Fabrication of stainless steel bipolar plates for fuel cells using dynamic loads for the stamping process and performance evaluation of a single cell

In this study, a dynamic load (square wave) is applied to bipolar plates in order to reduce forming defects from the stamping process. Four round (R) sizes of die (R 0.05, 0.1, 0.2, 0.3 mm) are applied to edges that ran from the channel to the rib of the stamping die. Fuel cell performance tests are carried out to analyse the depth and shape of bipolar plate channels formed according to the load conditions, and the effect of the die size on the fuel cell performance is evaluated. The depth of the bipolar plate channel increase with the round size of die regardless of the load type. The shape of the channel formed with a die of R 0.05 mm is trapezoidal, while that formed with a die of R 0.3 mm is triangular. Triangular channels have a higher current density than trapezoidal channels. A higher current density can be obtained with a square load than with a conventional straight load because the former produces a deeper and more uniform bipolar plate channel. The current density of a bipolar plate with a triangular channel formed by a square load with a die of R 0.3 mm is 531 mA cm−2. After TiN coating, the current density is 784 mA cm−2, which is about 58% of that of a graphite bipolar plate.