Progress on the electrode materials towards vanadium flow batteries (VFBs) with improved power density

The vanadium flow battery (VFB) has been considered as one of the most promising large-scale energy storage technologies in terms of its design flexibility, long cycle life, high efficiency and high safety. However, the high cost prevents the VFB technology from broader market penetration. Improving the power density of the VFB is an effective solution to reduce its cost due to the reduced material consumption and stack size. Electrode, as one of the main components in the VFB, providing the reactions sites for redox couples, has an important effect on the voltage loss of the VFB associated with electrochemical polarization, ohmic polarization and concentration polarization. Extensive research has been carried out on the electrode modification to reduce polarizations and hence improve the power density of the VFB. In this review, state-of-the-art of various modification methods on the VFB electrode materials is overviewed and summarized, and the future research directions helpful to reduce polarization loss are presented.