Large-Scale Construction of Multiscale-Structured Nano-Si@C/Graphite Composites toward a High-Stability Lithium Ion Battery Anode

Embedding Si nanoparticles in the graphite matrix to form silicon–carbon composite anodes is an effective approach to enhancing the battery performance of silicon anodes. However, poor adhesion at the graphite–silicon interface fails to fully accommodate silicon’s volume changes during cycling, causing the silicon–carbon composite to crack, consequently resulting in poor cycling stability. Here, we report a green and economical method to prepare nano-Si@carbon/graphite (Si@C/G) anode materials by encapsulating silicon nanoparticles within an industrial lignin-derived carbon shell to form core–shell Si@C nanoparticles, which are then embedded within a commercial graphite matrix to produce the Si@C/G composite. Compared to bare nano-Si, the Si@C nanoparticles exhibit stronger van der Waals interactions with graphite (−30.2 kcal/mol vs −24.7 kcal/mol) and a large interfacial contact area, attributed to efficient π–π stacking between the lignin-derived carbon shell and graphite. Additionally, the average adhesion force between Si@C nanoparticles and graphite (−1.039 ± 0.523 mN/m) is substantially greater than the adhesion force between Si and graphite (−0.369 ± 0.211 mN/m), confirming that the lignin-derived carbon coating dramatically enhances adhesion. This enhanced interface facilitates fast electron transport and contributes to the anode’s excellent mechanical stability. Furthermore, the graphite matrix buffers the overall volume expansion and boosts the conductive performance of the prepared anode. Consequently, the LIB employing the Si@C/G anode delivers 777.4 mAh·g–1 at a high current density of 5.0 A·g–1. The material also shows a notably stable cycling performance, maintaining a capacity of as high as 956 mAh·g–1 after 200 cycles at 1 A·g–1, corresponding to a capacity retention rate exceeding 77%. This study presents an economical strategy to fabricate next-generation Si/C anodes for LIBs while also offering a high-value utilization pathway for industrial lignin.