Secondary battery sealing process and secondary battery manufacturing method comprising the same

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

• manufacturing an electrode assembly by stacking an electrode and a separator;
• accommodating the electrode assembly in a pouch-type battery case;
• and
• thermally fusing and sealing a sealing portion that extends along an edge surface of the battery case,
• wherein the thermally fusing and sealing comprises:
• disposing the sealing portion between an anvil and a horn;
• pressing and fixing a first region of the sealing portion between the anvil and the horn;
• and
• applying a first ultrasonic wave to the first region of the sealing portion through the horn at a first frequency and a first amplitude for a first time, thereby thermally fusing the first region of the sealing portion,
• wherein the sealing portion has a stack structure that comprises a coating layer, a metal layer, and an insulating layer in a direction from an inside of the battery case toward an outside of the battery case, and a thickness of the coating layer is 30 μm to 85 μm.