Preparation And Performance Study Of Petroleum Coke Based Flexible Supercapacitors

As the demand for electronics becomes more personalised,flexible electronics such as folding mobile phones,electronic skins and implantable medical devices have begun to be used in large numbers in everyday life.In order to power flexible electronics,it is necessary to develop energy storage devices that are also flexible.As one of the flexible energy storage devices,flexible supercapacitors have the advantages of high power density,long cycle life,high safety,diverse electrode materials and device structures,and have great potential for use in small flexible electronics.However,the low energy density and limited mechanical flexibility limit the further application of flexible supercapacitors.The mechanical flexibility and electrochemical performance of flexible supercapacitors are mainly determined by electrode materials,so the development of high-performance flexible electrode materials is crucial to promote the development of flexible supercapacitors.In this thesis,from the structural design of high-performance flexible electrode materials,the petroleum coke based flexible carbon nanofibers materials with both high electrical conductivity and high flexibility were prepared by the strategy of reducing the size of graphite microcrystals and increasing the pores in carbon nanofibers,and their electrochemical performance was further enhanced by the strategy of compounding with polyaniline materials.performance.The main studies are as follows.(1)Petroleum coke-based flexible carbon nanofibers were prepared using petroleum coke as carbon source,combined with concentrated acid oxidation,electrospinning,pre-oxidation and high-temperature carbonization.Thanks to the small size of the graphite microcrystals and the large number of pores between the graphite microcrystals,the carbon nanofibers are able to relieve stress concentration during bending and reduce the stress load on the chemical bonds inside the graphite microcrystals,enabling the carbon nanofibers to have high graphitic carbon content and high flexibility at the same time,enabling the integration of high electrical conductivity and high flexibility in the carbon nanofibers.Benefiting from the excellent electrical conductivity,flexibility and well-developed microporous structure,petroleum cokebased flexible carbon nanofibers can be directly used as electrode materials for flexible supercapacitors without the addition of conductive agents and binders.The FCNF-1200 material exhibits a specific capacitance of 184 F/g(0.5 A/g)and a capacitance retention of 72%(0.5 A/g～20 A/g)in the three-electrode system.The all-solid-state flexible supercapacitor based on FCNF-1200 material has excellent mechanical stability and cycle stability,and successfully powers LED light bulbs,showing a certain practical value.(2)The petroleum coke-based flexible carbon nanofibers/polyaniline composites were prepared by growing polyaniline on the surface of the petroleum coke-based flexible carbon nanofibers material as structural support and conductive skeleton by cyclic voltammetry electrodeposition process.Thanks to the high specific capacitance of polyaniline and the high electrical conductivity and structural stability of petroleum coke based flexible carbon nanofibers,the FCNF/PANI composites have significantly improved specific capacitance compared to FCNF materials and maintain excellent flexibility.In addition,the content of polyaniline in the FCNF/PANI composites increased with the lap speed of the cycle deposition,and at a deposition lap speed of 20 laps,the FCNF/PANI composites shows the best electrochemical performance,exhibiting a high specific capacitance of 324 F/g(0.5 A/g)and58% capacitance retention(0.5 A/g～10A/g)in the three-electrode system.