Research On Electrochemical Performance Of Graphene Composite Materials Supercapacitor

With the diversification of market application,energy storage devices play a great role in areas such as consumer electronics,transportation,energy saving,green energy.Because of the high power density,long cycle life,wide operating temperature,safety and environmental protection,supercapacitor as supplement of battery,applied to the power quickly change field.At present the study of supercapacitor focus on the selection and modification of electrode materials.Due to its high conductivity and large specific surface area,graphene is a kind of excellent electrode material.Binary transition metal zinc oxide cobalt acid has good electrochemical performance and is a good choice of electrode materials.In this paper,we chose modified graphene fiber and cobalt acid zinc/graphene composite as the electrode material,and investigated the supercapacitor performance.The obtained results provide the basis for their application in market.The research content of this paper is as follows:(1)The capacitance properties of graphene fiber electrode have been investigated.Graphene were prepared using microwave irradiation method.We regulated the microwave time to study the influence of microwave time on the morphology,specific surface area,degree of reduction and electrochemical performance of graphene.The experimental results show that microwave time have a great influence on the morphology,specific surface area,degree of reduction and electrochemical performance of graphene.With increasing of microwave time,crimp degree of graphene aggravated,resulting in increasing specific surface areas,reduction degree and the conductivity of graphene.The sample with microwave time of 6 min(MW-6 min)has achieved optimal performance as high as 110 F/g at the current density of 1 A/g,which can still maintain87% at 30 A/g.The electrode also shows excellent cycling stability(90% capacitance retention after 3000 times at high current density 30 A/g).This results provide data reference for assembly of graphene.(2)The capacitance properties of flower-like zinc cobaltate/graphene electrode have been studied.Although single carbon material such as graphene show excellent performance,the theory capacitance of electric double layer material is far less than faradaic pseudocapacitance materials.Therefore,the graphene and zinc cobaltate have been chosen as electrode materials to improve the specific capacitance in ensuring strong mechanical strength.Flower-like zinc cobaltate/graphenethree-dimensional network structure has been prepared by facile hydrothermal.We study the influences of graphene oxide concentration on zinc cobaltate/graphene composite electrode capacitance performance by regulating the precursor graphene oxide concentration.The results showed that the sample with 1.75 mg/mL of GO(GO-1.75)achieved optimal performance of 670F/g at the current density of 1 A/g and kept 520 F/g at current density of 30 A/g.Furthermore,it can be seen that the specific capacitance values of 1.75 composites have the higher capacitance retention of 87% over 3000 charge/discharge cycles.We chose GO concentration of about 1.75mg/mL to synthetize materials.The composite material is better than single zinc cobaltate in specific capacitance,rate performance,cycle stability because of synergies between graphene and zinc cobaltate.(3)Research of capacitance performance for zinc cobaltate/graphene nanoarray structure.We developed a hydrothermal method to construct nanoarray structure of zinc cobaltate/graphene on Ni foam substrate.The results show that the composite material achieved specific capacitance values as high as 2400 F/g with the current density of 1 A/g in 2 MKOH solution.The electrodes provide a specific capacitance of 82.7% at current density of 30 A/g,exhibited remarkable rate capability performance,and good cycle ability that retention rate of specific capacitance was 86% after 3000 cycles test at current density of 10A/g.The excellent electrochemical performance of composite materials was attributed to the design of zinc cobaltate/graphene nanoarray structures.The nanoarray materials could offer a short electron transfer distance and facilitate electron transfer efficiency in the process of energy storage,significant increased the efficient diffusion of electrolyte ions and enhanced the utilization of active material.