Revealing the evolution of solvation structure in low-temperature electrolytes for lithium batteries

The structure of the ion solvation sheath is widely recognized as a significant lever for optimizing electrolyte availability and consequently, battery performance. Strategies based on regulation of the solvation structure have been proposed and implemented for high-energy-density and low-temperature lithium batteries. However, the investigations about evolution of solvation structure under various situations are not sufficient and whether a tailored solvation structure can maintain positive effects similar to the original envisioned state in operation temperature is questionable. Herein, temperature-dependent theoretical calculations and spectral characterizations were used to clarify the temperature response of solvation structures in three typical electrolyte formulas. The findings revealed that lower temperatures allowed solvents to gain more admission into the inner solvation sheath due to the faster growth of ion-solvent interaction. Introducing a co-solvent with a low dielectric constant, such as a fluorine-based solvent or non-solvent, was found to inhibit this variation. The optimized electrolyte not only demonstrated an anion-dominant solvation structure, but also inhibits temperature-response property of electrolyte, suggesting its potential positive impact over a broad temperature range This study paves the way for the development of advanced electrolytes with good temperature adaptability.