Lithium-containing composite oxide and its production method

Abstract

The present invention provides a lithium-containing composite oxide for a positive electrode for a lithium secondary battery, which has a large volume capacity density and high safety, and excellent durability for charge and discharge cycles and charge and discharge rate property, and its production method. The lithium-containing composite oxide is represented by the general formula LiNMOF(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≦1.2, 0.965≦x<2.00, 0<y≦0.035, 1.9≦z≦4.2, and 0≦a≦0.05), wherein when a powder of the lithium-containing composite oxide is classified into small particles with an average particle size of 2 μm≦Ds≦8 μm and large particles with an average particle size of 10 μm≦Dl≦25 μm, a content of the small particles is from 15 to 40% by weight and a content of the large particles is from 60 to 85% by weight, and 0.01≦ys≦0.06, 0≦yl≦0.02 and 0≦yl/ys<1, where (ys) is a ratio of the M element in the above general formula in the small particles and (yl) is a ratio of the M element in the general formula in the large particles.