To provide a square nonaqueous electrolyte secondary battery which is superior with respect to safety and corrosion resistance.
A square nonaqueous electrode secondary battery comprises a current cutting-off device for cutting off a current when a pressure inside a battery reaches a cut-off pressure, and a cleavage device for releasing the pressure inside the battery when the pressure inside the battery reaches a cleavage pressure, wherein the cleavage pressure is greater than the cut-off pressure. The current cutting-off device is sealed from the outside by an insulating portion 22, and a cut-off valve 12 constituting part of a conducting path disconnects the conducting path by having a curved shape reversed, when the pressure inside the battery exceeds the cut-off pressure. The cleavage device cleaves a cleavage valve 18 to release the pressure inside the battery directly to the outside, when the pressure reaches the cleavage pressure.
WATANABE AYATATSU
KAMEISHI TOSHIZO
KIHARA KOJI
WAKO DENSHI KK