Consistency analysis and resistance network design for vanadium redox flow battery stacks with a cell-resolved stack model

The problem of non-uniform electrolyte distribution and the presence of shunt current greatly limit the system performance of vanadium redox flow batteries (VRFBs). It is thus critical to delicately design the electrolyte flow frame in VRFB stack such that the overall system efficiency and stack consistency can be improved. In this work, first, a cell-resolved VRFB stack model coupling the flow resistance network model and equivalent circuit model is developed and validated for a VRFB stack, which can be used for stack consistency and performance analysis. Then, sensitivity analysis is carried out to examine the impacts of the distribution channel and manifold resistances on electrolyte distribution uniformity and cell voltage consistency as well as system efficiency of the stack in detail. Based on the above sensitive analysis, the resistance network for a 20-cell VRFB stack is finally optimized by designing the non-uniform distribution channel resistances. It is proved that this proposed non-uniform resistance network design can further improve the electrolyte flow and the voltage distribution uniformity between cells as well as the system efficiency.