S/O co-doped honeycomb-like porous carbon nanosheets with ultra-high edge defects for high-performance sodium storage

The sodium storage capacity of soft carbon anodes can be effectively enhanced by designing reasonable edge defect structures through heteroatom modification. However, limited edge heteroatom doping often leads to low sodium storage capacity and sluggish kinetics due to the difficulty in tailoring effective doping strategies in terms of precise molecular regulation. In this paper, a new strategy about in-situ sulfur grafting assisted by oxygen crosslinking is proposed to modify the edge defect sites of pitch-based porous carbon nanosheets (SOCN3). This strategy enables SOCN3 to have the structure of large carbon layer spacing, ultra-high edge heteroatomic content (18.27 at%) and abundant edge defect sites, which is beneficial to the adsorption and insertion of Na+, and ultimately results in high storage capacity and fast dynamics. Thus, SOCN3 anode exhibits extremely high ICE (65.3 %) and stable long cycle performance (401 mAh g−1 after 2000 cycles at 1 A g−1), its outstanding electrochemical performance is almost superior to all of previously reported pitch-derived carbon anode materials. Additionally, a new mechanism of this material is proposed through DFT calculation and in-situ characterization. This study provides a new idea for the precise control of microcrystalline structure of soft carbon anode materials for SIBs.