Preparation Of Graphene And Graphene Composites And Study On Properties Of Supercapacitors

Supercapacitor is a new type of energy storage device with long cycle life and can be charged and discharged under the condition of large current.However,electrode materials are an important factor affecting the performance of supercapacitors.Commonly used electrode materials include carbon materials,transition metal oxides/hydroxides and conductive polymers.At present,composite materials have become the research focus of electrode materials.In this paper,pure rGO,rGO/ZnO nanocomposite and rGO/ZnOx/NiO1-x nanocomposite with different proportions were prepared by hydrothermal synthesis-high temperature solid phase method.Supercapacitor electrodes were prepared from the composite materials,and electro-chemical properties of the composite materials were studied.Through the analysis of the data,the following conclusions are drawn:(1)Improvement was made on the preparation of GO by Hummers method..Natural flake graphite was used as raw material to prepare go with high degree of oxidation and homogeneous flake layer.Deionized water,ethanol and hydrazine hydrate were used as reducing agents to reduce go respectively,and graphene rGO-1,rGO-2 and rGO-3 with different reduction degrees were obtained.Through electrochemical testing,it was found that the specific capacitance was 144F/g,110F/g and 146F/g respectively at the current density of 0.5A/g,and the specific capacitance retention rates were 77.8%,77.3%and 73.3%respectively after 10000 cycles.At a higher current density(1A/g),larger specific capacitance 128F/g,98F/g and 133F/g can still be maintained,and rGO-1 has better capacitance and cycle performance.(2)rGO/ZnO nanocomposites were prepared by hydrothermal synthesis-high temperature solid phase method.Compared with GZ0.5,GZ2,GZ3 and GZ4,GZ1 with a mass ratio of 1:1 of rGO and ZnO showed good specific capacitance and cycling performance.At the high current density of 2A/g,the specific capacitance is 235 F/g,and the specific capacitance retention rate is 83.8%after 10000 cycles.(3)rGO/ZnOx/NiO1-x nanocomposites were prepared by hydrotherm synthesis-high temperature solid phase method.The doping of graphene,ZnO and NiO was very uniform.At current densities of 0.5A/g,lA/g and 2A/g,when x=0.35,the composite material GN1 has the best performance in specific capacity,respectively 563F/g,524 F/g and 504 F/g.After 10000 cycles,the specific capacitance is retained as 356F/g,312F/g and 300F/g respectively.The circulation capacity retention rates were 63.2%,60.1%and 59.6%respectively.