Highly stable side-chain-type cardo poly(aryl ether ketone)s membranes for vanadium flow battery

Vanadium flow batteries (VFBs) have drawn considerable attention as an emerging technology for largescale energy storage systems (ESSs). One of the pivotal challenges is the availability of eligible ion exchange membranes (ICMs) that provide high ion selectivity, proton conductivity, and stability under rigorous condition. Herein, a 'side-chain-type' strategy has been employed to fabricate highly stable phenolphthalein-based cardo poly(arylene ether ketone)s (PAEKs) membrane with low area resistance (0.058 Q cm2), in which flexible alkyl spacers effectively alleviated inductive withdrawing effect from terminal ion exchange groups thus enabling a stable backbone. The assembled VFBs based on PAEKs bearing pendent alkyl chain terminated with quaternary ammonium (Q-PPhEK) demonstrated an energy efficiency above 80% over 700 cycles at 160 mA/cm2. Such a remarkable results revealed that the side-chain-type strategy contributed to enhancing the ICMs stability in strong oxidizing environment, meanwhile, more interesting backbones would be woken with this design engaging in stable ICMs for VFBs.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.