The present disclosure relates to a lithium secondary battery with improved safety during thermal runaway. The lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte, and has a nominal voltage of 3.68 V or greater, and VT represented by Equation (1) below measured after manufacturing a test module by stacking four of the lithium secondary battery fully charged by being charged to 4.35 V is 4 Ah/sec or less: Equation (1): VT=Ctotal/t.