Lithium-ion hopping weakens thermal stability of LiPF6 carbonate electrolytes

Kee Sung Han; Mal Soon Lee; Namhyung Kim; Daiwon Choi; Sujong Chae; Jaegeon Ryu; Giovanni Maria Piccini; Roger Rousseau; Edwin C. Thomsen

doi:10.1016/j.xcrp.2023.101768

Lithium-ion hopping weakens thermal stability of LiPF₆ carbonate electrolytes

Kee Sung Han, Mal Soon Lee, Namhyung Kim, Daiwon Choi, Sujong Chae, Jaegeon Ryu, Giovanni Maria Piccini, Roger Rousseau, Edwin C. Thomsen

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

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 initial PF₆⁻ decomposition reaction that promotes thermal instability of LiPF₆-based electrolytes. Here, we find that lithium-ion hopping assisted by the overall reorientational motion of propylene carbonate molecules facilitates PF₆⁻ decomposition at elevated temperatures in 1 M LiPF₆/propylene carbonate electrolyte. Further, we demonstrate that urea additives, by preventing lithium-ion hopping, suppress the initial LiPF₆ decomposition reaction and enhance the thermal stability of the electrolyte. LIB cell tests with LiNi_0.6Mn_0.2Co_0.2O₂||Li₄Ti₅O₁₂ show improved LIB performance at elevated temperatures with the thermally stabilized electrolyte. 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.

Original language	English
Article number	101768
Journal	Cell Reports Physical Science
Volume	5
Issue number	1
DOIs	https://doi.org/10.1016/j.xcrp.2023.101768
State	Published - Jan 17 2024
Externally published	Yes

Funding

This work was conducted under the Laboratory Directed Research and Development Program (LDRD) at Pacific Northwest National Laboratory (PNNL), a multiprogram national laboratory operated by Battelle for the US Department of Energy under Contract DE-AC05-76RL01830. This work was also partly supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, and Geosciences & Biosciences (FWP 47319) and the US Department of Energy (DOE) Office of Electricity (OE) under contract no. 57558. We are also grateful for guidance provided by Dr. Imre Gyuk, the program manager of the Energy Storage and Power Electronics Program at DOE-OE. The NMR measurements were performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at PNNL, and partially supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the US Department of Energy, Office of Science, Basic Energy Sciences. Computational resources were provided by the PNNL Research Computing facility and the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory (LBNL). Conceptualization, K.S.H.; investigation, K.S.H. M.-S.L. N.K. D.C. S.C. J.R. G.P. R.R. and E.C.T.; writing – original draft, K.S.H, M.-S.L. and N.K.; writing – review & editing, K.S.H. M.-S.L, D.C. and N.K.; funding acquisition, K.S.H. M.-S.L. and D.C.; supervision, K.S.H. The authors declare no conflict of interest. This work was conducted under the Laboratory Directed Research and Development Program (LDRD) at Pacific Northwest National Laboratory (PNNL), a multiprogram national laboratory operated by Battelle for the US Department of Energy under Contract DE-AC05-76RL01830. This work was also partly supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, and Geosciences & Biosciences ( FWP 47319 ) and the US Department of Energy (DOE) Office of Electricity (OE) under contract no. 57558 . We are also grateful for guidance provided by Dr. Imre Gyuk, the program manager of the Energy Storage and Power Electronics Program at DOE-OE. The NMR measurements were performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at PNNL, and partially supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the US Department of Energy, Office of Science, Basic Energy Sciences . Computational resources were provided by the PNNL Research Computing facility and the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science User Facility located at Lawrence Berkeley National Laboratory (LBNL).

Funders	Funder number
DOE-OE
Joint Center for Energy Storage Research
U.S. Department of Energy	DE-AC05-76RL01830
Office of Science
Basic Energy Sciences
Biological and Environmental Research
Laboratory Directed Research and Development
Pacific Northwest National Laboratory
Chemical Sciences, Geosciences, and Biosciences Division	FWP 47319
Office of Electricity	57558

Keywords

AIMD
NMR
PF
PFG-NMR
carbonates
diffusion
electrolyte decomposition
lithium-ion batteries
nuclear relaxation

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1016/j.xcrp.2023.101768

Cite this

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title = "Lithium-ion hopping weakens thermal stability of LiPF6 carbonate electrolytes",

abstract = "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 initial PF6− decomposition reaction that promotes thermal instability of LiPF6-based electrolytes. Here, we find that lithium-ion hopping assisted by the overall reorientational motion of propylene carbonate molecules facilitates PF6− decomposition at elevated temperatures in 1 M LiPF6/propylene carbonate electrolyte. Further, we demonstrate that urea additives, by preventing lithium-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 show improved LIB performance at elevated temperatures with the thermally stabilized electrolyte. 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.",

keywords = "AIMD, NMR, PF, PFG-NMR, carbonates, diffusion, electrolyte decomposition, lithium-ion batteries, nuclear relaxation",

author = "Han, {Kee Sung} and Lee, {Mal Soon} and Namhyung Kim and Daiwon Choi and Sujong Chae and Jaegeon Ryu and Piccini, {Giovanni Maria} and Roger Rousseau and Thomsen, {Edwin C.}",

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year = "2024",

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doi = "10.1016/j.xcrp.2023.101768",

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AU - Han, Kee Sung

AU - Lee, Mal Soon

AU - Kim, Namhyung

AU - Choi, Daiwon

AU - Chae, Sujong

AU - Ryu, Jaegeon

AU - Piccini, Giovanni Maria

AU - Rousseau, Roger

AU - Thomsen, Edwin C.

PY - 2024/1/17

Y1 - 2024/1/17

N2 - 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 initial PF6− decomposition reaction that promotes thermal instability of LiPF6-based electrolytes. Here, we find that lithium-ion hopping assisted by the overall reorientational motion of propylene carbonate molecules facilitates PF6− decomposition at elevated temperatures in 1 M LiPF6/propylene carbonate electrolyte. Further, we demonstrate that urea additives, by preventing lithium-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 show improved LIB performance at elevated temperatures with the thermally stabilized electrolyte. 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.

AB - 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 initial PF6− decomposition reaction that promotes thermal instability of LiPF6-based electrolytes. Here, we find that lithium-ion hopping assisted by the overall reorientational motion of propylene carbonate molecules facilitates PF6− decomposition at elevated temperatures in 1 M LiPF6/propylene carbonate electrolyte. Further, we demonstrate that urea additives, by preventing lithium-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 show improved LIB performance at elevated temperatures with the thermally stabilized electrolyte. 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.

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KW - diffusion

KW - electrolyte decomposition

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KW - nuclear relaxation

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