Facile fabrication of sulfonated poly(aryl ether sulfone)/polybenzoxazine crosslinked membrane for vanadium flow battery application

A novel series of sulfonated poly(aryl ether sulfone) (SPAES)/polybenzoxazine (PBa) crosslinked membranes applied in vanadium redox flow battery (VRFB) are prepared and characterized. The introduction of PBa with vinyl groups by benzoxazine (Ba) ring-opening polymerization has a significant impact on the physical and chemical properties of the crosslinked membranes. Compared to pristine SPAES membrane, the crosslinked membranes exhibit a better thermal, dimension and chemical stability owing to the three-dimensional network structure and the hydrophobic segments of PBa. In addition, the narrow ion channel caused by low swelling ratio and protonated nitrogen atoms of SPBa can hamper the vanadium permeation immensely. As expected, the SPBa-33 membrane shows an extremely low vanadium permeability of 1.49 × 10−7 cm2 min−1. Moreover, the proton selectivity of SPBa-33 membrane (8.19 × 104 S min cm−3) is nearly four times higher than that of Nafion117 (2.32 × 104 S min cm−3).