Atomic-Level Growth Engineering of Si via Acetylene-Silane Co-Deposition for Enhanced Cycle Stability and High Li+ Dynamics in Si/C Anodes

Abstract

The practical implementation of chemical vapor deposition (CVD) silicon/carbon (Si/C) anodes is still limited by severe volumetric expansion, unstable solid electrolyte interphase (SEI) formation, and sluggish Li⁺ transport. Existing efforts largely focus on engineering carbon scaffolds, but currently available biomass-derived and resin-derived carbons suffer from either insufficient microporosity or high cost, offering limited control over Si nucleation and mechanical stability. Here, we systematically examine CVD-Si/C composites with controlled Si contents and identify poorly confined mesoporous Si domains as a major origin of early capacity decay. Based on this mechanistic insight, a silane–acetylene co-deposition strategy was introduced in the later stage of CVD to regulate the initial nucleation and growth of Si through local atomic-scale Si–C bonding interactions, leading to uniformly nanosized Si domains and strong Si–carbon coupling. The optimized CVD-silicon/activated carbon composite with a moderately co-deposited layer (ACS/SC@C-2) delivers an initial specific capacity of 1837.6 mAh g^-1, retains 94.4% of its initial capacity after 350 cycles and 91.4% after 100 cycles at 55 °C. This co-deposition method addresses the inherent limitations of carbon-framework engineering and provides an economical, structurally precise route to stabilize CVD-Si/C anodes, offering a broadly applicable pathway toward durable, high-energy-density silicon anodes.