Sulfur/nitrogen/oxygen tri-doped carbon nanospheres as an anode for potassium ion storage

S/N/O tri-doped carbon nanospheres anode exhibits superior reversible capacity and ultra-long cycling stability for PIBs (397.4 mA h g −1 at 100 mA g −1 after 700 cycles; 123.1 mA h g −1 at 3000 mA g −1 after 16500 cycles). • 1. The S/N/O tri-doped carbon nanospheres with abundant active sites, large interlayer spacing and high specific surface area are synthesized by in situ vulcanized polybenzoxazine. • 2. The anode achieves attractive reversible capacity and ultra-long cycling stability. • 3. In situ FT-IR analysis and DFT calculations demonstrate the reason for the excellent electrochemical performance. Carbonaceous materials are considered as ideal anode for potassium ion batteries (PIBs) due to their abundant resources and stable physical and chemical properties. However, improvements of reversible capacity and cycle performance are still needed, aiming to the practical application. Herein, S/N/O tri-doped carbon (SNOC) nanospheres are prepared by in-situ vulcanized polybenzoxazine. The S/N/O tri-doped carbon matrix provides abundant active sites for potassium ion adsorption and effectively improves potassium storage capacity. Moreover, the SNOC nanospheres possess large carbon interlayer spacing and high specific surface area, which broaden the diffusion pathway of potassium ions and accelerate the electron transfer speed, resulting in excellent rate performance. As an anode for PIBs, SNOC shows attractive rate performance (438.5 mA h g −1 at 50 mA g −1 and 174.5 mA h g −1 at 2000 mA g −1 ), ultra-high reversible capacity (397.4 mA h g −1 at 100 mA g −1 after 700 cycles) and ultra-long cycling life (218.9 mA h g −1 at 2000 mA g −1 after 7300 cycles, 123.1 mA h g −1 at 3000 mA g −1 after 16500 cycles and full cell runs for 4000 cycles). Density functional theory calculation confirms that S/N/O tri-doping enhances the adsorption and diffusion of potassium ions, and in-situ Fourier-transform infrared explores explored the potassium storage mechanism of SNOC.