Preparation Of Transition Metal Based Electrode Materials And Their Application In Supercapacitors

Supercapacitors,with the advantages of fast charge and discharge,long cycle life and high power density,have attracted a lot of attention and research and expected to be the next-generation energy storage device.The electrode material of supercapacitors plays a decisive role in the performance of supercapacitors,so most research have been focused on the development of high performance electrode materials.Pseudocapacitive electrode materials have a high theoretical specific capacitance and are considered to be one of the ideal electrode materials.Aim at producing high performance supercapacitor electrode materials,we first prepare the precursor and convert them to the final product.In this paper,we prepared polyaniline-intercalated molybdenum disulfide and vanadium based binary and ternary metal oxide and studied their electrochemical properties.The main research contents are as follows:?1?Polyaniline-intercalated MoS₂ composites with different morphologies?aggregated particles,nanowires,and nanotubes?were successfully prepared by a three-step method.Because of the sub-nanometer periodic structure of the precursor,the prepared material exhibit a unique intercalation structure,that is the intercalation of PANI into the interlayer of molybdenum disulfide.The intercalation structure enhances electron transfer,and the expanded interlayer of MoS₂ is beneficial for ion diffusion kinetics.Among the three composite materials,the tubular composite has the best capacitive property in terms of a high specific capacitance of 375 F g^-1 at a current density of 50 A g^-1 and good stability for charge-discharge cycling.This indicates that the hollow structure,compared with the other nanostructures,facilitates the exposure of the active sites of the material and the penetration of electrolyte.In addition,this work reveals the effect of electrode morphology on its electrochemical properties.?2?Amorphous nickel vanadium binary oxide?a-Ni-V-O?is prepared by refluxing the Ni-glycerate precursor.a-Ni-V-O is composed of nanoparticles,but the agglomeration of the nanoparticles is serious.However,thanks to the amorphous characteristics,a-Ni-V-O exhibits good electrochemical performance with a specific capacitance of 943F g^-1at a current density of 1 A g^-1,while also having high rate property and cycle life.This indicates that the amorphous or low crystallinity materials can be a promising class of supercapacitor materials.?3?In this section,we use the self-template method.First,NiCo-glycerate solid spheres were prepared as a precursor,and the final products were produced by hydrothermal reaction using the precursor as self-template.By adjusting the ratio of nickel to cobalt in NiCo-glycerate,the ratio of nickel to cobalt in the final products could be changed,thereby obtaining hollow spherical Ni₂CoV₂O₈ and yolk-shell structured NiCo₂V₂O₈ and Co₃V₂O₈.The unique hollow structure facilitates exposure to more redox active sites and diffusion of electrolyte ions.Comparing the specific capacitance and rate property of the three materials,the hollow spherical Ni₂CoV₂O₈exhibits the best electrochemical performance,with a high specific capacitance of 852F g^-1 at a current density of 1 A g^-1,and 82%of the initial value is maintained at 10 A g^-1.The results show that in the binary or ternary metal oxide,nickel element helps to obtain a high actual specific capacitance,and cobalt element helps to improve the rate property of the material.Furthermore,it is possible to controllably adjust the proportion of nickel to cobalt in the final product,which is of significance for the selective preparation of the metal oxide.