Structure Regulation And Electrochemical Performance Optimization Of Nickel-iron Based Binary Metal Oxides

Supercapacitors are widely used in portable electronic equipment,new energy vehicles,aerospace and other fields due to their advantages such as fast charging and discharging speed,long cycle life and large power density.Nickel-iron-based binary metal oxides have high electrochemical activity,low toxicity,and abundant natural reserves.It is expected to replace traditional precious metal materials and become a promising advanced electrode material.This article optimizes the electrochemical performance of nickel ferrite through three aspects:the construction and control of hollow microspheres,the adjustment of electronic structure,and the design of composite materials.The research content and results include the following:First,a simple one-step hydrothermal method was used to prepare nickel ferrite hollow microspheres with rough surfaces using the bubbles generated by the decomposition of urea as a soft template.The mechanism of the effect of the amount of NH₄F added on the microstructure of the product was studied.The reaction kinetics explains the formation mechanism of the hollow structure.Electrochemical tests showed that the sample prepared with 18 mmol NH₄F had the best performance.The specific capacitance reached 26.43 m Ah g^-1(211.44 F g^-1)at 1 A g^-1 current density.1000 charge and discharge cycles,the capacity retention rate was 90.1%.In addition,the effects of three different heat treatment atmospheres of oxygen,argon,and hydrogen-argon on the performance of nickel ferrite microspheres were studied in this paper.The results show that oxygen and argon do not significantly change the crystal structure of the material.After the heat treatment of the hydrogen-argon mixed gas,the nickel ferrite was partially reduced to produce elemental metal and generate oxygen vacancies.The electrical conductivity was significantly increased,which was 1.8 times higher than the capacitance before heat treatment.In order to further improve the energy density and cycle stability,g-C₃N₄ was introduced into the hydrothermal reaction liquid to synthesize the Ni Fe₂O₄@g-C₃N₄composite material with core-shell structure,and the effect of the composite content on the electrochemical performance was studied.The unique hollow core-shell structure of the sample alleviates the volume change during the charge and discharge process,which is conducive to the formation of a conductive network and the optimization of the ion transmission path.At a current density of 1 A g^-1,the specific capacitance of the Ni Fe₂O₄@g-C₃N₄ electrode heat-treated with hydrogen-argon mixed gas reached 85.27m Ah g^-1(682.16 F g^-1),and the capacity retention rate after 10000 cycles was 96.7%.