Graphitic Carbon Nitride (g-C₃ N₄ )-Derived N-Rich Graphene with Tuneable Interlayer Distance as a High-Rate Anode for Sodium-Ion Batteries

Heteroatom-doped carbon materials with expanded interlayer distance have been widely studied as anodes for sodium-ion batteries (SIBs). However, it remains unexplored to further enlarge the interlayer spacing and reveal the influence of heteroatom doping on carbon nanostructures for developing more efficient SIB anode materials. Here, a series of N-rich few-layer graphene (N-FLG) with tuneable interlayer distance ranging from 0.45 to 0.51 nm is successfully synthesized by annealing graphitic carbon nitride (g-C₃ N₄ ) under zinc catalysis and selected temperature (T = 700, 800, and 900 °C). More significantly, the correlation between N dopants and interlayer distance of resultant N-FLG-T highlights the effect of pyrrolic N on the enlargement of graphene interlayer spacing, due to its stronger electrostatic repulsion. As a consequence, N-FLG-800 achieves the optimal properties in terms of interlayer spacing, nitrogen configuration and electronic conductivity. When used as an anode for SIBs, N-FLG-800 shows remarkable Na⁺ storage performance with ultrahigh rate capability (56.6 mAh g^-1 at 40 A g^-1 ) and excellent long-term stability (211.3 mAh g^-1 at 0.5 A g^-1 after 2000 cycles), demonstrating the effectiveness of material design.