Polymer electrolyte fuel cell provided with a tightening pressure

A polymer electrolyte fuel cell comprising a cell stack having a plurality of unit cells tightened in a stacking direction of the stack, each unit cell comprising:

• an electrolyte membrane-electrode assembly comprising a hydrogen ion conductive polymer electrolyte membrane and first and second electrodes respectively placed on opposite major surfaces of the electrolyte membrane, each of the electrodes comprising a gas diffusion layer and a catalyst layer;
• the gas diffusion layer comprising a non-woven fabric, a first electrically conductive separator plate contacting the first electrode and having a first gas flow channel for supplying and exhausting a fuel gas to and from the first electrode;
• and a second electrically conductive separator plate contacting the second electrode and having a second gas flow channel for supplying and exhausting an oxidant gas to and from the second electrode, at least two laterally spaced-apart sealing members, each sealing member encircling a periphery of one of at least two laterally spaced-apart manifold holes in at least one of the separator plates, and
• end plates and tightening members being disposed so as to sandwich the cell stack for applying a tightening pressure to each of the first and second electrodes,
• wherein each of the sealing members is configured to be placed in contact with a surface of each first electrically conductive separator plate and each second electrically conductive separator plate,
• wherein the electrolyte membrane-electrode assembly has a short-circuit conductivity of not greater than 1.5 mS/cm2, which is measured by applying a constant DC voltage to the electrolyte membrane-electrode assembly to obtain a steady-state current or by applying a constant DC current thereto to obtain a steady-state voltage and converting the steady-state current or the steady-state voltage, by calculation, to the short-circuit conductivity of not greater than about 1.5 mS/cm2,
• wherein a tightening pressure applied to each of the first and second electrodes is about 4.0 to 8.0 kgf/cm2 of a contact area of each of the first and second electrodes with its respective electrically conductive separator plate, wherein the tightening pressure is obtained by subtracting an elastic recovery force of the sealing members of the separator plates from a total tightening load of the cell stack to obtain a tightening load to the electrode, and dividing the tightening load by the contact area,
• wherein at least one of the first gas flow channel and the second gas flow channel has a form of a groove having lateral groove walls, and wherein a groove wall of at least one of the first gas flow channel and the second gas flow channel is tapered so that a top of the groove is wider than a bottom of the groove.