Injection moulded low cost bipolar plates for PEM fuel cells

The development of bipolar plates that can be produced by standard mass production techniques is a main issue for the commercialization of PEM fuel cells, as bipolar plates contribute significantly to the cost structure of PEM stacks. In recent years, the University of Duisburg-Essen together with the Zentrum fur BrennstoffzellenTechnik GmbH (ZBT) has identified a number of carbon-polymer composites with densities of 1.6 g/cm(3) specific bulk conductivities between 5 and 150 S/cm and material prices between 2 and 10 euro/kg. Standard composite mixtures consist of a thermoplast and a carbon compound mixture with additional additives to increase the conductivity of the compound material. The composites generally show high corrosion resistance in the PEM fuel cell environment. Composite material samples proved to be absolutely stable in immersion tests in sulphuric acid and deionized water under pure oxygen atmosphere for several thousand hours. ZBT has successfully demonstrated the production of bipolar plates by injection moulding with cycle times of 30-60 s. With the help of tailored moulds injection moulding of bipolar plates becomes price competitive even for comparatively small series in the range of several thousand plates. PEM stacks with injection moulded bipolar plates of 2.5-4 turn thickness and an electrical power of up to 200 W have been constructed and successfully operated. (C) 2004 Elsevier B.V All rights reserved.