(361a) Relationship of Graphene Microstructrue and Ultracapacitive Property

  The excellent electrical, mechanical properties and extremely large surface areas of graphene make it a competitive candidate for electrochemical capacitors (ECs).However, it is almost inevitable for graphene to undergo thephase separation and irreversible agglomeration in the devices,which results in the loss of its surface areas as well as thereduction of the specific capacitance.Preparation of graphene electrode with reasonable microstructures is significant and beneficial for us to tackle the challenge. Two different microstructures, namely layer-by-layer (LbL) self-assembled multilayer films and graphenemacropore network, were designed and developed for supercapacitor application.

  We first fabricated stable multilayer films of polystyrene-based diazonium salts and graphene modified with p-phenyl-SO₃H groups through the electrostatic LbL adsorption method.The crosslinking between the components occurred during the multilayer formation process and was further achieved by the UV light irradiation after the film preparation.The large accessible surface area of graphenenanosheets and the crosslinking structure afforded the LbL films with high specific capacitance and excellent cyclic stability when used as supercapacitor electrodes. At a sweeping rate of 10 mV/s, the film with nine-bilayers exhibited a specific capacitance of 150.4 F/g with ideal rectangular cyclic voltammogram. Large capacitance retention of 97% was observed after 10000 charge-discharge cycles under 1000 mV/s.

  We further develop a simple method, coagulation, to construct 3D porous graphene materials in the view of colloid chemistry.Few efforts have been focused on the morphology and structure research of the formed graphene coagulation assemblies.We thus prepared3Dmacroporousgraphene network through PEI induced coagulation of graphene oxide dispersion. Supercapacitor made of graphene assemblies exhibited high surface areal supercapacitor values of 46.3μF/cm²,excellent rate performance as well as long cyclic life due to the face-to-edge aggregation mode resulting excellent exfoliation of graphene sheet in coagulation process.