Highly Stable Vanadium Redox‐Flow Battery Assisted by Redox‐Mediated Catalysis

With good operation flexibility and scalability, vanadium redox-flow batteries (VRBs) stand out from various electrochemical energy storage (EES) technologies. However, traditional electrodes in VRBs, such as carbon and graphite felt with low electrochemical activities, impede the interfacial charge transfer processes and generate considerable overpotential loss, which significantly decrease the energy and voltage efficiencies of VRBs. Herein, by using a facile electrodeposition technique, Prussian blue/carbon felt (PB/CF) composite electrodes with high electrochemical activity for VRBs are successfully fabricated. The PB/CF electrode exhibits excellent electrochemical activity toward VO2+ /VO2+ redox couple in VRB with an average cell voltage efficiency (VE) of 90% and an energy efficiency (EE) of 88% at 100 mA cm-2 . In addition, due to the uniformly distributed PB particles that are strongly bound to the surface of carbon fibers in CF, VRBs with the PB/CF electrodes show much better long-term stabilities compared with the pristine CF-based battery due to the redox-mediated catalysis. A VRB stack consisting of three single cells (16 cm2 ) is also constructed to assess the reliability of the redox-mediated PB/CF electrodes for large-scale application. The facile technique for the high-performance electrode with redox-mediated reaction is expected to shed new light on commercial electrode design for VRBs.