Covalent Coupled Sulfur-Deficient MoS2 Nanosheets on Carbon Nanotubes toward Polysulfide Catalytic Conversion in a Lithium Sulfur Battery

The lithium sulfur battery is an attractive energy storage device because of its high theoretical capacity and energy density, but its lifetime is seriously limited by the shuttle effect of polysulfides. Herein, a rational design of vertical MoS2 nanosheets anchored on conductive carbon nanotubes through Mo-O-C covalent coupling is proposed. In this composite, the strong chemical interaction ensures rapid charge transfer at interfaces, while the sulfur-deficient and metallic 1T phase-containing MoS2 enhances the affinity with polysulfides and accelerates the reaction kinetics of polysulfide conversion. Benefitting from these merits, the composite serves as a coating layer on the separator in the lithium sulfur battery, leading to the impressive electrochemical performance of the initial capacities of 1291 mA h g-1 at 0.5 C and 1330 mA h g-1 at 0.2 C. The battery also shows an enhanced cycling stability with a low capacity fading rate of 0.089% per cycle after 500 cycles at 0.5 C.