Study On Supercapacitor Performance Based On NiCo₂O₄ Micro/Nanostructured Materials

With the development of human society and the increasing improvement of people living standards,it has become more urgent to find sustainable and renewable energy.Among various electrochemical energy storage systems,supercapacitors have attracted widespread attention due to their rapid charge and discharge,high power density,and environmental friendliness.However,transition metal oxides exhibit the advantages of high specific capacitance and abundount resources and so on.However,most of transition metal oxides can cause volume expansion or contraction during charging/discharging due to their poor conductivity,which make the structure of the material change and affect the electrochemical performance.Therefore,how to reasonably design and prepare hybrid structured electrode materials with large specific surface area and multiple active sites becomes very important.In this work,the spinel structure of NiCo₂O₄ nanomaterials was studied,and the microstructure and electrochemical energy storage mechanism of the as-synthesized products were systematically studied.The main contents are as follows:NiCo₂O₄ nanowires were prepared through a simple hydrothermal method.The corresponding electrochemical performance was investigated.At 1 A g^-1,the specific capacitance of as-synthesized NiCo₂O₄ nanowire electrode can reach 830.8 F g^-1.After 20,000cycles,the capacitance retention rate can reach 96.36%.The assembled asymmetric device delivers a power density of 493.2 W kg^-1 at an energy density of 27.4 Wh kg^-1 and capacitance retention rate reaches 79.2%of initial capacitance after 10,000 cycles.Core-shell structured MnO₂@NiCo₂O₄ nanosheet electrode was prepared by two hydrothermal methods.The as-synthesized products deliver a specific capacitance of 638.5 F g^-1 at 2 A g^-1.Simultaneously,Core-shell structured MnO₂@NiCo₂O₄ nanosheets keep 98%of initial capacitance after 10000%cycles.The assembled MnO₂@NiCo₂O₄//AC device exhibits a high energy density of 70.1Wh kg^-1 at the power density of 2.4 kW kg^-1,and the capacitance retention reaches 97.3%after 6000 cycles.In order to further utilize the synergistic effect among different materials,sandwich structured MCo₂O₄@MCo₂S₄@PPy was prepared through a three-step reaction.As the electrode material of supercapacitor,specific capacitance of MCo₂O₄@MCo₂S₄@PPy structure is 1670.4 F g^-1 at 1 A g^-1 and capacitance retention reach 90.07%after 10,000 cycles.The voltage window of the as-synthesized device can reach 1.5 V.The assembled device delivers excellent cycle stability.