Positive electrode active material, and positive electrode and lithium secondary battery including same

Abstract

A positive electrode active material having low nickel disorder and high particle strength in a crystal structure, capable of implementing a battery having excellent capacity properties and capacity retention, and a positive electrode and a lithium secondary battery including the same. The positive electrode active material includes a large-diameter lithium transition metal oxide and a small-diameter lithium transition metal oxide whose average particle diameter (D) is smaller than that of the large-diameter lithium transition metal oxide. The large-diameter lithium transition metal oxide and the small-diameter lithium transition metal oxide each independently have a composition represented by Formula 1, and a crystal grain size of 100 nm to 150 nm. The difference in crystal grain size between the large-diameter lithium transition metal oxide and the small-diameter lithium transition metal oxide is less than 40 nm, and the positive electrode active material has a nickel disorder (Ni-disorder) of 1.5% or less.