Nanoscale Solid Superacid-Coupled Polybenzimidazole Membrane With High Ion Selectivity For Flow Batteries

Nanoscale solid superacid SO42-/ZrO2/WO3 is coupled into imidazole-hydroxyl-quaternary ammonium co-functionalized polybenzimidazole (PG112) to address the trade-off effect of membrane for large-scale flow battery application. Nanoscale SO42-/ZrO2/WO3 particles with high sulfonic groups are dispersed in membrane as redox-active ion barriers and proton carriers, which mitigate the electrolyte crossover and maintain high ion conductivity. The VO2+ permeability of the prepared membrane (7.86 x 10(-)(10) cm(2) s(-1)) is significantly lower than those of PG112 (3.93 x 10(-9) cm(2) s(-1)) and Nafion 212 (7.76 x 10(-8) cm(2) s(-1)) membranes. The vanadium flow battery with this membrane exhibits a longer self-discharge duration time of 231 h compared with Nafion 212 (35 h) and PG112 (88 h) membranes. High coulombic efficiencies of 97.5-99.2% at 40-120 mA cm(-2) are obtained for the prepared membrane, which are higher than those for Nafion 212 (78.0-92.8%) and PG112 membranes (96.2-98.6%). Stable cycle performance and low retention capacity are also observed, suggesting the excellent chemical stability of the prepared membrane in vanadium flow battery operation. This work provides a prospective and applicable membrane to enhance the performance of flow battery.