Controllable Interlayer Spacing of Sulfur-Doped Graphitic Carbon Nanosheets for Fast Sodium-Ion Batteries

The electrochemical behaviors of current graphitic carbons are seriously restricted by its low surface area and insufficient interlayer spacing for sodium-ion batteries. Here, sulfur-doped graphitic carbon nanosheets are reported by utilizing sodium dodecyl sulfate as sulfur resource and graphitization additive, showing a controllable interlayer spacing range from 0.38 to 0.41 nm and a high specific surface area up to 898.8 m² g^-1 . The obtained carbon exhibits an extraordinary electrochemical activity for sodium-ion storage with a large reversible capacity of 321.8 mAh g^-1 at 100 mA g^-1 , which can be mainly attributed to the expanded interlayer spacing of the carbon materials resulted from the S-doping. Impressively, superior rate capability of 161.8 mAh g^-1 is reserved at a high current density of 5 A g^-1 within 5000 cycles, which should be ascribed to the fast surface-induced capacitive behavior derived from its high surface area. Furthermore, the storage processes are also quantitatively evaluated, confirming a mixed storage mechanism of diffusion-controlled intercalation behavior and surface-induced capacitive behavior. This study provides a novel route for rationally designing various carbon-based anodes with enhanced rate capability.