POSITIVE ELECTRODE ACTIVE MATERIALS, POSITIVE ELECTRODES, AND RECHARGEABLE LITHIUM BATTERIES

A positive electrode includes a positive electrode active material that includes a lithium nickel-based composite oxide and is in a form of a single particle. A ratio of a volume cumulative average particle diameter (D) of the positive electrode active material measured using a particle size analyzer to a grain size of the positive electrode active material measured using backscatter electron diffraction after ion milling of the positive electrode is about 1.6 to about 1.8.