Structural and Mechanical Insights into Chemically Synthesized Si–C Composites for Lithium-Ion Battery Negative Electrodes

Numerous efforts have been made to utilize silicon-based negative electrodes in lithium-ion batteries (LiBs). The main challenge with Si-based anodes is their significant volume expansion and contraction during cycling, which degrades LiB performance . Silicon-carbon composites are known to address many of the challenges of large-volume expansion and can deliver high specific capacity alongside acceptable cycle life. In this study, various chemically synthesized Si-C composites with different porous hard carbon precursors were investigated to examine the evolution of the filling of the carbon precursor pores with Si during impregnation via chemical vapour deposition using SiH4 gas. These samples were later etched with a high-pH solution to remove the Si in several steps, returning the structure to that of the carbon precursor to backtrack the changes in the carbon precursor. The as-received carbon precursor and the etched samples were compared using small-angle X-ray scattering and X-ray diffraction. These techniques, combined with high-resolution transmission electron microscopy, compression testing of the samples, and electrochemical performance measurements, provide a broad view of the evolution of the carbon precursor structure during Si deposition and during the charge/discharge processes in the LiB negative electrode, providing insight into the structure-performance-properties correlation of CVD-based Si-C composites.