Positive electrode active material for lithium secondary battery, method for preparing same, and lithium secondary battery comprising same

1. A positive electrode active material for a lithium secondary battery, comprising

a lithium transition metal composite oxide represented by Chemical Formula 1:

Li a (Ni x Co y Mn 1-x-y ) b (M 1 Z M 2 1-z ) c O 2   [Chemical Formula 1]

wherein, 0.95≤a≤1.1, 0<b<1, 0<c<0.02, 0.5≤x<1, 0≤y≤0.2, and 0.65≤z<0.83; doping metals (M 1 and M 2 ) are doped to a lithium cation site in the lithium-transition metal composite oxide, and M 1 is aluminum (Al) and M 2 is molybdenum (Mo); and

an average oxidation number of the doping metals Al and Mo is in a range of 3.5 to 5, wherein the oxidation number of Al is +3 and the oxidation number of Mo is +6.

2. The positive electrode active material for a lithium secondary battery of claim 1 , wherein the x is greater than or equal to 0.8.

3. The positive electrode active material for a lithium secondary battery of claim 1 , wherein the c is greater than or equal to about 0.015.

4. The positive electrode active material for a lithium secondary battery of claim 1 , wherein the positive electrode active material for a secondary battery has an a-axis lattice parameter of 2.865 Å to 2.874 Å.

5. The positive electrode active material for a lithium secondary battery of claim 1 , wherein the positive electrode active material for a secondary battery has a c-axis lattice parameter of 14.180 Å to 14.214 Å.

6. The positive electrode active material for a lithium secondary battery of claim 1 , wherein the positive electrode active material for a secondary battery has c-axis lattice parameter/a-axis lattice parameter of 4.945 to 4.950.

7. A lithium secondary battery comprising

a positive electrode for a lithium secondary battery comprising the positive electrode active material of claim 1 ;

a negative electrode overlapped therewith; and

a separator interposed between the positive electrode and the negative electrode, and an electrolyte.