Fuel cell stack and method of producing fuel cell stack

A method of producing a fuel cell stack comprising a stack body comprising:

• a plurality of power generation cells stacked in a stacking direction, the power generation cells each comprising a membrane electrode assembly and metal separators provided on both sides of the membrane electrode assembly, the membrane electrode assembly comprising an electrolyte membrane and electrodes provided on both sides of the electrolyte membrane,
• the metal separator being provided with a seal line configured to prevent leakage of fluid from a portion between the membrane electrode assembly and the metal separator to outside, and
• the seal line comprising:
• a seal bead protruding from a surface of the metal separator on a side where the membrane electrode assembly is positioned;
• and
• a rubber seal member interposed between a top part of the seal bead and a frame provided in an outer peripheral portion of the electrolyte membrane or provided along an outer periphery of the electrolyte membrane,
• the method comprising the steps of:
• preparing the plurality of power generation cells;
• and
• applying a tightening load to the power generation cells in the stacking direction in a state where the plurality of power generation cells are stacked together, to deform the seal bead and the rubber seal member in the stacking direction, wherein
• the top part of the seal bead protrudes in a curved shape toward the membrane electrode assembly before the tightening load is applied to the stack body,
• in the step of applying the tightening load to the power generation cells in the stacking direction, the top part of the seal bead is deformed by being pressed in a direction opposite to the membrane electrode assembly, and the rubber seal member is deformed by compression, and
• a thickness, in the stacking direction, of the rubber seal member forming the power generation cell prepared in the preparing step is set such that, when the tightening step is performed, an amount of deformation of the rubber seal member in the stacking direction is larger than an amount of deformation of the seal bead in the stacking direction.