The Preparation Of PPy/NiO/CNTs Ternary Polymer Materials And Their Applications In Lithium-Ion Batteries

Supercapacitors are new energy storage and conversion devices with the advantages of high specific capacitance,high power density,long cycle life and environmental friendliness.It has been widely used in the field of new energy automobile,mobile communication,medical device,defense weapon and so on.The research of supercapacitors is mainly devoted to the development of electrode materials with high capacitance and long cycle life.The emphasis is on the combination of carbon based materials with pseudo-capacitor metal oxides and conductive polymers.In this paper,the characteristics of activated carbon nanotubes,transition metal oxides and conductive polymers were studied,and the composite electrode materials based on carbon nanotubes are developed.The composite electrode materials were characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD),specific surface area analysis,thermogravimetric analysis(TGA)and EDX energy spectrum.At the same time,cyclic voltammetry and constant current charge-discharge method were used to study their electrochemical properties.The composite was applied to lithium ion battery to investigate its effect on battery performance.The results of this study included:1.Synthesis of NiO/CNTs precursor material:NiO/CNTs complex was synthesized by hydrothermal method combined with high temperature annealing.X-ray diffraction,elemental analysis,thermogravimetric analysis and EDX spectra were used to characterize the results.It was proved that NiO was successfully loaded on CNTs.At the same time,cyclic voltammetry and constant current charge-discharge method were used to study its electrochemical performance.It was found that the electrochemical performance of the composite material had been greatly improved.When the current density was 10 A·g-1,the capacitance can reach 526 F·g-1,and it had good stability.When pure CNTs was used as electrode material,the current density was 10 A·g-1,the capacitance was only 69 F·g-1.The results showed that the composite of carbon material with transition metal oxide(NiO)had good electrochemical performance.2.In a very low temperature,the polypyrrole polymer was encapsulated in the surface of the precursor material NiO/CNTs by pyrrole monomer,forming the PPy/NiO/CNTs ternary complex material,to study the effect on the electrochemical performance and stability of composites.In the process of reaction,ammonium persulfate was used as polymerization initiator to oxidize pyrrole monomer into polypyrrole.The effects of the dosage and polymerization time of pyrrole on the properties of the composites were studied.The composite material obtained by electrochemical performance test results showed that the dosage of pyrrole monomer was 2%(V/V),polymerization time was 2 min,at the current density of 10 A·g-1,the specific capacitance of the composite material was 926 F·g-1.Under the same current density,through constant current charge and discharge cycle after 2000 times,its electric capacity remained at a rate of 87%.3.With NiO/CNTs、PPy/NiO/CNTs as anode materials for lithium ion batteries,metal lithium plate as positive electrode,microporous polypropylene film as membrane,1.0 mol·L-1 LiPF6 as electrolyte,it was assembled into button battery.The change of the capacitance was studied by the blue test system.When NiO/CNTs were used as negative electrode materials,at the current density of 100 mA·g-1,after the cycle test,the capacitance retention rate was 15%.At the same current density,pyrrole dosage was 20%(V/V),polymerization time was 2 min,the capacitance retention rate of the composite electrode materials was 22%.The retention rate increased by 47%than material which was not added pyrrole monomer.