Preparation And Electrochemical Energy Stirage Characteristics Of Nickel Cobalate Composite Electrode Materials

With the development of automation,information and intelligence,people’s demand for energy is increasing.To fundamentally solve the contradiction between energy supply and human needs,we must take the creation of a clean,low-carbon,safe,efficient and green energy system as the development goal.In the field of energy storage,supercapacitors have the advantages of high power density,long cycle life,high charge discharge rate and environmental protection.They have become the key devices for energy conversion and storage.The electrode material of supercapacitor plays a decisive role in energy storage.In this paper,nickel cobaltate nanowire film is the main research object.Through the strategies of doping and heterogene composite,a new composite electrode material is developed,and the relationship between microstructure and electrochemical energy storage characteristics is analyzed.The main contents are as follows:1.Preparation,structure and properties of fluorine doped NiCo₂O₄/NF electrode materialsUsing nickel and cobalt nitrate and urea as raw materials,NH₄F as morphology control agent and foam nickel as substrate,Ni-Co LDHs was synthesized by hydrothermal method in one step,and then NiCo₂O₄/NF nanowire film was formed by calcination.The effects of NH₄F content on the morphology and electrochemical properties of the composites were discussed by changing the Ni²⁺/F^-molar ratio.The results showed that the morphology and structure of NiCo₂O₄composites were chain hexagonal crystals when the Ni²⁺/F^-molar ratio was 1:3.In the electrochemical test,the specific capacity is 1226 F/g when the current density is 1 A/g,which is much higher than 653 F/g of NiCo₂O₄material.When the molar ratio of Ni²⁺/F^-is 1:6,the morphology of the prepared NiCo₂O₄composite shows a chain hexagonal crystal staggered by nanosheets.In the electrochemical test,when the current density is 1A/g,the specific capacity is 278 F/g.In addition,after 5000 cycles at 20 A/g current density,the capacitance retention of NiCo₂O₄composite with Ni²⁺/F^-molar ratio of1:3 is still 98%.The improvement of these electrochemical properties is due to the shape control effect of NH₄F on NiCo₂O₄nanowire film,increasing the contact area between electrode and electrolyte,increasing electrochemical active sites and improving the electrochemical properties of materials.The research shows that the doping of NiCo₂O₄material with non-metallic ions can improve the electrochemical properties of the material and has great application potential in the development of high-efficiency supercapacitors.2.Preparation,structure and properties of NiCo₂O₄@Ni-Fe LDHs composite electrode materialsFirst,the NiCo₂O₄/NF nanowire film with foamed nickel as substrate was prepared by hydrothermal method and calcination method.Then,Ni-Fe LDHs were deposited on NiCo₂O₄nanowire films by electrochemical deposition with nickel nitrate and iron nitrate as Ni and Fe sources.By adjusting the nickel/iron molar ratio and electrodeposition time NiCo₂O₄@Ni-Fe LDHs composites.The test results show that when the nickel/iron molar ratio is 1:2 and the electrodeposition time is 10 s,the prepared NiCo₂O₄@Ni-Fe LDHs has good electrochemical properties,and its morphology is wrapped by nanowires to form nanosphere structure.In the electrochemical test,the specific capacitance is 904 F/g at 1 A/g current density,which is much higher than 653 F/g of NiCo₂O₄electrode material.After 5000 cycles at 20 A/g current density,the capacitance retention is 99.99%.The reason for the improvement of these electrochemical properties is that the composite of Ni-Fe LDHs increases the specific surface area of NiCo₂O₄material,effectively shortens the path of charge transfer and ion diffusion,so that NiCo₂O₄@Ni-Fe LDHs composite electrode material can fully contact with electrolyte and expand the reaction area,so as to obtain excellent electrochemical properties.The results show that Ni-Fe LDHs can significantly improve the electrochemical performance of NiCo₂O₄and has application prospects in the field of energy storage.