Abstract
The electrolyte–electrode interface serves as the foundation for a myriad of chemical and physical processes. In battery chemistry, the formation of a well-known solid–electrolyte interphase (SEI) plays a pivotal role in ensuring the reversible operations of rechargeable lithium-ion batteries (LIBs)1,2. However, characterizing the precise chemical composition of the low crystallinity and highly sensitive SEI presents a formidable challenge3. Here, taking lithium fluoride (LiF)—a widely studied and considered crucial SEI component4,5,6,7—as an example, we use 19F solid-state nuclear magnetic resonance (NMR) and identify that LiF formed in SEI (LiFSEI) has fruitful spectroscopy features that originated from the formation of limited LiF–LiH solid solutions: H-rich phase (LiH1−yFy) and F-rich phase (LiF1−xHx), which is further validated by 6Li isotope NMR, synchrotron X-ray diffraction and cryo-electron microscopy (cryo-EM). By characterizing SEI formed in various electrolytes, we confirm the dominance of LiH1−yFy in high-coulombic-efficiency electrolyte, which can be rationalized by the fact that LiF–LiH solid solution shows improved ionic conductivity over LiF. As a proof of concept, we demonstrate that LiH1−yFy-rich coating layer presents obvious advantages compared with LiF-rich coating layer in lithium-metal batteries. This revised understanding of the heterogeneous nature of SEI components would provide new insights for electrode–electrolyte interface design.
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The data that support the findings of this study are available in the Source data provided with this paper. All other relevant data of this study are available from the corresponding authors on request.
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Acknowledgements
This work was supported by Research Center for Industries of the Future (RCIF) at Westlake University and Westlake Education Foundation, National Natural Science Foundation of China (grant nos. 22309148, 22402161 and 52271203) and Postdoctoral Science Foundation of China (grant no. 2023M733176). The calculations were performed at Westlake High-Performance Computing Center. We express gratitude to X. Lu and D. Gu from the Instrumentation and Service Center for Molecular Sciences at Westlake University for their support in the NMR measurements. We thank Y. Lin, Q. Jiang and P. Sheng from the Instrumentation and Service Center for Physical Sciences at Westlake University for their assistance with the cryo-EM EELS measurements. We thank J. Huang, X. Chen, Q. Lu, Y. Jin and M. Lin for valuable discussion. We sincerely appreciate S. Gao at Fudan University for his valuable assistance in the analysis of EELS data.
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X. Liu, Y.Z., Y.S. and Y.X. conceived and designed this work. X. Liu, D.G., X. Lu and Y.X. performed the solid-state NMR experiments. X. Liu, C.Y., B.Z. and G.C. performed electrochemical characterization and SEI sample preparation. S.L. and Y.C. performed the LiF1−xHx sample preparation and corresponding electrochemical characterizations. X. Liu, B.L. and H.L. performed diffraction experiments and corresponding data analysis. C.Y., Z.Y. and Y.Z. performed density functional theory calculations. X. Liu, B.Z., S.L., H.Q., Y.S., D.S. and Y.X. analysed the figures and wrote the paper. All of the authors participated in analysis of the experimental data and revised the paper.
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Liu, X., Li, S., Yuan, C. et al. Probing the heterogeneous nature of LiF in solid–electrolyte interphases. Nature 646, 102–107 (2025). https://doi.org/10.1038/s41586-025-09498-7
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DOI: https://doi.org/10.1038/s41586-025-09498-7
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