Study On The Preparation And Energy Storage Properties Of Carbon-cobalt Composites

In recent years,energy conversion and storage technology has been rapidly developed,and it has been widely used in the field of electric vehicles,new energy,and portable devices.Energy storage including supercapacitors(SCS)and lithium-ion batteries(LIBs),have received extensive attention in portable electronic devices.The electrode material is the core component of SCS and LIBs,which determines the energy density and power density of energy storage.Therefore,the research of electrode materials is of great significance to improve the performance of energy storage.Transition metal compounds have attracted wide attention because of their high specific capacity.Therefore,this thesis aims at spinel-type cobalt transition metal compounds,which studies the influence of different metal elements in spinel structure and combines different kinds of carbon materials to prepare spinel cobalt transition metal compounds and carbon composite electrodes.The electrochemical properties of composite electrodes in SCS and LIBs were tested.The details are as follows:(1)Second Co-zinc oxide-carbon nanotube(Zn Co₂O₄-CNT)composites were prepared by simple hydrothermal method.Carbon nanotube can compensate the electron transport performance of pure Zn Co₂O₄.As the cathode material for asymmetric supercapacitors,the specific capacity of the Zn Co₂O₄-CNT//AC device is 78.3 F g^-1.When the current density is 1 A g^-1.The specific capacity of 1200 m Ah g^-1 can be obtained at 200 m A g^-1 as a negative electrode material for lithium ion batteries after 120 cycles.(2)Cobalt sulfide copper/graphene(CuCo₂S₄-rGO)composites were prepared by hydrothermal method and applied to supercapacitors and lithium ion batteries.The graphene is coated on the surface of the CuCo₂S₄ material and enhances the electrical conductivity of the CuCo₂S₄.As the cathode material for symmetric supercapacitors,the specific capacity of the CuCo₂S₄-rGO//CuCo₂S₄-rGO device is 142.8 F g^-1 When the current density is 1 A g^-1.The specific capacity of 1050 m Ah g^-1 can be obtained at 200 m A g^-1 as a negative electrode material for lithium ion batteries after 140 cycles.(3)Using hydronthermal method,nickel cobalt oxide(Ni Co₂O₄/CC)composite grows on the surface of carbon cloth material.Self-supporting electrodes are constructed and applied to super capacitors and lithium ion batteries.The two-dimensional inter leaved network of carbon cloth provides more electronic transmission channels.As the cathode material for asymmetric supercapacitors,the specific capacity of the Ni Co₂O₄/CC//Ni Co₂O₄/CC device is 79.8 F g^-1 when the current density is 1 A g^-1.The specific capacity of 620.7 m Ah g^-1 can be obtained at 200 m A g^-1 as a negative electrode material for lithium ion batteries after 70 cycles.