Rationally designing a Ti3C2Tx/CNTs-Co9S8 heterostructure as a sulfur host with multi-functionality for high-performance lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries have been regarded as potential next-generation batteries owing to their ultrahigh theoretical capacity and abundance of sulfur. However, polysulfide shuttling, poor electronic conductivity, and severe volume expansion limit their commercial prospects. In this work, we rationally constructed a 3D porous Ti₃C₂T_x/CNTs-Co₉S₈ heterostructure derived from a zeolite imidazole framework (ZIF)/Ti₃C₂T_x MXene composite via carbonization and subsequent sulfidation. In this 3D porous Ti₃C₂T_x/CNTs-Co₉S₈ heterostructure, the 3D porous Ti₃C₂T_x MXene structure can provide facilitated ion and electron transport, good structural stability, and polar bonds to anchor sulfur and polysulfides. The formed CNTs can enhance ion diffusion and electron transport. The Co₉S₈ nanoparticles can accelerate the conversion reaction of polysulfides to Li₂S, which can further prevent polysulfide shuttling. The 3D porous structure can buffer the electrode volume change upon cycling. This rationally designed Ti₃C₂T_x/CNTs-Co₉S₈/S cathode exhibits a high initial capacity of 1389.8 mA h g⁻¹ at 0.1C, good cyclic stability (730.7 mA h g⁻¹ at 0.2C after 100 cycles), and excellent rate capacities (530.7 mA h g⁻¹ at 1C). When the S loading was 2.5 mg cm⁻², the Ti₃C₂T_x/CNTs-Co₉S₈/S cathode still exhibited a reversible capacity of 472.8 mA h g⁻¹ at 0.5C after 300 cycles.