Optimization of Conductive Coatings for Graphite–Carbon Felt Composites in Flow Batteries

The carbon felt electrode contacts the graphite bipolar plate through assembly pressure.The assembly pressure affects the battery's internal resistance.An electrically conductive adhesive (ECA) coating can effectively increase contact area and reduce internal resistance.In this study, a new type of graphite-carbon felt composite plate for a flow battery is proposed.The composite plate comprises three parts: a graphite bipolar plate, a conductive coating, and a hydrophilic carbon felt electrode.These parts can reduce the interfacial resistance between the graphite plate and the carbon felt.The ECA is applied between the graphite plate and the carbon felt to bond them as a whole module.To test the battery module assembled with a conductive coating, the interfacial resistance of the battery assembly and the cell performance were investigated.The optimal bonding parameters were determined using different ECA bonding techniques: coating method (brush painting), adhesive (high-viscosity commercial ECA), and number of coating layers (four).Herein, the conductive coating applied to the graphite-carbon felt composite plate reduces interfacial resistance from 2.15 to 0.85 Ω•cm 2 , achieving a >60% reduction and thereby addressing the interfacial resistance between the electrodes (key components of the battery) and the bipolar plate.Moreover, the conductive coating establishes a practical pathway for rapid electron transmission.Several conductive coatings were applied to the flow battery cell for performance testing, and the best performance improvement was achieved with four layers of high-viscosity commercial ECA at a current density of 60 mA/cm 2 , yielding a voltage efficiency of 90.4% and an energy efficiency of 81%.Energy efficiency increased by 8.4% compared with the battery without a conductive coating.