Polymer-derived carbon/nano-silicon/graphite composites for lithium-ion battery anodes with reduced expansion

Commercial graphite used in lithium-ion battery anodes has reached its theoretical capacity limit. Polymer-derived carbon, which offers numerous sites for lithium storage, has emerged as a promising alternative to meet the increasing demand for high-energy density batteries. In this study, we investigated polymer pyrolyzed carbon and nano-silicon composites prepared through three methods: liquid-phase mixing (SiC-L), ball mill blending (SiC-S), and further milling with graphite (SiCG). By optimizing the silicon-to-carbon ratio (1:9, 2:8, 3:7, and 4:6), core–shell structured composites Si20C80-L and Si20C80-S with an optimal 2:8 ratio were obtained. The Si20C80-S anode delivered a reversible capacity of 471 mAh g−1 after 200 cycles with a 56% expansion rate. Incorporation of flake graphite produced a hierarchical silicon–carbon–graphite composite (Si20C60G20), achieving 500 mAh g−1 after 200 cycles and reducing the expansion rate to 34%. The improved performance arises from carbon matrix confinement of silicon and an optimized conductive network that enhances structural integrity and lithium storage. This study provides a feasible route toward scalable fabrication of high-stability silicon-based anodes for next-generation lithium-ion batteries.