期刊
JOURNAL OF POWER SOURCES
卷 549, 期 -, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.jpowsour.2022.232147
关键词
Lithium difluorophosphate; Lithium bis(fluorosulfonyl)imide; Interface film; Low temperature; Interaction mechanism
资金
- Program of Science and Technology International Cooperation Project of Qinghai Province [21ZD4GA031]
- Gansu Province Major Special Fund [21JR7RA254]
- Natural Science Foundation of Gansu Province for Youths [2022A- 029]
- Gansu Provincial Department of Education: Innovation Fund Project [2021-1-152]
- Lanzhou Science and Technology Plan Project
- [2022-HZ- 809]
Introducing lithium difluorophosphate (LiDFP) as an additive in the electrolyte improves the electrochemical performance of graphite/Li half-cells at low temperature by generating a SEI film rich in LiF and Li3PO4.
Lithium-ion batteries (LIBs) suffering from severe performance degradation because of the unstable solid elec-trolyte interphase (SEI) on the anode at low temperature restricts their practical applications. Herein, lithium difluorophosphate (LiDFP) as the additive is introduced into lithium bis(fluorosulfonyl) imide (LiFSI) based electrolyte to improve the electrochemical performance of graphite/Li half-cells at low temperature. Contrary to the popular perception, we reveal at low temperature that LiDFP attenuates the decomposition of LiFSI by competing the hydrolysis reaction with LiFSI to generate a SEI film rich in LiF and Li3PO4 during prolonged cycling, rather than preferential decomposition. Additionally, the possible reaction equations and the interaction mechanism between LiDFP and LiFSI are proposed by combining in situ electrochemical impedance electro-chemical (PRIs-EIS) tests, spectroscopic characterization techniques and density functional theory (DFT) calcu-lations. It is demonstrated that the strong binding energy between LiF (from the decomposition of LiFSI) and LiDFP makes LiDFP easier deposit on the electrode surface. This work demonstrates the synergistic role combining the complementary advantage of film-forming additives and main lithium salts to improve the interfacial stability of LIBs at low temperature. Additionally, it can also pave the new pathway for the design of low temperature electrolytes in LIBs.
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