Investigation Of The Supercapacitor Properties Of Hierarchical Porous Carbon Materials

With continuous development of human society, population increasing, economy growing, energy consumption, non-renewable resources such as coal, oil reserves on the earth is short far from the needs. The excessive use of non-renewable resources has caused a series of environmental problems. There is an urgent need to develop renewable resources and effective energy storage. Developing new type of energy storage device possessing high energy density, high power density and long cycle life has been becoming a hot field in scientific research. Supercapacitor has become the representative new green energy storage devices because of its high charging/discharging speed, high power density, environment friendly, and long cycle life. However, supercapacitor shows low energy density. How to prepare supercapacitor with low cost, high energy density, and good stability has become a challenge for scientific research workers.Generally speaking, supercapacitor has great power density and good cycle stability, but its energy density is low. From the formula of energy density(2CV21E(28)), increasing working potential window and the specific capacitance will increase the energy density. Developing new electrode materials is the key for increasing material working potential window and the specific capacitance. We developed a new kind of porous carbon material that shows improved specific capacitance.In this work, a novel porous carbon material was obtained by pyrolysis of a carbon source of benzene/bibenzene-Si O2 prepared by hydrothermal method. Oxygen functional groups were generated on the surface of obtained carbon material during heat treatment process, which introduces pseudo-capacitance. Main contributions of the work is described as the following:1. Benzene-Si O2 was prepared by hydrothermal synthesis method as carbon source. A series of porous carbon materials with different size distributions and specific surface areas were obtained under different pyrolysis temperature. The material obtained under 1100 °C heat treatment shows the best electrochemical properties. The specific capacitance is of 195.5, 170.6, 156, and 134 F g-1 at the current density of 0.5, 1.0, 2.0, and 20 A g-1, respectively. The cycling stability test of the material under 1100 °C heat treatment by galvano-static charge-discharge(GC) measurement at 8 A g-1 in 2 M H2SO4 shows that the specific capacitance is increased 10% before 200 cycles and then remains constant.2. Bibenzene-Si O2 was prepared by hydrothermal synthesis method as carbon source. A series of porous carbon materials with different size distributions and specific surface areas were obtained under different pyrolysis temperature. The material obtained under 1000 °C heat treatment shows the best electrochemical properties in aqueous eletrolyte. The cycling stability test of the material under 1000 °C heat treatment by GC measurement at 10 A g-1 in 2 M H2SO4 shows that the specific capacitance is increased 25% before 1200 cycles, and then no capacitance loss was observed.