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.