Fine and dense bismuth electrocatalysts achieving high power density and cycling stability in vanadium flow batteries

Developing electrode materials that can work efficiently at high current densities while maintaining excellent stability is critical for reducing the unit cost of vanadium flow batteries (VFB). Herein, we report a Bi nanoparticles (∼10 nm) decorated thermal-active graphite felt (Bi@TGF) electrode fabricated through a simple polyvinylpyrrolidone guided approach. Fine and dense Bi electrocatalysts not only play an important role in catalyzing V2+/V3+ redox reaction, but also effectively suppress hydrogen evolution side reaction. As a result, the VFB assembled with Bi@TGF as negative electrode exhibits excellent rate performance (energy efficiency of 81.5 % at 200 mA cm−2) and extremely high peak power density (1023 mW cm−2 at 1250 mA cm−2). Moreover, Bi@TGF electrode demonstrates outstanding durability in 2500-cycle ultralong charge-discharge testing at 300 mA cm−2, with energy (voltage) efficiency retention rate of 99.2 % (98.9 %). The stable cycling ability of Bi@TGF under high operating current density endows its potential application in long-duration and high power density VFB.