N/S co-doping engineered flattened hollow carbon anode for high-performance sodium ion batteries

Structurally-engineered hollow carbon nanomaterials have emerged as frontier materials for advanced energy storage technologies, because of their inherent architectural merits, including expansive specific surface area and interconnected porosity, which enable efficient sodium ion storage mechanisms. Hollow carbon shells with flattened circular shapes were prepared using Fe₃O₄ as templates. By precisely tuning the N/S doping ratios, the electronic structure and surface properties of hollow carbon nanomaterials can be effectively modified. The regulatory mechanisms of nitrogen and sulfur synergistic doping on electron/ion transport, structural stability, and sodium ion diffusion kinetics were revealed. Specifically, it reveals that as a sodium-ion half-cell anode, the materials deliver 368.4 mAh g^-1 at 200 mA g^-1. Importantly, the full cell battery (Mg-NaVO//NSC-21) achieves 348.9 mAh g^-1 at 500 mA g^-1, demonstrating remarkable rate capability which sustains 101.7 mAh g^-1 even at 5000 mA g^-1. Characterization studies attribute these improvements to an optimized N/S-doped ratio of 12 can substantially boost sodium storage capabilities via coordinated enhancements in charge transport efficiency, ionic mobility and electrode integrity. This study establishes fundamental guidelines for designing architecturally controlled N/S-coordinated carbon matrices, directly propelling the engineering of high-efficiency sodium-ion batteries (SIBs), opening up new avenues for the development of advanced energy storage systems.