A lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a non-aqueous electrolyte. The positive electrode active material comprises at least one lithium-containing composite oxide represented by the following general formula: LixM11−yM2yO2 where M1 and M2 are different elements, M1 is Ni or Co, M2 is at least one selected from Ni, Co, Mn, Mg, and Al, 1≦x≦1.05, and 0≦y≦0.7. The negative electrode active material comprises at least one selected from the group consisting of silicon, tin, a silicon-containing alloy, and a tin-containing alloy. The non-aqueous electrolyte includes an organic peroxide.