To provide a method for manufacturing a lithium nickel compound wherein a part of Ni site is substituted with Mn in which uniformity of the composition of the lithium nickel compound oxide can be maintained, and to use the lithium nickel compound oxide produced with the manufacturing method as a cathode active material so as to obtain a lithium secondary battery having high capacity and an excellent cycle characteristics especially when used at high temperature.

Ni and Mn as an essential substituted element are separated out in a compound hydroxide by liquid-phase reaction method (precipitation method). Then mixing a lithium compound in this compound hydroxide and calcining and forming the mixed raw materials, the lithium nickel compound oxide is produced. The lithium nickel compound oxide product in this manner is used as a cathode active material and composing a lithium secondary battery.