Preparation And Electrochemical Energy Storage Performance Of Polyaniline Micro-nano Ordered Structure

Supercapacitor is a new type of renewable green energy,which is widely used in electronic energy storage devices because of its advantages of fast charge and discharge speed,long cycle life,high power density and wide operating temperature range.Polyaniline has the advantages of high theoretical capacitance,good conductivity,low synthesis cost and high environmental stability.It is a promising electrode material for supercapacitor.The preparation of polyaniline electrode material with high specific capacitance and good stability is an effective way to improve the electrochemical performance of supercapacitor.Here,polyaniline and its composite electrode materials with good electrochemical properties have been successfully prepared by electrochemical deposition,chemical oxidation,and template synthesis,including ordered polyaniline nanostructures and polyaniline nanoarray composite structures.The synthesis mechanism and electrochemical performance were systematically studied.1.One dimensional orderly polyaniline?PANI?nanowires array were prepared on conducting substate by using a galvanostatic current method.The effects of preparation factors,including concentration of aniline,working current density and kinds of protonic acid,on the morphology of the as-prepared PANI nanowires were investigated.It was found the best morphology of PANI nanowires array could be obtained when concentration of aniline was 0.1 mol/L and the working current density was 0.03 mA/cm²,Also,the PANI with uniform nanowires arrays had narrow diameters and were oriented electrode.The highest specific capacitance of PANI nanowire arrays was measured as 560 F/g at a charge-discharge current density of 1 A/g,and the PANI nanowire arrays also exhibited good capability and cycling stability with capacitance retentions of 89%after 1000 cycles,which is superior or close to some individual PANI nanostructures and PANI composite materials.2.PANI and other conductive polymers have poor mechanical properties,resulting in short cycle life of the prepared electrode materials,and studies have shown that the addition of conductive materials with strong mechanical properties,such as transition metal oxides and carbon materials,can enhance their stability.Here,the method of hydrothermal synthesis is introduced to prepare the titanium dioxide?TiO₂?tetragonal prism array on the conducting plane of fluorine-doped tin oxide?FTO?,and then the polyaniline?PANI?is coated on the surface of TiO₂ array by normal chemical oxidation to form the PANI/TiO₂ shell/core nanoarray.The array architecture of PANI/TiO₂ composite is further confirmed by SEM,XPS,XRD,UVevis and Raman spectroscopy.Compared with the individual component?PANI or TiO₂?,the PANI/TiO₂/FTO electrode possesses a higher specific capacitance as the supercapacitor electrode material.The maximum specific capacitances of 633 F/g at the rate of 10 mV/s and 781 F/g at the current density of 1 A/g are obtained in the PANI/TiO₂/FTO electrode and it is superior or close to individual PANI or PANIbased materials.The capacitance retention of PANI/TiO₂/FTO electrode keeps 75%of its initial value which is higher than that of the PANI/FTO electrode?65%?after 2000 cycles.Therefore,such array architecture composite can be promisingly used as the electrode material for electrochemical capacitive energy storage.3.Ordered polystyrene?PS?microspheres have a large specific surface area,so the monodisperse polystyrene?PS?microspheres were synthesized by emulsion polymerization.The diameter was about 1.5?m,and their surface was aminated.Then,Langmuir film analyzer?KN1001?was arranged on the FTO conductive surface to form a single layer PS microsphere array.Finally,the ordered polyaniline nanostructure was prepared by chemical oxidation method based on the substrate,and the PANI/PS shell/core composite was obtained.The diameter of the composite microspheres is about 1.7?m.The structure of PANI/PS/FTO composite electrode was characterized by SEM,XRD,Raman spectrum and electrochemical workstation.The results show that the composite electrode material has good electrochemical performance.The specific capacitance is 601 F/g at a scanning rate of 10 mV/s and 753 F/g at a current density of 1 A/g.The PANI/PS/FTO composite can be used as the electrode material for supercapacitors.4.Due to the increasing demand for flexible wearable electronic devices,so the orderly and highly dense polyaniline nanorod arrays have been successfully grown onto the surface of carbon nanofibers to form polyaniline/carbon nanofibers composite via a one step of facile chemical oxidation method.The specific capacitance of the single polyaniline/carbon nanofibers composite electrode is 758 F/g and 720 F/g at current densities of 1.0 and 5.0 A/g,respectively,while the cycling stability can maintain 85%of the initial capacitance after1000 charge-discharge cycles.Furthermore,two pieces of polyaniline/carbon nanofibers composite electrodes are fabricated into a symmetric all-solid-state flexible supercapacitor device to drive small electronic equipments using polyvinyl alcohol-H₂SO₄ hydrogel as solid electrolyte,while the normal filter paper acted as a separator.The as-prepared symmetric supercapacitor device has excellent electrochemical performance with SC value of 285 F/g at a current density of 0.5 A/g.The maximum energy density is 10.04 Wh/kg at a power density of 225 W/kg and shows no obvious decrease in the performance with a bending angle of 45°or 90°.The as-prepared symmetric all-solid-state flexible supercapacitor device has good promising applications in small wearable electronics.