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 Ti3C2Tx/CNTs-Co9S8 heterostructure derived from a zeolite imidazole framework (ZIF)/Ti3C2Tx MXene composite via carbonization and subsequent sulfidation. In this 3D porous Ti3C2Tx/CNTs-Co9S8 heterostructure, the 3D porous Ti3C2Tx 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 Ti3C2Tx/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 Ti3C2Tx/CNTs-Co9S8/S cathode still exhibited a reversible capacity of 472.8 mA h g-1 at 0.5C after 300 cycles.