SECONDARY BATTERY

The present invention relates to a secondary battery. The secondary battery according to the present invention comprises an electrode assembly in which a positive electrode, a separator, and a negative electrode are alternately combined to be stacked; and a pouch that accommodates the electrode assembly therein. The separator comprises a first separator disposed between the positive electrode and the negative electrode and having a through-hole penetrated in a direction that faces the positive electrode and the negative electrode, and a second separator covering the through-hole of the first separator and having an end connected to the pouch. When an internal gas is generated due to overcharging, the pouch is expanded to allow the second separator to move to open the through-hole of the first separator to cause the positive electrode and the negative electrode to contact each other via the through-hole.