Translated Abstract
Supercapacitor is widely used due to its high-power density and long cycle life. Because of its stable chemical properties and low cost, carbon electrode material has attracted extensive attention of scientists and engineers. In order to meet people＇s increasing demands on the performance, it is important to improve energy density meanwhile maintaining high power density of the supercapacitors.
In this paper, rice husk is selected as the raw material. And nickel nanoparticles are used as the catalyst to help form graphite-like structure. The catalytic conditions in terms of its effect on the samples’ physicochemical performance is systematically studied. After activation of KOH, this bio-source carbon exhibits three-dimensional porous graphene structures and obtains large specific surface area as well as excellent specific capacitance. The results are as follows:
Graphite-like carbon is prepared by nickel-catalyzed rice husks. It is found that the graphitelike structure begins to appear at 600 °C. And the as-prepared carbon matrix is composed of graphite-like structure and amorphous carbon. With the temperature increasing, the graphitelike structure layer which is catalyzed by nickel nanoparticles became thicker. The results reveal that graphite-like structure obtained at different catalytic temperatures affect the structure and properties of the samples.
In order to study the catalytic mechanism in terms of how it affects the structure and performanceof the final activated samples, different catalytic temperatures are selected followed by the same activation condition. The sample RHG-700 displays the optimized morphology with a three-dimensional porous graphene structure as well as high specific surface area and pore volume of 3831.5 m2/g and 2.889 cm3/g, respectively. At a current density of 0.1 A/g, RHG-700 has a high specific capacity of 349.7 F/g. And at a large current density of 20 A/g, the sample retention capacity is 82.4 %. The energy density maintains 10 Wh/kg at 4 kW/kg.
In order to produce electrode materials with improved volumetric specific capacity and larger effective specific surface area, the activation conditions are then investigated based on the fixed 700 °C catalytic process. The activation mechanism is studied with respect to the activation temperature and KOH content in terms of their effects on the structure and performance of the carbon. It is found that exceeded temperature or KOH content would destroy the graphite-like structure and therefore decrease the performance of the electrode. At a relatively lower temperture and KOH ratio, the graphite-like structure is well maintained. And the sample shows a large specific capacity and volumetric specific capacitance. At a current density of 0.1 A/g, RHG-700-600 displays a specific capacity of 473.2 F/cm3 and a specific capacitance of 38.8 μF/cm2. Then at a high current density of 10 A/g, the capacity remains 67.5 % retention, and the energy density is 16.4 Wh/L at 2.5 kW/L.
Translated Keyword
[Doping concentration, Piezoresistance, Preparation process, Temperature drift]
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