Dual electrocatalytic heterostructures for efficient immobilization and conversion of polysulfides in Li-S batteries

Lithium sulfur (Li-S) batteries have been investigated as ideal candidates for future high-density energy storage systems with the advantages of abundant reserves, high energy density and competitive cost. The key issues are the severe shuttling of polysulfides and sluggish redox kinetics. Herein, we report a novel metal-organic framework-derived Co2P-ZnS/ZnS-C nanocomposite constructed from inner Co2P-ZnS and outer ZnS-C heterostructures. Both the experimental results and theoretical calculations demonstrated that these dual electrocatalytic heterostructures enabled strong affinity with polysulfides and facilitated the reaction kinetics. Meanwhile, the hollow carbon polyhedron provided fast electron/ion transfer channels and effectively buffered volume expansion during cycling. As anticipated, a high initial capacity of 1503 mA h g(-1) was achieved at 0.2C with Co-Zn/Zn-C/S as a cathode, together with excellent stability after 500 cycles at 1C. Even a high reversible capacity of 540 mA h g(-1) was achieved at 1C after 200 cycles under an elevated sulfur loading of 3.65 mg cm(-2). This work presents a new strategy for designing dual electrocatalytic hosts for immobilization and conversion of polysulfides, which may offer more opportunities as cathodes in stable Li-S batteries with high energy density.