Preparation And Application Of 3D Co-based Nanocomposites For Supercapacitors

Supercapacitors is the important part of energy storage devices,due to the fast charge/discharge process,long cycling lifetime and so on.The importantance of electrode materials was one of the important means to enhance the performance of supercapacitors.As the active material of supercapacitors,cobalt-based nanomaterials have high theoretical specific capacitance,low price and friendly to the environment.However,single cobalt-based sulfide materials have poor cycle stability,and single cobalt-based oxide material have low conductivity.This major researches in this paper were improve the defect of cobalt-based sulfides and oxides,further enhancing the electrochemical performance of active materials,and preparing high electrochemical properties supercapacitors.For the goals,novels 3D CoS/NiCo₂S₄ and S-Co₃O₄-F were designed and prepared to study the electrochemical performance of the materials.The including were shown as followings:?1?Double-shell nanocages CoS/NiCo₂S₄ was successful prepared by solvent method,ion etching and chemical vapor deposition.The active material not only has high theoretical capacity,large specific surface areas and abundant channels,but also has stable framework structure retained from ZIF-67 and derived double-shell nanostructure with cavity.In a three-electrode system,the active electrode exhibited a high specific capacitance of 1230 F/g at a current density of 1 A/g.After 9000 cycles at 3 A/g,the CoS/NiCo₂S₄ can still maintain 76.6%of the initial capacitance.It means the active material has excellent electrochemical performance.The electrode material was assembled in an asymmetric supercapacitor.As an all solid states device,it can gain a high power density of 7056 W/kg at an energy density of 16.5W h/kg.At a high energy density of 31.6 W h/kg,a power density of 702 W/kg can be obtained.?2?A sulfur-doped flower-like Co₃O₄?S-Co₃O₄-F?was successful prepared.S-Co₃O₄-F was directly grow on the nickel foam surface,which reduced the interfacial resistance of the electrode material and the substrate.The doping of sulfur enhance the conductivity of the oxide,further facilitating electron transport.The flower-like nanostructures can increase a number of active sites to enhance the capacitance.In a three-electrode system,S-Co₃O₄-F exhibited a high specific capacitance of 1356 F/g at 1 A/g.After 8000 cycles at 3 A/g,S-Co₃O₄-F can still maintain 83.7%of the initial capacitance,reflecting the superior cycle stability.By assembling an all-solid asymmetric supercapacitors,the device exhibited a high power density of 8024W/kg at an energy density of 18.6 W h/kg.Even at a high energy density of 29.6 W h/kg,a power density of 804 W/kg can be obtained.