Preparation And Performance Of Supercapacitors Based On Nano-carbon Material Composites

In the 21st century,with the rapid development of social production,it is imperative to develop high-performance energy storage devices.As a typical representative of new energy storage devices,supercapacitors have the advantages of large specific capacity,fast charging and discharging rate and long cycle life.With the advent of many intelligent electronic products such as electronic sensors,flexible displays and health monitors,supercapacitors are widely used.As one of the core components of supercapacitors,electrode materials play an important role in the performance of supercapacitors.Therefore,the development of electrode materials with high specific capacity,high cycle life and good mechanical properties has become a research hotspot.Nano-carbon materials have large specific surface area,high conductivity and good mechanical properties,which show good application prospects in supercapacitor electrode materials.However,the specific capacity of nano-carbon materials as electrodes only needs to be improved.The performance of supercapacitors will be greatly improved by compounding nano-carbon materials with pseudo-capacitor materials,and the application of nano-carbon materials in supercapacitors will be promoted.In this paper,nano-carbon and pseudo-capacitor materials were used to prepare electrode materials and assemble supercapacitors to study their electrochemical properties.The main research contents are as follows:Firstly,using potassium hydroxide(KOH)to activate carbon nanotubes(CNT)to prepare activated carbon nanotubes(ACNT)with high specific surface area,ascorbic acid reduction to prepare reduced oxide graphene(RGO)and hydrothermal method to prepare manganese dioxide(MnO2).Three kinds of materials were deposited on foam nickel substrate by mixing and bonding,and ACNT/RGO/MnO2 electrode materials were prepared.The electrode material was characterized by specific surface area meter and scanning electron microscope.It was found that the composite electrode was porous and had large specific surface area and porosity,which was conducive to charge storage.Furthermore,ACNT/RGO/MnO2 was applied to supercapacitor electrodes,and all-solid-state supercapacitors were assembled using polyvinyl alcohol(PVA)/phosphoric acid(H3PO4)as electrolyte.When the current density is 0.2 A g-1,the specific capacitance of ACNT/RGO/MnO2 supercapacitor is 156 F g-1,which is larger than that of ACNT(57 F g-1)and ACNT/RGO supercapacitor(79 F g-1).After 5000 cycle life tests,the ACNT/RGO/MnO2 supercapacitor can maintain 90%of the initial capacitance,reflecting good cycle stability.Secondly,conductive polymer polypyrrole(PPy)and helium etched carbon nanotube film(HCNTF)were synthesized by helium plasma etching and electrochemical deposition.Carbon nanotube thin films(CNTF)with high flexibility,high strength and high conductivity were used as substrates to improve their hydrophilicity by He plasma etching.The contact angle measurements show that CNTF changes from hydrophobic to hydrophilic under the etching of He plasma,and the enhancement of hydrophilicity increases the ion and charge transfer ability between the film and the electrolyte.Infrared and Raman spectra show that the electrochemical method can deposit conductive polymer PPy nanospheres with good pseudocapacitive properties in HCNTF to prepare composite flexible electrodes of nano-carbon materials and pseudocapacitive materials.The composite electrode and PVA/H3PO4 electrolyte were assembled into PPy/HCNTF all-solid-state supercapacitor and its electrochemical performance was tested.Under the current density of 1 mA cm-2,the specific capacitance of PPy/HCNTF supercapacitor is 414 F g-1,which is higher than that of CNTF supercapacitor under the same conditions(170 F g-1),reflecting the excellent capacitance performance of PPy/HCNTF supercapacitor.PPy/HCNT supercapacitors also have good flexibility and flexural stability,and can maintain 96%of the initial capacitance after 500 bends.In a word,the ACNTT/RGO/MnO2 supercapacitor prepared in this paper has good capacitance performance and cycle stability.PPy/HCNTF supercapacitor has high capacitance,good flexibility and long cycle life,which shows good application prospects in the field of energy storage and flexible electronic devices.