A current interrupt device for rechargeable, electrochemical cells having a safety
valve, insulating spacer and a thin metal plate for coupling to an electrode assembly
is provided. The thin metal plate electrically couples to the safety valve by way
of a conductive polymer, preferably having a positive temperature coefficient characteristic.
The positive temperature coefficient characteristic is such that the impedance
of the polymer increases with increasing temperature. In normal operation, the
polymer conducts current. In high current situations, where internal components
heat due to parasitic resistances, the polymer becomes an insulator and disconnects
the cell from the exterior can. When gasses build within the cell, the safety valve
deforms, thereby causing the safety valve to separate from the thin metal plate.
Once the safety valve and thin metal plate have separated, the electrode assembly
is electrically isolated from the exterior can.
