Development of multifunctional carbon composite bipolar plate for vanadium redox flow batteries

The carbon/epoxy composite bipolar plate is a promising substitute for the conventional graphite bipolar plate for the vanadium redox flow battery due to its high mechanical property and productivity. The carbon/epoxy composite bipolar plate, a multifunctional structure, requires expanded graphite coating or additional surface treatments to decrease the interfacial contact resistance. However, expanded graphite coating has low durability under vanadium redox flow battery operating condition and surface treatments are costly to implement. In this work, excess resin-absorbing method is developed with polyester fabric to uniformly remove the resin-rich layer and expose carbon fibers on the surface of the carbon/epoxy composite bipolar plate. This method not only decreases the interfacial contact resistance by exposing carbon fibers but also forms a unique ditch pattern which is desirable to fix carbon felt electrode in place. Durability against acidic environment, mechanical property, and gas permeability of the composite bipolar plate manufactured by excess resin-absorbing method is investigated.