30 μm thin hexamethyl-p-terphenyl poly(benzimidazolium) anion exchange membrane for vanadium redox flow batteries

• Published in: Electrochemistry communications 2019-05, Vol.102, p.37-40
• Main Authors: Shanahan, Brian, Böhm, Thomas, Britton, Benjamin, Holdcroft, Steven, Zengerle, Roland, Vierrath, Severin, Thiele, Simon, Breitwieser, Matthias
• Format: Article
• Language: English
• Subjects: Anion exchange membrane; Coulombic efficiency; Energy storage; HMT-PMBI; Vanadium redox flow battery
• ISSN: 1388-2481; 1873-1902
• DOI: 10.1016/j.elecom.2019.03.016

We present the first results of an anion exchange ionomer membrane, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), in a vanadium redox flow battery. Anion exchange membranes exhibit superior vanadium crossover suppression compared to proton exchange membranes due to the Gibbs–Donnan effect. HMT-PMBI was benchmarked against a similarly thin Nafion XL membrane which allowed us to compare differences based solely on chemical properties of the ionomer materials. We report cycling data of 45 cycles at a current density of 150 mA/cm2 with excellent coulombic efficiency of >99.4%, energy efficiency of 80.6–74.2% and a low ohmic resistance of 0.219–0.255 Ω cm2. In addition, a three times lower self-discharge rate is obtained for the HMT-PMBI membrane compared to Nafion XL. HMT-PMBI is therefore a potential alternative for PFSA based ionomers in VRFB applications. •First application of an anion exchange membrane called HMT-PMBI in a VRFB.•A high coulombic efficiency of >99.4% and a low self-discharge is achieved.•Energy efficiencies between 80.6 and 74.2% at 150 mA/cm2 for 45 cycles are achieved.•A 30 μm thin membrane yielding low ohmic cell resistance of 0.219–0.255 Ω cm2.