Wide-temperature butyronitrile-based electrolyte: Structure dynamics and solvation behavior

Abstract

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 in-sights and experimental support for the design of wide-temperature electrolytes.