Preparation And Electrochemical Performance Of Graphene Self-Assembled Structure

In order to improve the performance of graphene hydrogels and expand its applications,two graphene self-assembled structures were prepared and studied in this thesis.The pore graded graphene self-assembled macrostructure was prepared and its electrochemical performance under large load was studied.The preparation process of the graphene self-assembled microstructure,the composite process with manganese dioxide and the electrochemical properties of the composite material are also studied.Graphene oxide is prepared from 2000 mesh and 5000 mesh graphite,and then the two graphene oxides and graphene oxide mixed with equal mass are used as raw materials,ascorbic acid is used as reducing agent,and graphene self-assembled macrostructures are prepared by chemical reduction method,named GH-2000,GH-5000 and mix-GH in turn.The results of the study show that GH-2000 and GH-5000 exhibit uniform pore structures of about 3μm and 1μm,respectively.While mix-GH has structural mutations with hierarchical pore structures,including uniformly distributed large pores with a diameter of about 10μm.There are even small holes on the hole wall.In this thesis,a secondary compression method was developed for electrode preparation,and the effect of loading on the electrochemical performance of mix-GH was studied.With the 8 mg/cm² mix-GH,the area specific capacitance is 1689.2 m F/cm² at 0.5 A/g and 1160.5 m F/cm² at 10 A/g,and the capacitance retention rate is 68.7%.After 10,000 cycles at 80 m A/cm²,mix-GH can maintain 97.71%of the initial capacitance,and the coulombic efficiency is always 100%.After being assembled into a symmetrical supercapacitor,When the power density is 500W/kg,the energy density can reach 25.3 Wh/kg.In this thesis,the hydrothermal reduction method to prepare graphene self-assembled microstructures（micro-GH）and the post-reduction process are studied.First,micro-GH with a short-range self-assembly structure is obtained by hydrothermal,and then ascorbic acid is added to perform chemical reduction at room temperature to obtain micro-GH-R with a suitable degree of reduction.Compound micro-GH-R and manganese dioxide to obtain micro-GH-R@MnO₂.The composite material maintains the short-range self-assembly structure of micro-GH,and theδ-MnO₂ sheets are arranged crosswise on the base of the graphene self-assembly structure.The specific capacitance of micro-GH-R@MnO₂ at 0.5 A/g is 252.5 F/g,and at 15 A/g,the capacitance retention rate is 60.5%.After 10,000 cycles at 10 A/g,the capacitance can maintain 97.9%,and the coulombic efficiency is 99.3%.