A Weak-Fluorine-Bond Molecule Stabilizes Hard Carbon Anodes for Practical Sodium-Ion Batteries

Yaqi Liao; Han Liu; Yangqian Zhang; Jiayi Yang; Haijin Ji; Donghai Wang; Lixia Yuan; Yunhui Huang; Yang Ren

doi:10.1021/acsnano.5c10983

A Weak-Fluorine-Bond Molecule Stabilizes Hard Carbon Anodes for Practical Sodium-Ion Batteries

Yaqi Liao (Co-first Author)
, Han Liu (Co-first Author)
, Yangqian Zhang
, Jiayi Yang^*
, Haijin Ji
, Donghai Wang^*
, Lixia Yuan
, Yunhui Huang
, Yang Ren^*

^*Corresponding author for this work

Research output: Journal Publications and Reviews › RGC 21 - Publication in refereed journal › peer-review

9 Citations (Scopus)

4 Downloads (CityUHK Scholars)

Abstract

Solid-electrolyte interphase (SEI) is essential for improving the cycling stability in sodium-ion batteries (SIBs) by preventing direct contact between electrolytes and hard carbon (HC) anodes. Conventional C-F bond molecules like fluoroethylene carbonate (FEC) show poor SEI formation due to early sodium-ion adsorption on HC, delaying additive reduction. Herein, methyl 2, 2-difluoro-2-(fluorosulfonyl) acetate (MDFA), a weak-fluorine-bond molecule, is proposed to facilitate early SEI formation and suppress parasitic reactions. The strong electron-withdrawing O=S=O group destabilizes the S-F bond, enabling preferential reduction of MDFA and formation of inorganic SEI components that enhance ionic conductivity and accelerate interfacial charge transfer. As a result, the HC with MDFA shows over 5000 stable cycles and delivers a high capacity of 252 mAh g^-1 at 5 C, outperforming 108 mAh g^-1 of that with FEC. A 4.6 Ah pouch cell with MDFA enables 89.3% capacity retention after 1000 cycles. These findings provide valuable insights into fluorine-bond chemistry for the electrolyte additive design in long-life SIBs. © 2025 American Chemical Society.

Original language	English
Pages (from-to)	30466-30475
Number of pages	10
Journal	ACS Nano
Volume	19
Issue number	33
Online published	16 Aug 2025
DOIs	https://doi.org/10.1021/acsnano.5c10983
Publication status	Published - 26 Aug 2025

Funding

The authors acknowledge the Shenzhen Science and Technology Program (JCYJ20220818101016034), the City University of Hong Kong (CityU 9610533, 9610658, and 9680351), the Centre for Neutron Scattering, and the Shenzhen Research Institute, City University of Hong Kong. The research work described in this paper was conducted in the JC STEM Lab of Energy and Materials Physics funded by The Hong Kong Jockey Club Charities Trust. The authors thank HUST’s Analytical and Testing Center and the State Key Laboratory of Materials Processing and Die & Mold Technology of HUST for characterizations. Thanks to eceshi (www. eceshi. com) for XPS analysis.

UN SDGs

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

SDG 7 Affordable and Clean Energy

Research Keywords

hard carbon anodes
preferential reductions
sodium-ion batteries
solid-electrolyte interphases
weak-fluorine-bond molecules

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This full text is made available under CC-BY 4.0. https://creativecommons.org/licenses/by/4.0/

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title = "A Weak-Fluorine-Bond Molecule Stabilizes Hard Carbon Anodes for Practical Sodium-Ion Batteries",

abstract = "Solid-electrolyte interphase (SEI) is essential for improving the cycling stability in sodium-ion batteries (SIBs) by preventing direct contact between electrolytes and hard carbon (HC) anodes. Conventional C-F bond molecules like fluoroethylene carbonate (FEC) show poor SEI formation due to early sodium-ion adsorption on HC, delaying additive reduction. Herein, methyl 2, 2-difluoro-2-(fluorosulfonyl) acetate (MDFA), a weak-fluorine-bond molecule, is proposed to facilitate early SEI formation and suppress parasitic reactions. The strong electron-withdrawing O=S=O group destabilizes the S-F bond, enabling preferential reduction of MDFA and formation of inorganic SEI components that enhance ionic conductivity and accelerate interfacial charge transfer. As a result, the HC with MDFA shows over 5000 stable cycles and delivers a high capacity of 252 mAh g-1 at 5 C, outperforming 108 mAh g-1 of that with FEC. A 4.6 Ah pouch cell with MDFA enables 89.3\% capacity retention after 1000 cycles. These findings provide valuable insights into fluorine-bond chemistry for the electrolyte additive design in long-life SIBs. {\textcopyright} 2025 American Chemical Society.",

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author = "Yaqi Liao and Han Liu and Yangqian Zhang and Jiayi Yang and Haijin Ji and Donghai Wang and Lixia Yuan and Yunhui Huang and Yang Ren",

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doi = "10.1021/acsnano.5c10983",

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journal = "ACS Nano",

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T1 - A Weak-Fluorine-Bond Molecule Stabilizes Hard Carbon Anodes for Practical Sodium-Ion Batteries

AU - Liao, Yaqi

AU - Liu, Han

AU - Zhang, Yangqian

AU - Yang, Jiayi

AU - Ji, Haijin

AU - Wang, Donghai

AU - Yuan, Lixia

AU - Huang, Yunhui

AU - Ren, Yang

PY - 2025/8/26

Y1 - 2025/8/26

N2 - Solid-electrolyte interphase (SEI) is essential for improving the cycling stability in sodium-ion batteries (SIBs) by preventing direct contact between electrolytes and hard carbon (HC) anodes. Conventional C-F bond molecules like fluoroethylene carbonate (FEC) show poor SEI formation due to early sodium-ion adsorption on HC, delaying additive reduction. Herein, methyl 2, 2-difluoro-2-(fluorosulfonyl) acetate (MDFA), a weak-fluorine-bond molecule, is proposed to facilitate early SEI formation and suppress parasitic reactions. The strong electron-withdrawing O=S=O group destabilizes the S-F bond, enabling preferential reduction of MDFA and formation of inorganic SEI components that enhance ionic conductivity and accelerate interfacial charge transfer. As a result, the HC with MDFA shows over 5000 stable cycles and delivers a high capacity of 252 mAh g-1 at 5 C, outperforming 108 mAh g-1 of that with FEC. A 4.6 Ah pouch cell with MDFA enables 89.3% capacity retention after 1000 cycles. These findings provide valuable insights into fluorine-bond chemistry for the electrolyte additive design in long-life SIBs. © 2025 American Chemical Society.

AB - Solid-electrolyte interphase (SEI) is essential for improving the cycling stability in sodium-ion batteries (SIBs) by preventing direct contact between electrolytes and hard carbon (HC) anodes. Conventional C-F bond molecules like fluoroethylene carbonate (FEC) show poor SEI formation due to early sodium-ion adsorption on HC, delaying additive reduction. Herein, methyl 2, 2-difluoro-2-(fluorosulfonyl) acetate (MDFA), a weak-fluorine-bond molecule, is proposed to facilitate early SEI formation and suppress parasitic reactions. The strong electron-withdrawing O=S=O group destabilizes the S-F bond, enabling preferential reduction of MDFA and formation of inorganic SEI components that enhance ionic conductivity and accelerate interfacial charge transfer. As a result, the HC with MDFA shows over 5000 stable cycles and delivers a high capacity of 252 mAh g-1 at 5 C, outperforming 108 mAh g-1 of that with FEC. A 4.6 Ah pouch cell with MDFA enables 89.3% capacity retention after 1000 cycles. These findings provide valuable insights into fluorine-bond chemistry for the electrolyte additive design in long-life SIBs. © 2025 American Chemical Society.

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KW - preferential reductions

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KW - solid-electrolyte interphases

KW - weak-fluorine-bond molecules

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DO - 10.1021/acsnano.5c10983

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ER -

A Weak-Fluorine-Bond Molecule Stabilizes Hard Carbon Anodes for Practical Sodium-Ion Batteries

Abstract

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