Intercalation-Conversion Hybrid Cathode Enabled by MXene-Driven TiO2/TiS2 Heterostructure for High-Energy-Density Li-S Battery

Abstract

A dense electrode with high sulfur loading is a straightforward approach to increasing the energy density of lithium-sulfur battery (LSB), but the development of dense electrodes suffers from both fabrication challenges and electron/ion transport limitations. In addition, the shuttle effect of soluble lithium polysulfides and sluggish reaction kinetics cause declined utilization efficiency of the active material and poor cycling stability. Herein, a dense intercalation-conversion hybrid cathode is prepared using MXene-driven TiS2 nano-needles decorated with TiO2 nanoparticles. The TiO2/TiS2 heterostructure simultaneously possessing a high adsorption capability (TiO2) and bidirectional electrocatalytic effect (TiS2) is observed to effectively suppress lithium polysulfide shuttling and facilitate the sulfur conversion reactions. Furthermore, it is believed that TiS2 provides additional capacity from the intercalation reaction and functions as a multichannel network to feed both Li+/e- to the active sulfur material due to its high electronic and ionic conductivities. Thanks to these synergistic effects, the LSB assembled using the TiO2/TiS2 heterostructure exhibits high gravimetric and volumetric energy densities of 331 Wh kg(-1) and 730 Wh L-1, respectively, as well as superior cyclability at a high sulfur mass loading of 7.5 mg cm(-2) and lean electrolyte of 2.5 mu L mg(-1).