Fluorinated Solvent Molecule Tuning Enables Fast‐Charging and Low‐Temperature Lithium‐Ion Batteries
Yanbing Mo, Gaopan Liu, Yue Yin, Mingming Tao, Jiawei Chen, Peng Yu, Yonggang Wang, Yong Yang, Congxiao Wang, Xiaoli Dong, Yongyao Xia
Abstract
Abstract Popularly‐used fluorination can effectively weaken Li + ‐solvent interaction to facilitate the desolvation process at low temperature; however, high fluorination degree sacrifices salt dissociation and ionic conductivity. Herein, functional fluorinations are well tuned with different amounts of F atoms to balance Li + ‐solvent binding energy and ion movement, which reveals the fluorination effect on the solvation behavior and low‐temperature performance. Noteworthily, the moderately‐fluorinated ethyl difluoroacetate (EDFA) successfully favors a lower binding energy than less‐fluorinated ethyl fluoroacetateand superior salt dissociation more than highly‐fluorinated ethyl trifluoroacetate, realizing the trade‐off between weak affinity and sufficient ionic conductivity. The well‐formulated EDFA‐based electrolyte exhibits a unique solvation sheath and generates inorganic‐rich solid electrolyte interphase with low resistance for smooth Li + diffusion, which enables graphite anodes with excellent fast‐charging capability (196 mAh g −1 at 6 C) and impressive low‐temperature performance with a reversible capacity of 279 mAh g −1 under −40 °C. Subsequently, the wide electrochemical potential window of EDFA‐based electrolyte endows the 1.2 Ah LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)||graphite pouch cells with a high reversible capacity retention of 58.3% at −30 °C and discharge capacity of 790 mAh at −40 °C. Such solvent molecules with a moderately‐fluorinated strategy promise advanced electrolyte design for lithium‐ion batteries operating under harsh conditions.