Structure Modification And Performance Of Graphene Oxide-based Electrode Materials For Supercapacitor

The growing energy crisis has made people more and more interested in high-efficiency energy storage devices.As a new type of energy storage,supercapacitor not only has the characteristics of high energy density of the battery,but also takes into account the advantages of the traditional capacitor with large capacity,high power density,long service life,and quick charge and discharge.Although supercapacitors have already been used in military,aerospace,hybrid electric vehicles and other fields,exploration of higher performance supercapacitors is still a workhorse for researchers.This article based on graphene oxide?GO?which was modified by graphene quantum dots?GQDs?and spring-like helical carbon nanotubes?HCNTs?.This structure can reduce the aggregation and stacking of GO to increase the specific surface area of the electrode while shortening the ion transport channel.A solution self-assembly method was used to prepare composite electrodes for a supercapacitor.The electrode using GO as a binder has a smaller internal resistance.At the same time,this paper adopts novel photochemical reduction method to perform photoreduction of the sample electrode under the NH₃ atmosphere,and the reduction and nitrogen doping process is completed in one step.The specific content includes the following sections:?1?The GO and GQDs were prepared in different proportions and mixed solution was directly coated on the foamed nickel current collector.After being reduced with mild ascorbic acid,a symmetrical two-electrode supercapacitor was assembled and its electrochemical performance was tested in KOH.The modification of GQDs effectively reduces the stacking of GO,generates additional micropores,increases the specific surface area of the electrode and shortens the ion transport channel.The results show that the addition of GQDs greatly improves the performance of the capacitor,and the supercapacitor quality is as high as 296 F g^-1.?2?Using GO as a binder,GQDs as a“separator”to prepare a mixed solution with a mass ratio of 6:1 and coating it onto nickel foam.Then,the samples were reduction and nitrogen in NH₃ atmosphere?NrGO/GQDs?using a homemade light reduction device.Due to the edge effect of GQDs,the nitrogen doping of the NrGO/GQDs sample reached 18.86 atom%,and the specific capacity of the reinforced supercapacitors reached to 344 F g^-1.When lithium sulfate is used as the electrolyte,the energy density of the supercapacitor can reach 43 Wh kg^-1 at a power density of 417 W kg^-1.?3?HCNTs were used as cross-linking agents,GO was used as a binder to prepare mixed solution,and the samples were subjected to light reduction and nitrogen doping?N-HCNTs/rGO?under NH₃ atmosphere using a homemade light reduction device.HCNTs are mixed with GO to form a fixed 3D all-carbon network structure by spiraling and winding to improving the overall mechanical properties,reducing the stacking of materials,increasing the binding area between HCNTs and GO,and facilitating the transmission of supercapacitor ions.Nitrogen doping improves the wettability of the electrode and the electrolyte,providing additional tantalum capacitance.The maximum specific capacitance of N-HCNTs/rGO after N-doping was 368 F g^-1,and it had good cycle stability(after 5000 cycles,the device maintains90.7%of its initial capacitanceonly at current density of 1 A g^-1).