Secondary battery and secondary battery control method

A secondary battery comprising:

• a power generation element having at least one unit cell layer including a positive electrode, a separator and a negative electrode stacked in that order;
• an electroconductive member disposed on at least one outward side of the power generation element in a direction in which the unit cell layer is stacked with an electrical insulation member interposed between the electroconductive member and the power generation element;
• an external short circuit electrically connecting the electroconductive member to an electrode of an opposite polarity to that of an electrode on an outermost layer of the power generation element where the electroconductive member is disposed;
• a current detector arranged to detect whether or not current is flowing to the external short circuit;
• and
• an external discharge safety circuit provided with an opening-closing device that electrically insulates a path between the positive electrode of the power generation element and the negative electrode of the power generation element when the current sensor has not detected current, and short-circuits the path between the positive electrode of the power generation element and the negative electrode of the power generation element outside the power generation element when the current sensor has detected current.