Ultralong cycle life sulfur-doped graphitic carbon anode for sodium-ion batteries: Optimizing sulfur doping strategy

Graphite exhibits excellent electrical conductivity and structural stability, however, low specific capacity of graphitic carbons seriously hinders its practical application as anode materials for sodium-ion batteries (SIBs). Optimized sulfur doping can effectively enhance its sodium storage performance. In this study, we synthesized the sulfur-doped graphitic carbon by utilizing carbon disulfide (CS 2 ) and Calcium carbide (CaC 2 ) as raw materials to systematically investigate the effect of sulfur doping content. The controllable sulfur doping effectively enlarges interlayer spacing and increases active sites while pore formation during calcination process generates additional active sites for Na + storage. Impressively, superior specific capacity of 102.8 mAh·g −1 is reserved at 5.0 A·g −1 after 7000 cycles in ester-based electrolyte, which could be ascribed to the enhanced pseudocapacitive behavior. It shows that the electrochemical performance in ether-based electrolytes is significantly superior to that in ester-based electrolytes, which exhibits a high reversible capacity of 255.8 mAh·g −1 at 1.0 A·g −1 with remarkable initial coulomb efficiency of 88.6%, and long-cycle stability, maintaining 192.3 mAh·g −1 after 2000 cycles at 10.0 A·g −1 . Furthermore, the SGM||Ether-based electrolyte||NVP full cell delivers a high capacity of 57.8 mAh·g −1 even after 400 cycles, with a capacity retention rate of 80.6%. This work provides a new route for the rational design sulfur-doped carbon anodes for SIBs.