Study On Preparation And Performance Of Nano-carbon Modified Zinc Cobaltate Electrode Matrial

Supercapacitors have the advantages of high-power density,good coulomb efficiency,low cost etc,and they have received extensive attention in the field of energy storage.The electrode material of supercapacitors is one of the most important factors affecting the performance of the device.Cobalt-based metal oxide materials have a variety of oxidation states and rich faraday redox reactions can effectively improve the electrochemical performance of supercapacitors.Spinel zinc cobaltate has broad development prospects due to its low cost,abundant resources and environmental friendliness.Therefore,this thesis chooses zinc cobaltate as the research object.Carbon-based composite zinc cobaltate electrode materials are prepared.The samples are characterized by using nitrogen gas adsorption-desorption,X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron spectra.Cyclic voltammetry,constant current charge/discharge,and AC impedance are involved to investigate the electrochemical properties of the materials.The research content is as follows:1.ZnCo₂O₄/CMK-3 mesoporous composite electrode materialUsing mesoporous silica SBA-15,the mesoporous carbonCMK-3 was prepared by template-assisted technology,and the ZnCo₂O₄/CMK-3 mesoporous composite electrode material was successfully prepared by the co-precipitation method.The specific surface areas of CMK-3 and ZnCo₂O₄/CMK-3 are 1120.23 m²/g and 392.06m²/g,respectively,and the average pore diameter of both samples is about 3 nm.The composite material with the CMK-3 of 60 wt%has a regular structure.The specific capacitance can reach 260 F/g at the current density of 1 A/g together with good rate performance.The lower charge transfer resistance and diffusion resistance effectively promote the rapid electrolyte diffusion for charge storage.These results are attributed to the fact that CMK-3 has a uniform pore size distribution,ordered mesoporous channels and a higher specific surface area.The loaded ZnCo₂O₄ can fully contact the electrolyte,which expands the reaction area and improves the capacitance performance.2.Hierarchical structure ZnCo₂O₄/CDs composite electrode materialFirstly,carbon quantum dots were prepared by the bottom-up method.Then,a hierarchical structure of ZnCo₂O₄ nanowire array was constructed on the foamed nickel substrate by hydrothermal method,and carbon quantum dots are introduced meanwhile to obtain a hierarchical structure ZnCo₂O₄/CDs composite electrode material.Carbon quantum dots with an average particle size of 2.06 nm are distributed uniformly.ZnCo₂O₄/CDs composite material presents flower-like microspheres assembled by nanowires.ZnCo₂O₄/CDs composite material has a high peak current and integral area,exhibiting better electrochemical performance than these of ZnCo₂O₄.The specific areal capacitance of the material reaches 2013 F/g at a current density of 0.5 A/g,when the solution volume of added carbon quantum dots is0.5 m L.The rate performance keeps 78.5%with increasing current density to 8 A/g.This excellent electrochemical performance is because the zinc cobaltate material has a unique spinel structure.More importantly,the introduction of carbon quantum dots increases the active sites on the surface of the material,reduces the electrode impedance,effectively shortens the charge transport efficiency,enhances the faraday redox process.These advantages improve the electrochemical performance.The above research results show that the carbon-based composite zinc cobaltate is a cheap electrode material with high specific capacitance for supercapacitors.They exhibit great potential application in the field of energy storage.