Bipolar plates play a crucial role in terms of weight and volume reduction of a fuel cell stack. For automotive application lightweight and thin metallic plates are inevitable to enhance power density and thus to raise market appeal of fuel cells. Shown bipolar plate has been designed within the project MIFULAS.
Coating as key technology
The use of metallic materials enables new possibilities in terms of flow field design and high-capacity production. One fuel cell stack in a car contains round about 370 bipolar plates. For though metallic surfaces underlie corrosion and accordingly passivation under fuel cell conditions, a conductive and chemically inert coating as well as a cost-efficent and scalable process is unavoidable. Shown bipolar plate has been designed within the project MIFULAS.
Benefits at a glance
By using metallic bipolar plates a distinct decrease of the weight and volume can be reached in comparison with carbon-based materials. For instance, with an electrical power density of 0.5 W/ccm and a channel depth of 0.7 mm (material thickness 0.1 mm) 80 % of weight and 60 % of volume can be saved.
Cell measurements with PRECORS bipolar plates reveal a high performance comparable with Gold coated plates that were prepared by PVD-technique. This has resulted in a cell thickness of 1.7 mm. Additionally, the hydrophilic behavior of the PRECORS coating prevents droplet formation and channel blockage. Stainless steel 316L was employed as substrate material for all coatings
Interfacial contact resistance
The contact resistance at the interface bipolar plate and gas diffusion layer is a characteristic parameter for fuel cells. PRECORS-coated bipolar plates comprise a very low contact resistance (comparable to Gold) and a high efficiency.