POSITIVE ELECTRODE ACTIVE MATERIAL FOR SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING SAME

The present invention provides a positive electrode active material for a secondary battery which includes a nickel-based lithium composite transition metal oxide including nickel (Ni), wherein the lithium composite transition metal oxide satisfies Equation 1 and Equation 2 below. 80nm≤crystallitesizeFWHM≤150nmΔsizecrystallitesizeIB−crystallitesizeFWHM≤20 wherein, in Equation 1 and Equation 2, crystallite sizeFWHM is a crystallite size obtained by calculating from X-ray diffraction (XRD) data using a full width at half maximum (FWHM) method, and crystallite sizeIB is a crystallite size obtained by calculating from XRD data using an integral breadth (IB) method.