Electrolyte design for aqueous batteries

Aqueous batteries, with their inherent safety, operational simplicity, and cost-effectiveness, have emerged as promising candidates for grid-scale energy storage applications. However, the relatively low output voltage of aqueous systems continues to limit their achievable energy density. The aqueous electrolyte occupies a central role in addressing this limitation because it mediates ion transport and interfacial reactions at both the cathode and anode; accordingly, advances in electrolyte design are indispensable to meet future performance demands. In this review, we elucidate the core bottlenecks in aqueous electrolyte design, distill molecular-level design principles, and outline feasible pathways for future practical implementation. We aim to guide the development of next-generation aqueous electrolytes that harmonize outstanding electrochemical performance, thereby accelerating the transition from laboratory concepts to transformative energy solutions.