Preparation Of Carbon-coated Nickel-cobalt Sulfide Nanocomposites And Application Of Supercapacitor

As a new type of energy storage device,supercapacitor has become a hot research topic with its advantages of fast charge and discharge rate,long cycle life,high power density and environmental friendliness.It has a very broad application prospect.The electrode materials currently used for tantalum capacitors are mainly classified into two types,transition metal（hydrogen）oxides and transition metal sulfides.Among them,a transition metal binary sulfide,or a ternary metal sulfide,as a supercapacitor of an electrode material,has higher conductivity and richer redox reaction than the corresponding oxide.Carbon-coated metal sulfide as a new type of core-shell electrode material,because of its combination of inner transition metal sulfide and outer shell carbon layer,both high power properties of carbon materials and high ratio of transition metal sulfides Capacitors and other advantages have broad prospects in the application of supercapacitor electrode materials.In order to further improve the capacitance performance of nickel-cobalt sulfide,NiCo₂S₄ nanomaterials with different morphologies were prepared by hydrothermal method,solvothermal methodandthermaldecompositionmethod,andcarbon-coatedNiCo₂S₄nano-particles were developed by thermal decomposition method.Through electrochemical testing,the carbon-coated NiCo₂S₄ nanomaterials have greatly improved the electrochemical performance based on NiCo₂S₄ nanomaterials.The main research results of this thesis are as follows:（1）NiCo₂S₄ nanoparticles were prepared by a simple one-step hydrothermal method,and NiCo₂S₄ nanoparticles were carbon coated by high temperature thermal decomposition method using dopamine hydrochloride as a carbon source.By controlling the carbon source dose,a carbon-coated NiCo₂S₄ nanoparticle with complete morphology was prepared.After electrochemical testing,both nanomaterials showed good electrochemical performance.When the current density is 5A g^-1,the carbon-coated NiCo₂S₄ can reach 925F g^-1,and the capacity retention rate is 80.3%after 5000 cycles of charge and discharge.Due to the introduction of highly conductive carbon materials,the specific capacitance of the material is increased.The test results show that the electrochemical performance of carbon-coated NiCo₂S₄ is improved compared with NiCo₂S₄.（2）NiCo₂S₄ hollow mesoporous nanospheres with different particle sizes were prepared by controlling the particle size of the silica template from the template method and hydrothermal method.By introducing dopamine hydrochloride as a carbon source,a carbon-coated NiCo₂S₄ double-layer hollow sphere with good morphology was prepared by controlling the dose of carbon source.After electrochemicaltesting,bothnanomaterialsshowedgoodelectrochemical performance.At the same time,when the current density is 2A g^-1,the carbon-coated NiCo₂S₄ can reach 1555F g^-1,and the capacity retention rate is 83.38%after 6000cycles of charge and discharge.The carbon-coated nanomaterial of the double-layer hollow sphere structure greatly increases the specific surface area and spherical structure stability of the material.The test results show that the electrochemical performance of carbon-coated NiCo₂S₄ is improved compared with NiCo₂S₄.（3）NiCo₂S₄ nanoparticles were prepared by one-pot hydrothermal method.Through the introduction of PVP,the dose of PVP was controlled,and NiCo₂S₄@PVP composites with different particle sizes were prepared.The carbon-coated NiCo₂S₄material was prepared by carbonization by thermal decomposition.After electrochemical testing,all three materials exhibited significant tantalum capacitance characteristics.And the electrochemical performance of NiCo₂S₄@PVP composites is significantly better than that of single NiCo₂S₄ nanoparticles,while the carbon coated NiCo₂S₄ nanomaterials obtain the best electrochemical performance.When the carbon-coated NiCo₂S₄ material is 2A g^-1,the specific capacitance can reach 1302F g^-1.After 5000 cycles of charge and discharge,the specific capacitance can reach 80.79%of the initial specific capacitance.The results of the introduction of high conductivity carbon materials show that the electrochemical properties of carbon-coated NiCo₂S₄are improved compared with NiCo₂S₄.