Synchronized dual-modified graphite felt electrodes for all-vanadium redox flow batteries with high power density and ultra-long lifespan

All-vanadium redox flow battery (VRFB) with high safety and long lifespan is recognized as promising large-scale energy storage system for intermittent renewable energy sources. However, the large-scale development of VRFBs is still hindered by untreated graphite felt electrodes with poor electrocatalytic performance. In this work, we report a modified GF electrode with synchronous etching of the electrode surface and loading of nitrogen-rich biomass carbon, which allows the formation of pores on the GF electrode surface while introducing enriched nitrogen as active sites. The obtained electrode N-EGF exhibits superior wettability, and the structural modification also contributes to the catalytic activity and reversibility of the vanadium redox reaction. The voltage efficiency (VE), energy efficiency (EE) and discharge capacity of the VRFB single cell with N-EGF are improved at current densities from 80 to 280 mA cm−2. Significantly, the power density of the VRFB achieves a peak value of 804.6 mW cm−2. In addition, the N-EGF exhibits excellent stability and ultra-low EE decay rate (0.0018 %) after long-term cycling operation (1285 cycles) at a current density of 200 mA cm−2.