Study On Preparation And Performance Of Flexible All-solid-state Supercapacitor Based On Nitrogen-doped Graphene/Carbon Nanotubes/Manganese Dioxide

As a new type of energy storage device,supercapacitor has become a research focus due to its high power density,long cycle life and short charging time.At the same time,with the rapid development of wearable and portable electronic devices,flexible supercapacitors have attracted widespread attention.The performance of flexible supercapacitors mainly depends on the electrode materials.Therefore,it is of great significance to prepare supercapacitor electrode materials with excellent electrochemical performance and flexibility.The main research contents of this thesis include:(1)Firstly,graphene oxide solution,carbon nanotubes and urea were injected into the glass capillary tube,and nitrogen-doped graphene/carbon nanotubes(N-rGO/CNTs)fiber was prepared through a simple hydrothermal reaction.In addition,rGO fiber without carbon nanotubes and urea was prepared for performance comparison.At the same time,the most suitable amount of nitrogen was explored by changing the amount of urea added.At a current density of 0.5 A cm-3,the specific capacitances of rGO fiber and N-rGO/CNTs fiber were 63.1 F cm-3 and 154.1 F cm-3.The capacitance retention rate of N-rGO/CNTs fiber was 94.8%after 5000 charge-discharge cycles.(2)Secondly,In order to further improve the electrochemical performance of N-rGO/CNTs fiber,the fibers were immersed in KMnO4 solution and heated at 80?for different times,and different amounts of MnO2 were grow on the surface of the fibers through a redox reaction,thus the nitrogen-doped graphene/carbon nanotubes/manganese dioxide(N-rGO/CNTs/MnO2)fibers were successfully prepared.N-rGO/CNTs/MnO2-2h fiber exhibited a high specific capacitance of 367.7 F cm-3 at a current density of 0.5 A cm-3,and the capacitance retention rate was 92.2%after 5000 charge-discharge cycles.(3)Finally,PVA-LiCl gel electrolyte was used to assemble two N-rGO/CNTs/MnO2-2h fiber electrodes in parallel to form a flexible all-solid-state supercapacitor device.The supercapacitor device showed excellent electrochemical performance,high flexibility and mechanical stability.The supercapacitor device exhibited a specific capacitance of 68.5 F cm-3 and a high energy density of 5.9 mWh cm-3 at a current density of 0.5 A cm-3,maintaining 86.7%of the original capacitance after 5000 charge-discharge cycles.The supercapacitor device can be bent in the angle range of 0-120°,and its capacitance was only reduced by 3.1%after 500 times of bending at 90°,showing its great potential as a flexible energy storage device.