Hollow Sb nanocrystals confined in N, S Co-doped carbon nanofibers boosting sodium-ion transport for high-performance sodium-ion batteries

Abstract

Herein, N, S co-doped carbon fibers encapsulating hollow Sb nanocrystals (h-Sb@NS-CNFs) were synthesized by a simple ion exchange and electrospinning process. The hollow Sb nanocrystals, in conjunction with the confinement effect of the carbon fibers, can offer faster Na⁺ pathways, decrease the Na⁺ diffusion barriers, and effectively mitigate the structural degradation of the electrode caused by the volume changes of Sb, thereby extending the cycle life of batteries. Additionally, the dual-element co-doping strategy employing nitrogen and sulfur provides more active sites for the Na⁺ reaction and increases the electronic conductivity while simultaneously enhancing the ionic diffusion kinetics, as indicated by density functional theory (DFT) and kinetic analysis. Therefore, h-Sb@NS-CNF exhibits excellent cyclic stability (305.3 mAh g⁻¹ at 2 A g⁻¹ for 900 cycles) and a high-rate capacity (209.3 mAh g⁻¹ at 10 A g⁻¹) as an anode material for sodium-ion batteries.