Mathematical modeling and numerical analysis of alkaline zinc-iron flow batteries for energy storage applications

Abstract The alkaline zinc-iron flow battery is an emerging electrochemical energy storage technology with huge potential, while the theoretical investigations are still absent, limiting performance improvement. A transient and two-dimensional mathematical model of the charge/discharge behaviors of zinc-iron flow batteries is established. After validated by experimental data, numerical analysis is carried out focusing on the influences of electrolyte flow rate and electrode geometry towards the electrochemical performance. The results demonstrate that a high flow rate, high electrode thickness, and porosity are favorable for battery performance. Following this finding, the parameters of a zinc-iron flow battery are optimized by utilizing a high flow rate of 50 mL min−1, an asymmetrical structure with a negative electrode of 7 mm and a positive electrode of 10 mm, and high porosity of 0.98. With the optimal flow rate and geometry, the electrolyte utilization, coulombic efficiency, and energy efficiency attain 98.62%, 99.18%, and 92.84%, respectively, significantly higher than those of the un-optimized design. This work provides a comprehensive strategy allowing for the improvement of the practical design of zinc-iron flow batteries.