Ti3C2Tx nanosheet wrapped core–shell MnO2 nanorods @ hollow porous carbon as a multifunctional polysulfide mediator for improved Li–S batteries

Abstract

Lithium–sulfur (Li–S) batteries are regarded as potential next-generation energy storage systems due to their high theoretical energy densities. However, the dissolution of lithium polysulfides (LiPSs) upon cycling can result in severe capacity degradation. Achieving high rate capabilities with good cycling stability remains a huge obstacle for the practical implementation of Li–S batteries. Here we developed a novel, multifunctional, hierarchical structure by self-assembling core–shell MnO₂ nanorods @ hollow porous carbon with 2D Ti₃C₂T_x nanosheets, labelled as MCT, as an efficient polysulfide mediator for Li–S cathodes. The integration of the polar MnO₂ core and hollow porous carbon shell captures LiPSs two ways: physical confinement and chemisorption. The conductive Ti₃C₂T_x nanosheets construct a continuous and conductive network, which not only promotes charge transfer and ion diffusion but also boosts LiPS adsorption and conversion. Based on these merits, the MCT/S cathode delivers good rate capability (688 mA h g⁻¹ at 2.0C) and outstanding long-term cyclability (0.044% capacity decay per cycle over 600 cycles at 2.0C).