Research On Carbon Materials For Supercapacitors

As a novel energy storage device with high power density and long cyclelife, superapacitors have attracted great interests in recent years due to its widepotential applications in electric vehicles, uninterrupted power sources andrenewable energy, et al. Porous carbon material plays a crucial role insupercapacitors. In this paper, four high quality porous carbon electrodematerials including nitrogen-enriched carbon, hierarchical porous carbon,pitch-based carbon, and nano-CaCO₃templated carbon were synthesized forsupercapacitors by different strategies.A novel method were proposed to prepare nitrogen-enriched porouscarbon by direct pyrolysis of nitrogen-containing organic salt, tetrasodium saltof ethylenediamine tetraacetic acid （EDTA） for example under inert atmospher.The effect of carbonization temperature （600-900℃） on the specific surfacearea, pore structure, nitrogen content and electrochemical performance of thecarbons were investigated in detail. With the carbonization temperatureincreases, the specific surface area increases while the nitrogen content decreases. Due to the co-contribution of the electric double layer andpseudo-capacitance, the carbon material prepared at700℃presents acapacitance as high as244F/g in6mol/L KOH electrolyte. As the currentdensity increases to20A/g, the specific capacitance also retains188F/g,indicating good rate performance.Hierarchical porous carbon with high surface area were simply preparedby one-step NaOH activation of PVDC for supercapacitors. The carbonpresents a developed hierarchically porous structure comprising micropores,mesopores and macropores with a high specific surface area of2815m²/g. Theunique microstructure enables the carbon present high capacitance in both6mol·L^-1 KOH （376F/g） and1mol/L Et₄NBF₄/AN electrolyte （170F/g）, withgood rate performance. When current density increases to10A/g, the specificcapacitance also retains268F/g and144F/g in both6mol·L-1KOH and1mol/L Et4NBF4/AN, respectively, indicating a promising electrode material forsupercapacitors.Pitch-based activated carbons with high capacitance were prepared byNaOH activation. The BET suface area of the pich-based carbon reaches1423m²/g and the pore volume is0.746cm³/g. Its gravimetric capacitance is up to276F/g and the volumetric capacitance reaches218F/cm³in6mol·L^-1 KOHwith good rate performance. Even when the current density increases to20A/g, the capacitance can remain189F/g.Various carbons with different morphology from carbon nanosheet to carbon nanocage were prepared by CVD method using methylbenzene ascarbon source and nano-CaCO₃as template, which have wide potentialapplications in the field of electrochemical energy storage.