Preparation And Electrical Properties Of Cobalt-based Binary Metal Oxide Electrode Materials For Supercapacitors

Supercapacitors(SC)have the advantages of high energy density,long life,fast charging and discharging speed,etc.,so they have attracted widespread attention.In particular,pseudocapacitance capacitors(PCs)are more popular due to their excellent performance.A lot of research focuses on the development of pseudocapacitance capacitors with fast charging time,high conductivity,high energy density,and good cycle stability.The performance of supercapacitors mainly depends on the electrode materials.Transition metal oxides as capacitor electrode materials are also one of the research hotspots.In this study,three cobalt-based metal oxide electrode materials were prepared by simple hydrothermal and annealing treatments,and their electrochemical properties were tested.The main research contents are as follows:(1)ZnCo₂O₄@NiO nano-array electrode materials were prepared by reflow and annealing.The morphology and crystal structure of the materials were characterized by XRD,XPS,SEM,and TEM.And the electrochemical performance tests show that the specific capacitance is 1156 F g^-1at the current density of 1A g^-1.At the same time,an asymmetric supercapacitor assembled with ZnCo₂O₄@NiO as the positive electrode material and activated carbon(AC)as the negative electrode material has excellent energy storage performance(the energy density reaches 40.1 Wh kg^-1when the power density is 348 W kg^-1),and has excellent cycle stability(82%capacitance retention after 10,000 cycles).(2)Using carbon paper as a template,the cubic-shaped MnCo₂O₄nano-array electrode material was grown on carbon paper by hydrothermal and annealing method.And the urea content,solution concentration and the addition amount of ionic liquid in the electrolyte were systematically studied.Study on the electrochemical performance of MnCo₂O₄shows that the MnCo₂O₄electrode material has excellent specific capacitance of 1088 F g^-1and cycle performance(91%of capacitance retention after10,000 cycles).Finally,an asymmetric supercapacitor(HASC)is assembled with MnCo₂O₄as the positive grade material.When the power density is 373.2 W kg^-1,the energy density is 43.7 Wh kg^-1,and the capacitance retention rate is still 87.3%after10,000 cycles at a current density of 5 A g^-1,showing good energy storage performance.(3)NiCo₂O₄nanoflower electrode material was prepared by one-step hydrothermal method,and the effect of NH₄F on the energy storage and morphology of the electrode material was studied.The electrochemical test shows that NiCo₂O₄has excellent electrochemical performance.Its specific capacitance is as high as 1651 F g^-1under 1A g^-1,and it also shows excellent energy storage performance under the two-electrode system.The energy density of the assembled asymmetric supercapacitors at a current density of 0.5 A g^-1can reach 53.1 W h kg^-1,and the maximum power level can reach10897 W kg^-1.