Preparation Of Pseudocapacitive Composites Based On Graphene Microspheres And Their Energy Storage Properties

Among the numerous new types of energy storage devices,supercapacitors have attracted extensive attention due to their high power density,fast charge and discharge rates,excellent cycle stability,wide operating range,and environmental friendliness,and have shown great potential in various application fields.At present,the research of supercapacitor electrode materials mainly includes carbon materials,transition metal oxides and conductive polymers,and composite materials.As a two-dimensional carbon material,the excellent electrical and mechanical properties of graphene make it the most promising electrode material for supercapacitors.Graphene has excellent double-capacitor properties and outstanding electrical conductivity.limiting the performance of graphene in practical applications,it is difficult to meet the high specific capacity requirements of supercapacitors.In this paper,starting from this problem,graphene is prepared into a three-dimensional spherical structure by spray drying,which improves the gaphene agglomeration problem and improves the specific surface area of the graphene microspheres,which is beneficial to its application in supercapacitors.Transition metal oxides have excellent pseudocapacitance perfor-mance.Therefore,in view of the low energy of graphene.we use low-cost manganese-nickel oxides and graphene microspheres to prepare pseudo-capacitance composites with high specific capacitance and high energy density,which give full play to the performance advantages of each material and make up for the lack of each other.The SEM,TEM,XRD.TGA and electrochemical tests were used to analyze the structure and properties of the prepared materials.The results of the study are shown below:(1)Conductive carbon black is used as a ball forming agent to obtain graphene microsphere material by spray drying.When the mass ratio of graphene to carbon black is 2:1.the graphene microspheres have a more uniform morphology structure with an average diameter of about 2.5 ?m.Moreover,the BET test results show that the spherical material has a superior pore size distribution and specific surface area(161 m2/g),the maximum pore size is 2.0 nm,and the maximum pore volume is 0.076 m3/g.Electrochemical performance tests show that the mass specific capacitance of the graphene microspheres can reach 89 F/g at a current density of 1 A/g,and the outstanding double layer reversibility perforrmance is also exhibited at high current densities.(2)In this paper,Mn304 nanosheets were successfully prepared and uniformly supported on graphene microspheres by one-step hydrothermal synthesis.The results show that the composite material forms a three-dimensional porous network structure that facilitates the ion transport of the electrolyte and greatly improves the pseudo-capacitance of the material.Through comparison and analysis of CV,GCD and EIS,Mn304 NPs/GSs composites are superior in electrical properties to flaky graphene composites.At a scan rate of 10 mV/s,the specific capacitance is as high as 317 F/g.Moreover,under 4000 cycles of galvanostatic charge-discharge cycles,the material also exhibited outstanding cycle stability performance,and the capacitance value remained almost unchanged.(3)In the research of nickel-based composites,the reaction of nickel sulphate and urea under hydrothermal conditions has realized the growth of flower-like Ni(OH)2 on the surface of graphene microspheres.The effects of different conditions on the moiphology of Ni(OH)2/GSs composites are investigated.SEM characterization results show that when the molar ratio of NiS04 to CH4N2O is 1:4 and the hydrothermal reaction at 150 ? for 3 h,the composite material has better micro-morphology and structural integrity,and the surface-loaded flower-like nickel hydroxide is thinner,which is more conducive to the performance of the faradaic pseudocapacitance.In electrochemical performance tests,Ni(OH)2/GSs composites also exhibited good electrical and.capacitive properties.At a current density of 0.5 A/g,the composite material has a mass specific capacitance of about 1262 F/g.It shows that the prepared composite material has both the performance characteristics of each component and has a great prospect in the field of energy storage applications.