Carbon composite hybrid bipolar plates with bypass-connected gas diffusion layers for PEM fuel cells

Abstract

The bipolar plates of proton exchange membrane (PEM) fuel cell systems serve many functions, such as electrically connecting cells in series, separating gases in adjacent cells and providing structural support for the stack and flow channels of water and gases. Although carbon fiber composite bipolar plates have high strength and stiffness as well as corrosion resistance in acidic environments, they do not yield a sufficiently high electrical conductance, which compromises the efficiency of PEM fuel cells.To increase the electrical conductance of the bipolar plate, a composite hybrid bipolar plate with bypass-connected gas diffusion layers (GDLs) has been developed. The graphite foil coating method, which was developed in preceded study, is applied to decrease the contact resistance between the bipolar plates and the GDLs. Moreover, to minimize the contact resistance between the hybrid bipolar plates and gas diffusion layers by allowing continuous electron conduction though the unit cell, a bypass connection is made between the bipolar plates and the GDLs. The experimental results show that the developed hybrid bipolar plate has a 98% lower electrical resistance than the conventional composite bipolar plates.