Prepaeation And Supercapacitor'sproperties Of MOF-Derived Transition Metal Sulfide

Supercapacitors have become hot energy storage device in recent years due to their advantages such as high power density,fast charge and discharge speed,low maintenance costs and long cycle life.Electrode materials play a vital role in supercapacitors,so it is of great significance to develop electrode materials with excellent electrochemical performance.Metal-organic frameworks?MOFs?are periodic porous structures composed of metal ions and organic ligands.MOFs can be used as precursors for building complex functional materials.These MOF derived nanostructures are ideal electrode materials due to the advantages of high porosity,high specific surface area,and sufficient electrochemically active sites.This thesis includes the following two works for MOF-derived transition metal sulfides:Firstly,the hollow Co-Ni-S nanocage material was successfully prepared by solvothermal method using ZIF-67 as the precursor,and the morphology and structure characterization of the material were performed by SEM and XRD.Electrochemical tests showed that the material has excellent electrochemical performance.At a current density of 1 A g^-1,the mass specific capacitance is 941 F g^-1,and the capacitance retention rate after 1 thousand cycles is 72.8%.Second,ZIF-L-Co nanowedge arrays ZIF-L-Co-NWAs?nanowedge arrays?were used as precursors,and hollow Co-Ni-S NWAs were prepared by vulcanization and etching.The adjustment of the solvothermal time indicates that the etching of internal defects in solid ZIF-L-Co nano-wedges is the main reason for the formation of hollow Co-Ni-S nano-wedges.The unique hollow nano-wedge structure and composition advantages ensure excellent electrochemical performance of hollow Co-Ni-S NWAs.The area capacitance at a current density of 5 mA cm^-2is 2.57 F cm^-2.The capacitance retention rate after 2000 cycles is 78%.In addition,a Co-Ni-S//AC asymmetric supercapacitor?ASC?is also assembled.At a power density of 1.64 mW cm^-2(112 W kg^-1),the energy density of the ASC device is 0.22 mWh cm^-2(15 Wh kg^-1).Even at a high power density of 24.75 m W cm^-2(1671 W kg^-1),it still has a high energy density of0.11 mWh cm^-2(7.9 Wh kg^-1),showing good application performance.The results show that Co-Ni-S NWAs/NF is a promising high-performance binder-free electrode for supercapacitors.