| Supercapacitors that have high power density and long cycle life are an important part of the new generation of energy conversion devices.But,its low energy density limits the application areas of supercapacitors.Metal-organic framework（MOF）is a relatively new class of supercapacitor electrode materials,which have the advantages of porosity,large specific surface area,and high specific capacity.However,the poor conductivity of metallic organic framework（MOF）and structural instability in aqueous solutions make it difficult to perform optimally in supercapacitors.Based on this,this paper takes vanadium metal-organic frameworks as research objects,prepares vanadium-nickel bimetallic organic frameworks and derivative electrodes with different proportions,and explores the optimization mechanism of their electrochemical performance.The specific research is as follows:In view of the problems of poor conductivity and structural instability of MOF materials,different proportions of vanadium-nickel metal MOF electrodes（VNi-MOF-n）were prepared by hydrothermal method based on nickel foam,and the effects of introducing different concentrations of nickel atoms on the performance of supercapacitors were discussed.By introducing nickel atoms,the problem of poor conductivity of MOF materials is effectively improved,and the charge transport and electron transport capacity are improved.The performance test shows that the VNi-MOF-4 with Ni=40%V ratio has the best supercapacitor energy storage characteristics,and the area specific capacity can reach 2412 m F cm-2 at a current density of 3 m A cm-2,which is about 4 times the specific capacity of V-MOF,which verifies that the appropriate introduction of nickel atoms can enhance the charge storage capacity of V-MOF.During the preparation of MOF materials,the pores are easily occupied by organic solvent molecules,which makes it difficult for the pore structure in the MOF system to play the role of energy storage.Based on this,the MOF derivative array（aVNi-MOF-n）was prepared by high-temperature calcination using VNi-MOF-n nanosheet array as the precursor.The results show that the impurities in the pores of aVNi-MOF-4 annealed by heat treatment are removed,which is conducive to enhancing the permeability of the pores and improving charge transport capability,thereby improving the specific capacity and cycle stability of the electrode material.The specific capacity of aVNi-MOF-4 increased from 2412 m F cm-2 to 4022 m F cm-2 at the same current density(3 m A cm-2).At the same time,after 9000charge-discharge cycles at high current density,the capacity retention rate is still61%.aVNi-MOF-4 and commercial activated carbon were formed into an asymmetric solid supercapacitor to test its supercapacitor performance.The results show that the device has a wide voltage window of 1.75 V,and an energy density of0.049 m Wh cm-2 at a power density of 3.528 m W cm-2,which can be stable for 9000charge-discharge cycles with an initial capacity of 68%. |
