Preparation Of Graphene Via Thermal Expansion Method And Study On The Capacitance Performance Of Graphene

Supercapacitor was a new type of energy storage devices which has a potentialof quickly charging speed, long cycle life, super temperature characteristic andenvironment friendly. The choice of the electrode material was very important to thesupercapacitor. The researches about supercapacitors was now mainly concentrated onhigh performance electrode materials mainly.In this paper, the electrochemical performance of the supercapacitors withgraphene and graphene composites as their materials was studied. In addition, theinfluence of prepare technology to supercapacitor were also researched. Themorphologies and characteristics of samples were studied by XRD, SEM, TEM andXPS.A series of experiments to modify Hummers method by changing the oxidantamount and reaction time were carried out. The graphite oxide were prepared indifferent method as material to produce graphene in the400℃Nitrogen circumstance.The result showed that the optimized reaction condition was57.5ml sulfuric acid,10gpotassium permanganate and15min high-temperature reaction, and the capacitancecan reach to342F·g-1at the current density of1mA·cm-2.Nickel hydroxide was a kind of common super capacitor electrode materials,which can provide higher capacitance, as pure Ni(OH)2material were conductivitybad, lower specific surface area which were not suitable for used as super capacitormaterials. Through the compound with carbon materials can effectively improve theabove disadvantages. The Ni(OH)2/graphene composites were synthesized by usinggraphene and Ni(AC)2as raw material. The composite showed a good character ofpsuedocapacitance. At the current density of10mA·cm-2, the specific capacitance canreach to680F·g-1. After100charge/discharge cycles, the specific capacitance couldalso maintain at663F·g-1, with only about2.5%discount. This composite has a highquality of reversibility.The carbon materials were used as the electrode material of organic electrolytecapacitor with the more wide voltage, which can provide higher energy density. In thispaper, the electrochemical performance of graphene was studied in1mol·L-1LiPF6(DMC+EC) electrolyte. The first cycle discharge/charge capacitance of the battery were1228F·g-1and920F·g-1at the current density of100mA·g-1during thevoltage range of0.01~3.5V. After30cycles of charge/discharge, the dischargecapacity can still be920F·g-1and charge capacity was917F·g-1, which showed arelatively high reversible capacity.