Lithium Secondary Battery

A lithium secondary battery comprising:

• a positive electrode including a first lithium cobalt oxide and a second lithium cobalt oxide, wherein the first lithium cobalt oxide and the second lithium cobalt oxide have different average particle diameters (D50) from each other;
• a negative electrode including first graphite and second graphite, wherein the first graphite and the second graphite have different average particle diameters (D50) from each other;
• and
• an electrolyte including a first additive comprising 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.