Positive Electrode Active Material, Positive Electrode and Lithium Secondary Battery Including the Same

A positive electrode active material including a lithium composite transition metal oxide containing nickel, cobalt, manganese, and aluminum. The amount of nickel among metals other than lithium in the lithium composite transition metal oxide is 90 mol. % or greater, and a molar ratio Al/Ni of aluminum to nickel is 0.015 to 0.034. A positive electrode comprises the positive electrode active material, and a lithium secondary battery comprises the positive electrode.