Preparation Of Graphene-based Fiber Electrodes And Their Capacitance Performance

With the rapid growth of energy consumption,energy conversion and storage devices play an important role in industry and modern society.Among the numerous energy storage devices,supercapacitors are considered to be the most promising one due to their superior power density,fast charge/discharge rate,and long cycle life.Particularly,if a supercapacitor can be made into a fibrous shape,it can meet the requirements of flexibility and wearability of an electronic device.As an active material in the field of supercapacitors,graphene fibers have shown great potential due to their unique and adjustable nanostructures,high electrical conductivity,excellent mechanical flexibility,light weight,and easy functionalization,and have attracted great attention.In this dissertation,a one-step hydrothermal method was used to heat the gelation of graphene oxide?GO?mixed solution in a fixed fibrous device to prepare hybrid fibers,and they were assembled into supercapacitors for performance investigation.The specific research content is as follows:?1?The preparation and electrochemical performance of rGO/CNT hybrid fiber based supercapacitor.The rGO/CNT hybrid fibers were prepared by a one-step template hydrothermal method and the precursor solution was prepared by uniformly dispersing the carbon nanotubes?CNTs?into GO solution via ultrasonication.The cross-section,surface morphology and microstructure of the hybrid fibers were observed by scanning-electron microscopy?SEM?.It was found that the agglomeration of GO sheets was effectively inhibited after the introduction of CNTs,resulting in the formation of interpenetrating multi-hole structures.The mechanical and electrical properties of the hybrid fibers were tested and the results showed that the strength of the hybrid fibers gradually decreased with the increase of the CNT amount;while the electrical conductivity increased with the increase of the CNT content.When the CNT content reached 30%,the conductivity of the fibers reached a maximum value of 48 s cm^-1,and it shows good electrochemical performance as a supercapacitor.?2?The preparation and electrochemical performance of rGO/MnO₂ hybrid fiber based supercapacitor.The same one-step template hydrothermal method was used for in-situ synthesis of rGO/MnO₂ hybrid fibers.By adjusting the contents of potassium permanganate and manganese sulfate,rGO/MnO₂ hybrid fibers with different manganese dioxide contents were obtained.The characterization was carried out by XRD and XPS,and the results showed that the prepared MnO₂ was pure quadrangular phase?-MnO₂.Transition metal oxides with pseudocapacitance characteristics and graphene oxide with high conductivity play a synergistic role in improving the electrochemical properties of the hybrid fibers.The electrochemical performance of fibers was gradually enhanced with the content increase of MnO₂ precursors,and it was found that the hybrid fiber based supercapacitor showed the best electrochemical performance when the MnO₂ precursor content reached 30%.In addition,based on the assembly of rGO/CNT and rGO/MnO₂ into an asymmetrical supercapacitor,they showed high electrochemical performance.The volume ratio and energy density of supercapacitor reached 120.38 F cm^-3?3.12mWh cm^-3,respectively,which were better than those of most fiber-based supercapacitors.