Research On Preparation And Properties Of Nickel-cobalt Hydroxide/Multilayer Graphene Composites For Supercapacitor

In recent years,new energy storage devices such as supercapacitors have attracted more and more attention.Its low production cost,excellent cycle stability and high power and energy density have become the main research directions in the energy field.The choice of polar materials has a large impact on the performance of supercapacitors.In this thesis,nickel-cobalt hydroxide was grown on multi-layer graphene sheets by hydrothermal method,and its electrochemical energy storage performance was studied.The main research contents are as follows:?1?The nickel hydroxide/multilayer graphene composites were prepared by hydrothermal reaction.The effects of preparation process on the microstructure and electrochemical properties of the composites were investigated,and the best preparation process of the composites was obtained.The performance of the composite material can reach: the specific capacity is 1378 F g^-1 when the current density is 1 A g^-1,and the specific capacity retention rate reaches 66% after 5000 cycles of charge and discharge.?2?Nickel hydroxide/multilayer graphene composites were used as cathode materials,and activated carbon was used as anode material to assemble asymmetric supercapacitors.The capacitor voltage window is 0-1.7 V.The specific capacitance is 94 F g^-1 at a current density of 2 m A cm^-2,the power density is 220 W kg^-1,and the energy density is 38 Wh kg^-1.After 3000 cycles of charge and discharge at a current density of 6 m A cm^-2,the capacity retention rate reaches 83%,and the cycle stability is excellent,with good practical potential and development prospects.?3?Cobalt-nickel double hydroxide/multilayer graphene composites prepared by hydrothermal reaction.The effect of the molar ratio of cobalt and nickel on the composite was studied.The best performance of the sample was obtained when the molar ratio of cobalt to nickel was 0.5:1.The specific capacity of the sample at 1 A g^-1 was 1940 Fg^-1.4 A g^-1 current capacity density cycle retention rate of up to 82% after 5000 cycles of charge and discharge.?4?A cobalt-nickel double hydroxide/multilayer graphene composite was used as the positive electrode material,and activated carbon was used as the negative electrode material to assemble an asymmetric supercapacitors.The capacitor voltage window is 0-1.6V,with a specific capacitance of 147 F g^-1 at a current density of 2 m A cm^-2,a power density of 166 W kg^-1,and an energy density of 52 Wh kg^-1.Capacity retention rate reached 60.4% after 1000 cycles of charge and discharge at a current density of 6 m A cm^-2.