Preparation And Electrochemical Energy Storage Properties Of Carbon Nanotubes And Graphene Supported NiSe Nanostructures

In order to design and prepare high performance carbon-based energy storage materials,several carbon nanomaterials/nickel selenide nanocomposites are constructed.The carbon nanomaterials/nickel selenide composite structure is prepared by electroless plating on the surface of carbon nanotubes and graphene,and then selenide treatment by chemical vapor deposition(CVD)or hydrothermal method.In this paper,the effects of electroless plating time,CVD selenization temperature and synthesis route on the morphology,structure and energy storage properties of the composites are systematically studied.At the same time,the electrochemical activity of the composite can be improved to the greatest extent by properly designing the interface and introducing defects and functional groups.In addition,it is found that the synergistic effect among carbon nanomaterials,nickel and nickel selenide has a significant contribution to the capacitance performance and cycle efficiency.On this basis,asymmetric supercapacitor and lithium-ion battery are assembled by the composite materials,and both devices show excellent energy storage performance.In this paper,the composite preparation and application of carbon nanomaterials and transition metal selenides are as follows:(1)Carbon nanotubes/nickel(CNTs/Ni)structure is prepared by electroless plating.Then,the Se doped CNTs/nickel selenide(Se-CNTs/NiSe)coaxial core sheath cable composite structure is obtained by selenidation of nickel loaded CNTs at 400-800?by CVD.Due to the unique interface characteristics of nickel,the CNTs/Ni structure is uniformly dispersed in the whole matrix.After the reaction of nickel and selenium on carbon nanotubes to form nickel selenide,the combination of carbon nanotubes and nickel selenide is firm,making full use of the conductivity of carbon nanotubes.At the same time,at high temperature,part of the carbon nanotube ports is cut open to form graphene ribbons,which are doped with layered NiSe to form new heterojunction nanoribbons.The three electrode test results show that the specific capacity of Se-CNTs/NiSe electrode material reaches 340 m Ah g^-1(3419 F g^-1)at the current density of 1 Ag^-1.The CNTs/NiSe//AC asymmetric supercapacitor has a specific capacity of196 F g^-1 at a current density of 1 Ag^-1.When the power density of the asymmetric supercapacitor is 803 W kg^-1,it has a high energy density of 70 Wh kg^-1.When the energy density is 27.6 Wh kg^-1,it has a high-power density of 15757.4 W kg^-1.In addition,when the asymmetric supercapacitor is cycled for 10000 cycles at a current density of 10 Ag^-1,the capacity retention rate of the device is 65%.When Se-CNTs/NiSe is used as the anode of Li ion battery,the specific capacity can reach 600m Ah g^-1 at the current density of 0.1 Ag^-1.Moreover,after 400 cycles at a current density of 0.5 Ag^-1,the lithium-ion battery still retains 62.58%of its capacity.(2)Controlling the plating time of electroless nickel plating process to obtain Graphene/nickel(Graphene/Ni)nanoparticles with different morphologies and structures,and then using CVD technology for selenium treatment to prepare unique Graphene/Nickel@Nickel selenium(Graphene/Ni@NiSe)Structure.Uniform dispersion on graphene sheet Ni@NiSe.The single particle structure not only gives full play to the high conductivity of graphene and nickel,but also increases the specific surface area and provides more active sites.The specific capacity of the composite reaches 302 m Ah g^-1(2716 F g^-1)at current density of 1 Ag^-1.Assemble into Graphene/Ni@NiSe//AC,the asymmetric supercapacitor has a specific capacity of 170 F g^-1 at a current density of 1 Ag^-1.The device has a high energy density of 68 Wh kg^-1 at 853 W kg^-1 and 16737 W kg^-1 at 22 Wh kg^-1.At the same time,the capacitance retention of the device is 72.53%after 10000 cycles at a current density of 10 Ag^-1.(3)Three-dimensional structure of Carbon nanotubes-graphene/Nickel@Nickel selenide(CNTs-graphene/Ni@NiSe)are prepared by mixing carbon nanotubes and graphene and then seleniding them by hydrothermal method.Due to the synergistic effect of carbon nanotubes and graphene,the capacitance performance and cycle life of the composites have been improved.Three electrode test results show that the specific capacity of the composite is 286 m Ah g^-1(2576 F g^-1)at 1 Ag^-1 current density,and the retention rate is 81.38%after 2000 cycles at 10 Ag^-1 current density.Assembled into CNTs-graphene/Ni@NiSe//AC,the asymmetric supercapacitor has a specific capacity of 172 F g^-1 at a current density of 1 Ag^-1.The device has a high-power density of 69Wh kg^-1 at 851.5 W kg^-1 and 16499.3 Wh kg^-1 at 25.2 W kg^-1.At the same time,the capacitance retention of the device is 89.62%after 10000 cycles at a current density of10 Ag^-1.After the lithium-ion battery is assembled,the specific capacity of the structure is 390.8 m Ah g^-1 at 0.1 Ag^-1 current density and 92.79%stable capacity retention is obtained after 500 cycles at 0.5 Ag^-1 current density.