Preparation and Properties of Densely Cross-linked Fluorinated Poly(arylene ether) Anion Exchange Membranes

In order to develop anion exchange membranes (AEMs) with simutaneously good anion conductivity, low vanadium ion permeability, excellent mechanical property, and high chemical stability, a fluorinated poly-(arylene ether) (FPAE) containing tertiary amine groups was condensation polymerized and then cross-linked with decabromopropyl pillar[5]arene (P5Br) via the nucleophilic substitution reaction. After that, iodomethane was introduced to convert the remaining tertiary amine groups into quatemary ammonium groups. A series of densely cross-linked FPAE AEMs, namely QAFPAE-P5Br-x, were prepared with high gel contents in polar aprotic solvents. As the loading amount of P5Br is increased from 0.5% to 5%, the water uptake, swelling ratio, anion conductivity and VO2+ permeability of the membranes are decreased, but the ion selectivity, tensile strength, arca resistance and oxidative stability of the membranes are increased. The QAFPAE-P5Br-1% with only 1% of P5Br loaded has both low area resistance and low VO2+ permeability, which are promising for VRFB applications. At a current density of 80 mA.cm(-2), the VRFB assembled with QAFPAE-P5Br-1% shows an energy efficiency of 86.5%, which is 7.7% higher than that of the VRFB assembled with Nafion 212. Besides, the VRFB assembled with QAFPAE-P5Br-1% has excellent cycling stability, high discharge capacity retention and good anti-self-discharge performance. Therefore, the dense cross-linking is an effective protocol to enhance the overall performance of AEMs. [GRAPHICS] .