Rechargeable lithium metal (Li0) batteries (RLMBs) are considered attractive for improving Li-ion batteries. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) has been extensively used as a conducting salt for RLMBs due to its advantageous stability and innocuity. However, LiTFSI-based electrolytes are corrosive towards aluminium (Al0) current collectors at low potentials (>3.8 V versus Li/Li+), thereby excluding their application in 4-V-class RLMBs. Herein, we report on a non-corrosive sulfonimide salt, lithium (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (LiDFTFSI), that remarkably suppresses the anodic dissolution of the Al0 current collector at high potentials (>4.2 V versus Li/Li+) and significantly improves the cycling performance of Li(Ni1/3Mn1/3Co1/3)O2 (NMC111) cells. In addition, this sulfonimide salt results in the growth of an advantageous solid electrolyte interphase on the Li0 electrode. The replacement of either LiTFSI or LiPF6 with LiDFTFSI endows a Li0||NMC111 cell with superior cycling stability and capacity retention (87% at cycle 200), demonstrating the decisive role of the salt anion in dictating the electrochemical performance of RLMBs.
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The authors declare that all data supporting the findings of this study are available within the paper and its Supplementary Information. Additional data are available from the corresponding authors upon reasonable request.
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This work was supported by the Fundamental Research Funds for the Central Universities, HUST (grant no. 2020kfyXJJS095), and the Basque Government through the ELKARTEK-2016 programme. L.Q. thanks the Chinese Scholarship Council for financial support (grant no. 201808370162). We thank Neware (Shenzhen, China) for offering the battery cycler.
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Extended Data Fig. 1 Digital images (top row) and the zoomed-in images (bottom row) of the Al° electrode after the chronoamperometry measurements in various liquid electrolytes at 60 °C.
The pitting corrosion of the Al° are marked by small purple arrows in the LiTFSI-based electrolyte.
Extended Data Fig. 2 X-ray photoelectron spectra (XPS) of the cycled Li° electrodes in the Li° || NMC111 cells using different electrolytes after C-rate tests at room temperature.
a, C 1s. b, O 1s. c, F 1s and d, Li 1s. See the detailed discussions associated with the results in the Supplementary Information.
Extended Data Fig. 3 XPS spectra of the cycled NMC111 electrodes in Li° || NMC111 cells using different electrolytes after C-rate tests at room temperature.
a, C 1s. b, O 1s. c, F 1s. See the detailed discussions associated with the results in the Supplementary Information.
Extended Data Fig. 4 XPS spectra of the Al° electrodes recovered from the Li° || Al° cells after the chronoamperometry (CA) tests (see in Fig. 3a) at room temperature.
a, Al 2p spectra. b, F 1s spectra. c, O 1s spectra. d, C 1s spectra. See the detailed discussions associated with the results in the Supplementary Information.
Extended Data Fig. 5 Cycling performance of the Li° || NMC111 cells using the LiDFTFSI-, LiTFSI-, and LiPF6-based electrolytes at 60 °C.
a, Discharge capacity and CE versus cycle number for these three electrolytes at 60 °C. b, Cyclability of these three electrolytes-based cells after C-rate tests at 60 °C. c-e, Charge/discharge profiles of various liquid electrolytes at different C-rates at 60 °C: LiDFTFSI-based electrolyte (c), LiTFSI-based electrolyte (d) and LiPF6-based electrolyte (e). Note that in Extended Data Fig. 5d, the charge/discharge profiles of the 15th, 20th, and 25th cycles are nearly superimposed due to their extremely low specific capacities, and for clarity, a zoomed-in plot is provided in Supplementary Fig. 30. See the detailed discussions associated with the results in the Supplementary Information.
Extended Data Fig. 6 X-ray diffraction (XRD) patterns of the pristine and cycled NMC111 cathodes (after C-rate tests at room temperature) using different liquid electrolytes.
See the detailed discussions associated with the results in the Supplementary Information.
Extended Data Fig. 7 Scanning electron microscopy (SEM) images of the pristine and cycled NMC111 cathodes (after C-rate tests at room temperature) using different liquid electrolytes.
See the detailed discussions associated with the results in the Supplementary Information.
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Qiao, L., Oteo, U., Martinez-Ibañez, M. et al. Stable non-corrosive sulfonimide salt for 4-V-class lithium metal batteries. Nat. Mater. 21, 455–462 (2022). https://doi.org/10.1038/s41563-021-01190-1