Safety device and secondary battery using the same

摘要

A safety device having a thin plate (20, 20A, 20B, 5) of a brittle material adapted to be ruptured by a difference between pressures exerted on opposite sides thereof; and a conductive path (30, 10) provided on the thin plate (20, 20A, 20B, 5) and adapted to be cut off by the rupture of the thin plate (20, 20A, 20B, 5). One surface of the thin plate (20, 20A, 20B, 5) is present in a reference pressure chamber (50, 6). The safety device with its reference pressure chamber (50, 6) being sealed is incorporated in a secondary battery. When the secondary battery is overcharged, the pressure difference between the opposite sides of the thin plate (20, 20A, 20B, 5) is increased, so that the thin plate (20, 20A, 20B, 5) is ruptured to cut off the conductive path (30, 10).