A vanadium-chromium redox flow battery toward sustainable energy storage

With the escalating utilization of intermittent renewable energy sources, demand for durable and powerful energy storage systems has increased to secure stable electricity supply. Redox flow batteries (RFBs) have received ever-increasing attention as promising energy storage technologies for grid applications. However, their broad market penetration is still obstructed by many challenges, such as high capital cost and inferior long-term stability. In this work, combining the merits of both all-vanadium and iron-chromium RFB systems, a vanadium-chromium RFB (V/Cr RFB) is designed and fabricated. This proposed system possesses a high theoretical voltage of 1.41 V while achieving cost effectiveness by using cheap chromium as one of the reactive species. Experimentally, the system attains a peak power density of over 900 mW cm−2 at 50°C and demonstrates stable performance for 50 cycles with an energy efficiency of over 87%, presenting this system as a promising candidate for large-scale energy storage. [Display omitted] •A vanadium-chromium redox flow battery is demonstrated for large-scale energy storage•The effects of various electrolyte compositions and operating conditions are studied•A peak power density of 953 mW cm−2 and stable operation for 50 cycles are achieved Huo et al. demonstrate a vanadium-chromium redox flow battery that combines the merits of all-vanadium and iron-chromium redox flow batteries. The developed system with high theoretical voltage and cost effectiveness demonstrates its potential as a promising candidate for large-scale energy storage applications in the future.