Process for producing lithium-containing composite oxide for positive electrode for lithium secondary battery

Abstract

To provide a cathode active material for a lithium secondary battery, which is low in gas generation and has high safety and excellent durability for charge and discharge cycles even at a high charge voltage. A process for producing a lithium-containing composite oxide represented by the formula LiLNMOF(wherein L is at least one element selected from the group of B and P, 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, alkaline earth metal elements and transition metal elements other than N, 0.9≦p≦1.1, 1.0≦q<0.03, 0.97≦x<1.00, 0≦y≦0.03, 1.9≦z≦2.1, q+x+y=1 and 0≦a≦0.02), wherein a lithium-containing composite oxide powder containing an N element and, if necessary, an M element and fluorine, is preliminarily prepared; the lithium-containing composite oxide powder is mixed with an aqueous solution containing the L element source; from the obtained mixture, an aqueous medium is removed, followed by the firing in an oxygen-containing atmosphere at from 300 to 1,050° C.