Abstract

AbstractA membrane with low vanadium ion permeability and excellent electrochemical stability is crucial for a vanadium flow battery (VFB). Herein, a highly stable anion exchange membrane based on a bi‐guanidinium crosslinking quaternized poly(arylene ether sulfone) (PSF) is reported. The positively charged guanidinium groups can not only form continuous and smooth ion transport channels but also prevent the mutual penetration of vanadium electrolyte at positive and negative sides, respectively, based on the Donnan exclusion effect. Moreover, the crosslinking structure endows the membrane high mechanical strength to meet the requirements of the harsh environment of VFBs. As a result, the anion exchange membrane fabricated by the poly(arylene ether sulfone) crosslinked with bi‐guanidinium (BG‐PSF) shows an impressive VFB performance with a coulombic efficiency of 99.8% and an energy efficiency of above 85.8% at a current density of 80 mA cm−2, which is much higher than that of Nafion115. Furthermore, this battery can continuously work for over 200 cycles at a current density of 80 mA cm−2, indicating good stability of the membrane. Therefore, the rationally designed BG‐PSFs are promising for VFB applications.

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