Recent advances in multifunctional generalized local high-concentration electrolytes for high-efficiency alkali metal batteries

Alkali metal batteries (AMB, A=Li, Na, K) are considered to be the most promising energy storage devices to achieve high energy density. As the blood of the battery, to realize stable energy storage in high-energy-density alkali metal batteries, the electrolyte needs to be properly designed. Over the past three decades, electrolytes have evolved from regular concentration electrolytes, ionic liquid electrolytes, and high-concentration electrolytes to localized ionic liquid electrolytes, localized high-concentration electrolytes, and quasi-localized high-concentration electrolytes. Due to the wide variety of alkali metal battery electrolytes, this review first proposes the concept of generalized local high-concentration electrolyte (g-LHCE) based on the characteristics of the solvation structure, supplements the descriptor values of different solvents, and summarizes the design principles of g-LHCE. Then the progress of g-LHCE in recent years in terms of high voltage, solid-liquid interface, low temperature, and nonflammability is summarized. Finally, the future development of g-LHCE is prospected. High-entropy generalized local high-concentration electrolytes and local high-concentration aqueous electrolytes will become important research directions for advanced electrolyte design in the field of high energy density and high power density alkali metal batteries.