LITHIUM SECONDARY BATTERY

The lithium secondary battery according to the embodiments of the present disclosure may include a cathode which includes a cathode active material layer including a cathode active material including a lithium metal oxide having a secondary particle form in which a plurality of primary particles are aggregated, and doped with a doping element; an anode disposed to face the cathode. In addition, the lithium secondary battery may include a separation membrane interposed between the cathode and the anode, and including a substrate film and a ceramic coating layer formed on at least one surface of the substrate film. The primary particles may have an aspect ratio of 1.4 to 7.0, and a ratio of the thickness of the ceramic coating layer to the total thickness of the separation membrane may be 0.13 to 0.44.