Hierarchical Configuration of Double-Shelled Silicon Composite Anode Coated With Porous Silica and Reduced Graphene Oxide for Enhanced Li-Ion Battery Stability

Abstract

This study explores the optimization of double-shelled silicon (Si) composite anodes for lithium-ion batteries (LIBs) by examining the coating sequence of tetraethyl orthosilicate (TEOS) and reduced graphene oxide (rGO). The Si₅₅@TEOS₂₉@rGO₁₆ anode, which features an inner TEOS-derived layer and outer rGO shell, exhibits an initial capacity of 1763 mAh g⁻¹ at 0.1 C and maintains 1153 mAh g⁻¹ after 300 cycles at 0.5 C, achieving a capacity retention of 85.5% when incorporating the tris(trimethylsilyl) phosphate (TMSPi) electrolyte additive. The performance improvement is attributed to the hierarchical structure, where the porous SiO₂ layer effectively passivates the Si core, while the rGO shell enhances conductivity and structural stability. Comparative analysis reveals that the optimized coating sequence and TEOS content significantly enhance cycling stability, with the Si₅₅@TEOS₂₉@rGO₁₆ anode surpassing other configurations in specific capacity after 129 cycles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses confirm the uniform coating and structure stability after cycling. Electrochemical impedance spectroscopy (EIS) shows reduced impedance, and cyclic voltammetry (CV) indicates stable lithiation/delithiation processes. The inclusion of the TMSPi additive further stabilizes the solid electrolyte interphase (SEI) and inhibits capacity fading during initial cycles. This study demonstrates that optimizing the coating sequence, SiO₂ content, and electrolyte additives can significantly improve the electrochemical performance and durability of Si-based anodes, positioning them as strong candidates for next-generation LIBs.