Graphite/resin composite bipolar plate has aroused wide public concern due to its good moldability, high flexural strength and electrical conductivity, good corrosion resistance. In this paper, carbon nanofibers's high strength,high electrical and thermal conductivity as well as excellent surface size effect was utilized to enhance the performance of graphite / resin composite bipolar plates.
Expanded graphite is widely used as the conductive filler, polyimide and benzoxazine as binder. The mixing method of expanded graphite and resin with large density difference was studied and the effect of resin content, molding temperature and pressure, holding time were also investigated. Using artificial graphite as the conductive filler and the above two kinds of resin as the binder, the paper investigated the effect of resin content, molding pressure and holding time on the properties of composite bipolar plate. The experiment focused on flexural strength, through-plane conductivity, in-plane conductivity and corrosion rate of the composite bipolar plate.
The catalyst was prepared by incipient wetness impregnation. Carbon nanofibers/graphite composite material was synthesized by the method of catalytic chemical vapor deposition through in-situ growth of carbon nanofibers on the surface of expanded graphite and artificial graphite. After mixing the composite material with the resin, the composite was shaped by thermal molding technique. The effect of carbon nanofibers under different catalyst loading and growth time of carbon nanofibers on the performance of the composite bipolar plate were studied. The results showed that appropriate amount of carbon nanofibers on the surface of expanded graphite could enhance the through-plane conductivity, however,the in-plane conductivity decreased significantly and flexural strength changed slightly. Artificial graphite/resin composite bipolar plate has high performance in many aspects, but the performance declined after carbon nanofibers were grew on the surface of artificial graphite.