Synergistic Hierarchical Design of a 3D CNT Conductive Network and N,S-Doped Carbon Coating for Ultrastable Silicon...

Silicon anodes, despite their high theoretical capacity, face critical challenges such as severe volume expansion (> 300%), sluggish reaction kinetics, and unstable solid electrolyte interphase (SEI) formation. Herein, we report a hierarchical Si@C/N,S@CNT composite, integrating an N,S-doped carbon shell with an interwoven carbon nanotube (CNT) network. This design synergistically accommodates strain, establishes rapid electron pathways, and stabilizes the interface. In situ EIS analysis verifies the formation of a stable, low-impedance interface and enhanced charge-transfer kinetics. Density functional theory (DFT) calculations reveal that the N,S co-doping induces a built-in electric field at the carbon-silicon interface, significantly boosting Li⁺ adsorption and reducing its diffusion barrier. Consequently, the Si@C/N,S@CNT anode delivers an outstanding combination of properties: a high initial Coulombic efficiency of 87.2%, exceptional long-term cyclability (1325 mAh g^-1 after 1000 cycles at 1 A g^-1), and a Li⁺ diffusion coefficient nearly three orders of magnitude higher than that of bare silicon. When paired with a LiFePO₄ cathode, the full cell exhibits remarkable stability, retaining 82.5% capacity after 1000 cycles. This work demonstrates a potent multiscale design principle, where a 3D conductive network synergizes with an engineered interface to effectively overcome the fundamental limitations of silicon anodes.