Single-membrane pH-decoupling aqueous batteries using proton-coupled electrochemistry for pH recovery†

Abstract

pH-decoupling in aqueous redox flow batteries (ARFBs) represents a promising strategy for enhancing cell voltage and expanding the repertoire of redox pair combinations. Effective management of acid–base crossover and the implementation of cost-effective pH recovery methods are pivotal for long-term stability of pH-decoupling ARFBs. We introduce a pH-decoupling design integrated into a conventional single-membrane ARFB architecture. This approach reduces the area specific resistance while suppressing acid–base crossover to an acceptable level. We explore various electrolyte pairs, ranging from anions to cations, acids to bases, always dissolved to electrodepositing, showing the flexibility afforded by this design in selecting electrolyte compositions. Furthermore, we demonstrate the utility of proton-coupled electrochemical reactions as proton pumps, facilitating in situ or ex situ pH recovery within pH-decoupling batteries. Our findings potentially offer benefits including improved energy efficiency, increased areal power output, and decreased capital costs, thereby advancing the prospects for scalable and sustainable energy storage solutions.