Zeolitic-imidazolate framework combined with MnO₂ as the sulfur host material with excellent performance in lithium-sulfur batteries

In this study, we reported a new synthesis of ZIF-67@S@MnO₂ composite based on the ZIF-67, an universal porous MOF material with excellent thermal stability and chemical stability, which can effectively alleviate sulfur volume expansion and dissolution of polysulfide. Here, the ZIF-67 can provide more active sites for sulfur attachment after vacuum treatment. The MnO₂ coated on the surface of ZIF-67@S was introduced through the redox reaction of KMnO₄ under ice bath with high purities, which can also effectively form a sandwich structure to encapsulate the sulfur particles attached to the surface of the MOF. The MnO₂ can chemically bind polysulfdes strongly and further relieve volume expansion, which might enhance the performance of lithium-sulfur battery. This combination of physical adsorption of ZIF-67 itself and filling of MnO₂ can effectively encapsulate sulfur to obtain high specific capacity. When the ZIF-67@S@MnO₂ composite is initially discharged, the specific capacity can reach about 1250 mAh g⁻¹ at 0.5 C. In addition, the as-obtained composite exhibits stable specific capacities of 895 mAh g⁻¹ at 0.5 C, 686 mAh g⁻¹ at 1 C and 484 mAh g⁻¹ at 2 C after 100 cycles, respectively. The encouraging compartment structure and excellent electrochemical performance can be recommended for energy storage applications.