Current distribution in a zinc–bromine redox flow battery: Modeling and simulation

In this article, we conducted a numerical investigation into the current distribution within the half-cell compartments of a zinc‑bromine redox flow battery. To achieve this, a 2D dynamic model that incorporates a two-step electron transfer mechanism for both electrode reactions was developed. The simulation results were then validated against experimental data from the literature, covering a range of current densities. The outcomes of this study revealed distinct patterns: in the positive half-cell compartment, the redox reaction occurs uniformly across the electrode surface. In contrast, in the negative half-cell compartment, the redox reaction concentrates near the separator and current collector. Notably, only 24 % of the electrode in this half-cell compartment experienced zinc deposition under typical conditions. However, this ratio increased significantly to 80 % when the reaction kinetics slowed down tenfold. Moreover, the model predictions indicated that the thickness of deposition near the separator decreases along the height of the cell due to the reduction in zinc (II) ion concentration as the electrolyte moves toward the outlet of the half-cell compartment. These findings offer potential avenues for enhancing the performance and maintenance of zinc‑bromine redox flow batteries. By reducing the risk of separator damage or electrolyte pathway blockage caused by the zinc deposition, improvements in the battery efficiency and longevity can be achieved.