Positive Electrode Active Material For Lithium Secondary Battery And Preparation Method Thereof

A positive electrode active material in the form of a single particle and a lithium secondary battery containing the positive electrode active material thereof are provided. The positive electrode active material has a nickel-based lithium composite metal oxide single particle. The single particle has a plurality of crystal grains. An average particle size (D50) of the single particle is from 3.5 μm to 8 μm. The single particle includes a metal doped in the crystal lattice thereof.