Wide-Temperature Butyronitrile-Based Electrolyte: Structure Dynamics and Solvation Behavior^†

Due to their high dielectric constant, low melting point, and high boiling point, nitrile-based solvents exhibit significant potential in wide-temperature-range electrolytes. In this study, a wide-temperature electrolyte system composed of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), dimethyl carbonate (DMC), and butyronitrile (BN) in a molar ratio of 1:3:9 was designed. Using variable-temperature infrared (IR) spectroscopy with carbonyl (C=O) and cyano (C≡N) groups as IR probes, combined with molecular dynamics simulations and density functional theory calculations, the temperature-dependent evolution of the Li⁺ solvation structure and molecular dynamics were systematically investigated over the range of −45 °C to 45 °C. The results show that the introduction of BN not only significantly enhances the low-temperature ionic conductivity and high-temperature stability of the electrolyte, but also optimizes the solvation structure and interfacial characteristics of lithium ions through strong coordination interactions. This work provides both theoretical insights and experimental support for the design of wide-temperature electrolytes.