Confronted with peak oil and the climate change strong efforts have been made to ensure individual mobility in the future, too. Different types of drive systems based on electricity have been developed to a high degree of efficiency. But whether fuel cell, super capacitor or battery: the output power and therefore the efficiency are reduced by the contact resistance of the metallic foils used as current collectors in these systems. Bipolar plates consisting of stamped stainless steel foils for example can reduce the assembly dimension as well as the weight of PEM fuel cell stacks for mobile applications compared to those made from graphite. Unfortunately, the passive layer of stainless steel shows a high electrical resistance. This reduces the electrical output of each cell. To overcome this problem, we developed a surface modification treatment to remove the passive layer and to replace it by graphite like carbon (GLC) using a modified PVD arc technique. First results show that this surface modification reduces significantly the contact resistance of the material compared to uncoated stainless steel. Furthermore, the corrosion resistance of the coated stainless steel is increased. This surface modification treatment can be applied to the current collectors of batteries and supercaps as well.
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