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Vanadium redox flow batteries (VRFBs) have attracted much attention in the field of energy storage systems owing to their safety, long-cycle life, and feasible scalability. However, the market penetration of VRFBs is still hindered by the poor performance of current carbon-based electrodes. Herein, spent asphalt is employed as an efficient and low-cost precursor to generate carbon decorating carbon felt for VRFB applications. By thermal decomposition treatment, the spent asphalt is converted into highly active pyrolytic carbon and deposited on surfaces of carbon felt. The as-prepared carbon felt with increased active sites and improved hydrophility displays superior performance towards redox reactions of VO 2 + /VO 2 + in terms of better electrochemical reversibility and faster reaction kinetics. Therefore, the VRFB cell with the carbon felt decorated with carbon derived from spent asphalt as cathode shows 85% energy efficiency which is higher than the pristine carbon felt cathode by 9%. Meanwhile, the energy efficiency and voltage efficiency are both stable during the cell cycling. This strategy can raise the value of the spent asphalt and improve the performance of VRFBs with the decorated carbon felt electrode shedding light on their commercial applications for large-scale energy storage.

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