In Situ Crosslinking of Tröger Base-Based Membranes with Improved Vanadium Flow Battery Property

The high conductivity of anion exchange membrane (AEM) remains a great challenge in achieving high-performance vanadium flow batteries. In this work, this is achieved by designing a series of microporous crosslinked quaternary ammonium membranes (QDTTB-Xs), which is synthesized by in situ reacting of iodomethane with a series of novel crosslinked microporous Tröger base membranes (DTTB-Xs) that prepared by condensation of 2, 6 (7)-diamino-triptycene and 2, 6 (7)-13-triamino-triptycene through in situ crosslinking. Compared with linear microporous QDTTB-0, the crosslinked QDTTB-X membranes showed higher conductivity. The QDTTB-35 membrane displays both higher coulombic efficiency and voltage efficiency, and 80% of energy efficiency is realized at 200 mA cm^-2. Outperforming N117 and other reported anion exchange membranes. This is due to the increased triamino-triptycene molar ratio in the membrane resulting in both higher N⁺ concentration and improved micropores concentration. Moreover, positively charged N⁺ groups combined with the low swelling ratio also help in restricting the vanadium ions permeation. These results give great perspectives in designing high-performance AEMs for VRFB applications.