The present invention is directed to a lithium secondary battery comprising an anode comprising an anode active material, a cathode comprising a cathode active material, and a polymer membrane, wherein the polymer membrane is disposed between the cathode and the anode, wherein the anode active material comprises a mixture of at least two kinds of lithium metal oxide particles having different mass median particle diameters D50, wherein the lithium metal oxide particles are secondary particles comprising primary particles, the mixture comprises first lithium metal oxide particles having a mass median particle diameter D50 of 1 nm to less than 3 μm, second lithium metal oxide particles having a mass median particle diameter D50 of 3 μm to 30 μm, and a mix ratio of the first lithium metal oxide particles to the second lithium metal oxide particles is 70:30 to 30:70.