Method for cooling battery

A method for cooling a battery including

• a power generation element including an all-solid-state battery stack, and
• an exterior member including a laminate film housing the power generation element and having a peripheral edge joined by thermal welding to seal the power generation element,
• an electrode terminal of the power generation element extending from a joint portion of the exterior member, the method comprising:
• detecting a terminal temperature of the joint portion from which the electrode terminal extends;
• cooling the joint portion by fully opening a flow rate control valve provided in a flow path of a heat exchanger corresponding to the joint portion and increasing a flow rate of a heat medium in the flow path in a case where the terminal temperature is higher than a first predetermined value;
• and
• cooling the battery by the heat medium flowing through an entire flow path of the heat exchanger in a case where the terminal temperature is equal to or lower than the first predetermined value, wherein
• the heat medium flowing through the flow path is a liquid cooling medium, and
• a thermoplastic resin sheet is disposed between the electrode terminal and the exterior member at the joint portion.