Monofluorinated Phosphate with Unique P-F Bond for Nonflammable and Long-Life Lithium-Ion Batteries

• Published in: Angewandte Chemie International Edition p. e202412108
• Main Authors: Wang, Yuankun, Zhao, Yintong, Zhang, Shu, Shang, Long, Ni, Youxuan, Lu, Yong, Li, Yixin, Yan, Zhenhua, Miao, Zhiwei, Chen, Jun
• Format: Journal Article
• Language: English
• Published: Germany 09.10.2024
• Subjects: solid electrolyte interphase; Lithium-Ion battery; Phosphate-Based Electrolyte; Safety; Ion-dipole interaction
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202412108

Lithium-ion batteries (LIBs) with conventional carbonate-based electrolytes suffer from safety concerns in large-scale applications. Phosphates feature high flame retardancy but are incompatible with graphite anode due to their inability to form a passivated solid electrolyte interphase (SEI). Herein, we report a monofluorinated co-solvent, diethyl fluoridophosphate (DEFP), featuring a unique P-F bond that allows a trade-off between safety and electrochemical performance in LIBs. The P-F bond in DEFP weakens ion-dipole interactions with Li+ ions, lowering the desolvation barrier, and simultaneously reduces the lowest unoccupied molecular orbital (LUMO) of DEFP, promoting the formation of a robust and inorganic-rich SEI. Additionally, DEFP exhibits improved thermal stability due to both robust SEI and the inherent flame-retardant properties of the P-F bond. Consequently, the optimized DEFP-based electrolyte exhibits improved cyclability and rate capacity in LiNi0.8Co0.1Mn0.1O2 || graphite full cells compared with triethyl phosphate-based electrolytes and commercial carbonate electrolytes. Even at a low E/C ratio of 3.45 g Ah-1, the 1.16 Ah NCM811||Gr pouch cells achieve a high capacity retention of 94.2% after 200 cycles. This work provides a promising approach to decouple phosphate safety and graphite compatibility, paving the way for safer and high-performance lithium-ion batteries.