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.