High Ambient Pressure Tolerant Battery Cell

Disclosed herein is a design for an electrochemical energy-storage cell that can withstand high pressure environments. The cell has a gas-tight cell housing that encloses an electrolyte in contact with an electrode assembly. The cell housing defines a cell volume. A pressure-equalizing member is connected to the cell housing and constructed to displace a portion of the cell volume to equalize a pressure differential between an external pressure on the cell and an interior pressure of the cell. The electrolyte remains in a liquid or gas phase when the pressure-equalizing member displaces the portion of the cell volume and equalizes the pressure differential.