N/O/S Tri‐Doped Hard Carbon From Polyaniline With Boosted Sodium‐Ion Storage

ABSTRACT In this study, N/O/S tri‐doped polyaniline‐based hard carbons (D‐PANI‐HCs) have been synthesized through a sequential process involving in situ aniline polymerization, rotary evaporation, and subsequent calcination. The residual ammonium persulfate functions as a critical multifunctional precursor, simultaneously enabling heteroatom doping and acting as an in situ gaseous template during the calcination process. The resulting D‐PANI‐HCs demonstrates superior structural properties compared to undoped PANI‐HCs, including larger interlayer spacing, more closed nanopores and active sites. Therefore, the electrochemical performances of D‐PANI‐HCs as anode materials for sodium‐ion batteries demonstrate significant enhancement compared to undoped PANI‐HCs. Specifically, the initial Coulombic efficiency of D‐PANI‐HCs increases to 67.9%, up from 46.9% of undoped PANI‐HCs, while the specific capacity of D‐PANI‐HCs at 0.05 A·g −1 reaches 318 mAh·g −1 , a notable improvement over the 175 mAh·g −1 for un‐doped PANI‐HCs. Furthermore, D‐PANI‐HCs exhibits excellent cycling stability, retaining 295 mAh·g −1 (92.5% retention) after 200 cycles at 0.05 A·g −1 and 171 mAh·g −1 (86.4% retention) after 1000 cycles at 0.3 A·g −1 .