Construction Of NiCo₂O₄ Nano-micro Structures And Their Supercapacitive Properties

In the field of energy storage devices,supercapacitors is regarded as one of the most leading energy storage technologies.There are signification applications in some field including heavy trucks,port cranes,load balancing systems in intermittent energy sources,and light rail vehicles.However,commercial supercapacitors are significantly lower than lithium ion batteries and fuel cells in output energy density,and the lack of energy density limits their widespread application.To achieve raised energy density without sacrificing power density,the development of new electrode materials is an indispensable step.Binary metal oxides NiCo₂O₄,possessing several orders of magnitude higher conductivity than single metal oxides NiO and Co₃O₄,are systematically investigated as high-performance electrodes application.The NiCo₂O₄-based electrodes store charge through fast transition metal redox reactions happening on surface or near-surface of electrode materials.In addition,the structural features of electrode materials can directly influence its charge storage capability.Compared to bulk materials,powder materials with micro-nano structure exhibit larger specific surface area,which can provide more reactive sites and faster redox reactions.In this paper,main works are focused on the preparation of high-performance electrode materials,and details are as follows:?1?The mesoporous NiCo₂O₄ microflowers structures are synthesized by solvothermal methods.The specific surface area value of 66.3m²/g and the pore volume value of 0.308cm³/g are obtained,and can provide more reactive sites.The microflowers powder are applied to prepare battery-type electrodes and high concentration KOH solution are served as electrolyte.The test results The discharge specific capacity value at the current density of 1A/g is 122.5C/g.More importantly,78.3%capacity retentions after 6000 cycles at 2A/g indicates long cycle stability.?2?The porous NiCo₂O₄ nanosheets grown on conductive nickel foam substrate are synthesized with absolutely ethanol as solvent.The areal specific capacity value of electrodes at 1mA/cm² is 0.605C/cm².In addition,after 6000 cycles at 5mA/cm²,the capacity retention ratio is 75.7%.?3?The mesoporous NiCo₂O₄ nanoneedle arrays grown on nickel foam substrate are prepared by hydrothermal methods with PEG20000 as template agents.The three-electrode test shows that the areal specific capacity value at 2mA/cm² is0.998C/cm².The retention ratio value of 80.8%are obtained after 12000 cycles at20mA/cm².The micro-supercapacitor of diameter 1cm is assembled with mesoporous nanoneedle electrode as positive electrode and activated carbon electrode as negative electrode.The energy density value of micro-supercapacitor is 0.33mWh/cm³ at the power density of 12mW/cm³.