Sulfur, fluorine, and nitrogen tri-doped carbon hollow spheres for enhanced electrochemical performance in sodium-ion batteries

Sulfur, fluorine, and nitrogen tri-doped carbon hollow spheres (SFNHCS) were simply prepared through a polymerization process using polydopamine (PDA) as the source of carbon and nitrogen and ionic liquid 1-vinyl-3-ethylimidazole bisfluoromethane sulfonimide salt as the source of sulfur and fluorine. This unique triple doping of S, F, and N and hollow structure design makes SFNHCS exhibit outstanding conductive performance, larger electrode/electrolyte interface, and interlayer spacing, thus enhancing battery performance. When using SFNHCS as the anode material for sodium-ion batteries, it exhibits excellent high-rate performance of 217.2, 195.2, 168.5, 147.6, 135.4, 123.5, and 117.4 mAh g⁻¹ at 0.1, 0.2, 0.5, 1, 2, 5, and 10 A g⁻¹, respectively. After 1000 cycles at 5.0 A g⁻¹, its specific capacity still remains at 115.6 mAh g⁻¹, showing excellent durability.