnated particles to heat treatment at from 400 to 1,000° C., to obtain the surface modified lithium-containing composite oxide, wherein the amount of titanium contained in the surface layer is from 0.01 to 1.95 mol % to the amount of lithium-containing composite oxide used as a base material.