Hierarchical heterostructure of vacant carbon-box erected MoSe2-x nanosheets as a functional mediator for high-performance lithium-sulfur batteries

The shuttle effect of polysulfides and short cycling life are serious obstacles to the commercialization of lithium–sulfur (Li–S) batteries. One of the effective solutions is the use of polar materials as electrocatalysts to increase the conversion and adsorption efficiency of polysulfides in Li–S cells. Herein, an ingenious design of hierarchical hollow nanoboxes composed of ultrathin C and MoSe2-x nanosheets was successfully fabricated via the stencil etching and selenization processes. The peculiar nanoboxes architecture exhibited plentiful catalytic active sites for polysulfides due to abundant outer nanosheets. Particularly, density functional theory (DFT) calculations demonstrated that the existing Se vacancies of C-MoSe2-x nanoboxes can validly suppress the shuttle effect of Li–S batteries when they serve as catalysts to modify separators. As a result, the Li–S battery-based C-MoSe2-x functional interlayer showed excellent discharge capacity and cycling life of 528.36 mAh/g (470.20 mAh/g) after 500 cycles at a discharge current of 0.5 C (1 C), and delivered 440.61 mAh/g even after 150 cycles at 0.1 C with an S loading of 5 mg cm−2. This work provides a novel design for carbon-based transition metal chalcogenide hybridized materials and offers insightful perspectives for other energy fields.