Alkaline Stability of Pure Aliphatic-based Anion Exchange Membranes Containing Cycloaliphatic Quaternary Ammonium Cations
Zhongyang Wang, Javier Parrondo, Shrihari Sankarasubramanian, Kaustava Bhattacharyya, Manasi Ghosh, Vijay Ramani
Abstract
The alkaline stability of functional cations tethered to anion exchange membranes (AEMs) is essential for long-term operation in electrochemical devices. Here, we report the use of AEMs with pure aliphatic polymer backbones containing N-spirocyclic quaternary ammonium cation groups as highly conductive, crosslinked, and reinforced separators. Synthesizing these pure aliphatic-based AEMs via irradiation with ultraviolet (UV) light at room temperature avoids the use of carcinogenic solvents and the solution casting step generally used in AEM preparation. The resultant aliphatic-based AEMs have a chloride ion conductivity of 82 mS cm −1 at 70 °C with an ion exchange capacity (IEC) of 3.0 ± 0.2 mmol g −1 . The aliphatic-based AEM retains 40% of its initial IEC after immersion in 1 M KOH at 80 °C for 30 d. A direct nucleophilic substitution degradation mechanism is proposed for such AEMs, based on FT-IR, solid state 13 C-NMR spectroscopy, and XPS.