A Zinc–Bromine Flow Battery with Improved Design of Cell Structure and Electrodes

Abstract

AbstractThe zinc–bromine flow battery (ZBFB) is regarded as one of the most promising candidates for large‐scale energy storage owing to its high energy density and low cost. However, because of the large internal resistance and poor electrocatalytic activity of graphite‐ or carbon‐felt electrodes, conventional ZBFBs usually can only be operated at a relatively low current density, which limits their widespread application. Herein, we propose an asymmetrical cell by replacing the conventional thick felt electrode with a thin and electrocatalytically active carbon‐paper (CP) electrode interfacing with a flow‐field structure. With the enhanced electrocatalytic activity of CP for the Br2/Br− redox reaction and the reduced internal resistance of the thinner electrode, the ZBFB with this newly proposed structure exhibits an energy efficiency of up to 83.5 % at a current density of 40 mA cm−2, much higher than that with a graphite‐felt electrode of only 73.0 %. Remarkably, the battery can even be operated at a high current density up to 100 mA cm−2 while maintaining an energy efficiency of more than 70 %, demonstrating an excellent rate capability.