Preparation And Electrochemical Performance Of Flexible Supercapacitors Electrode Material Fabricated By Electrospinning Nanofiber Yarns

With the development of intelligent wearable electronic devices and flexible portable electronic devices that can monitor the daily activities and state of human body and have communication function,how to prepare a flexible,braided,linear,high-capacity electronic components has become a new research hotspot and difficulty in the field of supercapacitors.In order to solve the problems of flexibility and braidability of supercapacitors,this paper takes one-dimensional electrostatic spinning nanofiber yarn as the basic research objective,and adopts the technical means of plasma grafting,surface coating and nanofiber yarn doping to produce flexible electrode of supercapacitor.The electrochemical properties of the modified electrospun nanofilament yarns as electrode materials for supercapacitors were studied.In this paper,the study reads as follows:（1）In order to improve the hydrophilicity and surface adhesion fastness of polyacrylonitrile nanofiber yarn,polyacrylonitrile nanofiber yarn was grafted with acrylic acid by plasma at room temperature and pressure,and then PAN-AA/PPy conductive nanofiber yarn was prepared by in-situ polymerization.The effects of plasma treatment conditions on the grafting rate and hygroscopic rate of PAN nanofiber yarn,as well as the effects of pyrrole concentration,ferric chloride concentration,hydrochloric acid concentration and polymerization time on the electrical conductivity of PAN-AA/PPy nanofiber yarn were studied.The electrochemical properties of PAN-AA/PPy nanofiber yarn were also studied.The results showed that when the temperature was 40℃,the volume fraction of acrylic acid was 50%,the optimal parameters of plasma grafting were as follows:power 100 W,flow rate of He 35 L/min,flow rate of O₂0.5 L/min,plasma head moving speed 10 mm/s,grafting twice,grafting time 4 h each.The optimum process parameters were obtained:pyrrole concentration0.6 mol/L,ferric chloride concentration 0.8 mol/L,hydrochloric acid concentration 0.6mol/L,and the reaction time was 4 h at 0℃.After plasma grafting,the conductivity of the conductive yarn is 4.589 S/cm under the optimal in-situ polymerization parameters,which is greatly improved compared with that of the conductive yarn without plasma grafting only.（2）In order to improve the electrical conductivity of nanofiber yarn,the method of preparing CB/PAN nanofiber yarn was adopted by adding carbon black in the spinning liquid and then coating carbon black;At the same time,the optimum concentration（mass fraction）of carbon black ink was explored.The results show that the content of carbon black has a great influence on the mechanical properties of the nanofiber membrane.The more carbon black content,the worse the mechanical properties.With the increase of carbon black ink concentration,the resistance of CB/PAN nanofiber yarn decreased,and the electrical conductivity of CB/PAN/PPy nanofiber yarn increased.According to the mechanical properties of the CB/PAN nanofiber yarn and the resistance of the PAN/CB nanofiber yarn coated with carbon black,the mass ratio of PAN and CB was selected as 4:1.The concentration of carbon black ink was selected as1%according to the degree of shedding of carbon black on the surface of CB/PAN nanofiber yarn after drying.（3）In order to prepare flexible carbon nanofiber electrode materials,and to meet the requirements of green chemistry,using carbon black and polyacrylonitrile with rich oxygen-containing functional groups as raw materials,flexible carbon nanofibers were prepared by electrospinning technology,and CBCNF/PPy carbon nanofibers were prepared by in-situ polymerization.It not only solved the problems of toxic gas release,long preparation period and high risk coefficient in the preparation of carbon nanofibers,but also prepared the carbon nanofibers with good flexibility and excellent electrochemical performance.The results show that when the current density is 0.5 A/g,the specific capacitance of CBCNF-16 can reach 223.8 F/g,and that of CBCNF-8 is159.55 F/g.the CBCNF-8 is 100.6 F/g,and the capacity retention rate can arrive to63.1%.At the current density of 1 A/g,the capacity retention rate is 99.43%after 500cycles.Under the current density of 0.5 A/g,CBCNF/PPy-8 carbon nanofibers specific capacitance of the electrode is 351.5 F/g,.92%after 500 cycles.