Development of ultralight and thin bipolar plates using epoxy-carbon fiber prepregs and graphite composites

Using the excellent mechanical strength and in-plane electrical conductivity of epoxy-carbon fiber prepregs, we design and fabricate ultrathin composite bipolar plates (BPs) for fuel cells. For the successful fabrication of prepreg-based BPs, it is essential to increase the through-plane electrical conductivity of pristine prepregs and reduce the electrical contact resistance due to excessive surface resin extruded during compression molding. In addition, the moldability of prepreg layers should be greatly improved for the proper construction of a serpentine flow field on the prepreg surface. To resolve all these technical issues, we suggest a multilayer BP structure in which prepreg layers, pure graphite layers, and graphite-resin composite layers are combined and compression-molded. The multilayered prepreg BP is approximately 0.6 mm thick and exhibits good electrical behavior (in-plane conductivity of 172 S cm⁻¹and through-plane conductivity of 38 S cm⁻¹), with a high-quality serpentine flow channel configuration. The test results clearly demonstrate that the low through-plane electrical conductivity and poor moldability of pristine prepregs are greatly improved by our proposed BP design and fabrication.