Crosslinked sulfonated poly (arylene ether sulfone)/sulfonated poly (vinyl alcohol) membrane formed by in situ casting and reaction for vanadium redox flow battery application

The in situ crosslinked membranes for vanadium redox flow battery (VRFB) application, prepared from sulfonated poly (arylene ether sulfone) (SPAES) and poly (vinyl alcohol) (PVA) as well as sulfonated poly (vinyl alcohol) (SPVA), are detailedly evaluated in this paper. The results of scanning electron microscope (SEM) and Xray diffraction (XRD) reveal that the cross reaction improved the compatibility between SPAES and SPVA, and reduced the crystallinity in the membrane. The highly homogeneous dispersed structures of the crosslinked membrane are found under the electronic microscope. The crosslinked structure effectively reduces the water uptake, swelling ratio, and vanadium ion permeability, and more importantly improved the mechanical performance and stability of the membranes. Due to the introduction of sulfonic groups into the PVA, the proton selectivity of SPAES crosslinked SPVA (SPAES-C-SPVA) reaches to 3.37x10(5) S min cm(-3) which is 8 times higher than that of Nafion117. The VRFB single cell tests show that the cell assembled with SPAES-C-SPVA membrane significantly displays higher energy efficiency (70.1% vs 60.9% at 100 mA cm(-2)) and much longer self-discharge time than Nafion117 (98 h vs 41 h). After 100 charge-discharge cycling test, the crosslinked membrane still maintains excellent stability. The above results indicate the crosslinked membranes could be a promising candidate used in VRFB applications.