Cell separator plate used in fuel cell stacks

In a fuel cell stack comprising a plurality of fuel cell units, each said fuel cell unit comprising an anode, a cathode, an electrolyte in contact on one side with the electrolyte facing face of said anode and in contact on the opposite side with the electrolyte facing face of said cathode, and a separator plate forming an anode chamber between the anode facing face of said separator plate and said separator plate facing face of said anode and said separator plate forming a cathode chamber between the opposite cathode facing face of said separator plate and the separator plate facing face of the cathode of an adjacent said fuel cell unit, said anode chamber in gas communication with fuel gas supply and outlet and said cathode chamber in gas communication with oxidant supply and outlet, the improvement comprising;

• said electrolyte terminating inwardly from the periphery of said separator plate, said separator plate having a electrolyte seal structure extending outwardly from each face, said electrolyte seal structure contacting the periphery of said electrolyte completely around the periphery of said electrolyte forming a separator plate/electrolyte seal under cell operating conditions, said separator plate extending beyond the periphery of said electrolyte and having a separator plate peripheral seal structure spaced beyond the periphery of said electrolyte and extending outwardly from each face of said separator plate, and sealing means at said separator plate peripheral seal structure to form with adjacent separator plates when in said fuel cell stack a peripheral separator plate seal completely around the periphery of said separator plate thereby forming a peripheral compartment between said separator plate/electrolyte seal and said peripheral separator plate seal.