Study On The Preparation Of Graphene/Activated Carbon Composites And Their Supercapacitor Performance

As a new generation of energy storage devices,supercapacitors have the features of high power density,environmental friendliness and good cycle stability,among which the electrode material is the key factors in supercapacitors.Activated carbon materials have become a research hotspot of supercapacitor electrode materials,because of its advantages of rich pores,stable structure and large specific surface area.However,due to its low energy density,its application is limited.In this paper,the graphene with high specific capacitance and high conductivity is introduced into the activated carbon material,which improves the microstructure and specific capacitance of the activated carbon material.Graphene/activated carbon composites were prepared by selecting different organic compounds as precursors.The relationship between the structure of the electrode material and the electrochemical performance was explored,and a high-power,long-life button-type supercapacitor was assembled,and a wide voltage window electrolyte was used to increase the energy density of the overall device.In this paper,a large area of high-quality graphene oxide was prepared by the modified Hummers method.On the basis of this,different graphene/activated carbon composites were obtained by adjusting experimental conditions and methods.The main contents are as follows:1.Based on the PVDF emulsion as a carbon source and KOH as an activator,a graphene/activated carbon composite?PGC?was obtained by adding graphene oxide,one-step carbonization and activation treatment.The phase,morphology and electrochemical performance of PGC carbon electrode materials were analyzed.The results show that the addition of graphene improves the conductivity of the activated carbon material and increases its specific capacitance.In the 6 M KOH electrolyte,the specific capacitance of the PGC electrode material was 151.4 F·g^-1 at a current density of 0.5 A·g^-1,and the capacity retention rate was 98.6%after 10,000 cycles.At the same time,the water-based symmetric supercapacitor device was assembled,and the application of the electrode material in practice was explored.This experiment demonstrates the feasibility of a composite material composed of graphene composite activated carbon material as a supercapacitor electrode material.2.A high specific surface area hierarchically porous carbon material?HPCs?was prepared by a one-step carbonization and activation method using a chemical reagent KOH as a pore former and polyvinyl alcohol?PVA?as a precursor.The microstructure and electrochemical properties of the material are controlled by controlling the different amounts of graphene added.Various characterization methods were used to characterize the structure,morphology and pore distribution of the material,and the optimal material was found based on the electrochemical test results.The results of XRD and SEM show that this method can successfully combine graphene with activated carbon materials to obtain three-dimensional interconnected hierarchically porous carbon materials,which supports the rapid transport and migration of electrolyte ions.The specific surface area of the composite material?HPC-50?with a GO addition of 50 mL is 2078.4 m²·g^-1.In a three-electrode test system,its specific capacitance is 201 F·g^-1 at a current density of0.5 A·g^-1.In the two-electrode test system,the effects of different electrolytes on the electrochemical performance of symmetric capacitors were investigated.The TEATFB/PC electrolyte with the widest voltage window was selected,and the button type supercapacitor device was assembled.The HPC-50//HPC-50 BSSC device has a high energy density of 47 Wh·kg^-1 at a power density of 0.15 kW·kg^-1,and still maintains 33.75 Wh·kg^-1 at high power density(15 kW·kg^-1).3.A series of graphene/activated carbon composites?SGACs?with different GO addition amounts were prepared by using edible wheat starch immobilized crosslinked graphene oxide and further KOH activation treatment.The material was characterized by microstructural characterization and surface element analysis using various characterization methods.When the amount of added GO is 5 mL,the prepared carbon material?SGAC-5?has a three-dimensional porous crosslinked network structure,which brings a high specific surface area(1887.8 m²·g^-1)and a high specific capacitance(141 F·g^-1).A button-type asymmetric supercapacitor device was assembled with SGAC-5 as the negative electrode and reduced graphene oxide?RGO?as the positive electrode,with high energy density(48.5 Wh·kg^-1).The results show that the material has great potential in the field of electrode materials.