Provided is a lithium secondary battery including a discharge unit capable of delaying or preventing a battery explosion. The lithium secondary battery includes a discharge unit disposed parallel to a battery body. The discharge unit includes a first electrode connected to a positive electrode of the battery body, a second electrode connected to a negative electrode of the battery body, and a discharge material film, disposed between the first electrode and the second electrode, inducing a abrupt discharge above a predetermined temperature. The discharge material film, e.g., a abrupt metal-insulator transition (MIT) material film can induce a abrupt discharge, thereby preventing or delaying a battery explosion.