Preparation Of NiCo₂O₄、CuCo₂O₄ And CuFe₂O₄ Electrode Materials And Their Supercapacitive Properties

Recently,supercapacitors have attracted significant research attention because of their advantages of a high power density,a high energy density,long lifespan,fast charge and discharge process,and excellent reversibility.The performance of supercapacitors is highly dependent on the electrode materials.The spinel-type metal composite oxides owe high thermal stability,good chemical stability,better electrical conductivity and abundant surface active sites,thus they have extensive application prospect as the electrode materials.In this paper,three kinds of spinel-type electrode materials were synthesized,and their morphology features,structure and supercapacitive property were analyzed.This thesis mainly consists of these following sections:1、The spinel Ni Co₂O₄ crystals,used as active substance of supercapacitor electrode material,were successfully prepared by solvothermal method and characterized by XRD,XPS,FT-IR,SEM and electrochemical activity tests.We discussed the effects of the reaction time on the morphology and electrochemical supercapacitive properties of Ni Co₂O₄ crystals.The results showed that the morphology of Ni Co₂O₄ crystal prepared at 120℃for 12 hours was spherical particle with a diameter of about 4μm.The spherical particle was composed of a large number of needle shaped nano-monomers gathered radially from the center with a good electrochemicalperformance.NiCo₂O₄sphericalparticlesperformedobvious pseudocapacitive behavior as electrode material,and it has a good reversibility and a better rate capability.The specific capacitances of the NiCo₂O₄ spherical particles were 503.8 F/g at a current density of 0.5 A/g.The capacitance retention of the NiCo₂O₄ remains 94.2%after1000 cycles at a current density of 3 A/g,indicating the excellent electrochemical cycle stability.2、Using urea as the precipitating agent,the spinel CuCo₂O₄ crystals were successfully synthesized by one step hydrothermal method,and its supercapacitive property was studied.The different morphology of CuCo₂O₄ crystals were prepared by controlling the types of raw material.Chrysanthemum-like CuCo₂O₄ crystals structure（CuCo₂O₄-C）was produced when we used the hydrochloride as reaction material.Nitrate,as material,was used to obtain rose-like CuCo₂O₄ crystals sample（CuCo₂O₄-N）.Chrysanthemum-like sample can provide a more abundant channel structure.The electrochemical tests showed that CuCo₂O₄-C electrode exhibited a better supercapacitive performance in 6 mol/L KOH solution.The specific capacitances of the CuCo₂O₄-C were 335.8 F/g at a current density of 0.5 A/g,while the CuCo₂O₄-N were 235.3 F/g at the same condition.The capacitance retention of the CuCo₂O₄-C remains 84.6%after 2000 cycles at a current density of 3 A/g,and the CuCo₂O₄-N electrode was only 67.1%.3、With ethylene glycol as solvent and PVP as dispersant,high-purity spinel-type CuFe₂O₄ samples were successfully synthesized by solvothermal method,and their composition,crystal structure and morphology were characterized.The prepared CuFe₂O₄particles have high purity,uniform morphology and no obvious agglomeration,with average diameter of 100 nm.CuFe₂O₄ samples using as active material of the electrode,the supercapacitor performances in different concentrations of electrolyte were discussed.The results of the electrochemical tests showed that CuFe₂O₄ electrode exhibited a better supercapacitive performance in 6 mol/L KOH solution.CuFe₂O₄ electrode showed an excellent rate performance at high current densities（at a current density of 0.5 A/g maintained80%）.The internal resistance of CuFe₂O₄ working electrode in 6 mol/L KOH solution was small,and the mass transfer resistance was small,so the electrochemical performance was excellent.