Patent ID: 7718292

Claim:
A manufacturing method for a fuel cell stack, wherein the fuel cell stack includes plural cells respectively comprising: a membrane electrolyte assembly having a polymer electrolyte membrane and two electrodes, the two electrodes, which are constituted by a catalyst electrode layer and a porous gas diffusion layer, supporting the polymer electrolyte membrane from both sides; and a separator including a gas passage which supplies fuel gas or oxidizer gas to the gas diffusion layer, said manufacturing method comprising the steps of: repeating a cycle of applying and removing a load on the gas diffusion layer during manufacture of the gas diffusion layer, while comparing the thickness (T n−1 ) of the gas diffusion layer in a non-loaded state following the end of an (n−1)th cycle with the thickness (T n ) of the gas diffusion layer in a non-loaded state following an nth cycle, wherein the cycle is repeated until an amount of change (T n−1 −T n ) in a thickness of the gas diffusion layer in a non-loaded state before and after the load is applied falls to or below a predetermined value so that the electric resistance of the gas diffusion layer converges at a fixed value; forming the membrane electrolyte assembly from the gas diffusion layer after the repeating step; and laminating the cells each having the membrane electrolyte assembly, and then fastening the laminated cells.