Synthesis And Study Of Electrode Materials Of Different Morphology Transition Metal Sulfide Supercapacitors Based On MOF Template

Supercapacitor is a new type of energy storage device.Because of its advantages such as faster charging and discharging process,high power density,long cycle life,relatively low cost and environmental friendliness,supercapacitor has been considered to be one of the most promising energy storage devices.For supercapacitors,the selection of electrode materials plays a decisive role in their electrochemical performance.For supercapacitors,the choice of electrode materials is crucial.In materials such as carbon-based materials,transition metal compounds,and conductive polymer materials,although transition metal oxides/hydroxides cause high specific capacitances,they are not conducive to rapid electron transmission due to their poor conductivity.Considering that the electronegativity of sulfur is lower than that of oxygen,and elemental sulfur has more redox valence states,compared with transition metal oxides/hydroxides,it has higher conductivity,more ideal electrochemical activity,mechanical and thermal stability.,making them more important candidates for supercapacitor electrode materials.In view of the synergistic effect between metals,binary or multiple transition metal sulfides can provide more redox sites from multiple paired elements than single element sulfides,which results in better electrochemical activity and higher specific capacitance.Organometallic framework compounds(MOFs)have a specific structure,large surface area and multi-functional advantages,which have caused extensive research in various fields including gas storage and catalysis.Because of its high porosity and open metal center sites,it is prone to reversible redox reactions.MOF came into being as the electrode material of supercapacitors.In this paper,Co-Ni-S composite and Ni-Co-Sn-S composite were synthesized by hydrothermal method with transition metal sulfide as the research object and MOF as the precursor.The effects of hydrothermal time,hydrothermal temperature and the concentration of sulfurization on the electrochemical properties of the composite were discussed.The morphology,crystal structure,surface elements and electrochemical properties of the composite were characterized by SEM,XRD,XPS and electrochemical tests.The main research contents are as follows:(1)The Co-Ni-S composite material with unique bud-like structure was synthesized by hydrothermal method and used as supercapacitor electrode material for electrochemical performance test.The electrochemical test results show that the Co-Ni-S composite material has a high specific capacitance,good rate performance and excellent cycle stability.Using composite Co-Ni-S as positive electrode and activated carbon as negative electrode to assemble asymmetric supercapacitor,the electrochemical tests were carried out in two electrode system.The results show that the potential window of ASC can reach 1.6 V under the synergistic effect of pseudo capacitance and double electric layer capacitance.When the power density of Co-Ni-S//AC capacitor is 980 W kg-1,the energy density is as high as 78.4 Wh kg-1;when the power density is 980 Wkg-1,the energy density reaches the maximum value of 97.314Wh kg-1,which is obviously superior to other reported asymmetric supercapacitors assembled by nickel cobalt sulfide.(2)Design and synthesize Ni-Co-Sn-S composite material with special three-dimensional porous spherical Sn S cutting micro/nano sheet structure.The electrochemical test showed that the Ni-Co-Sn-S composite with better electrochemical performance could be obtained when the concentration of Na₂S solution was 0.1 mol L^-1,the hydrothermal temperature was 120?,and the hydrothermal time was 9 h.At a current density of 1 A g^-1,the specific capacitance of the Ni-Co-Sn-S composite material is as high as 1310.75 F g^-1,showing good electrochemical characteristics.