Positive active material including a shell including a metalcation, manufacturing method thereof, and positive electrode and lithium battery including the positive active material

A positive active material comprising a lithium transition metal oxide having a core-shell structure,

• wherein the lithium transition metal oxide is represented by Formula 2:
• xLi2MnO3-(1-x)LiNiaCobMncO2 Formula 2
• wherein in Formula 2,
• 0<x<1, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1,
• wherein a shell layer of the core-shell structure comprises a metal cation doped therein,
• wherein the metal cation is V, and
• wherein an amount of the metal cation is in a range of about 0.1 mole percent to about 10 mole percent, based on 1 mole of the lithium transition metal oxide.