N, P co-doping for microstructural regulation of pitch-derived carbon toward high-rate sodium storage

Pitch, a byproduct of the coal and petroleum chemical industries, is an economical and high-yield carbon source used for synthesizing carbon anodes in sodium-ion batteries (SIBs). Enhancing sodium storage requires preventing the long-range graphitization of microcrystals within the pitch structure during high-temperature carbonization. In this study, we propose a novel strategy to inhibit graphitization in pitch-derived carbon, uncovering the relationship between sodium storage performance and heteroatom doping and/or structural defects. By introducing ammonium dihydrogen phosphate during the carbonization process, we achieve effective N and P co-doping in the carbon material, expanding interlayer spacing and blocking liquid-phase carbonization to suppress the formation of graphitized microcrystals. This one-step pyrolysis method, free of acid leaching and metal contamination, yields N, P co-doped carbon material with enhanced rate properties. When applied as an anode material for SIBs, the pitch-derived carbon exhibits a high reversible capacity of 186.2 mAh g−1 after 5000 cycles at 5 A g−1. Furthermore, a full cell assembled with a Na3V2(PO4)3 cathode and the pitch-derived carbon anode delivers an impressive energy density of 280 Wh kg−1.