Zirconium oxide nanotube-Nafion composite as high performance membrane for all vanadium redox flow battery

Abstract

A high-performance composite membrane for vanadium redox flow battery (VRB) consisting of ZrO2 nanotubes (ZrNT) and perfluorosulfonic acid (Nafion) was fabricated. The VRB operated with a composite (Nafion-ZrNT) membrane showed the improved ion-selectivity (ratio of proton conductivity to permeability), low self-discharge rate, high discharge capacity and high energy efficiency in comparison with a pristine commercial Nafion-117 membrane. The incorporation of zirconium oxide nanotubes in the Nafion matrix exhibits high proton conductivity (95.2mScm−1) and high oxidative stability (99.9%). The Nafion-ZrNT composite membrane exhibited low vanadium ion permeability (3.2×10−9cm2min−1) and superior ion selectivity (2.95×107Smin cm−3). The VRB constructed with a Nafion-ZrNT composite membrane has lower self-discharge rate maintaining an open-circuit voltage of 1.3V for 330h relative to a pristine Nafion membrane (29h). The discharge capacity of Nafion-ZrNT membrane (987mAh) was 3.5-times higher than Nafion-117 membrane (280mAh) after 100 charge-discharge cycles. These superior properties resulted in higher coulombic and voltage efficiencies with Nafion-ZrNT membranes compared to VRB with Nafion-117 membrane at a 40mAcm−2 current density. © 2016 Elsevier B.V.