Synthesis Of Porous Carbons And Study On Their Performance In Supercapacitors

Supercapacitors are widely used in the power supply, laser pulse, smart grid, energy-efficient building, aerospace and other fields, when high power density, long cycle life, high safety and environmental friendliness are required. Currently, carbon-based electrodes are the key to improving the performance of supercapacitors. However, the contact resistance between active materials and current collectors, the resistance of the ion transport through the long narrow pores and the low conductivity of the electrode materials lead the supercapacitors directly to the decrease of the performance including energy density, power density and cycle life. Therefore, design and synthesis of new carbon materials are important for practical application. In this paper, through molecular self-assembly and in-situ growth techniques, microporous hybrid carbon nanosheets and nickel foam-based porous carbon materials were synthesized, and the relationship between structures and capacitive performances was studied. Specifically, this work includes the following two parts:(1) With graphene oxides as structure-directing agents, poly-(benzoxazine-co-resol) as carbon precursor, microporous hybrid carbon nanosheets (MHCN) were synthesized with layer thickness of30-40nm by sol-gel method and pyrolysis. MHCN with a thin layer and reduced graphene oxides not only facilitate the ions transport through the long narrow pores but also improve electrical conductivity. MHCN compared to conventional activated carbon materials performed a more ideal capacitor behavior and higher power density. After steam activation process, the specific surface area of activated carbon materials (MHCN-act) increased to1293m2g-1, and the capacitance value reached190F g-1in aqueous electrolyte solutions. Meanwhile, MHCN-act exhibited high gravimetric and volumetric energy densities of22.4Wh kg-1and17.3mWh cm-1in organic electrolyte solutions respectively, which is higher than the values reported in the literatures.(2) Nickel foam-based porous carbons were synthesized with different pore-size distributions and carbon content by an in-situ polymerization approach. The contact resistance was reduced, due to the intimate contact between carbon materials and the skeleton of nickel foam. Moreover, the carbon layer can be obtained with the thickness below5μm, resulting in the reduction of the ion transport resistance. Meanwhile, nickel foam-based mesoporous or microporous carbon materials were prepared with or without the surfactant F127. After the electrochemical tests, nickel foam-based mesoporous Carbon materials showed more excellent supercapacitive performance with the capacitance of190F g-1. And Nickel foam-based porous carbon electrodes with high carbon content can be available with multiple dipping, which also has a good performance. And the amount of charge stored reached3F, which was higher than that stored in the lower carbon content electrodes.