Experimental study on efficiency improvement methods of vanadium redox flow battery for large-scale energy storage

All-vanadium redox flow battery (VRFB) is a promising large-scale and long-term energy storage technology. However, the actual efficiency of the battery is much lower than the theoretical efficiency, primarily because of the self-discharge reaction caused by vanadium ion crossover, hydrogen and oxygen evolution side reactions, vanadium metal precipitation and other operational factors. Based on the above analysis, this paper proposes effective strategies and methods for improving the efficiency of the VRFB. The experimental results indicate that the voltage efficiency and system efficiency increased by 1.86% and 0.48%, respectively, when constant flow rate and variable current density charge/discharge methods are used. Meanwhile, when variable flow rate and current density charge/discharge methods are employed, the energy efficiency and system efficiency increased by 9.07% and 8.34%, respectively, resulting in significant improvement in energy storage capacity. The experiment has verified that this method can improve the efficiency and performance of VRFB, and can promote the development of VRFB.