Heterojunction-Engineered N, S Co-Doped Carbon-Coated Silicon Anodes via Supramolecular Self-Assembly for...

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, a novel strategy is proposed that synergistically combines supramolecular self-assembly techniques with heterojunction engineering to fabricate N, S co-doped carbon-coated silicon composites (Si/SiO_x@C/N, S). The designed heterostructure mitigates mechanical degradation, enhances electronic conductivity, and stabilizes the SEI. In situ X-ray diffraction (XRD) confirms the highly reversible lithiation/delithiation process, while in situ EIS verifies the formation of a stable SEI. Furthermore, density functional theory (DFT) calculations reveal that the heterojunction between SiO_x and N, S co-doped carbon induces an internal electric field, significantly accelerating Li⁺ diffusion and improving charge transport. Electrochemical evaluation reveals that the optimized MSi@SiO_x@C/N, S electrode achieves an initial Coulombic efficiency of 86.1% and maintains a reversible capacity of 1331.7 mAh g⁻¹ after 500 cycles at 1 A g⁻¹, along with excellent rate capability. Moreover, full-cell tests with a LiFePO₄ cathode exhibit a capacity retention of 82.7% after 500 cycles, demonstrating the composite's robust performance. This research presents a scalable and effective methodology for overcoming the inherent limitations of silicon anodes, offering valuable insights into the development of next-generation lithium-ion battery materials.