Derivatized cardo-polyetherketone anion exchange membranes for all-vanadium redox flow batteries
By Yun, Sukhwan; Parrondo, Javier & Ramani, Vijay
Published in J. Mater. Chem. A
The Royal Society of Chemistry
2014
Abstract
Cardo-polyetherketone (PEK-C) based anion exchange membranes (AEMs) were synthesized by chloromethylation of PEK-C followed by quaternization using trimethylamine (TMA). The ion exchange capacity (IEC) of the AEM was 1.4 +/- 0.1 mmol g-1. The sulfate ion conductivity and vanadium(iv) permeability were 5.6 +/- 0.5 mS cm-1 and 8.2 +/- 0.2 [times] 10-9 cm2 s-1 at 30 [degree]C. The chemical stability and mechanical integrity of the AEMs were investigated upon exposure to 1.5 M VO2+ solution by monitoring the ionic conductivity, ultimate tensile strength, elongation at break, and chemical structure over 1500 hours. 1-D and 2-D NMR spectroscopy confirmed the chemical stability of the AEM over this period. The ionic conductivity of the AEM decreased from 5.6 to 4.4 mS cm-1 over the first 48 hours but subsequently stabilized and was reversible, while the ultimate tensile strength and the elongation at break were reduced by ca. 35%. The PEK-C based AEMs were stable during operation in a vanadium redox flow battery (VRFB) for 100 hours of testing. The coulombic and energy efficiencies of the VRFB were 98% and 80%, respectively. Post-mortem analysis of the AEM using 1-D and 2-D NMR spectroscopy showed a 15% reduction in the number of quaternary ammonium groups in the AEM.