Broad temperature adaptability of vanadium redox flow battery–part 4: Unraveling wide temperature promotion mechanism of bismuth for V2+/V3+ couple

Vanadium flow battery (VFB) is a fast going and promising system for large-scale stationary energy storage. However, drawbacks such as low power density and narrow temperature window caused by poor catalytic activity of graphite felt (GF) electrodes limit its worldwide application. In this paper, bismuth, as a low-cost, no-toxic and high-activity electrocatalyst, is used to modify the thermal activated GF (TGF) via a facile hydrothermal method. Bismuth can effectively inhibit the side reaction of hydrogen evolution in wide temperature range, while promoting the V2+/V3+ redox reaction. As a result, the VFB assembled with Bi/TGF as negative electrode demonstrates outstanding rate performance under the current density up to 400 mA cm−2, as well as a long-term stability over 600 charging/discharging cycles at a high current density of 150 mA cm−2. Moreover, it also shows excellent temperature adaptability from -10 °C to 50 °C and high durability for life test at the temperature of 50 °C.