Modification and application of spiral flow fields in vanadium redox flow batteries

Abstract

A suitable flow field structure could improve the mass transfer inside vanadium redox flow batteries (VRFB). However, previous flow fields based on the serpentine flow field (SFF) or the interdigitated flow field (IFF) with complex structures cannot balance the compromise between pressure drop and overpotential inside VRFBs. To further improve the mass transfer inside VRFBs and efficiently design simpler flow field structures, a 3D model is established for simulating the charge and discharge of VRFBs with different flow fields. After validating the model with experimental and simulated results, we use it to analyze the reason for the weaker performance of VRFB with the origin spiral flow field (OSFF), from which the position and number of the inlet and outlet of OSFF are minimally modified to obtain double spiral flow field with outlets at the center (DSFF(OC)) and double spiral flow field with inlets at the center (DSFF(IC)). Results indicate that under the same flow rate, DSFF(OC) could slightly improve the discharge performance of VRFB compared to SFF, resulting in the lower pressure drops than IFF. When the same pump power is applied, DSFF(OC) and DSFF(IC) both increase the energy efficiency by 7.40 % and 6.21 %, respectively, compared with SFF. Additionally, VRFB with DSFF(OC) exhibits the highest net power efficiency, especially at the lower SOC.