Yolk–Shell Silicon–Carbon Anodes with Interconnected N-Doped Carbon Networks for Stable Lithium-Ion Storage

Silicon-based anodes are considered promising alternatives to graphite anodes owing to their high theoretical lithium-storage capacity and abundant reserves. However, silicon nanoparticle anodes are severely limited by large volume expansion, unstable interfacial chemistry, and poor electrical connectivity during repeated lithiation/delithiation. Herein, we develop a yolk–shell N-doped carbon network (NCN) strategy to construct Si@void@NCN composites. The optimized Si@void@NCN-1 achieves a balanced architecture between void buffering and carbon network integrity, delivering a high initial discharge capacity of 1245.5 mAh g−1 and an initial charge capacity of 735.8 mAh g−1. It also demonstrates stable long-term cycling performance, retaining a reversible capacity of 402.5 mAh g−1 after 500 cycles at 0.5 A g−1 with a capacity retention of 68.66%, and shows improved rate reversibility and electrode structural stability, with an electrode thickness increase of only 80.4% after rate cycling, much lower than that of densely carbon-coated Si@C. Kinetic analysis, post-cycling structural characterization, and in situ EIS further reveal that the yolk–shell void-buffering structure and the N-doped three-dimensional conductive network act synergistically to mitigate Si volume expansion, enhance structural stability, and facilitate electron/ion transport. This study emphasizes the importance of integrating buffering structures with Si/C composites, providing guidance for the rational design of advanced silicon-based electrode materials.