Enhanced conductivity of fuel cell plates through controlled fiber orientation

Manufacturers of polymeric composite bipolar plates have been relying on high loadings (60 to 90 v/o) of discrete and conductive graphite/carbon filler particles to meet fuel-cell plate conductivity targets. Unfortunately, at these loadings, the plate materials are inherently brittle and result in high scrap rates and the inability to mold thin plates (less than 1 mm) required for high stack volumetric power densities. Low loadings of high-aspect-ratio conductive fillers, a fiber/flake alignment process, and a conductivetie layer (CTL) were used to simultaneously increase the plate conductivity and toughness. The alignment process reduces the bulk resistance in the current-flow direction, and the CTL reduces the contact resistance at the plate-to-diffusion medium interface. Although a significant reduction in plate resistance is realized, high filler loadings are still required to meet conductivity targets.