Research On Preparation Of Sheet Hydroxide On Multilayer Graphene Surface And Its Energy Storage Application

Supercapacitors are a new type of energy storage device.Their high power density,long cycle life and low environmental pollution have attracted widespread attention in recent years.The performance of supercapacitors depends directly on the characteristics of the electrode materials.Lamellar hydroxides have excellent redox performance and large specific capacity,they have important applications in the positive electrode materials of asymmetric supercapacitors,but lamellar hydroxides have the disadvantage of poor conductivity.In this thesis,lamellar hydroxides were prepared on the surface of multilayer graphene by hydrothermal reaction,which has an important effect on improving the conductivity of the lamellar hydroxides.The main research contents are as follows:?1?The nickel hydroxide/multilayer graphene composites for supercapacitors were prepared by hydrothermal reaction.The effects of the ratio of N,N-dimethylformamide?DMF?to distilled water?H₂O?,the reaction temperature,and the amount of urea added on the microstructure and electrochemical performance of the composites were studied.Among them,when the ratio of DMF and H₂O is 6:4,the reaction temperature is 150?,and the amount of urea added is 40 mg,the performance of the sample reaches the best.When the current density is 1 A g^-1,the specific capacity of the sample is 1325 F g^-1,and at 10 A g^-1,the specific capacity is 1279 F g^-1.The composite material has a high specific capacity and excellent rate performance.After 5000 charge and discharge cycles at 4 A g^-1,the specific capacity is reduced to 54%of the initial specific capacity.?2?The cobalt-nickel bimetal hydroxide/multilayer graphene composites for supercapacitors were prepared by hydrothermal reaction.The effects of the addition amount of cobalt acetate tetrahydrate,the reaction temperature,the ratio of DMF and H₂O on the microstructure and performance of the composites were studied.When the amount of cobalt acetate tetrahydrate is 70 mg,the reaction temperature is 150?,and the ratio of DMF and H₂O is 7:3,the sample has the best electrochemical performance.At 1 A g^-1,the specific capacity of the sample is 2045 F g^-1.After 5000 cycles of charge and discharge,the specific capacity retention rate reaches 65%.?3?The negative electrode material was activated carbon?AC?,and the positive electrode material was cobalt-nickel bimetallic hydroxide/multilayer graphene composite material,which was assembled into an asymmetric supercapacitor.The working voltage range of the asymmetric supercapacitor is 0-1.6V,when the current density is 2 m A cm^-2,the specific capacity is 132 F g^-1,the power density is 133 W kg^-1,and the energy density is 47 Wh kg^-1.After 1000 cycles of charge and discharge at 4 m A cm^-2,the specific capacity is reduced to62%of the initial capacity.