Positive Electrode Active Material, Method of Preparing the Same, Positive Electrode Including the Positive Electrode Active Material, and Secondary Battery Including the Positive Electrode

A positive electrode active material includes a core and a coating layer disposed on the core, wherein the core includes LiMO, wherein M is at least one element selected from the group consisting of nickel (Ni), cobalt (Co), and copper (Cu), and 1≤x≤5 and 0≤y≤2, and the coating layer includes carbon-based particles, wherein the carbon-based particle includes a structure in which a plurality of graphene sheets are connected, the carbon-based particle has an oxygen content of 1 wt % or more in the carbon-based particle, and the carbon-based particle has a D/G peak ratio of 1.55 or less during Raman spectrum measurement. A method of preparing the positive electrode active material, a positive electrode including the positive electrode active material, and a secondary battery including the positive electrode are also provided.