A Fluorine‐Free Solvent Based on Dual Descriptors for Ultrawide‐Temperature Lithium Metal Batteries (−105°C to 70°C)

Abstract

ABSTRACT Fluorinated solvents are widely employed in electrolytes for lithium metal batteries (LMBs) due to their broad liquid‐phase temperature range. However, their use entails significant challenges, including undesirable interfacial parasitic reactions at elevated temperatures and lithium‐salt precipitation at low temperatures. In this study, we propose a fluorine‐free electrolyte design strategy based on synergistic optimization of molecular geometry and electron density distribution. The tailored solvent, 2‐ethylbutyl acetate (2EA), plays a critical role in modulating intermolecular interactions and Li + coordination. The 2‐ethylbutyl group introduces substantial steric hindrance while exerting electron‐donating inductive effects, thereby effectively weakening the binding affinity between carbonyl oxygen and Li + . Concurrently, steric hindrance inhibits intermolecular interaction of solvent molecules at cryogenic temperatures, resulting in an ultra‐low melting point (below −100°C). Furthermore, the synergistic steric and electronic effects reorganize the solvation structure into an anion‐dominated configuration, facilitating Li + desolvation and promoting a robust, inorganic‐rich interphase. As a result, the 2EA‐based electrolyte enables high‐voltage Li||LiCoO 2 cells to achieve exceptional cycling stability (80% capacity retention after 1500 cycles at 25°C), remarkable rate capability (90% capacity retention at 10°C), and stable operation over an ultrawide temperature range from −60°C to 70°C.