Prepation And Supercapacitor Performance Of Manganese Dioxide Matrix Composites

As fossil fuels become unrenewable and polluted to the environment,people have to develop new energy sources,such as wind,solar and tidal power.But the unsustainability of new energy sources lead people to develop energy-storage devices.Supercapacitors stand out among many energy storage devices because of their features which has fast charging and discharging process,high power density and long cycle life.The key to develop supercapacitors is the development of electrode material.In the work,we synthesize the manganese base materials on nickel foam without any binder by simple electrodeposition and hydrothermal method.And the corresponding characterization and electrochemical performance test were carried on,the main work is as follows:?1?The Na⁺/K⁺-inserted MnO₂ nanosheets were successfully synthesized on Ni foam without any binder via using manganese acetate and sulfate as reactants.When the current density at 0.3 m A cm^-2,with a roughly measured active mass-loading of 1.5 mg cm^-2,the areal capacitance of the Na_xK_yMnO₂/Ni nanosheets can reach 374 m F cm^-2(amount to specific capacitance of 249 F g^-1 at 0.3 mA cm^-2).When the scan rate at 100 mV s^-1,the capacitance retention rate of the Na_xK_yMnO₂/Ni nanosheets is 82%after 10 000 cycles,implying a good cycling stability.The ASC was assembled by exploiting the Na_xK_yMn O₂/Ni nanosheets as the positive electrode and the Ti₃C₂T_x/NF as the negative electrode.The ASC has a large areal capacitance of 249 mF cm^-22 at 1 mA cm^-22 and the capacitance retention rate of 86%after 5 000 cycles in 0-1.9 V with a two-electrode system.?2?The Co?OH?F@K_xMnO₂ were successfully synthesized on Ni foam via electrodeposition and hydrothermal method using cobalt acetate and lithium fluoride as reactants.The electrochemical test was carried on a three-electrode system,When the current density at 1 m A cm^-2,the areal capacitance of the Co?OH?F@K_xMnO₂/Ni nanosheets can reach 1 046 mF cm^-2.After 3 000 cycles,the capacitance retention rate of nanosheets is 118%.These results indicate that the Co?OH?F@K_xMnO₂/Ni composite electrodes could be a promising electrode material for high-performance electrochemical capacitors.