Shape-controlled Preparation And Study On Electrochemical Performance Of Transition Metal Oxide Materials

In recent years,supercapacitors have become one of the hotspots in the field of energy because of their higher energy density and power density than traditional capacitors.This article mainly studies the addition of surfactants to generate a polymorphic metal oxide framework materials with a specific morphology,and composites it with fine Ni O nanoparticles.The structure,morphology and electrochemical performance of the composite materials are studied by changing the holding time and hydrothermal temperature.In this paper,new multi-component Mn Co₂O₄@Ni O nanocomposites and Ni O-MFe₂O₄nanocomposites were successfully synthesized by solvothermal and hydrothermal methods.The main findings are as follows:(1)In this paper,isopropyl alcohol and triethylene glycol are used as the reaction solvent,and the surfactant hexamethylenetetramine(HMTA)was added to successfully prepare porous nanoplatelet-shaped Mn Co₂O₄samples,which were then compounded with Ni O to obtain a new multi-component Mn Co₂O₄@Ni O nanocomposite,which is a porous nanosheet structure with a unique interconnected network.This unique structure has a high specific surface area and a uniform pore size distribution,which can not only effectively ensure the synergy of two pseudocapacitor materials(Mn Co₂O₄and Ni O),it can also promote the diffusion and migration of electrolyte ions during rapid charge and discharge.As a result,the Mn Co₂O₄@Ni O composite electrode exhibits an extremely high specific capacitance(508.3 F/g at a current density of 2 A/g).And at a current density of 10 A/g,after 2000cycles,the retention rate of the capacitor was still as high as 89.7%,showing excellent cycle stability.(2)In this paper,Ni Fe₂O₄and Co Fe₂O₄samples were prepared by adding CH₃COONa and CO(NH₂)₂as surfactants,respectively,and then combined with Ni O to obtain new Ni O-Ni Fe₂O₄and Ni O-Co Fe₂O₄composites.It was found through experiments that the addition of CH₃COONa and CO(NH₂)₂during the preparation had little effect on the crystal structure of Ni Fe₂O₄and Co Fe₂O₄samples,but had a greater effect on the surface morphology of the materials.Most of the samples obtained by using CO(NH₂)₂have porous sheet-like morphology,uniform pore size distribution and larger specific surface area,which can provide more active sites for electrochemical reactions,the specific capacitance of Ni Fe₂O₄material is 103.6 F/g at a current density of 1 A/g;the specific capacitance of Co Fe₂O₄sample is 96.3 F/g.In addition,the composite Ni O has improved its electrochemical performance more effectively.The experiment found that the reaction temperature and holding time also affected the electrochemical performance of the composite samples.When the reaction time was 24 h and the hydrothermal temperature was 160?,the Ni O-MFe₂O₄composite electrode showed the largest specific capacitance value(in At a current density of 1 A/g,the specific capacitance of Ni O-Ni Fe₂O₄is 255.1 F/g,and the specific capacitance of Ni O-Co Fe₂O₄is 261.4 F/g).And at a current density of 10A/g,after 2000 cycles,the retention rates of the capacitors were as high as 83.3%and85.2%,respectively,showing excellent cycle stability.