Lithium Secondary Battery

Abstract: The present invention relates to a lithium secondary battery having improved safety in the event of thermal runaway, the lithium secondary battery comprising: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; and an electrolyte, wherein the lithium secondary battery has a nominal voltage of at least 3.68 V, and a value of VP, represented by the following formula (1), of at most 4 mbar·Ah-1·sec-1. Formula (1): VP = ?P / (tmax × C) In formula (1), ?P is the difference between the maximum pressure (Pmax) in a chamber and the initial pressure (P0) in the chamber, the maximum pressure (Pmax) being measured after charging the lithium secondary battery to 4.35 V and then placing the lithium secondary battery in the chamber under an inert atmosphere and heating and exploding the lithium secondary battery, tmax is the time it takes to reach Pmax , and C is a discharge capacity measured by CC-CV charging and CC discharging the lithium secondary battery in a voltage range of 2.5 V-4.35 V at 0.33C at 25?.

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