Strategies for improving the design of porous fiber felt electrodes for all-vanadium redox flow batteries from macro and micro perspectives

All-vanadium redox flow batteries (VRFBs) have emerged as a research hotspot and a future direction of massive energy storage systems due to their advantages of intrinsic safety, long-duration energy storage, long cycle life, and no geographical limitations. However, the challenges around cost constrain the commercial development of flow batteries. Increasing the power density and energy efficiency of the flow batteries is key to breaking through the cost bottlenecks, which is closely related to porous fiber felt electrodes (PFFEs), in which redox reactions take place. Therefore, it is essential to summarize advanced strategies for improving the design of electrodes, which are conducive to the further expansion of low-cost and high-performing flow batteries. This paper reviews the growth rate and market size of the flow batteries, and summarizes the latest research progress in the improvement strategies of PFFEs from macro and micro perspectives, including structure design based on the data model, intrinsic treatment, and introduction of catalysts. Finally, this review summarizes the practicability of the above strategies and the prospective modification approaches, and looks forward to the future optimization directions of PFFEs, such as exploring the modification mechanisms using advanced in situ characterization techniques, introducing high-entropy catalysts, adopting new preparation technologies, and incorporating artificial intelligence. The review offers the optimization strategies of PFFEs for flow batteries and bridges the gap between the academic literature and industrial manufacturing.