Enhanced lithium storage in silicon anodes via Sn-Ni heterostructures and graphene conductive networks: interface...

Silicon-based anodes are considered promising candidates for next-generation lithium-ion batteries because of their ultrahigh theoretical capacity. However, their practical application is still hindered by severe volume variation, low electronic conductivity, and unstable interfacial evolution during repeated lithiation/delithiation. In this work, a Sn-Ni@Si heterostructured silicon-based anode with tunable graphene content was constructed through a facile solution-assisted route followed by thermal treatment. Among the investigated samples, the optimized Sn-Ni@Si-2 composite with 25 wt% graphene exhibited the best overall electrochemical performance, delivering an initial coulombic efficiency of 87.81% at 0.1C and maintaining a reversible capacity of 677.09 mAh g^-1 after 100 cycles at 0.5C. Structural and electrochemical analyses suggest that the improved performance is associated with the synergistic effects of a continuous graphene conductive framework, improved dispersion of active components, and a stabilized interfacial chemical environment involving Si-O-Sn bonding. The optimized composite also shows reduced charge-transfer resistance and enhanced Li⁺ diffusion kinetics compared with the graphene-free counterpart. In addition, density functional theory calculations based on a simplified interfacial model indicate that interfacial electronic coupling may contribute to the enhanced charge-transfer behavior observed experimentally. This work provides a feasible strategy for improving the lithium storage performance of silicon-based anodes through synergistic interfacial regulation and conductive-network design.