Achieving high electrochemical performance of PEMFCs with ultrathin and highly conductive graphite-resin composite bipolar plates

Proton exchange membrane fuel cells (PEMFCs) with ultrahigh power density are highly required in recent years. In this work, breakthrough is achieved in electrical conductivity and anticorrosion capacity for the graphite-resin composite bipolar plates (BPs) under the limitation of greatly reduced thickness by high molding and high impregnation pressures (HH-BP). Interconnected laminar structure of expanded graphite (EG) is well preserved during the resin impregnation process. The power density (>1 W/cm²@ 2.75 A/cm², 75 % RH) and limiting current density (∼3.25 A/cm²@ 0.3 V, 75 % RH) are much higher for fuel cells assembled with HH-BP compared to those under other different combinations of molding and impregnation pressures. The enhancement in power density is attributed to the decreased ohmic resistance induced by the ultrahigh electrical conductivity as confirmed in electrochemical impedance spectroscopy (EIS). Ultrathin composite BPs with high electrical conductivity provide an effective approach for enhancing the power density of PEMFCs.