Relationship between Silicon Percentage in Graphite Anode to Achieve High-Energy-Density Lithium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• High-weight-percentage silicon (Si) in graphite (Gr) anodes presents commercialization challenges for lithium-ion batteries (LIBs).
• Optimizing the Si/Gr ratio is crucial for fabricating high-energy-density LIBs using existing manufacturing lines.
• Existing literature lacks a thorough examination of the optimal Si/Gr ratio.

Purpose of the Study:

• To systematically evaluate Si content (5-20 wt%) in commercial graphite to optimize the Si/Gr ratio.
• To enhance specific capacity while mitigating Si limitations like cyclic stability and first-cycle irreversible capacity loss.
• To provide insights for the commercial viability of Si/Gr composite anodes.

Main Methods:

• Systematic evaluation of Si content (5-20 wt%) in commercial graphite.
• In situ electrochemical impedance spectroscopy for interface analysis.
• Rate capability assessment (up to 3 C-rate), Li diffusion coefficient measurement, and cyclic stability evaluation.

Main Results:

• Increasing Si content to 15% (Si₁₅Gr₇₅) significantly improved lithiation/delithiation capacities by ~16.8% and ~16.0%.
• The Si₁₅Gr₇₅ anode achieved an initial Coulombic efficiency of ~82.9%, comparable to pure graphite.
• Excellent cyclic stability was observed, retaining ~60% capacity after 215 cycles at 0.5 C, with strong full-cell performance against NMC622.

Conclusions:

• The optimized Si₁₅Gr₇₅ anode composition offers a viable pathway to high-energy-density LIBs.
• This study provides critical data for the commercial development of advanced Si/Gr composite anodes.
• The findings highlight the potential of Si/Gr anodes for next-generation energy storage solutions.