In this study, we report a novel copper sulfide (CuS) nanoflower-modified carbon felt (CuS-CF) electrode for polysulfide–ferrocyanide redox flow batteries (PFRFBs). Flow batteries possess several attractive features including long cycle life, flexible design, ease of scaling up, and high safety. They are considered an excellent choice for large-scale energy storage. In. Electrochemical testing revealed that the Bi/C-TCF electrode significantly outperformed the conventional TCF electrode, exhibiting reduced polarization during charge-discharge cycles and enhanced catalytic activity as evidenced by its superior reaction rate constants K 0 (2. It uses the change in the redox state of active materials in the solution. The vanadium redox flow battery (VRFB) has been regarded as one of the best potential stationary electrochemical storage systems for its design flexibility, long cycle life, high efficiency, and high safety; it is usually utilized to resolve the fluctuations and intermittent nature of renewable. These three methods are all important and effective means to modify carbon felt electrodes for flow batteries, which can effectively improve the operational efficiency and overall performance of all vanadium flow batteries.