The Study On Biomass Based-activated Carbon And Its Performances Of Supercapacitors

With the rapid development of global electronic equipments, automotive industry and the grim situation of fossil energy is depleted excessively, the exploration of the energy storage and conversion devices with sustainability and environmental friendliness for the growing demand of energy is always a hot topic in current scientific research. Supercapacitor, a novel electrochemical storage energy device, has attracted numerous attentions in recent years. Compared with the conventional electrostatic capacitor, supercapacitor has higher energy density and specific capacitance. Simultaneously, supercapacitor has greater power density, high charge/discharge efficiency and long cycle life comparing with the batteries. Therefore, supercapacitor attracts researchers’ attention extensively. According to the difference in the electrode materials, supercapacitors are roughly divided into carbon-based supercapacitors, conductive polymer-based supercapacitors, metal oxide-based supercapacitors and hybrid supercapacitors. The metal oxide and conducting polymer bear the shortcomings of the poor electrical conductivity and bad cycle stability so that the two kinds of materials are difficult to be applicated widely. By contrast, carbon materials with the merits of environmental benignity and good cycle performance have been widely used as the electrode materials. Sustainable biomass-activated carbon material because of the unique advantages of natural abundance, simple preparation, low cost and wide working temperature range have been widely attracted researchers’ attention. Nowadays, many countries are devoting to develop the carbon electrode material for supercapacitors with high energy density and high power density, and combining with the appropriate electrolytes to prepare the superior supercapacitors. Based on the above facts, in this paper, the biomass based-activated carbon materials using the biomasses of β-cyclodextrin, glucose and bean dregs as carbon sources were prepared by hydrothermal, carbonization and activation treatments, and used as the electrodes of supercapacitors. The electrochemical performance tests of them were carried out in 6 M KOH and copper ion redox electrolytes, respectively. The primary contents are as follows:1. In this chapter, β-CD@G based-activated carbon materials using β-CD and G as the binary carbon source was prepared by hydrothermal treatment, carbonized and one-step activation method. The optimum prepared conditions of β-CD@G based-activated carbon have been explored by the orthogonal experiments. The results indicate that the specific capacitance of β-CD@G electrode can reach 254 F g-1 at the current density of 0.5 A g-1 with 6 M KOH electrolytes. And the specific capacitance retention rate was 73.1% after 1000 cycles when the current density is 1 A g-1.2. A bean-dregs based porous activated carbon(BDACG) using bean-dregs as carbon source has successfully been prepared by hydrothermal reaction, carbonization, and two-step activation method. And we use BDACG as the electrode to assemble supercapacitors combining with KOH electrolytes. The physical properties of as-prepared materials and electrochemical performance of the electrodes were studyed. Research shows that the bean-dregs based porous activated carbon electrode exhibits 210 F g-1 of the high specific capacitance at the current density of 0.5 A g-1. What’s more, the specific capacitance can reach 95.1% of the initial specific capacitance after 5000 cycles at the current density of 1 A g-1.3. A bean dregs-based activated carbon/copper ion supercapacitors has been prepared by combining as-prepared BDACG as electrodes with copper ion redox electrolytes. Meanwhile, the electrochemical properties of BDACG electrodes in the copper ions redox electrolyte were systematically studied. The results show that the bean-dregs based activated carbon electrode reaches 492 F g-1 of high specific capacitance with 2M CN+NN copper ion redox electrolytes at the current density of 1 A g-1. Moreover, the specific capacitance retention rate still remained 84.1% after 10000 cycles at 1 A g-1.