Regulating the sodium storage sites in nitrogen-doped carbon materials by sulfur-doping engineering for sodium ion batteries

Due to their abundant resources and adjustable interlayer distance, carbon materials have great potential to be applied in sodium ion batteries (SIBs) anodes. N-doping is a commonly used strategy to increase the sodium storage sites in carbon materials, which largely enhances the extra capacitive capacity for SIBs. However, there is still a room to enlarge the interlayer distance in N-doped carbon materials to enhance the intercalation capacity. Herein, we use a S-doping strategy to expand the interlayer distance, which is conducive for the Na+ intercalation, and simultaneously optimize the doping sites in carbon materials to graft high proportion of edge-N atoms. As a result, the optimized sample (NSCRs) exhibits a high reversibly capacity (479.5 mAh g−1 at 100 mA g−1 over 200 cycles) and achieves an ultra-long cycling stability (181.3 mA h g−1 at 5 A g−1 over 10,000 cycles). Theoretical simulation confirms the superiority of Na+ adsorption in NSCRs. The full-cell performance further confirms the practical application potential of NSCRs in SIBs. This work contributes to further understand the optimization of secondary large doping atom to improve the sodium storage sites in N-doped carbon materials.