Facile Synthesis of Heterostructured MoS₂-MoO₃ Nanosheets with Active Electrocatalytic Sites for High-Performance Lithium-Sulfur Batteries

In order to overcome the shuttling effect of soluble polysulfides in lithium-sulfur (Li-S) batteries, we have designed and synthesized a creative MoS₂-MoO₃/carbon shell (MoS₂-MoO₃/CS) composite by a H₂O₂-enabled oxidizing process under mild conditions, which is further used for separator modification. The MoS₂-MoO₃ heterostructures can conform to the CS morphology, forming two-dimensional nanosheets, and thus shorten the transport path of lithium ion and electrons. Based on our theoretical calculations and experiments, the heterostructures show strong surface affinity toward polysulfides and good catalytic activity to accelerate polysulfide conversion. Benefiting from the above merits, the Li-S battery with a MoS₂-MoO₃/CS modified separator exhibits good electrochemical performance: it delivers a high discharge capacity of 1531 mAh g^-1 at 0.2 C; the initial capacity can be maintained by 92% after 600 cycles at 1 C, and the discharge capacity decay rate is only 0.0135% per cycle. Moreover, the MoS₂-MoO₃/CS battery still achieves good cycling stability with 78% capacity retention after 100 cycles at 0.2 C with a high sulfur loading of 5.9 mg cm^-2. This work offers a facile design to construct the MoS₂-MoO₃ heterostructures for high-performance Li-S batteries, and may also improve one's understanding on the heterostructure contribution during polysulfide adsorption and conversion.