High-Voltage Electrolytes for Aqueous Energy Storage Devices

Aqueous energy storage devices have been considered as one of the most promising candidates for large-scale energy storage owing to their high safety and low cost. However, the narrow stability voltage window of electrolytes originating from the decomposition of water limits their energy density. In this Minireview, we discuss the limited energy density of aqueous energy storage devices in detail, and then the water decomposition mechanism and corresponding key factors. Furthermore, we present the comprehensive overview of the strategies for increasing the stability of aqueous electrolytes, including redox-active additives, pH regulation of electrolytes, utilization of water-in-salt electrolytes, and selection of highly stable electrolyte salts. Finally, this Minireview also offers insights in the design of high-voltage aqueous electrolytes.