Preparation Of Graphene Based Electrode Materials For Supercapacitor Application And Investigation Of Its Electrochemical Performance

With the surging demand for energy,the environment problem caused by traditional energy is increasingly prominent.Therefore,people turn to develop green energy,such as wind,solar etc.And among the various new energy instruments,supercapacitor becomes the research focus,with its quick charging,long cycle life and pollution free characteristics.Electrode material is one of the key factors which influence supercapacitors' performance,and the material mostly is porous structure and has high surface area.Graphene(RGO),with its unique crystal structure,high theoretical surface area,and excellent conductivity,is regarded as the ideal electrode materials.However,it is hard to separate completely during the preparing process,leading to low specific surface area.Further,compared with the metal oxide,the specific capacitance of graphene is lower,which limits its further application.Surrounding the issue,this paper has done the following work:(1)We prepared Ce doped MnO2/graphene composite through simple hydrothermal method.The results show that the samples has high specific surface area(243 m2·g-1),and the average pore size is 7.9 nm,which is convenient for ion transportation and more available contact with electrode material.The specific capacitances are 149 F·g-1 and 124 F·g-1 at current density of 0.1 A·g-1 and 2 A·g-1,respectively.And the specific capacitance retention rate is 83%,having excellent rate performance.After 1000 cycles,the specific capacitance remain 85.2%,which indicates the sample has good structure stability.(2)In order to improve the problem of graphene aggregation,enlarge the distance of graphene layers,we prepared nitrogen doped 3D reduced graphene oxide.The results indicate that the specific capacitance of sample is higher at the condition of reacting for 3 h at 90?.At the current density of 1 A·g-1,the specific capacitance is 174 F·g-1.After 1000 cycles,the retention rate is 83%.Otherwise,the samples has low resistance and perform excellent capacitance behavior.(3)What's more,we also compounded three dimensional reduced graphene oxide with ZnCo2O4 to study its electrochemical performance.The nitrogen adsorption-desorption test shows the specific surface area of samples changes little,the specific surface area is around25 m2·g-1,pore volume is 0.08 cm3·g-1 and average pore size is 14 nm,mainly exist inmesoporous,which is convenient for the contacts between electrolyte and electrode material,and the transportation of electrolyte ions.The results show that the specific capacitance of sample reacting for 5 h at 160? is higher,the specific capacitance is 304 F·g-1 at 1 A·g-1.When the current density increase to 20 A·g-1,the specific capacitance is 217 F·g-1,remaining71.4%.After 1000 cycles,the specific capacitance retention rate is 92%.Otherwise,the samples show excellent EIS performance.