Lithium Secondary Battery

The present invention provides a lithium secondary battery which includes a positive electrode including a first lithium cobalt oxide and a second lithium cobalt oxide which have different average particle diameters (D) from each other, a negative electrode including first graphite and second graphite which have different average particle diameters (D) from each other, and an electrolyte including a first additive as a nitrile-based compound, wherein the first lithium cobalt oxide and the second lithium cobalt oxide each independently contain aluminum in a concentration of 2,500 ppm to 4,000 ppm.