Transient modeling and performance analysis of redox-targeted all-vanadium redox flow battery

Abstract

All-vanadium redox flow battery (VRFB) is a large-scale energy storage technology with great development potential, but its progress is hindered by high costs and limited energy and power densities. Adding targeted materials to the tank is expected to increase capacity and reduce costs of VRFB. A transient mathematical model for redox-targeted all-vanadium redox flow battery (RT-VRFB) is established and verified under different current densities. The model combines electrolyte flow, fluid–solid targeting reaction and electrochemical reaction. The charge conservation, mass conservation and ion crossover are considered. The correlation analysis between multi-parameters and RT-VRFB performance shows that the current density has a negative effect on the performance of RT-VRFB, especially for the specific energy, and the volumetric fraction of targeted materials has a good positive effect. The reaction rate constant of the targeted reaction significantly affects the utilization rate of the targeted material at different vanadium concentrations. However, its impacts on specific energy and specific capacity diminish as the vanadium concentration increases. For 1.6 M commercial vanadium electrolyte, when volumetric fraction of targeted materials reaches 25 %, specific capacity and energy are increased by 22.9 % and 17.6 %. When the energy efficiency is 80 %, the main factor affecting the maximum current density is the internal resistance of RT-VRFB, followed by the reaction rate constant of targeted reaction and volumetric fraction of targeted materials. The maximum current density can be enhanced through parameter optimization.