Chiang Mai Journal of Science

A novel composite membrane consisting of sulfonated poly(ether sulfone) (SPES) and short-carboxylic multi-walled carbon nanotube (denoted as SPES/SCCT membrane) was prepared and employed as the separator for vanadium redox flow battery system (denoted as VRB) to evaluate the vanadium ions permeability and cell performance. The SPES/SCCT composite membrane exhibits dramatically lower vanadium ions permeability and better cell performance compared to the pristine SPES membrane, and Nafion221 membrane. The vanadium ion permeability of SPES/SCCT membrane is one order of magnitude lower than that of Nafion221 membrane. In the further work, the single cell with SPES/SCCT membrane shows significantly lower capacity loss, higher coulombic efficiency (>91.7%) and higher energy efficiency (>84.1%) than Nafion221 membrane. In the self-discharge test, SPES/SCCT membrane showed 2.0 times longer duration in the open circuit decay than Nafion221 membrane. With all the good properties and low cost, this new kind of composite membrane is of excellent commercial prospects as an ion exchange membrane for VRB systems.