A study on continuous carbon/epoxy composite bipolar plates for PEM fuel cells

Abstract

In this study, in order to increase the electrical conductivity, a carbon composite-metal hybrid bipolar plate has been developed using pre-forming method followed by surface treatments. The pre-formed metal foil reduces the residual stress between the composite and metal foils, which helps prevent delamination between the composite and metal foils. The composite surface has been treated both with graphite coating and plasma treatment to increase the contact area between the carbon fiber and the gas diffusion layer (GDL). The conductive particles were embedded into the bipolar plate to reduce the bulk resistance of the composite bipolar plates. Carbon black and the natural graphite powder were used with spraying method. Unit cell test results have proved that the developed composite-metal hybrid bipolar plates with reduced total electrical resistance increase the cell performance. Conventional bipolar plates for proton exchange membrane (PEM) fuel cells should use rubber gaskets to seal the stack, which requires additional curing process at high temperature and increases the manufacturing and assembling time. In order to reduce assembling time of fuel cell stacks and obtain the gas sealability without using extra gasket and curing cycle, innovative gasketless carbon composite bipolar plates were developed. To ease the assembling of cell stacks, special grooves on the edge of the composite bipolar plate were provided for mechanical joining, whose behavior under the stack compaction pressure conditions were investigated by FE analysis. The sealability of the gasketless bipolar plate with grooves was tested to verify the integrity of the design. Various surface modifications were applied to increase the sealability of the gasketless bipolar plate under the multi-stacking condition. The multi-groove behavior of the treated surface under compaction pressure was investigated by FE analysis. The multi-layer gas sealibility test with a sub-gasket material (PTFE) was ...