Hierarchical N/S co-doped carbon anodes fabricated through a facile ionothermal polymerization for high-performance sodium ion batteries

Abstract

Engineering the structure and increasing the near-surface reaction of hard carbon are promising strategies for designing high-performance sodium ion batteries (SIBs). In this study, a series of N, S-co-doped hierarchical porous carbon materials are designed and prepared through an easy one-pot ionothermal approach. The carbon structure is controlled by designing the precursors and changing the reaction temperature. Benefiting from a molecular-engineering strategy, the obtained porous carbon shows a homogeneous distribution of nitrogen and sulfur atoms at the atomic level, and its application as anode materials for SIBs is reported. pTTPN@600 delivers a high reversible capacity (134 mA h g⁻¹ at 1 A g⁻¹, corresponding to a capacity retention of 88.7% after 100 cycles and excellent rate capabilities of 248 mA h g⁻¹ at 0.05 A g⁻¹ and 95 mA h g⁻¹ at 5 A g⁻¹). Even at a current density of 10 A g⁻¹, a specific capacity of 74 mA h g⁻¹ is maintained after 2000 cycles. The outstanding performance is attributed to the large amount of heteroatoms (N 7.52 wt% and S 1.63 wt%) and several mesopores (mesoporous volume 0.48 cm³ g⁻¹) in pTTPN@600. We propose increasing the mesoporous volume and heteroatom amount to enhance the electrochemical performance of porous carbon materials. This study provides an easy route to fabricate hierarchical porous electrode materials for SIBs and provides new insights into the sodium storage behavior in hierarchical porous materials.