Research On Preparation Of Nickel Hydroxide/Multilayer Graphene Composite And Supercapacitor Performances

Supercapacitors have the advantages of low cost,low pollution,high energy density,high cycle stability,etc,and become a very important research direction in the field of energy storage.The electrode materials of supercapacitors play a key role in the performance of supercapacitors.Among them,the lamellar metal hydroxide has a large specific surface area and excellent redox performance,which can be used as an ideal positive electrode material for supercapacitors.However,the conductive properties of lamellar metal hydroxides are poor,and it is necessary to improve their conductive properties through composite carbon materials.In this thesis,nickel hydroxide is compounded on the surface of multi-layer graphene by hydrothermal method to improve the performance of nickel hydroxide supercapacitors.The main research contents are as follows:By controlling the ratio of the mixed solvent and the concentration of the nickel source,standing and flat sheets of nickel hydroxide were prepared on the surface of the multilayer graphene.When the ratio of DMF to H₂O is 7:3,Ni Cl₂is 170.4 mg,and the amount of urea added is 70 mg,the synthesized nickel hydroxide nanosheets grow close to vertical on the surface of the multilayer graphene,forming a porous nickel hydroxide porous film.The material has excellent performance,and its specific capacity can reach 1611 F g^-1 at a current density of 1 A g^-1.When the ratio of DMF to H₂O is 2:8,Ni Cl₂ is 53.5 mg,and the amount of urea added is 70 mg,the synthesized nickel hydroxide nanosheets grow on the surface of the multilayer graphene along the graphite surface,forming a flat large-size hydrogen Nickel oxide nanosheets.This composite material shows good rate performance,the specific capacity at 1 A g^-1 current density is 1053.33 F g^-1,and the initial capacity is still 93%at 10 A g^-1,After 5000 charge and discharge cycles,the capacity The retention rate is 66.67%.The obtained composite material was used as the positive electrode,and the activated carbon and the Fe₂O₃/multilayer graphene material prepared in the laboratory were respectively used as the negative electrode to prepare an asymmetric supercapacitor,and the electrochemical performance of the asymmetric supercapacitor was studied.The thesis further explored the preparation of all-solid asymmetric supercapacitors based on composite materials and tested their performance.In order to improve the cycle stability of the nickel hydroxide/multilayer graphene composite material,the study of composite copper oxide was carried out on the surface of the material.The obtained spherical copper oxide is composed of nanoparticles and is evenly distributed on the nickel hydroxide porous film.After testing,the cycle stability of the composite material at a current density of 4 A g^-1 increased from 44.5%to 64.6%.The material and activated carbon are used as the positive and negative electrodes to assemble an asymmetric supercapacitor.At a current density of 1 m A cm^-2,the specific capacity of the asymmetric supercapacitor is 64.81 F g^-1.When the current density is 10 m A cm^-2,the capacity retention rate reaches 72%.After 5000cycles at a current density of 4 m A cm^-2,the capacity retention rate was 59%,showing a good cycle life.