Amphiprotic Side-Chain Functionalization Constructing Highly Proton/Vanadium-Selective Transport Channels for High-Performance Membranes in Vanadium Redox Flow Batteries.

A novel amphiprotic side-chain-functionalized membrane was for the first time designed for vanadium redox flow battery (VFB). Different from frequently used blending amphiprotic membranes, the one proposed here is allowed to possess high anion-exchange capacity (IEC) without sacrificing the cation-exchange capacity (IEC) because both IEC and IEC increased with the grafting degree of side chains. Having a high IEC, the membrane prepared here exhibits an ultralow vanadium permeability (<10 cm s), which leads to very high Coulombic efficiencies (97-98% at 40-200 mA cm) of VFB and good cell self-discharge durability.