Sulfur-Doping Biomass Based Hard Carbon as High Performance Anode Material for Sodium-Ion Batteries

The intercalation/deintercalation of Na + in the hard carbon (HC) has been widely investigated for the construction of high performances sodium-ion batteries (SIBs). In this work, a variety of sulfur-doped HCs were obtained by simple pyrolysis of the sublimated sulfur and the camphor tree (S-Cmph) derived material. When used as anode for SIBs, the S-Cmph-700 (pyrolyzed at 700°C) delivered a capacity of 616.7 mAh g -1 with an ICE of 66.61%, high than that of the untreated material pyrolyzed at 1500°C (50.11%) (Cmph-1500). Furthermore, excellent rate performance with specific capacities of 372.3, 323, 282.6, 252.6, 221, 181.2 mAh g -1 at 40, 80, 200, 400, 800 and 2000 mA g -1 can be achieved, respectively. When the current density returned at 40 mA g -1 , the anode recovered a specific capacity of 356.8 mAh g -1 . In addition, the as-acquired anode material exhibited good cycling performance with a reversible capacity of 145.6 mAh g -1 over 500 cycles at 2000 mA g -1 . The improved electrochemical performances of Cmph-HC anode can be attributed to the benefit of the S-doping, leading to the increase of the interlayer spacing of the anode material, which facilitates the intercalation/deintercalation of Na + ions in the interlayer spacing of the HC material, and provided more active sites in the Cmph-HC anode for the Na + ions storage. In addition, sulfur can reversibly react with Na + , limiting the irreversible consumption of Na + and increase the intercalation rate of Na + inside the anode material. This work presents a low cost, simple and effective way to synthesize a high performances anode material for the commercialization of SIBs.