Preparation And Modification Of Electrode Materials Based On Mxene And Nickel-cobalt Composites

As a new type of green energy storage device,supercapacitors have attracted extensive attention due to their high power density and excellent cycling performance.However,compared with traditional energy storage devices,supercapacitors still suffer from low energy density and other disadvantages.In order to make up for the deficiency,how to design reasonable electrode materials has become the focus of current research.Transition metal-based materials and MXene materials are widely used in supercapacitor electrode materials because of their multiple active sites and tunable surface groups.At the same time,these materials also have the advantages of easy synthesis,non-toxic and harmless,and easy availability of raw materials.In this paper,based on MXene and transition metal materials,a series of MXene and nickel-cobalt-based composite nanomaterials were prepared by a simple method,and their structural characterization and electrochemical performance tests were carried out to explore their application in supercapacitors.The main research contents are as follows:（1）NiCo-MOF was directly grown on nickel foam by hydrothermal method,using NiCo-MOF/NF as precursor,and a solution containing MXene,Ni²⁺and Co²⁺as electrolyte,MXene-Ni-Co-O@NiCo-MOF/NF nanosheets were prepared by electrodeposition process.The redistribution of metal cations between the MXene layers resulted in the resulting nanosheets exhibiting a unique hexagonal morphology.This unique morphology can improve the electrochemical performance of the material,while the specific capacitance can reach 855.0 C g^-1(2137.5 F g^-1)at 1 A g^-1,and the capacity decays only 24.7%after 5000 cycles.The device was assembled with this material as the positive electrode and activated carbon as the negative electrode,achieving a high energy density of 32.6 Wh kg^-1at 699.6 W kg^-1.（2）A composite nanomaterial with flower-like array morphology was prepared by hydrothermal method and electrodeposition process using carbon cloth as a substrate,in which MXene was used as a structure directing agent,so the composite material was named M-NiCo₂O₄@NiCo-MOF/CC.Theoretical calculations by density functional theory（DFT）show that the density of states（DOS）changes at the heterojunction demonstrate that the electronic properties of the material are effectively improved after recombination.Benefiting from its unique flower array structure,the M-NiCo₂O₄@NiCo-MOF/CC electrode can achieve a high specific capacity of 1150.0 C g^-1(2091.0 F g^-1)at 1 A g^-1,and after 6000 cycles,the capacity remained at 90.3%.Furthermore,the assembled NiCo₂O₄@NiCo-MOF/CC//AC asymmetric supercapacitor exhibits a high energy density of 56.7 Wh kg^-1at 750 W kg^-1,while exhibiting excellent cycling performance.（3）A nanocomposite was synthesized by electrodeposition process using Co-MOF as the reactive substrate,which was named M-Ni-Co-O@Co-MOF/CC due to the use of MXene as the additive.The formed three-dimensional network structure can provide more channels for the transmission of electrons and ions,and at the same time can effectively prevent the material from agglomeration after multiple charging and discharging.EIS test confirmed that the material has high electrical conductivity,which can reach a high specific capacity of 790.5 C g^-1(1581 F g^-1)at 1 A g^-1,and can still retain 79.6%of the capacity after 5000 cycles.