A high-rate and long-life zinc-bromine flow battery

Zinc-bromine flow batteries (ZBFBs) offer great potential for large-scale energy storage owing to the inherent high energy density and low cost. However, practical applications of this technology are hindered by low power density and short cycle life, mainly due to large polarization and non-uniform zinc deposition. In this work, a systematic study is presented to decode the sources of voltage loss and the performance of ZBFBs is demonstrated to be significantly boosted by tailoring the key components (electrolyte, electrodes, and membranes) and operating conditions (flow rate and temperature). Results show that the optimized battery exhibits an energy efficiency of 74.14 % at a high current density of 400 mA cm⁻² and is capable of delivering a current density up to 700 mA cm⁻². Furthermore, a peak power density of 1.363 W cm⁻² and a notable limiting discharge current density of ∼1.5 A cm⁻² are achieved at room temperature. More remarkably, the battery is stably operated for over 1200 cycles (∼710 h) at 200 mA cm⁻² and 60 mAh cm⁻², which sheds light on the development of high-rate and long-life ZBFBs for next-generation energy storage.