Study On Synthesis And Performance Of Conductive Polyaniline And Its Composite Materials For Supercapacitor

Supercapacitor,also known as electrochemical capacitor,is a new kind of energy storage device in between conventional capacitor and secondary battery,and has the characteristics of high power density,fast charge and discharge,long cycle life,and has become one of the hot spots in the field of new energy research and development.The electrode material determines the performance of supercapacitor,and the innovation of the electrode material is the core content and the technology development trend of supercapacitor research.Conductive polyaniline(PANI)electrode material is a conducting polymer electrode material with a great developmental potential with respect to its excellent properties such as available raw materials,simple synthesis procedure,low cost,as well as good chemical stability,electrical conductivity,high pseudocapacitance energy storage and unique acid-base doped mechanism.In this thesis,PANI and its composites with high performance were prepared by a facile easy method.The morphology and structure of PANI and its composites were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray powder diffraction(XRD),Raman spectroscopy analysis(Raman),Fourier transform infrared spectroscopy(FTIR),and thermal gravimetric analysis(TG)means.These materials regarded as electrode materials were assembled into supercapacitor.The electrochemical performance and cyclic performance of supercapacitor were evaluated by cyclic voltammetry(CV),electrochemical impedance spectorscopy(EIS),and galvanostatic charge/discharge tests.The main conclusions can be summarized as follows:(1)Ordered molecular assembly(OMA)was constructed by using nonionic surfactant Tween-20 and 1-butyl-3-methylimidazolium hexafluorophosphate((Bmim)PF6)ionic liquid,and was used as an emulsifier and a soft template to synthesize P-PANT nanomaterials.SEM,XRD and other characterization results show that P-PANI is three-dimensional nanofibrous structure with uniform size and hole distribution,and the fiber diameter is about 80-110 nm.In 1.0 mol L-1 H2SO4 electrolyte,the electrode materials were tested by CV and galvanostatic charge-discharge.The specific capacitance of P-PANi is 535.4 F g-1 at the current density of 0.1 A g-1.After 500 times continuous charge-discharge cycles,its capacitance retention is 64.3%.The results show that P-PANI has high specific capacity and good cycling stability.(2)PANI doped with p-aminobenzene sulfonic acid(p-ABSA/PANI)were prepared by emulsion polymerization with ammonium sulfate(APS)as oxidant,p-ABSA as dopant and Tween-20 as emulsifier.SEM,XRD,FTIR and TG test results show that p-ABSA doped PANI chains successfully,and the appropriate amount p-ABSA is conducive to uniform dispersion of PANI,formation of porous structure and improvement of thermal stability of PANI.CV and EIS test results show that the doped PANI has good pseudocapacitance characteristics and redox reversibility.When np-ABSA:nAN is 1:20,specific capacity of p-ABSA/PANI is as high as 524.1 F g-1 and greater than that of the undoped PANI.Its capacitance is 325.3 F g-1 after 500 cycles,maintaining 63.0%.p-ABSA/PANI electrode materials display good capacitance characteristics.(3)N-CNTs were prepared by a series of reactions through mixed acid oxidation,Curtius rearrangement.When PANI was grafted covalently onto the N-CNTs surface,PANI/N-CNTs composites were prepared by in-situ chemical polymerization.The water solubility experiment results show that the modified carbon nanotubes have good dispersion stability.SEM,TEM,XRD and other tests results show that PANI/N-CNTs is shell-core structure composite,presenting fiber shape,and PANI covers uniformly the N-CNTs.Electrochemical testing results show that PANI/N-CNTs has both pseudo-capacitance and electric double layer capacitance characteristics.The specific capacitance of PANI/N-CNTs electrode is 406.6 F g-1 at the discharge current density of 0.1 A g-1,and its capacitance is 303.2 F g-1 after 500 cycles,maintaining 74.6%.The study show that PANI and N-CNTs connected by the interaction of covalent bond can mitigate effectively volume expansion and contraction of PANI molecular chains due to doping ions in the process of charge and discharge,so that cycle life of PANI/N-CNTs electrode material is improved.(4)MnO2/CNTs was prepared by in situ hydrothermal synthesis and used as an oxidant template to synthesis PANI/CNTs composite by in-situ polymerization.SEM,TEM,XRD and other tests results show that the prepared MnO2 is a mixed crystal phase of y-MnO2 and ?-MnO2,MnO2 well coats on the carbon nanotubes surface.PANI/CNTs is a nuclear shell structure,PANI evenly covers on the CNTs,the fiber diameter is about 34?65 nm,the morphology is conducive to full contact of the composite materials and electrolyte and improvement of the electrochemical performance of the composite electrode materials.Under the discharge current density of 0.1 A g-1,the specific capacity of PANI/CNTs is 435.7 F g-1,and the capacity is still 313.9 F g-1 after 500 cycles of constant current charging/discharging,and its retention rate is as high as 72.0%.