Double-shelled NiS/SnS@N-doped carbon nanoboxes engineered from NiSn(OH)6 cube templates for advanced sodium-ion battery anodes

Overcoming the sluggish reaction kinetics and volume effects of metal sulfides as anodic materials for sodium-ion batteries remains a challenging task. In this study, a multistep template-engaged strategy is employed for the first time to fabricate hierarchical double-shells NiS/SnS@nitrogen doped carbon (NiS/SnS@NC) nanoboxes, utilizing NiSn(OH)6 cubes as starting templates. The synergistic combination of sophisticated sulfide components and the double-shell structure effectively mitigates volume variation, reduces nanoparticle cohesion, and enhances electrode reaction kinetics. Notably, NiS/SnS@NC exhibits outstanding stability under high current density while maintaining a high capacity. Comprehensive kinetics analysis reveals that the enhanced sodium storage of NiS/SnS@NC can be attributed to its low interface reaction resistance, significant capacitive contribution, and rapid mass-transfer kinetics. The stepwise (de)sodiation processes of the NiS/SnS@NC anode are elucidated through various in/ex-situ characterization techniques, confirming the alternating reaction activity alternations between two components, which acts as a self-buffering and self-conductivity mechanism to enhance sodium storage. Finally, a practical application is demonstrated, where a well-designed NiS/SnS@NC||Na3V2(PO4)2F3/C full cell shows promising performance, achieving a high capacity of 265 mAh/g after 1000 cycles at 2.0 A/g. This work′s synthesis strategy and research findings contribute to advancing the exploration and application of NiSn(OH)6 and its derivatives in the field of energy storage and beyond.