Two-Dimensional Conductive Mesopore Engineering of Ultrahigh Content Covalent Sulfur-Doped Carbon for Superior Sodium Storage

Abstract

Ultrahigh content (>20 wt%) covalent sulfur-doped carbons (USC) 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 bond, and tardy ion and electron transport in carbon matrixes. Here, we report one 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 characterizations and kinetics analysis reveal that the 2D conductive mesoporous engineering strategy efficiently activate C-S bonds, and accelerate ion and electron transfer, confering USC high capacity sodium ion storage with pseudocapacitive-like behavior. As a result, the obtained MesoUSC@Ti3C2 delivers a high capacity of 950 mAh g–1 at 0.1 A g–1 and superior rate performance of 463 mAh 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.