Low-Impedance Hybrid Carbon Structures on SiOX: A Sequential Gas-Phase Coating Approach.

Abstract

Carbon coating on SiO_X surface is crucial for enhancing initial Coulombic efficiency (ICE) and cycling performance in batteries, while also buffering volume expansion. Despite its market prevalence, the effects of the carbon layer's quality and structure on the electrochemical properties of SiO_X remain underexplored. This study compares carbon layers produced via gas-phase and solid-phase coating methods, introducing an innovative technique that sequentially uses two gases to develop a low-impedance hybrid carbon structure. In this approach, C₃H₈ is first deposited to create a short-range, vertically ordered carbon architecture, followed by C₂H₂ to establish a long-range, layered structure, effectively filling the gaps. This results in a dense hybrid carbon layer characterized by minimal defects, high crystallinity, and excellent electronic conductivity. The dominant vertical configuration enhances Li-ion migration. The SiO@C₃H₈@C₂H₂ prepared through this method yields a specific surface area of 1.14 m² g⁻¹ and a high reversible capacity of 1574.9 mAh g⁻¹, alongside an ICE of 83.7%. It showcases remarkable cycling stability, retaining 86.6% capacity after 1000 cycles at room temperature, and performs effectively under varied temperatures and discharging conditions. This low-impedance carbon structure provides a significant reference for other anodes that also require a carbon layer.