Bio-Templated Fabrication of SnO ₂ /SnS Nanoparticles Anchored in S-Doped Hollow Carbon Tubes as Anode Materials Sodium-Ion Batteries

Tin-based oxides/sulfides (SnO 2 /SnS) have emerged as highly attractive anode materials for sodium-ion batteries (SIBs) due to their excellent theoretical specific capacity. However, the dramatic volume change (>250%) upon charge/discharge results in electrode pulverization and structural collapse, significantly limiting their cycling stability and practical application. Herein, we propose a “bio-template replication-carbonization-active material loading” strategy. Utilizing absorbent cotton as a three-dimensional structural biotemplate and carbon source, SnO 2 /SnS nanoparticles anchored in S-doped hollow carbon tube composite (SnO 2 /SnS/SC) is successfully fabricated via tin salt impregnation, controlled calcination, and in situ sulfidation. This hierarchical structural design achieves precise integration of active components with the conductive matrix and the in situ construction of heterointerfaces. Electrochemical tests demonstrate that the SnO 2 /SnS/SC anode exhibits excellent sodium storage performance and rate capability. It delivers a reversible capacity of 531.1 mA h g –1 with 99.13% capacity retention after 50 cycles at 0.1 A g –1 . Even after 600 cycles at 2.0 A g –1, it still maintains stable capacity of 371.4 mA h g –1 . At high current density of 5.0 A g –1, it retains discharge capacity of 228.5 mA h g –1 . This superior performance is attributed to the combined contributions of the hollow carbon tube framework for mechanical buffering, the built-in electric field at the SnO 2 /SnS heterojunction interface that promotes charge transfer, and the improved conductivity and pseudocapacitive active sites introduced by sulfur doping in the carbon matrix. The designed synthesis strategy is simple, environmentally friendly, and scalable, offering an approach for designing high-performance biomass-derived carbon-based composite electrode materials.