High-Capacity Retention Thermally Reinforced Pore-Filled Anion Exchange Membrane for All-Vanadium Flow Batteries

In this work, we report a thermally annealed pore-filled anion exchange membrane (PFAEM) with excellent mechanical and chemical stability effected by a polypropylene support and impressive electrochemical properties induced by a pore-filled poly (4-vinyl pyridine) matrix followed by its successful demonstration in vanadium redox flow batteries (VRFBs). As expected, a low swelling ratio synergized with Donnan exclusion resulted in low vanadium ion diffusion. The calculated permeability rates for V+3, VO2+, and VO2+ were 4.80 × 10–7, 7.11 × 10–7, and 9.4 × 10–7 dm s–1, respectively. An exceptionally low dimension change (∼4.5%) was observed in 1.6 M VO2+/2 M H2SO4 solution over 15 days. The assembled VRFB exhibited a Coulombic efficiency (CE) of 98.6% and energy efficiency (EE) of 69.2% over 50 charge/discharge cycles at 150 mA cm–2 with a high-capacity retention of 70% and average capacity decay of 0.63% per cycle. The observed peak power density was 340 mW cm–2. Finally, the autopsy of the membrane after battery performance suggested negligible depreciation in mechanical and electrochemical properties, confirming its potential applicability in VRFBs.