Numerical modeling of interdigitated flow fields for scaled-up redox flow batteries

Abstract

Flow fields play a crucial role in determining the electrochemical performance and pumping consumption of flow batteries. In this work, a three-dimensional model coupling fluid flow, mass transport and electrochemical reactions is developed to numerically optimize the interdigitated flow field for high-performance flow batteries. Key design parameters including the aspect ratio (length to width ratio) and the channel fraction are systematically investigated. It is revealed that large aspect ratios and small channel fractions reduce the stagnant zone within the porous electrodes, leading to superior battery performance. However, when the aspect ratio exceeds a critical value, the extremely long and narrow structure leads to uneven distribution of reactants along the channel, thereby resulting in remarkable concentration loss. By taking both the electrochemical loss and pumping consumption into consideration, the flow fields with unit widths from 1.5 to 2.5 mm and channel fractions from 0.125 to 0.375 enable the vanadium redox flow battery to deliver the lowest total power loss. Furthermore, the systematic simulation is also applied to optimize a larger unit with an active area of 540 mm2 for identifying the design principles in the scale-up. It is shown that larger aspect ratios are desirable to alleviate the dramatically increasing pumping loss.