Preparation And Electrochemical Performance Of Cobalt-based Sulfides As Electrode Material

Supercapacitor is a new type energy storage device which is different from chemical energy and electrical energy.Compared with the traditional capacitor and secondary battery,supercapacitor exhibit some excellent properties,such as high power density,fast charge and discharge rate and environment friendly.The core part of supercapacitor is the electrode material,which would directly influence the performance of the whole system.Therefore,the preparation of the excellent performance supercapacitor electrode material is very important when facing the challenges of energy storage.This thesis is focused on factors of influence the supercapacitor electrode material performance and synthesize the cobalt base sulfide nanomaterials with porous structure in order to improve the electrochemical performance.The main results were outlined as following:（1）The mesoporous cobalt base sulfide materials were prepared via ion exchange hydrothermal method,which achieves richer redox ability,exhibits higher conductivity and more chemical reaction active site.By changing the ratio of raw material and solvent type,it can improve the electrochemical properties of cobalt based sulfide material,Moreover,we have successfully fabricated aqueous asymmetric supercapacitor using cobalt-based sulfides and N-doped graphene（NG）composites as the anode and cathode electrode,respectively.（2）The composite（NiCo₂S₄-HL）of the supercapacitor electrode materials was synthesized using halloysite nanotubes（HL）as template.The composite electrode materials（NiCo₂S₄-HL）achieved a specific capacitance of 589 C g^-1 at a current density of 1 A g^-1,and displayed excellent cyclability.These electrochemical performance benefit from uniqueness structure and element of the composite（NiCo₂S₄-HL）.Introducing of HL makes the composite（NiCo₂S₄-HL）by self-assembly to form porous structure,which provides wider diffusion channels for ion migration and electronic transmission,richer chemical reaction of the active site.（3）Using nitric acid copper and cobalt chloride as raw material,the methenamine（HMT）as precipitator,CuCo-LDH nanoparticles precursor was obtained via the low temperature hydrothermal preparation.After high temperature calcination and vulcanization,CuCo₂O₄ and CuCo₂S₄ were formed respectively.Data of the electrochemical performance showed that CuCo₂S₄ has excellent rate capability and cycle stability.The excellent performances are benefit from lower forbidden band width of sulfur from Cu-Co sulfide,higher conductivity and more active site.（4）Four different morphology of copper and cobalt sulfides were synthesized with ethylene glycol and glycerin as solvent,thiourea and thiosemicarbazide for sulfur source.The characterization and electrochemical performance of four different samples were tested.The Co₂CuS₄ exhibits an specific capacitance of 126Cg^-1 at current density of 1Ag^-1 with excellent rate performance and cycling stability.