Seal for an electrochemical cell

1. An electrochemical cell, comprising:

(a) an open ended container, said container comprising a first electrode in contact with said container, a separator in contact with said first electrode, a second electrode in contact with said separator and electrolyte in contact with said first and second electrodes and said separator; and

(b) a vent assembly, having a longitudinal axis, concentrically aligned with and secured to the open end of said container, said vent assembly comprising:

i) an electrically conductive cup shaped terminal cover having a recessed central region and a rolled back edge that is approximately perpendicular to the central region;

ii) a disc shaped rupturable seal member made of a polymeric material, said seal member comprising an upstanding perimeter wall compressed between said container and said cover's rolled back edge, a terminal cover reception channel located adjacent the upstanding perimeter wall, said rolled back edge disposed within said cover reception channel, and a thin rupturable diaphragm region having a first edge and a second edge, said diaphragm region located between the seal member's upstanding perimeter wall and a centrally located hub which defines an opening through said seal member, said seal member comprising a hinge located adjacent the first edge of the thin diaphragm region and a vent located adjacent the second edge of the thin diaphragm region, said hinge having an elevation, relative to the longitudinal axis of the vent assembly, that is closer to an elevation of the vent than to an elevation of the cover's central region;

iii) a vent deflection zone, said zone defined as the space below the cover, above the diaphragm region and between the diaphragm's first edge and second edge, said zone devoid of any structural element, wherein in response to an undesirable increase in the cell's internal pressure, said seal ruptures along at least a portion of said thin diaphragm region's second edge thereby creating a vent flap and an orifice through which pressurized gas in the cell can escape, said flap rotates about the hinge and through the vent deflection zone without contacting any object; and

iv) an electrically conductive current collector that contacts said hub, extends through the opening in said seal member and contacts said second electrode, wherein said second edge of said thin diaphragm region comprises a grooved section and a nongrooved section, said grooved section defining the location of said vent and said nongrooved section defining an anchor which secures said diaphragm region to said hub.

2. The electrochemical cell of claim 1 , wherein said groove is arc shaped and concentrically aligned with the central opening in said seal member.

3. The electrochemical cell of claim 1 , wherein said nongrooved section forms at least a 30° arc.

4. The electrochemical cell of claim 1 , wherein said nongrooved section forms approximately a 100° arc.

5. The electrochemical cell of claim 1 , wherein said nongrooved section forms less than a 180° arc.

6. The electrochemical cell of claim 1 , wherein said grooved section forms an arc greater than 180°.

7. The electrochemical cell of claim 1 , wherein said grooved section forms an arc greater than 220°.

8. The electrochemical cell of claim 1 , wherein said grooved section forms an arc greater than 250°.

9. The electrochemical cell of claim 1 wherein said hinge's elevation is between the elevation of the vent and the elevation of the cover's central region.

10. The electrochemical cell of claim 1 wherein said hinge is arc shaped and concentrically aligned with the central opening in said seal member.

11. The electrochemical cell of claim 1 wherein said seal member comprises a buttress wall abutting said diaphragm region and said cover when said cell is pressurized, said buttress wall positioned to resist the compressive force exerted on said diaphragm by an increase in the cell's internal pressure.

12. The electrochemical cell of claim 1 wherein said polymeric material is selected from the group consisting of nylon, polypropylene and impact modified polystyrenes.

13. The electrochemical cell of claim 1 wherein a structural element contacts said seal member's hub.

14. The electrochemical cell of claim 1 wherein a structural element compresses said hub against said current collector.

15. An electrochemical cell, comprising:

(a) an open ended container containing at least a first electrode in contact with said container, a separator in contact with said first electrode, a second electrode in contact with said separator and electrolyte in contact with said first and second electrodes and said separator; and

(b) a vent assembly, having a longitudinal axis, concentrically aligned with and secured to the open end of said container, said vent assembly comprising:

i) a first structural element which is an electrically conductive cup shaped terminal cover having a recessed central region and a rolled back edge that is approximately perpendicular to the central region;

ii) a second structural element which is a disc shaped rupturable seal member made of a polymeric material, said seal member comprising an upstanding perimeter wall compressed between said container and the rolled back edge of the cover, a terminal cover reception channel located adjacent the upstanding perimeter wall, said rolled back edge disposed within said cover reception channel, and a thin rupturable diaphragm region having a first edge and a second edge, said diaphragm region located between the upstanding perimeter wall of the seal member and a centrally located hub, said hub defining an opening through said seal member, said seal member further comprising a hinge located adjacent the first edge of the thin diaphragm region and a vent located adjacent the second edge of the thin diaphragm region, said hinge having an elevation, relative to the longitudinal axis of the vent assembly, that is closer to an elevation of the vent than to an elevation of the central region of the cover;

iii) a third structural element which is an electrically conductive current collector that contacts said hub, extends through the opening in said seal member and contacts said second electrode; and

iv) a vent deflection zone defined as the space below the cover and above the diaphragm region, wherein in response to an undesirable increase in the cell's internal pressure, said seal ruptures along at least a portion of said thin diaphragm region's second edge thereby creating a vent flap and an orifice through which pressurized gas in the cell can escape, wherein said zone between the cover and the flap is devoid of any other structural element such that the flap rotates about the hinge and through the vent deflection zone without contacting any object, wherein said second edge of said thin diaphragm region comprises a grooved section and a nongrooved section, said grooved section defining the location of said vent and said nongrooved section defining an anchor which secures said diaphragm region to said hub.

16. An electrochemical cell, comprising:

(a) an open ended container containing at least a first electrode in contact with said container, a separator in contact with said first electrode, a second electrode in contact with said separator and electrolyte in contact with said first and second electrodes and said separator; and

(b) a vent assembly, having a longitudinal axis, concentrically aligned with and secured to the open end of said container, said vent assembly comprising:

i) a first structural element which is an electrically conductive cup shaped terminal cover having a recessed central region and an edge that is approximately perpendicular to the central region;

ii) a second structural element which is a disc shaped rupturable seal member made of a polymeric material, said seal member comprising an upstanding perimeter wall compressed between said container and the edge of the cover, a terminal cover reception channel located adjacent the upstanding perimeter wall, said edge disposed within said cover reception channel, and a thin rupturable diaphragm region having a first edge and a second edge, said diaphragm region located between the upstanding perimeter wall of the seal member and a centrally located hub, said hub defining an opening through said seal member, said seal member further comprising a hinge located adjacent the first edge of the thin diaphragm region and a vent located adjacent the second edge of the thin diaphragm region, said hinge having an elevation, relative to the longitudinal axis of the vent assembly, that is closer to an elevation of the vent than to an elevation of the central region of the cover;

iii) a third structural element which is an electrically conductive current collector that contacts said hub, extends through the opening in said seal member and contacts said second electrode; and

iv) a vent deflection zone defined as the space below the cover and above the diaphragm region, wherein in response to an undesirable increase in the cell's internal pressure, said seal ruptures along at least a portion of said thin diaphragm region's second edge thereby creating a vent flap and an orifice through which pressurized gas in the cell can escape, wherein said zone between the cover and the flap is devoid of any other structural element such that the flap rotates about the hinge and through the vent deflection zone toward the cover without contacting any object, wherein said second edge of said thin diaphragm region comprises a grooved section and a nongrooved section, said grooved section defining the location of said vent and said nongrooved section defining an anchor which secures said diaphragm region to said hub.