Surface modified lithium-containing composite oxide for cathode active material for lithium ion secondary battery and its production process

Abstract

To provide a surface modified lithium-containing composite oxide having excellent discharge capacity, volume capacity density, safety, durability for charge and discharge cycles, and high rate property. A surface modified lithium-containing composite oxide, comprising particles of a lithium-containing composite oxide having a predetermined composition and a lithium titanium composite oxide containing lithium, titanium and element Q (wherein Q is at least one element selected from the group consisting of B, Al, Sc, Y and In) contained in the surface layer of the particles, wherein the lithium titanium composite oxide is contained in the surface layer of the particles in a proportion of the total amount of titanium and element Q in the lithium titanium composite oxide contained in the surface layer to the lithium-containing composite oxide particles is from 0.01 to 2 mol %, and the lithium titanium composite oxide has a peak at a diffraction angle 2θ within a range of 43.8±0.5° in powder X-ray diffraction measurement in which CuKα rays are used.