Ionic Liquid Electrolytes for Extreme Temperature Conditions: Challenges and Perspective

The increasing applications of electrochemical energy-storage systems in transportation, aerospace, and grid applications impose stringent requirements on electrolytes capable of operating safely and efficiently across extreme temperatures. Conventional carbonate- or ether- based electrolytes suffer from performance degradation and severe safety hazards in extreme thermal environments. Ionic liquid electrolytes (ILEs), distinguished by their intrinsic nonflammability and remarkable resistance to temperature-induced property fluctuations, are recognized as promising alternatives. Nonetheless, the development of wide-temperature ILEs is constrained by their complex temperature-dependent physicochemical behaviors and interfacial instabilities. In this review, the effects of temperature on the molecular configurations, physicochemical properties, and interfacial chemistry of ILEs are systematically elucidated. The challenges associated with ILEs operation under low- and high-temperature conditions are subsequently delineated, with particular emphasis on recent advances in molecular design and co-solvent strategies aimed at improving the wide-temperature performance of ILEs. Furthermore, the interfacial chemistry and electrode compatibility of ILE-based systems are examined to demonstrate their roles in dictating interphase stability and electrochemical durability. Integrating molecular-level insights with macroscopic performance characteristics, this review presents a unified framework correlating the structure of ILEs with temperature-dependent performance, providing valuable guidance for the rational design of next-generation wide-temperature ILEs toward high-safety and high-energy-density rechargeable batteries.