Background: Vanadium redox flow batteries (VRFBs) have received considerable attention
as large-scale electrochemical energy storage systems. In particular, VRFBs offer a higher power and
energy density than other RFBs and mitigate undesirable performance fading, such as inevitable ion
crossover, because of the unique advantage that only the vanadium ion is employed as the active species
in the two electrolytes.
Description: The key constituent of VRFBs is a separator to conduct protons and prevent cross-mixing
of the positive and negative electrolytes. For this purpose, ion exchange membranes like sulfonated
polymer membranes can be used. Although this type of membrane does not have ion exchange groups,
it can achieve an ion exchange capacity by the formation of pores.
Conclusion: This review highlights the patents on the preparation of non-fluorinated membranes (sulfonated
aromatic polymer membranes and porous membranes) as alternatives to high-cost perfluorinated
polymers and their VRFB performance.