Secondary battery and method for manufacturing the same

A method for manufacturing a secondary battery, the method comprising:

• manufacturing an electrode assembly in which electrodes and a separator are alternately stacked;
• inserting the electrode assembly into a battery case through an opening;
• covering the opening of the battery case;
• injecting an electrolyte into the battery case through an injection hole formed in the battery case;
• closing the injection hole;
• performing a pre-formation process;
• applying external force to a switch of a gas discharge device positioned along one surface of the battery case, thereby linearly moving a gasket of the gas discharge device and opening a gas discharge hole, such that a first gas generated in the battery case is discharged to an outside of the battery case during the performing of the pre-formation process, the gas discharge device including a restoring part having first and second opposite ends, the first end contacting an inner wall of the battery case that faces the gas discharge hole, and the second end connected to the gasket, such that that elastic energy generated by the applying of the external force to the switch is stored within the restoring part;
• and
• removing the external force from the switch, thereby allowing the elastic energy stored within the restoring part to restore a position of the gasket and close the gas discharge hole.