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

A positive electrode active material includes: a lithium nickel-based oxide having a Ni content of about 60 mol % to 80 mol % among total metals excluding lithium; and a coating layer containing Ti and formed on a surface of the lithium nickel-based oxide. The lithium nickel-based oxide is of a single-particle-type including 50 or fewer nodules and has a thermal stability index (TSI) of about 42.5 or less as represented by Equation 1 according to the present disclosure. In Equation 1, the TSI is represented by “HFA×MPH/(T−150),” and HFA, MPH, and Tl are values measured from a differential scanning calorimetry (DSC) analysis graph obtained by heating a lithium secondary battery fabricated using the positive electrode active material from 25° C. to 400° C. at a heating rate of 10° C./min.