Volume 64, Issue 30 e202507688
Research Article

In Situ Solid Conversion into Mechanically Adaptive LiF-Rich Solid Electrolyte Interphase via MgF2 Precursor on Si Surface in Lithium-Ion Batteries

Jiayang Sun

Jiayang Sun

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

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Linze Lv

Linze Lv

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

Huaying New Energy Materials. Co., Suzhou, Jiangsu, 215000 P.R. China

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Yuchen Li

Corresponding Author

Yuchen Li

School of Materials Science and Engineering, Suzhou University of Science and Technology, Suzhou, Jiangsu, 215011 P.R. China

E-mail: [email protected]; [email protected]; [email protected]

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Yan Wang

Corresponding Author

Yan Wang

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

Huaying New Energy Materials. Co., Suzhou, Jiangsu, 215000 P.R. China

E-mail: [email protected]; [email protected]; [email protected]

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Longfei Wang

Longfei Wang

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

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Weixing Xiong

Weixing Xiong

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

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Lei Huang

Lei Huang

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

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Qunting Qu

Qunting Qu

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

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Honghe Zheng

Corresponding Author

Honghe Zheng

College of Energy & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215006 P.R. China

Huaying New Energy Materials. Co., Suzhou, Jiangsu, 215000 P.R. China

E-mail: [email protected]; [email protected]; [email protected]

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First published: 23 May 2025

Graphical Abstract

MgF2 coating with high coating integrity is in situ constructed on Si nanoparticles. During electrochemical cycling, the MgF2 layer undergoes in situ conversion into LiF and Mg, thereby forming a robust solid electrolyte interphase (SEI) with high mechanical adaptability, excellent electronic insulation, and high ionic conductivity. This unique transformed SEI layer effectively mitigates mechanical degradation and interfacial side reactions, contributing to significantly enhanced electrochemical properties of the Si anode.

Abstract

Silicon (Si) anodes hold exceptional promise for high-energy-density lithium-ion batteries (LIBs) due to their ultrahigh theoretical capacity (∼4200 mAh g⁻¹). However, their commercialization is severely hindered by the significant volume expansion (∼300%) and unstable solid electrolyte interphase (SEI). Conventional SEI, predominantly composed of organic species, suffers from low ionic conductivity, low electronic insulation, and poor mechanical robustness, leading to rapid capacity decay. Herein, we propose an interface engineering strategy by decorating Si nanoparticles with an in situ conversed MgF2 layer (with coating integrity of 94.2%). During initial lithiation, the applied MgF2 layer is in situ conversed into SEI film with high ionic conductivity, electronic insulation, and better mechanical adaptability. The prepared Si@MgF2-1 anode achieves a high initial coulombic efficiency (91.7%), superior rate capability (2000 mAh g⁻¹ at 10 C), and remarkable cycling stability (1794.9 mAh g−1 after 500 cycles). Full-cell based on the Si@MgF2-1 anode and NCM811 cathode further validate the practicality of this approach. The robust conversion strategy for the construction of a mechanically adaptive LiF-rich SEI layer holds significant promise for the advancement of durable silicon-based LIBs.

Conflict of Interests

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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