Building a Flexible and Highly Ionic Conductive Solid Electrolyte Interphase on the Surface of Si@C Anodes by Binary...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Silicon-carbon (Si@C) composites are promising high-capacity anodes for lithium-ion batteries (LIBs).
• Volume expansion of Si@C during cycling causes solid electrolyte interphase (SEI) instability, leading to poor battery performance.
• Electrolyte additives offer a cost-effective strategy to stabilize the SEI layer.

Purpose of the Study:

• To investigate the synergistic effect of vinyl carbonate (VC) and lithium difluorophosphate (LiDFP) as electrolyte additives for Si@C anodes.
• To improve the interfacial properties and electrochemical stability of Si@C anodes in LIBs.
• To elucidate the mechanism behind the enhanced SEI formation and performance.

Main Methods:

• Electrochemical testing of Si@C anodes with VC and LiDFP additives in half-cells.
• Surface characterization using spectral techniques.
• Computational analysis using density functional theory (DFT).

Main Results:

• VC forms a flexible SEI, mitigating Si particle fragmentation but increasing impedance.
• LiDFP decomposition products (LiF, Li3PO4) form an inorganic SEI layer, enhancing Li+ transport and reducing interfacial impedance.
• The combined VC + LiDFP additive strategy creates a robust SEI with improved flexibility and ionic conductivity.
• Capacity retention of Si@C/Li half-cells improved from 68.2% to 85.1% after 100 cycles.

Conclusions:

• Synergistic VC and LiDFP additives effectively stabilize the SEI layer in Si@C anodes.
• This approach significantly enhances the cycling stability and rate capability of Si@C-based LIBs.
• The study provides a simple yet effective method for developing high-performance Si-based LIBs.