Cyclodextrin templated nanoporous anion exchange membrane for vanadium flow battery application

A beta-cyclodextrin (beta-CD) based template method is proposed for fabricating high performance nanoporous anion exchange membranes for vanadium flow batteries (VFBs). The beta-CD template can be uniformly dispersed in hydroxyl modified polysulfone precursor membrane with a low degree of quaternization; removal of the template will result in the formation of AEMs with well controlled pore structure. This new template method is advantageous due to the hydrogen bonding between the beta-CD and polymer so that aggregation of beta-CD in the membrane can be minimized. The well dispersed beta-CD is beneficial for fabricating porous AEM with small pores, and further for selective transport of protons and anions in the battery. The fabricated porous AEM has low IEC, high conductivity and low vanadium ions permeability. The VFB employing such a membrane showed a coulombic efficiency of 99% and an energy efficiency of 80% at 120 mA cm(-2). This work demonstrates the synergistic effect of nanopore and imidazolium cation for high performance VFB membrane fabrication.