| abstract |
Provided is a cathode active material including a compound represented by Formula 1 below. In the surface portion of the particles of the positive electrode active material, A, the molar ratio [Me / M] of an element represented by Me to an element represented by M in Formula 1, is 0.05 ≦ A ≦ 0.60, and the entire particle of one positive electrode active material is As a reference, B, which is the molar ratio [Me / M] of the element represented by Me to the element represented by Me in Formula 1, is 0.003 ≦ B ≦ 0.012, and at least a kind of Me in the inner portion of the particles of the positive electrode active material. The difference in concentration between any two points of the indicated element is less than 0.02 wt% . [Chemical Formula 1] Li 1 + x M 1 - k Me k O 2 -0.2≤x≤0.2, 0 <k≤0.05 M is one selected from Ni, Mn, Co, and a combination thereof, Me is one selected from Al, Mg, Ti, Zr, B, Ni, Mn, and a combination thereof, and M is the same element as Me Is not or does not contain the same element. |