Experimental And Numerical Study On Microporous Graphene Film-based EDLCs For Energy Storage

As a fast-rising type of electrochemical energy storage devices with advantages of high power density and stability as well as low contamination risk to the environment,supercapacitors have appealed tremendous research interests.Graphene,for its huge specific surface area and great electrical and mechanical properties,has also turned into the most shining carbon materials in recent years.In this thesis,we prepared high quality graphene films(rGO)by reduction of graphite oxide solutions with hydrazine hydrate and vacuum filtration,which showed highly compact,stacked and wrinkled structures.As supercapacitor electrode materials,it showed good capacitive performance of 116.6 F/g under 20 mV/s and 120.6 F/g under 1 A/g.However,the specific capacitance experienced obvious decline when the scan rate and current density increased,which indicated that the compact sheets structure restricted the adequate transfusion of electrolyte then limited the full use of the material's area and impacted its energy storage.To promote the electrolyte transfusion in the electrode materials and exploit the energy storage potential,we introduced two kinds of orderly arrayed micro pores to rGOs by photolithography and oxygen plasma etch,whose lengths and gaps were separately 10 ?m×50 ?m and 100 ?m×500 ?m.The microporous structure was easy to control by adjusting specific photolithography and plasma etch parameters.The specific capacitance of 10 ?m-rGO and 100?m-rGO were 136.3 F/g and 124.7 F/g under 20 mV/s,and 146 F/g and 138 F/g under 1 A/g separately.This great improvement in capacitive performance verified the introduction of micro pores effectively promoted the electrolyte's transfusion and infiltration,while EIS and CD results also revealed that mirco pores broke the uniformity of electrodes,which led to the increase of its internal resistance.Lattice Boltzmann method was then adopted to simulate the transfusion of electrolyte.LBGK model and Shan-Chen model were firstly used to study on Poiseulle flow in rough microchannels,on Laplace law and contact angel to test this numerical tool's validity.Based on some simplification of rGO's real structures,Quartet structure generation set(QSGS)was adopted to randomly generate like-rGO porous structures corresponding to three different experimental rGOs.Then LBGK and Shan-Chen models were used to simulate the electrolyte's transfusion process.Results showed good agreement with experiments.And based on the simulation,mechanism analysis of electrolyte transfusion process was performed from perspectives of transfusion driving and resisting forces.