Research Of Novel Carbon Materials For Supercapacitor

Supercapacitors have attracted increasing attention for their advantages of rapid charge–discharge rate,high power density and long cycle-life.Carbon materials are the most dominant material for supercapacitor electrode because of its thermal and chemical inertness.Surface area and electrical conductivity are the most critical factors for carbon-based supercapacitor for the reason that the former directly determines the specific capacitance and the later determines the power performances.Therefore,methods for preparing novel carbon materials has been proposed.from two aspects of improving the specific surface area and improving the electronic conductivity,and high-performance carbon materials have been synthesized successfully.The main contents of our work can be summarized as follows:First,we use pre-carbonization and KOH-activation methods to convert the vinasse which is abundant byproduct of liquor industry into high-performance carbon material with ultra-high specific surface area value.During the synthesis,we found that the introducing of ball milling treatment in the mixing of KOH and carbonized vinasse not only ensures a good contact of the carbonized vinasse with KOH,but also produces numerous hydroxyl groups on the surface to improve the wettability of carbon,which solidly favor the highly efficient activation of KOH.Thus,the obtained carbon is endowed with a much high SSA value(3728 m² g^-1)and a unique graphene nanoplatelet microstructure.The existence of this microstructure has boosted electronic conductivity of as-obtained carbon materials.The as-prepared carbon exhibits high specific capacitances of 329 F g^-1 and 311 F g^-11 in 2 M KOH and 1 M H₂SO₄ electrolyte at 1 A g^-1 respectively.In 1 M TEABF₄/AN electrolyte,a high working voltage of 3 V and high specific capacitances of 164 F g^-1can be obtained based on a two-electrode full cell.The energy density of the supercapacitor can reach 49.5W h kg^-1.These performances are superior to the commercial activated carbons and most of the biomass derived carbons.Second,the introduction of alkali metal activation on the basis of the previous step,especially sodium activation,can obtain a new type of porous carbon materials which both have high specific surface area and high graphitization at 800?.Sodium atoms can easily penetrate into the interior of carbon material to react with oxygen-containing functional groups and induce rearrangement of carbon material to realize the graphitization.As-prepared carbon materials have unique 3D architecture in which graphene belts serve as skeleton,amorphous carbon and graphene nanoplatelets disperse among them.The specific surface area values of all new graphitic carbons are more than 2600 m² g^-1,which are1.5¹0 times of that of other graphitic carbons.The graphene belts have endowed new carbon material with more excellent electrical conductivity,so the rate performances and cycle performances have been enhanced.Even in a large current density of 100 A g^-1,the specific capacitance retention corresponding to that of 1 A g^-1 is up to 73%.The specific capacitance retains as high as 93%after 13000 cycles.In the organic electrolyte,the power density has been improved significantly,which can reach as high as 12.8 kW kg^-1.More importantly,this synthetic method of sodium activation under low temperature and and mechanism explanation may be valuable for the preparation of graphitic carbon.