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A Cost-effective Nafion Composite Membrane as a Super Vanadium Ions Barrier for Vanadium Redox Flow Batteries.

Ion exchange membrane plays a key role in all vanadium redox flow battery (VRFB). The mostly available commercial membrane for VRFB is Nafion. However, its disadvantages, such as high cost and severe vanadium ions permeation, become obstacles for large-scale energy storage. It is crucial to develop efficient membrane with low permeability of vanadium ions and low cost to promote commercial applications of VRFB. In this study, graphene oxide (GO) is employed as an additive into Nafion 212 matrix and a composite membrane named rN212/GO is obtained. The thickness of rN212/GO has been reduced to only 41 μm (compared with 50 μm Nafion 212), which indicates directly lower cost. Meanwhile, rN212/GO shows lower permeability of vanadium ions and area-specific resistance compared to Nafion 212 membrane due to the abundant oxygen-containing functional groups of GO additives. The VRFB cells with rN212/GO membrane show higher Coulombic efficiencies and lower capacity decay than those of VRFB cells with Nafion 212 membrane. Therefore, the cost-effective rN212/GO composite membrane is a promising alternative to suppress migration of vanadium ions across the membrane to set up VRFB cells with better performances.