Optimization of electrolyte flow and vanadium ions conversion by utilizing variable porosity electrodes in vanadium redox flow batteries

摘要

The proper flow and uniform distribution of vanadium electrolyte inside the electrode are crucial factors to improve battery performance. In this study, the novel gradient and double-layered porous electrode (GPE and DLPE) with optimized properties were investigated. More vanadium ions conversion occurs due to more uniform distribution of electrolyte flow with promptly supplementing of reactants and timely removing of products. Thus, the larger cell capacity and output power as well as higher energy efficiency are obtained in the electrodes with a linear or stepwise increasing in porosity at the same inlet flow rate. In the other case with the same pressure difference between the inlet and outlet, the larger cell capacity and efficiencies occur in the electrodes with a constant maximum porosity or a linear decreasing porosity due to the larger average inlet flow velocity. The better battery performance can be obtained by optimizing porosity arrangement in the electrodes.