Composite positive electrode active material, method of preparation, and related device including same

The invention relates to a composite positive electrode active material and a preparation method thereof, and a related device comprising the composite positive electrode active material. The composite positive electrode active material comprises a conductive tubular body and an active material layer arranged on the surface of the conductive tubular body, the active material layer comprises a compound with the molecular formula of Li1 + xMnyNizCo (1-x-y-z) O2, x is more than 0 and less than 1, y is more than 0 and less than 1, z is more than 0 and less than 1, and x + y + z is more than 0 and less than or equal to 1. When the composite positive electrode active material is applied to a battery monomer, the rate capability of the battery monomer can be improved.