Synthesis And Supercapacitive Properties Of Nickel Cobalt Binary Metal Sulfides Composite Electrode

Due to its many advantages containing quick discharge-charge rate,long recycle life,high power density, environmental amity and so on, supercapacitor has been expected as one of energy storage devices possessing great development potentials. The transition metal sulfides have attracted widly attention of researchers, which have some virtues such as wealthy redox reaction,higher specific capacity and electrochemical response and so on. In order to obtain electrode material with excellent capacitive properties, the optional conditions of preparing transition metal sulfide electrode material and its composite were discussed in this dissertation.The Ni foam was used as substrate to synthesize NiCo₂S₄ with two-step hydrothermal method, then NiCo₂S₄ was characterized by XRD,XPS and EDS. The tests of SEM showed that NiCo₂S₄ displayed well dispersion when CTAB was added. It was indicated that NiCo₂S₄ electrode with a hydrothermal time of 2 h shows more excellent electrochemical performance after adding CTAB,the specific capacity is up to 1268 F/g under the condition of a current density of 1 A/g,and retained capacitance ratio is 74.8% after 1000 cycles at a current density of 5 A/g.The Ni foam was used as substrate, then GO, nickel and cobalt nitrate and methanol were used to synthesize composite materials by two-step hydrothermal method. The composite electrode material was proved to be Ni@rGO/NiCO2S4 by XRD test. The composite electrode material keeped a nanowire structure by SEM analysis. From the results of electrochemical performance, the specific capacitance of the electrode reaches 1560 F/g under the condition of a current density of 1 A/g and retained capacitance ratio is 79.6% after 1000 cycles at a current density of 5 A/g.With the Ni@NiCo₂S₄ substrate and KMnO4 as raw materials, a hydrothermal method was used to synthesize the NiCo₂S₄/MnO2 composite electrode. NiCo₂S₄/MnO2 composite electrodes were characterized by XRD test. NiCo₂S₄ was covered by spherical MnO2 with relatively high concentration of KMnO4 solution. The electrochemical performance of the electrode is excellent. The specific capacitance is up to 1490 F/g when the current density is 1 A/g. It retained 72.4% capacitance ratio after 1000 cycles at a constant current charge and discharge of 5 A/g.