Understanding and enhancing the under-rib convection for flow-field structured vanadium redox flow batteries

Abstract

The under-rib convection, driven by the pressure differences between neighboring channels, plays a crucial role in determining the performance of flow-field structured vanadium redox flow batteries. However, the correlation between key geometric characteristics and under-rib convection is unclear, limiting the exploration of flow-related transport mechanisms and the development of high-performance flow fields. In this work, a three-dimensional model integrating fluid flow, mass transport, and electrochemical reactions is developed, and the under-rib convection is enhanced by tailoring the critical geometric characteristics adopting a rotary serpentine flow field as an example. Results show that variations in channel fraction and channel depth can mitigate concentration polarization by influencing the active material transport velocity within a localized region (i.e., under-rib convection intensity) without deteriorating the distribution of active material transport. More remarkably, the battery with the optimal geometric characteristics is able to deliver a preferable total pump-based efficiency (91.4 %) at a current density of 150 mA cm⁻² and a flow rate of 40 ml min⁻¹. This study offers a comprehensive analysis of the correlation between flow field geometric characteristics and under-rib convection to serve as guidance for the design of high-performance vanadium redox flow batteries.