The Study On Polyaniline Based Supercapacitor Electrodes

Supercapacitors（SCs）are one kind of new-type energy storage devices.They have been extensively studied because of their higher power output and longer cycle life than secondary batteries,and greater energy output than traditional dielectric capacitors.The electrode materials have an important influence on the electrochemical performances of SCs.As a type of conducting polymer,polyaniline（PANI）has the advantages of simple synthesis,high electrical activity,good environmental stability,and low cost,which has been widely studied.PANI can be prepared by chemical and electrochemical methods.Compared with the chemical methods,the electrochemical methods can directly grow the electroactive materials on the current collectors,theryby advoiding the use of an insulating binder.However,the conductivity and cycle stability of PANI electrodes are poor,which seriously affects their application in supercapacitor electrodes.This study firstly develops a simple and mild one-step electrochemical co-deposition method to prepare PANI-CNTs composite electrodes,also prepare sulfuric acid and perchloric acid co-doped PANI electrodes.Finally,we investigate the effect of different test parameters on the cycle stability of PANI electrodes in detail.These studies improve the application of PANI in SCs.The research contents of this thesis are as follows.（1）The PANI-CNTs composite electrodes were prepared by a one-step electrochemical co-deposition method,and the influence of carbon nanotubes with higher and lower carboxylation degree on the electrochemical performance of the prepared composite electrode was researched.The morphology and composition composite electrode materials were characterized through Fourier transform infrared spectroscopy（FT-IR）,scanning electron microscope（SEM）,X-ray energy spectroscopy（EDS）and X-ray photoelectron spectroscopy（XPS）.Electrochemical test results showed that the introduction of CNTs significantly improved the supercapacitive performance of the PANI electrode,and the PANI-CNTs electrode prepared by CNTs with a higher degree of carboxylation exhibited better supercapacitive performance than PANI-CNTs prepared from CNTs with a lower degree of carboxylation.The former achieved a specific capacitance of578.2 F g^-1,which can be attributed to the introduction of more CNTs,resulting in enhanced supercapacitive performance.（2）SP-PANI was prepared by electropolymerization,and single-doped electrodes（S-PANI and P-PANI）were prepared by the same method.The composition,morphology and roughness of the prepared electrode materials were characterized by FT-IR,EDS,SEM and Atomic Force Microscope（AFM）.The test results indicated that the SP-PANI electrode had significantly enhanced electrochemical capacitance performance compared with S-PANI and P-PANI electrodes.This can be attributed to the co-doping strategy changed the morphology,conductivity,and roughness of the prepared PANI electrode.In addition,we also assembled the prepared SP-PANI electrodes into a flexible solid-state supercapacitor,which exhibited an area specific capacitance of 149.3 mF cm^-2,as well as high mechanical flexibility and cycle stability.（3）The effects of different test parameters,including CV scan rate and GCD current density,on the cycling stability of the prepared PANI electrodes were researched in detail.The results showed that the cycle stability of PANI electrode increased with the increase of CV scan rate and GCD current density.This indicates that the cycling stability of the PANI electrode is closely related to the test parameters.The test parameters of high scan rates usually lead to excellent cycle stability results,and the test parameters of low scan rates leads to poor cycle stability results.This can be attributed to the difference in the amount of PANI electroactive materials that can be used for charge storage at different scan rates.