Electrode active material for lithium secondary battery

1. A method for preparing an electrode active material comprising:

mixing a lithium-containing precursor with a transition metal-containing precursor under the condition that a molar ratio of a transition metal to lithium is higher than 1; and

heating the resulting mixture at a higher temperature, wherein the heating temperature is 10° C. or higher than a heating temperature at which lithium transition metal oxide having a layered crystal structure is prepared from a mixture of a lithium-containing precursor and a transition metal-containing precursor under the condition that the ratio of the transition metal to lithium is 1, and is lower than an oxygen deintercalation temperature of the lithium transition metal oxide,

wherein the electrode active material comprises a nickel-based lithium transition metal oxide containing nickel (Ni) and at least one transition metal selected from the group consisting of manganese (Mn) and cobalt (Co), wherein a content of nickel is 50% or higher, based on the total weight of transition metals, and

wherein the nickel-based lithium transition metal oxide has a layered crystal structure and an average primary diameter of 3 μm or higher.

2. The method according to claim 1 , wherein the ratio of the transition metal to lithium is 1.005 to 1.30.

3. The method according to claim 1 , wherein the amount of Ni 2+ taking the lithium site of the layered crystal structure is 5.0 atom % or less.

4. The method according to claim 1 , wherein the amount of Ni 2+ taking the lithium site of the layered crystal structure is 0.1 to 5.0 atom %.

5. The method according to claim 1 , wherein the amount of Ni 2+ taking the lithium site of the layered crystal structure is 0.1 to 4.0 atom %.

6. The method according to claim 1 , wherein the nickel-based lithium transition metal oxide an average primary diameter of 3 μm to 10 μm.