Construction Of Graphene With Multidimensional Structure And Its Performance In Supercapacitor

Graphene, as a new allotropicity of carbon, can be a great value for scientific researchand application.It can be the ideal electrode materials in supercapacitor, which howeverhas some deficiencies. Firstly, the sample prepared from different method can havedifferent micro morphology which has a great influence on the cycle stability; secondly,graphene will restack during the preparation, so that the specific surface area of actualsample will be lower than the theory of value. In this way, it can be a focal point for us toprevent the restack of graphene and construct graphene with hierarchical structure, whichcan provide higher specific capacitance; at last, the cost for preparing graphene is muchhigher, which limits the application of graphene in supercapacitor, so preparing thecomposite of graphene and other materials can be the right way.In this way, we focus onthe research for graphene supercapacitor in this paper from the following aspects.We prepared graphene using hydrazine hydrate and thermal expansion as the reducemethod, then we study the cycling stability of the products. The sample rGO-Hz reducingwith hydrazine hydrate exhibits nice cycling stability, but the sample rGO-T shows a poor.When analyzed why cycling stability of the sample rGO-T is poor, it can be attributed tothe elimination of unstable oxygen-containing functional group during cycling, causingthe decay of faradaic pseudocapacitance and the stacking of graphene sheets, which leadsto the poor cycling stability.We firstly prepared the precursor of PS coated with GO, then treated the precursorwith different temperature, finally obtained the product with hierarchical structure. Whentreated under700℃, the obtainedsample HG7exhibits a specific capacitance of162F/g atthe current density of0.5A/g, and it still has a capacitance of112F/g when the currentdensity increased to16A/g, and the cycling stability under various current density canreach up to90%. Meanwhile, the knee frequency and equivalent internal resistance is12.598Hz and0.465respectively, which indicates a fast responding of behavior ofcapacitance and good electrical conductivity. We controlled the mass ratio of KAC and GO and prepared the composite materialthrough hydrothermal reaction. When the mass ratio between KAC and GO is2:1, thesynergistic effect of product GKAC2reach maximum, the behavior, theelectricalconductivity and the specific capacitance reach maximum at the same time. The specificcapacitance of GKAC2can reach205F/gand175F/g with aqueous and organicelectrolyterespectively at the current density of2A/g, it can still be152F/gand143F/g when thecurrent density increasing to16A/g. In addition, the power density and energy density ofGKAC2withorganicelectrolyteis higher than with aqueouselectrolyte, it can be9.1kW/kgand26.3Wh/kg when using1mol/LTEABF4/AN as the electrolyte. As a result, we reducethe cost when preparing compositematerials replacing pure graphene and promote theperformancein the meantime.