Patent ID: 7632589

Claim:
A fuel-cell stack, comprising: a layer-stacked structure of a first cell and a second cell, wherein each cell includes a membrane electrode assembly having a polyelectrolyte membrane, and an anode and a cathode arranged so as to sandwich the polyelectrolyte membrane, wherein the anode and the cathode each comprise a catalytic layer formed on a surface of the polyelectrolyte membrane and a gas diffusion layer formed on an outer surface of the catalytic layer, and a pair of separators having groove portions formed on surfaces thereof, the separators being arranged so as to interpose the membrane electrode assembly therebetween and so as to form gas flow passages by bringing the surfaces having the grooved portions into contact with the gas diffusion layers, respectively, wherein each gas diffusion layer includes a gas-diffusion-layer base material, wherein (a) the gas-diffusion-layer base material of each anode of the first and second cells comprises a first direction and an elongation such that the gas-diffusion-layer base materials have elongation variations that are different in the anode of the first cell and the anode of the second cell in the first direction, or (b) the gas-diffusion-layer base material of each cathode of the first and second cells comprises a first direction and an elongation such that the gas-diffusion-layer base materials have elongation variations that are different in the cathode of the first cell and the cathode of the second cell in the first direction, wherein the first direction is both (i) parallel to the surfaces having the grooved portions and (ii) perpendicular to a primary direction of flow in the gas flow passages.