Molecular engineering of backbone electronic effects for high-performance ion-exchange membranes in redox flow batteries.

Abstract

Deciphering the intricate correlation between polymer backbone chemistry and electrochemical performance remains a pivotal challenge in the rational design of ion-exchange membranes for flow batteries. Herein, we design and synthesize two sulfonated poly(arylene) membranes with identical ion-exchange capacity yet divergent backbone architectures, and systematically interrogate their performance in redox flow batteries. We unveil that the electronic nature of the bridging groups critically dictates thermal stability, ionic conductivity, area resistance, and ion permselectivity. Impressively, the SPAEKES membrane affords an energy efficiency of 86.6% at 200 mA cm-2 in AZIFBs, sustaining stable operation up to an ultrahigh current density of 540 mA cm-2, while its acid-treated counterpart (SPAESEK-H) exhibits superior proton conduction and effectively suppresses vanadium crossover in VRFBs, delivering an energy efficiency of 74.5% at 200 mA cm-2 and a peak power density of 500 mW cm-2. Both membranes demonstrate exceptional durability under prolonged cycling. Collectively, our findings establish a molecular-design strategy for ketone- and sulfone-modified sulfonated poly(arylene) membranes, in which tuning the electronic nature of the bridging groups addresses the distinct demands of acidic versus alkaline systems, offering a rational pathway toward high-performance, application-tailored ion-exchange membranes.

Abstract as supplied by the indexing source. © the authors / publisher.