Roll-to-Roll Coating and Forming of Stainless Steel for Metallic Bipolar Plates

Bipolar plates are an essential component of electrochemical cells and are used in fuel cells for media supply and electrical contacting, for example. The media supply is realized by flow fields, which are introduced into the plates by shaping processes. Metallic bipolar plates are coated to increase their electrical conductivity and service life. There is a considerable need for research into materials, processes and manufacturing strategies in order to develop cost-effective solutions that are suitable for mass production. Manufacturing strategies based on roll-to-roll processes offer considerable potential and are being further developed for this purpose. The latest developments in this area were addressed within a Fraunhofer project. Both the coating of steel strip with carbon-based coatings and the subsequent forming of the steel strip were investigated. It was shown that PVD coatings from strip processes and batch processes are electrically and electrochemically comparable. Furthermore, it was shown that the coated steel strips are formable and that the production of bipolar half-shells is possible.