Preparation Of Nickel-cobalt Compound Based Composite Electrode Materials And Study On Properties Of Supercapacitor

With the continuous growth of global energy demand and the increasingly serious environmental problems,the development of a safe,environmentally friendly,efficient and stable energy storage equipment is very important in current human life.As a promising device among electrochemical energy storage components,supercapacitors have been widely used in various industries.They show unique advantages such as high power density,high energy density,fast rate capacity and long cycle life.Among them,the electrode material is a very important and indispensable structure in the supercapacitor,which has a direct impact on the electrochemical performance and energy storage mechanism of the supercapacitor.Therefore,the research focus of the supercapacitor is to explore the composition of new electrode materials and new composite materials.In this paper,the structure of nickel-cobalt compound based composite materials was studied,and core-shell nanostructures were formed by composite with other electrode materials to prepare electrode materials with excellent performance.Specific work contents and research results are as follows:（1）Preparation and Electrochemical Performance of NiCo₂O₄@Ni-MOF Core-shell Nanoarray:NiCo₂O₄@Ni-MOF core-shell structure was successfully prepared by simple hydrothermal method and annealing process.In this core-shell structure,transverse and longitudinal NiCo₂O₄nanosheets act as the core layer to form an interconnected 3D network.The Ni-MOF growing on the nanosheets will shorten the diffusion distance between ions considerably,making the electrolyte easier to diffuse to the inside of the electrode.The synergistic effect of NiCo₂O₄nanosheets and Ni-MOF forms a tight conductive network.The electron transport is accelerated,the specific surface area and more active sites are obtained,and the electrochemical performance is improved.In addition,growing the NiCo₂O₄@Ni-MOF electrode material directly on nickel foam avoids the creation of"dead volume".The test results also show that when the current density is 5 m A cm^-2,NiCo₂O₄@Ni-MOF core-shell structure exhibits a higher area-specific capacitance:4.23 F cm^-2,significantly better than Ni-MOF(current density of 5 m A cm^-2,area specific capacitance of 0.24 F cm^-2)and NiCo₂O₄(current density of 5 m A cm^-2,area specific capacitance of 2.25 F cm^-2)electrode,Compared with NiCo₂O₄and Ni-MOF,it has excellent cyclic stability（83.9%after 8000 cycles）.The assembled asymmetric supercapacitor device NiCo₂O₄@Ni-MOF//AC has a higher energy density of 0.29 m W h cm^-2when the power density is 3.90 m W cm^-2.（2）Preparation and Electrochemical Properties of NiCo₂S₄@NiWO₄Core-shell nanoarrays:NiCo₂S₄@NiWO₄core-shell nanostructures were successfully prepared by hydrothermal method and annealing treatment.In this core-shell structure,due to the synergistic action of NiCo₂S₄and NiWO₄,both of them provide abundant electron and ion channels and excellent electrical conductivity,with excellent electrochemical performance.In addition,the open space between these core-shell nanostructures can support the volume expansion of NiCo₂S₄@NiWO₄composite materials during the long-term cycle process,which improves the cycle stability.In addition,growing the NiCo₂S₄@NiWO₄electrode material directly on nickel foam avoids the creation of"dead volume".The test results also show that NiCo₂S₄@NiWO₄core-shell nanostructure exhibits a higher area specific capacitance of 4.59 F cm^-2when the current density is 6 m A cm^-2,which is significantly higher than that of NiCo₂S₄(current density is 6 m A cm^-2,the performance of area-specific capacitance of 1.33 F cm^-2and NiWO₄(current density of 6 m A cm^-2,the performance of 1.17 F cm^-2)electrode is better.The assembled asymmetric supercapacitor device NiCo₂S₄@NiWO₄//AC has a higher energy density of 0.35 m W h cm^-2when the power density is5.77 m W cm^-2.