A positive active material is provided. The positive active material includes particles of lithium nickelate and an olivine compound having an olivine crystal structure, wherein surfaces of the particles of lithium nickelate are covered with the olivine compound. The lithium nickelate is expressed by a general formula LiyNi1-zM′zO2 where 0.05≦y≦1.2 and 0≦z≦0.5, and M′ includes Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, Sr and mixtures thereof. The olivine compound is expressed by a general formula LixMPO4 where 0.05≦x≦1.2, and M includes Fe, Mn, Co, Ni, Cu, Zn, Mg and mixtures thereof. A non-aqueous electrolyte secondary battery including the positive active material is also provided.