Overcharge protection battery vent

A cell cap subassembly for controlling pressure build-up in a cell, said cell cap subassembly comprising:

• a terminal contact for making electrical contact with an external circuit;
• a conductive deflection member in electrical contact with said terminal contact and including a pressure rupturable region;
• and
• a conductive pathway making a pressure contact with said conductive deflection member, said conductive pathway providing at least a portion of a pathway for electrons flowing between said pressure contact and an electrode, wherein said conductive deflection member deflects under a first defined pressure such that said pressure contact is opened and said pressure rupturable region ruptures under a second defined pressure which is greater than said first defined pressure.

A method for controlling pressure build-up in a cell, the method comprising the following steps:

• providing a cell having a cell cap subassembly and a cell interior, the cell cap subassembly including a flip-burst disk having a substantially dome shaped flip portion in electrical communication with a terminal contact, said flip portion being provided in a position in which it protrudes away from said terminal contact under a pressure that is below a first defined pressure and provides contact to an electrical pathway to an electrode in the cell, said flip portion also having an inverted position in which it protrudes toward said terminal contact and does not make contact with said electrical pathway, and said flip portion also having a pressure rupturable region;
• inverting said flip portion when exposed to said first defined pressure in the cell, whereby electrical contact is opened between said electrode and said cell terminal contact;
• and
• rupturing said flip portion at said pressure rupturable region when exposed to a second defined pressure in the cell which is greater than said first defined pressure, whereby a fluid pathway is provided from the cell interior to the cell exterior when the flip portion breaks.

A lithium ion cell comprising:

• (a) a cell container having a cell cap subassembly including
• (i) a terminal contact for making electrical contact with an external circuit,
• (ii) a conductive deflection member in electrical contact with said terminal contact and including a pressure rupturable region, and
• (iii) a conductive pathway making a pressure contact with said conductive deflection member, said conductive pathway providing at least a portion of a pathway for electrons flowing between said pressure contact and an electrode, wherein said conductive deflection member deflects under a first defined pressure such that said pressure contact is opened and pressure rupturable region ruptures under a second defined pressure which is greater than said first defined pressure;
• (b) an anode provided within the cell container and capable of intercalating lithium during charge and deintercalating lithium during discharge, the anode including a specified anode material;
• (c) a cathode provided within the cell container and capable of taking up lithium on discharge and releasing lithium on charge, the cathode including a specified cathode material;
• and
• (d) an electrolyte conductive to lithium ions and provided within said cell container.