Advanced anion exchange membranes with selective swelling-induced ion transport channels for vanadium flow battery application

Abstract Anion exchange membranes with attractive advantages are highly promising for vanadium flow battery (VRFB) applications, but high area resistance limits their uses in high-power-density VRFB. Increasing the ion exchange capacity (IEC) is long considered as the primary choice to enhance the membrane conductivity, which unfortunately results in highly swelling and much sacrifice of the membrane selectivity and stability. In this work, new quaternized phenyl and adamantane containing poly(aryl ether ketone ketone) (QPAPEKK) membranes with selective swelling-induced ion transport channels are prepared. QPAPEKK membranes with much low IEC (0.62 mmol g−1) are selective swelled with H3PO4 to form ion transport channels. Consequently, the area resistance of resulting QPAPEKK-110 membrane (0.24 Ω cm2) is nearly one-fifth of QPAEKK-virgin membrane (1.21 Ω cm2). Moreover, VRFB utilizing QPAPEKK-90 membrane exhibit impressive battery performance (energy efficiency 91.4% at 80 mAcm−2; energy efficiency 80.0% at 220 mAcm−2). The QPAPEKK membranes combined high battery performance and high chemical stability are promising for high-power density VRFB application.