The Studies On Modified Of Graphene Aerogel And Performance Of Supercapacitor

Supercapacitors are one of energy storage devices with high power density,high practicality,and environmental friendliness.Graphene has excellent properties such as high specific surface area,cycle stability,and good electrical conductivity.It is an ideal electrode material for supercapacitors,but its specific capacitance is lower.The focus of current researches is controlling the graphene by micro-morphology,or to select another electrode material with high Faraday quasi-capacitance through combination to obtain superior performance.In this paper,graphite oxide(GO)was prepared by modified hummers method.Graphene aerogel(GA)was prepared by solvothermal method,chemical redox method using ascorbic acid as reducing agent and microwave digestion method.At the same time,the morphology and electrochemical performance of three kinds of GAs were analyzed.The results show that the structure and properties of graphene aerogels(rGA)prepared by solvothermal method are the best.The overall appearance of the graphene aerogels is thin and transparent cross-linked three-dimensional network structure.The specific capacitance of the single electrode is 285 F g-1 for the rGA material at a current density of 1 A g-1 in 6 M KOH electrolyte.After two-electrode rGA button capacitor is charged and discharged for 1000 cycles,the capacitance is maintained at about 68 F g-1,and the capacitance attenuation is small.Based on the preparation of rGA,three-dimensional porous graphene aerogel material(PrGA)was prepared through ammonium chloride as the blowing agent.The influences of experimental factors such as foamer dosage,reaction temperature and reaction time on the electrochemical performance of PrGA were discussed,and the optimal preparation conditions of PrGA material were determined.The study found that the surface of PrGA material has a well-developed pore size distribution,showing a three-dimensional porous structure.Compared with rGA material,the former has increased its specific surface area from 492 m2g-1 to 673 m2g-1.At a current density of 1 A g-1,the single-electrode specific capacitance value is 379 F g-1,which is nearly 33%higher than that of the rGA material(285 F g-1).After 1000 times of constant current charge and discharge,the capacitance of the two-electrode PrGA button capacitor is maintained at about 88 F g-1,and the capacitance attenuation rate is less than 4%.The PrGA/NiO precursor was synthesized by one-step solvothermal method using nickel nitrate hexahydrate as the nickel source,and then three-dimensional porous graphene aerogel/nickel oxide composite(PrGA/NiO)was prepared by high-temperature calcination.Through the analysis of morphology,it was found that nickel oxide particles grow in the three-dimensional network structure of PrGA,NiO accounts for about 20%of PrGA/NiO composite materials.Electrochemical performance test results:When the current density is 1 A g-1,the specific capacitance of the single-electrode PrGA/NiO composite reaches 473 F g-1,which is nearly 25%and 66%higher than that of PrGA and rGA,respectively.The double-electrode PrGA/NiO composite button capacitor has a capacitance of about 110 F g-1 and a capacitance retention rate of 94.6%after 1000 times of constant current charge and discharge,showing excellent cycle stability.