Two-dimensional conductive mesopore engineering of ultrahigh content covalent sulfur-doped carbon for superior sodium storage

Abstract

Ultrahigh content (>20 wt%) covalent sulfur-doped carbon (USC) materials exhibit significant potential as cathode materials for sodium–sulfur batteries. Despite sulfur-based redox reactions offering high capacity, their reaction kinetics is limited by poor activity of robust covalent C–S bonds and slow ion and electron transport in carbon matrices. Here, we report a novel 2D mesoporous USC vertically grown on Ti₃C₂ nanosheet (MesoUSC@Ti₃C₂) heterostructure, which shows a 2D hexagonal structure, a high surface area (∼256 m² g⁻¹) and abundant covalent sulfur content (∼26.2 wt% in USC). Spectroscopic characterization studies and kinetics analysis reveal that the 2D conductive mesopore engineering strategy efficiently activates C–S bonds, and accelerates ion and electron transfer, endowing USC with high capacity sodium ion storage and pseudocapacitive-like behavior. As a result, the obtained MesoUSC@Ti₃C₂ delivers a high capacity of 950 mA h g⁻¹ at 0.1 A g⁻¹ and a superior rate performance of 463 mA h g⁻¹ at 5 A g⁻¹. This work opens up new ways to promote the practical applications of sulfur-doped carbon-based materials for advanced energy storage systems.