Nanoscale Interfacial Carbon Engineering Coupled with Solvent-Directed Growth of SnS ₂ for Enhanced Sodium-Ion Storage Kinetics

Sodium-ion batteries (SIBs) with abundant resources are considered a promising energy storage technology. Tin disulfide (SnS2) is a potential anode material owing to its high capacity and layered structure, but large volume expansion and poor conductivity limit its rate capability and cycling stability. In this study, two strategies are adopted to synthesize SnS2 as efficient anode materials for SIBs. Solvent regulations using deionized water and ethanol are applied to control the crystallinity and morphology of SnS2. SnS2 synthesized with a mixed solvent exhibits vertically aligned nanosheets with enlarged interlayer spacing, resulting in improved rate capability and cycling performance. Furthermore, polydopamine (PDA)-derived carbon coating is introduced to improve conductivity and buffer structural stress. The SnS2 and N-doped carbon composites (SnS2/NC) preserve nanosheet architecture with coating thickness increasing with polymerization time. The optimal SnS2/NC (SnS2/NC 6h) achieves high specific capacities of 1023.6 and 765.9 mAh/g in the first and second cycle at 0.05 A/g, respectively, and delivers a reversible capacity of 473.7 mAh/g after 100 cycles at 0.1 A/g. Moreover, SnS2/NC 6h exhibits the highest Na+ diffusion coefficients over the entire potential range, confirming superior ion transport kinetics. This work demonstrates that solvent selection and controlled carbon coating are effective strategies for developing high-performance SnS2 anodes for SIBs.