Mechanically and chemically robust sandwich-structured C@Si@C nanotube array Li-ion battery anodes.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Silicon anodes offer high specific capacity for advanced batteries.
• Volume expansion of silicon during cycling causes electrode degradation and capacity fade.
• Existing silicon anode designs struggle with mechanical and chemical stability.

Purpose of the Study:

• To develop a stable and high-performance silicon anode for next-generation batteries.
• To address the challenges of volume change and solid-electrolyte interphase (SEI) instability in silicon anodes.
• To investigate the structural and electrochemical properties of a novel carbon-silicon-carbon nanotube composite.

Main Methods:

• Fabrication of a carbon-silicon-carbon (C@Si@C) nanotube sandwich structure.
• Electrochemical testing to evaluate capacity, Coulombic efficiency, and cycling stability.
• In situ scanning electron microscopy (SEM) to observe structural changes during lithiation/delithiation.
• Mechanical modeling to assess strain distribution within the nanotube structure.

Main Results:

• The C@Si@C nanotube array achieved a capacity of ~2200 mAh g⁻¹ (~750 mAh cm⁻³), surpassing commercial graphite anodes.
• Demonstrated high structural and electrochemical stability with a Coulombic efficiency of ~98% over 60 cycles.
• In situ SEM revealed reversible expansion and elongation of nanotubes during cycling, indicating excellent volume accommodation.
• Mechanical modeling suggested reduced plastic strain in nanotubes compared to nanorods, mitigating low-cycle fatigue.

Conclusions:

• The C@Si@C nanotube sandwich structure effectively enhances silicon anode stability and energy density.
• This design provides a robust solution to silicon's volume expansion and SEI instability issues.
• The generalizability of the sandwich nanotube design offers a promising pathway for various emerging electrode systems.