Aqueous decoupling batteries: Exploring the role offunctional ion-exchange membrane

The relentless pursuit of sustainable and safe energy storage technologies hasdriven a departure from conventional lithium-based batteries toward other relevantalternatives. Among these, aqueous batteries have emerged as a promisingcandidate due to their inherent properties of being cost-effective, safe,environmentally friendly, and scalable. However, traditional aqueous systemshave faced limitations stemming from water's narrow electrochemical stabilitywindow (-1.23 V), severely constraining their energy density and viability inhigh-demand applications. Recent advancements in decoupling aqueous batteriesoffer a novel solution to overcome this challenge by separating the anolyteand catholyte, thereby expanding the theoretical operational voltage windowto over 3 V. One key component of this innovative system is the ion-selectivemembrane (ISM), acting as a barrier to prevent undesired crossover betweenelectrolytes. This review provides a comprehensive overview of recent advancementsin decoupling aqueous batteries, emphasizing the application of varioustypes of ISMs. Moreover, we summarize different specially designed ISMs andtheir performance attributes. By addressing the current challenges ISMs face,the review outlines potential pathways for future enhancement and developmentof aqueous decoupling batteries.