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.