Optimizing Si─O Conjugation to Enhance Interfacial Kinetics for Low‐Temperature Rechargeable Lithium‐Ion Batteries

Abstract With the growing demand for high‐voltage and wide‐temperature range applications of lithium‐ion batteries (LIBs), the requirements for electrolytes have become increasingly stringent. While fluorination engineering has enhanced the performance of traditional solvent systems, it has also raised concerns regarding cost, environmental hazards, and low reduction stability. Through strategic molecular bond design, a novel class of low‐temperature (LT) solvents—siloxanes—is identified, meeting the demands of LT and high‐voltage applications in LIBs. The d‐p conjugation of the Si─O bond enhances voltage resistance and weakens the Li⁺‐solvent interactions. By modulating the number of Si─O conjugated bonds, the type of anion clusters in the solvation structure can be controlled, ultimately leading to the formation of a LiF and Si─O‐rich interfacial layer and facilitating rapid Li⁺ conduction. Consequently, the graphite||NCM811 pouch cell (2.3 Ah, 4.45 V) with a siloxane‐based electrolyte retains 75.1% of room temperature capacity (RTC) at −50 °C. The rapid interface kinetics allow a superior reversible charging capacity retention of 67.6% at −40 °C, with good cycle stability at −20 °C. This study provides new insights into solvent design to fortify LIB performance in harsh conditions.