Preparation Of Porous Carbon Materials And Their Electricity Storage Properties For Symmetric Supercapacitors

Supercapacitor electrode materials mainly include carbon materials, metal oxides and conducting polymers. Among them, carbon materials have drawn much attention because of their super high specific surface area, developed porosity, good conductivity, excellent physical and chemical stability. How to design and control the structure of carbon materials is the key to improve their electrochemical properties. In this paper, carbon materials for supercapacitor with different structures are prepared from coal tar(CT) or petroleum pitch(PA) by using different template coupled with KOH activation, including hollow porous carbon nanospheres(HPCNs), hierarchical porous carbon shells(HPCSs), corrugated graphene nanosheets(CGNSs). The morphology of carbon materials was characterized by field emission scanning electron microscopy, nitrogen adsorption-desorption, X-ray photoelectron spectroscopy, transmission electron microscopy, Raman spectrum analysis, etc. The electrochemical properties of the carbon-based electrodes were tested by galvanostatic charge/discharge, cyclic voltammetry, electrochemical impedance. The main conclusions are as follows.HPCNs were prepared for supercapacitor with Zn(CH3COO)2·2H2O as template. HPCN6-24-12 made with the mass of CT, Zn(CH3COO)2·2H2O, KOH at 6 g, 24 g, 12 g in Ar atmosphere possesses the average pore size of 7.41 nm and the specific surface area of 1374 m2/g. In 6 M KOH electrolyte, HPCN6-24-12 shows high capacitance(reaching 216 F/g at 0.05 A/g), excellent rate performance(remaining 174 F/g at 20 A/g) and superior cycle stability(remaining 97.2% after 1000 charge-discharge cycles at 1 A/g).HPCSs with different structures were prepared for supercapacitor with ZnO as template by changing the mass ratios of raw materials and the final calcination temperature. The specific surface area and the average pore size of HPCSs ranges from 1766 to 2646 m2/g and from 0.96 to 1.47 cm3/g, respectively. HPCS2-19-6-850 made with the mass of PA, ZnO, KOH at 2 g, 19 g, 6 g at 850 oC possesses the biggest surface area(2646 m2/g) and pore volume(1.47 cm3/g). In 6 M KOH electrolyte, the HPCS2-19-6-850 electrode exhibits a high capacitance of 296 F/g and energy density of 10.26 Wh/kg at 0.05 A/g. Moreover, HPCS2-19-6-850 also shows a high capacitance retention of 78.8% at 20 A/g and an outstanding cyclce stability with 96.2% of the initial capacitance after 1000 cycles in 6 M KOH electrolyte.CGNSs were prepared for supercapacitor with MgO as template. CGNS3-18-6-800 made with the mass of PA, MgO, KOH at 3 g, 18 g, 6 g at 800 oC possesses a surface area of 2132 m2/g. When evaluated as the supercapacitor electrode, CGNS3-18-6-800 exhibits a high capacitance of 280 F/g and 233 F/g in 6 M KOH electrolyte at 0.05 A/g and 20 A/g, respectively. At the same time, CGNS3-18-6-800 exhibits an outstanding cyclce stability with 96.2% of the initial capacitance after 1000 cycles in 6 M KOH electrolyte.