Current Progress and Perspective of Rechargeable Zinc-Bromine Flow Batteries

Zinc-bromine flow batteries (ZBFBs) are considered one of the most promising candidates for large-scale energy storage due to their high energy density and low cost. It has been commercially available for several years in both residential energy storage and grid-scale applications. Due to the low conductivity of the electrolyte and the high polarization in the positive electrode, this design suffers from low power density. A sluggish redox reaction occurs on bromine cathodes, leading to several drawbacks, including poor reaction kinetics, highly corrosive Br species that can cause separator corrosion and poison anodes, and volatile Br species that cause increased internal pressures. However, many opportunities remain to enhance the efficiency and stability of these batteries for long-term operation. For these purposes, it would be crucial to improve the electrolyte and electrode performance and manage the physical properties of the battery. This review focuses on the fundamental electrochemistry and functional components of ZBFBs, specifically on reaction chemistry, the development of functional materials, and their application in ZBFBs.