Hierarchical van der Waals heterostructure with dual-defect sites for bidirectionally catalyzing Li2S nucleation and decomposition in lithium-sulfur batteries

The lithium-sulfur batteries hold a promising option for the next generation of energy storage systems. Nevertheless, the shuttle effect of soluble lithium polysulfides and their slow reaction kinetics lead to extremely low efficiency and poor stability, thereby limiting the commercial viability of lithium-sulfur batteries. Herein, MoSe2/Ti3C2 van der Waals heterostructure is synthesized with a dual-defect strategy, and its electrocatalytic performance is further improved through solution coating treatment (SCT), which involves the addition of glucose during the hydrothermal process. The conductive Ti3C2 scaffold effectively inhibits the aggregation of MoSe2 nanoflakes, thereby validating a larger active surface area. Meanwhile, the nitrogen dopant and selenium vacancy dual-defects in MoSe2 provide abundant active sites for anchoring polysulfides and catalyzing their conversion. As a result, the synergistic interaction between MoSe2 and Ti3C2 bidirectionally catalyzes the Li2S nucleation and decomposition through a heterointerface effect. The lithium-sulfur battery equipped with MoSe2/ Ti3C2-SCT heterostructure modified separator exhibits outstanding discharge specific capacity of 1496.9 mAh g- 1 at 0.1C, and a low decay rate per cycle of 0.059 % after 500 cycles at 1C. The discharge specific capacity recovers to 89.3 % of the initial capacity when the current density is decreased from 5C to 0.1C. This work highlights the potential of defect engineering in transition metal selenides to enhance the performance of lithium-sulfur batteries. It offers a new approach to designing composite electrocatalysts for high-performance lithium-sulfur batteries.