Development of Carbon-Polymer Composite Bipolar Plates for Vanadium Redox Flow Battery

Composite bipolar plates for vanadium redox flow battery (VRFB) were fabricated with the expanded graphite and poly(vinylidene fluoride) (PVDF). Swelling in the 5 M sulfuric acid and surface morphology of the bipolar plates were measured for the PVDF content of 3, 6, and 9%. Swelling ratio and cracks on the surface of the bipolar plates decreased with increase of the PVDF content. Swelling ratio was negligible when PVDF content is over 6%. It is because the hydrophobic and acid resistant PVDF was introduced into porous expanded graphite matrix. Based on this result, vanadium permeability test, corrosion test, through-plane resistance measurement were conducted for the bipolar plate with 6% PVDF. Smooth surface and 5 times reduced vanadium permeability was observed for the PVDF added bipolar plate. And it showed enhanced corrosion resistance and slight increase for through-pane resistance. As these results, it is considered that this composite bipolar plate is suitable for VRFB.