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 MnO(2 )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. TheMnO(2) 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. (C) 2019 Published by Elsevier B.V.