May 10, 2024
Journal Article

Lithium-ion hopping weakens thermal stability of LiPF6 carbonate electrolytes


Lithium hexafluorophosphate (LiPF6)-based carbonate electrolytes are widely used in commercial lithium-ion batteries (LIBs), but their thermal instability limits the cycle life and safety of LIBs at elevated temperatures. Few studies have yielded insight into the PF6- decomposition reaction that promotes thermal instability of LiPF6-based electrolytes. Here, with nuclear magnetic resonance techniques and ab initio molecular dynamics simulations, we find that Li+ ion hopping assisted by the overall reorientational motion of propylene carbonate solvent molecules facilitates PF6- decomposition at elevated temperatures in 1 M LiPF6/PC electrolyte. Further, we demonstrate that urea additives, by preventing Li+ ion hopping, suppress the initial LiPF6 decomposition reaction and enhance the thermal stability of the electrolyte. LIB cell tests with LiNi0.6Mn0.2Co0.2O2 || Li4Ti5O12 (NMC || LTO) show improved LIB performance at elevated temperatures in the presence of urea additives. This study provides key insights into the design of thermally stable LiPF6-based carbonate electrolytes for improving the cycle life, calendar life, and safety of LIBs in elevated-temperature applications.

Published: May 10, 2024


Han K., M. Lee, N. Kim, D. Choi, S. Chae, J. Ryu, and G. Piccini, et al. 2024. Lithium-ion hopping weakens thermal stability of LiPF6 carbonate electrolytes. Cell Reports Physical Science 5, no. 1:Art. No. 101768. PNNL-SA-189727. doi:10.1016/j.xcrp.2023.101768

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