The present invention relates to a positive active material for an electrochemical cell including a compound having a nano-shape and represented by the following Formula 1. Lix[Li1-y-zM1yM2z]O2-αDα  [Formula 1] wherein, 0.8≦x≦1.1, 0≦y≦0.5, 0≦z≦0.5, and 0≦α≦0.05, M1 and M2 are independently selected from transition elements, and D is selected from the group consisting of O, F, S, P, and combinations thereof. The positive active material of the present invention has high reversible capacity and an excellent cycle life characteristic, and in particular, an excellent cycle life characteristic at a high rate.