Provided is a lithium secondary battery with improved t electrochemical characteristics through improvement of the structural stability by including a cathode active material doped with molybdenum (Mo). The lithium secondary battery includes a cathode; an anode; a separator positioned between the cathode and the anode; and an electrolyte. In particular, the cathode active material includes molybdenum (Mo) doped on a composite oxide of lithium and metal including manganese (Mn) and titanium (Ti).