Holey-engineered electrodes for advanced vanadium flow batteries

Vanadium flow battery (VFB) has received tremendous attention because of its advantages such as long lifespan, easy to scale and flexible operation. Fabricating novel electrodes with high power density and wide operating temperature is critical to promote the practical application of VFB for all-climate energy storage. In this work, we describe a well-controlled method to prepare holey-engineered porous graphite felt (PGF) electrodes, in which nanosized pores are evenly distributed on the microscale graphite fibers of the graphite felt. Owing to its excellent electrolyte wettability and greatly enhanced surface area, the as-prepared PGF electrode exhibits high electrochemical activity towards VO2+/VO2+ and V2+/V3+ redox couples. As a result, the VFB single cell assembled with PGF electrodes demonstrates outstanding rate performance under current density up to 300 mA cm−2. The resulting PGF electrode also exhibits superior long-term stability over 3000 charging-discharging cycles at a high current density of 150 mA cm−2, and wide temperature adaptability from − 20 °C to 60 °C.