A convection-enhanced flow field for aqueous redox flow batteries

In this work, we propose and fabricate a convection-enhanced flow field for aqueous redox flow batteries. Similar to the conventional single serpentine flow field, the new flow field here has an inlet and outlet, but the repatterned flow path induces higher pressure differences between adjacent flow channels over the entire electrode surface, thereby enhancing the under-rib convection between adjacent flow channels. The application of the new flow field to a vanadium redox flow battery enables substantial performance improvements. At 1.67 mL min⁻¹ cm⁻², which is a typical flow rate for a kilowatt-class VRFB stack, the energy efficiency, and electrolyte utilization reach 75.3% and 49.6% at a current density of 250 mA cm⁻², increasing by 10.0% and 33.3% as opposed to the use of the conventional serpentine flow field, respectively. Three-dimensional numerical modelling shows that the improved performance is ascribed to the more uniform in-plane distribution of reactants and current with the new flow field. Another important finding of this work is that there is a critical flow rate above which energy efficiency tends to stabilize for a given current density.