Review of materials and processing methods used in the production of bipolar plates for fuel cells

The bipolar plate is by weight, volume and cost one of the most significant components of a fuel cell stack. The existence or creation of materials to produce bipolar plates which meet all the property requirements and can be readily manufactured to impart the fine channels represents the major challenge. Bipolar plates can be made from various materials with the most common being graphite, metal, carbon/carbon and polymer composites. Each type of material has its strengths and weaknesses. The traditional graphite plates are highly conductive and have good corrosion resistance, but are brittle and require costly machining. The metal plate has excellent bulk conductivity but its major drawback is the expense in imparting the channels and the need for a corrosion resistant coating. Carbon/carbon also requires high machining costs and the plates are subject to warping owing to chemical vapor infiltration (CVI). Materials for polymer composites are relatively inexpensive, and channels can be formed by means of a moulding process. The key is to develop a balance between sufficient electrical conductivity, processability of the resin and the mechanical properties.