In the recent years, redox flow batteries (RFBs) have attracted particular attention as promising energy storage systems in large-scale energy storage and electric vehicles because of their unique feature of decoupling energy density and power. Aqueous RFBs use water as the solvent for the anolyte and catholyte, as this offers several advantages, including fast reaction kinetics, low cost, nonflammability, and high conductivity. However, aqueous RFBs suffer from two major problems: limited cell voltage owing to the narrow electrochemical window of water and low energy density.

In contrast, lithium-metal-based nonaqueous redox flow batteries (LRFBs) have high operating voltage and large theoretical energy density, yet the large-scale applicability of LRFBs is limited by the poor availability and high cost (approaching 40% of the total battery cost) of the critically important ion-selective membranes.