Study On The Preparation Of Nickel-cobalt-based Compounds And Their Capacitance Performance

With the rapid development of the times and society,the demands for energy storage devices are growing.Supercapacitor is a new energy storage device between ordinary capacitor and battery which has many advantages such as short charging time,high power density,long service life,environmental protection and low maintenance cost.Supercapacitors are widely used in electric vehicle,mobile communication and wearable electronic equipment.The structure of electrode material has a very important influence on the performance of supercapacitor which has attracted great attention over researchers.In this paper,nickel cobalt sulfide nanosheet arrays?NiCo₂S₄?with honeycomb-like structure were evenly grown on the carbon cloth through hanging-hydrothermal reactions for high-performance flexible electrode,and nickel cobalt molybdate(Ni_1-xCo_xMoO₄)with tunable morphologies were prepared by a chemical coprecipitation method.The details are as follows:A facile hanging-hydrothermal method was used to directly generate uniform NiCo₂S₄ nanosheet arrays on carbon cloth?NiCo₂S₄/CC?,which was then utilized as the positive electrode for flexible supercapacitors.Taking advantage of the unique and uniform honeycomb-like structure of NiCo₂S₄ nanosheets,NiCo₂S₄ eletrode has high specific surface areas and conductivity,showing high specific capacitance(1638 F?g^-1 at 1?A?g^-1).A two-electrode flexible supercapacitor was assembled using NiCo₂S₄/CC as positive electrode and activated carbon as negative electrode and revealed a high energy density of 25.2 Wh kg^-1 at a power density of 799.6 W kg^-1,highlighting its great potential for flexible supercapacitor applications.Ni_1-xCo_xMoO₄ with tunable morphologies was synthesized through Co-doping by a facile chemical co-precipitation method.Among them,Ni_0.85Co_0.15MoO₄ electrode displays an excellent specific capacitance(1301 F?g^-1 at 1?A?g^-1),which is higher than NiMoO₄ electrode(1050.4 F?g^-1 at 1?A?g^-1)and Ni_0.7Co_0.3MoO₄ electrode(755.2 F?g^-1 at1?A?g^-1).In addition,Ni_0.85Co_0.15MoO₄ electrode shows excellent cycling stability with 86%retention of its original capacitance after 3000 cycles.Additionally,an asymmetric supercapacitor?ASC?device can be fabricated using Ni_0.85Co_0.15MoO₄ as positive electrode and activated carbon as negative electrode.The as-fabricated ASC achieves a high energy density of 37.26 Wh kg^-1 at the power density of 400 W kg^-1,highlighting its potential application for the efficient energy storage devices.