Preparation And Electrochemical Properties Of Mno₂/pani/mwcnt As Supercapacitor Cathode Materials

Supercapacitor is a new type of green large capacity energy storage device,whose performance is superior to traditional energy storage methods such as batteries.Due to its characteristics of high specific capacity,fast charging discharging speed,no pollution to the environment and long service life.Therefore,the supercapacitor has a strong application value.The performance of supercapacitors mainly depends on the electrode material.In recent years,composite materials have become a research hot spot in supercapacitors.Generally,the electrode materials of supercapacitors are of three types,carbon materials,conducting polymers and transition metal oxides.Each of them has its own advantages and disadvantages.Therefore,binary or ternary composites have been synthesized and investigated for use in supercapacitors as a way of obtaining materials with a combined and balanced merit of the three kind materials.Therefore,in this work,new ternary composite of Manganese dioxide?MnO₂?,polyaniline?PANI?and multi-walled carbon nanotubes?MWCNT?were successfully synthesized by two-step method.The main content of this article is divided into the following aspects:?1?Introduction of supercapacitorsFirst,this paper made a detailed introduction of supercapacitors,which introduced the development history and classification of supercapacitor and made a detailed introduction of the electrode material and electrolyte of supercapacitor.?2?Preparation and Characterization of MnO₂ with Different Morphologies Electrode MaterialsControl over the structure and morphology of MnO₂ can be easily obtained due to the concentration of H₂SO₄ under hydrothermal method method.The composition,structure and morphology of the electrode materials were characterized by SEM,XRD and FTIR.The electrochemical properties of the samples were tested by CV,CD and EIS in different electrolytes.The results showed that MnO₂ with rodlike,microsphere,petaloid and lycheelike structure morphologies had been successfully prepared.MnO₂ electrode with petaloid morphology exhibited a high specific capacitance of 171 F g^-1 when electric current density of 1 A g^-1,which is much higher than that of other three manganese oxides electrodes with different morphologies.?3?Synthesis and Characterization of composite MnO₂/PANI/MWCNTIn this paper,a new class of ternary coaxial hierarchical nanofibers was fabricated by two-step strategy.Conducting polymer PANI was coated on the outer surface of MWCNT to form PANI/MWCNT composite nanofibers.Then,MnO₂in-situ grows on PANI/MWCNT nanofibers to obtain ternary hierarchical nanofibers MnO₂/PANI/MWCNT by in-situ chemical reaction between PANI/MWCNT and KMnO₄ under mild conditions.The composition,structure and morphology of the electrode materials were characterized by TEM,XRD and FTIR,and the effects of different KMnO4 contents on the structure and properties of the composite were also discussed.The results show that the maximum specific capacity of the ternary composites synthesized by the synergistic effect of MnO₂,PANI and MWCNT is up to 395 F g^-1,which is greater than the specific capacitance of the binary composites.