Patent ID: 7226687

Claim:
A fuel cell stack including two or more planar electrochemical fuel cells with metallic bipolar separators disposed between the anode face of one electrochemical fuel cell and the cathode face of an adjacent electrochemical fuel cell, each of the planar electrochemical fuel cells comprising: a structural core formed of a first porous electrode material having at least one active power producing area and at least one inactive area; a plurality of fuel gas flow grooves crossing the active power-producing areas on one side of the core; a plurality of oxidant gas flow grooves arranged on the other side of the core; a dense electrolyte layer covering the active power producing areas on one side of the core; a layer formed of a second porous electrode material covering the dense electrolyte layer; and a dense electronic insulator layer covering the structural core except in the active power-producing areas; wherein each of the metallic bipolar separators comprises: a metallic plate having a first fuel gas contacting surface and a second oxidant gas contacting surface; an outer edge and inner edges surrounding interior openings through the metallic plate; and at least a portion of each of the outer edge and inner edges curled to form a tubular bead with a lumen and a seam parallel to an axis of the tubular bead.