Carbon fiber/polyethylene bipolar plate-carbon felt electrode assembly for vanadium redox flow batteries (VRFB)

The vanadium redox flow battery (VRFB) is a promising energy storage system (ESS) which can decrease the risk of power outage by storing electricity energy at non-peak time, and using at peak time. Among various ESSs, the VRFB is one of the safest and most flexible systems due to its unlimited capacity, non-explosiveness, and infinite lifetime. Since the compaction pressure on the carbon felt electrode (CFE) inside the stack of VRFB is relatively small, the electrical contact resistance between the CFE and bipolar plate (BP) largely affects the cell efficiency. In this study, a carbon fiber/polyethylene (PE) composite BP-CFE assembly has been developed to decrease the contact resistance between the BP and CFE by embedding the CFE into the PE matrix of the carbon fiber composite BP through local thermoplastic welding process to decrease the electrical contact resistance. To evaluate the performances of the BP-CFE assembly, the areal specific resistance (ASR) and gas permeability were measured. Also the acid aging tests were performed to measure the stack reliability. Finally, the performances of the BP-CFE assembly were measured and compared with those of the conventional bipolar plate during the charge/discharge cycles of a VRFB stack.