LITHIUM-CONTAINING NICKEL-MANGANESE COMPOSITE OXIDE, PREPARATION METHOD THEREFOR, AND POSITIVE POLE PIECE, SECONDARY BATTERY AND ELECTRIC DEVICE COMPRISING SAME

The present application provides a lithium nickel manganese-containing composite oxide, a preparation method thereof, and a positive electrode plate, a secondary battery and an electrical device. The lithium nickel manganese-containing composite oxide is a particle with a monocrystal morphology or a quasi-monocrystal morphology, the lithium nickel manganese-containing composite oxide has a spherical or spherical-like grain shape, and the lithium nickel manganese-containing composite oxide has a general formula of LiNiMzMnAO, -0.2 < x < 0.5, -0.2 < y < 0.2, 0 < z < 0.2, 0 < a < 0.2, 0 < k < 0.2, A includes one or more selected from Si, P and S, M includes one or more selected from a metal-doping element. The lithium nickel manganese-containing composite oxide provided in the present application may improve the capacity exertion, energy density and cycling life of the secondary battery.