Ultrahigh edge‑nitrogen-doped porous carbon anode materials for high-capacity and fast-charging lithium-ion batteries

Most reported nitrogen-doped carbon anode materials of lithium-ion batteries (LIBs) own finite capacities and inferior initial coulombic efficiency (ICE). One effective method to enhance capacities and capacities of the nitrogen-doped carbon anode materials is edge‑nitrogen doping. It still endures obstacles to realize a high edge‑nitrogen doping level owing to the difficulty to control of the nitrogen doping types. In this work, a series of edge‑nitrogen-doped porous carbon (ENPC) with different edge‑nitrogen doping levels are synthesized by annealing sucrose and g-C3N4 in a sealed graphite crucible. The edge‑nitrogen doping level from 8.88 at.% to 12.93 at.% for the ENPC-T can be regulated by changing the annealing temperature. Serving as LIBs anodes, the ENPC-800 exhibits an excellent capacity (1251.1 mAh g−1 at 0.1 A g−1), high ICE (82.9 %) and remarkable cycle life (650.5 mAh g−1 at 1 A g−1 after 1000 cycles with an exceptional capacity retention of 99.3 %). More significantly, by correlating the capacity and conductivity with the nitrogen doping configuration of the ENPC-T materials, the results highlight the effect of edge‑nitrogen on the capacity and conductivity. Meanwhile, the electrochemical characterizations of CV, GITT and EIS illustrate that a higher edge‑nitrogen doping level improves the capacity, electronic conductivity and fast-charging performance of ENPC-T. This new strategy can pave a new approach for the investigation and application of nitrogen-doped carbon anodes.