Fluorine-Doping Carbon-Modified Si/SiO_x to Effectively Achieve High-Performance Anode

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Silicon-based anodes are crucial for high-performance lithium-ion batteries (LIBs) but suffer from poor cycling stability, low initial coulombic efficiency (ICE), and interface issues.
• Existing silicon/silicon oxide (Si/SiOx) anodes require improved strategies to overcome inherent limitations for practical applications.

Purpose of the Study:

• To develop high-performance Si/SiOx@F-C composites by in situ coating a fluorine-doped carbon layer on Si/SiOx.
• To enhance the electrochemical performance, cycling stability, and interfacial compatibility of silicon-based anodes for LIBs.

Main Methods:

• Preparation of Si/SiOx@F-C composites via high-temperature pyrolysis with in situ fluorine-doped carbon coating.
• Electrochemical testing of Si/SiOx@F-C electrodes in LIBs, including cycling, rate capability, and long-term stability assessments.
• Material characterization to analyze the structure, conductivity, and interface properties of the fluorine-doped carbon layer.

Main Results:

• Si/SiOx@F-C electrodes achieved a high ICE of 79%, significantly outperforming Si/SiOx@C (71%) and Si/SiOx (43%).
• Excellent rate performance was observed, retaining 603 mAhg⁻¹ at 5000 mAg⁻¹.
• Exceptional long-term cycling stability was demonstrated, with 829 mAhg⁻¹ at 1000 mAg⁻¹ over 1400 cycles and 588 mAhg⁻¹ at 3000 mAg⁻¹ over 2400 cycles (82.12% retention).

Conclusions:

• The fluorine-doped carbon layer effectively enhances electrical conductivity and prevents structural degradation of Si/SiOx anodes.
• Increased LiF concentration in the solid electrolyte interface (SEI) film due to fluorine doping improves interfacial compatibility.
• The straightforward and effective Si/SiOx@F-C composite preparation offers a promising route for advanced silicon anodes in LIBs.