Secondary Battery

A secondary battery comprises: a pouch; an electrode assembly mounted within the pouch and having a structure in which electrodes and separators are alternately laminated, the electrode assembly having a tab connection part in which electrode tabs extending from ends of the electrodes overlap each other; a lead comprising a first lead having one end electrically connected to the tab connection part and a second lead having one end electrically connected to the first lead and the other end extending outside of the pouch, each of the first lead and the second lead being fixed to respective portions of an inner surface of the pouch; an adhesion unit mechanically and electrically coupling the first lead and the second lead to each other; and a high-voltage decomposition material that is configured to generate a gas when a high voltage having a predetermined level or more is applied to the adhesion unit.