Synthesis and Modification of Pore-Filled Membranes for Efficient All-Vanadium Redox Flow Batteries

Redox flow batteries (RFBs) are one of the promising energy storage devices that utilizing the oxidation and reduction of electroactive species for charging and discharging, respectively [1,2]. All-vanadium redox flow batteries (VRFBs) can be used for large-scale intermittent storage systems such as wind turbines and solar cells as well as applications which requires high capacity and high power output such as an electric vehicle. The VRFBs consists of electrolytes with redox couples of V/V and VO/VO2 + for both compartments, a battery cell, circularatory pumps, and an ion-exchange membrane for separation and ion transport [3]. Ion exchange membranes have significant roles for the reliability of of the VRFBs. Conventional VRFBs with commercial Nafion membranes has been widely studied in terms of the ion selelctivity and permeation of metal species. Anion-exchange membranes are also advantageous for lower metal permeations with high proton transport [4]. In addition, pore-filled membranes with ion-exchange resins and polyelectrolytes have been reported, showing better chemical stabilities based on the inert substrate [3,4].