| Electrochemical super capacitor,also known as electrical double-layer capacitor, has the advantages of fast charging and discharging, high specific capacitance and good circulation service life. Super capacitor has a great application prospect in the electronic products, electric cars and military products. Especially in recent years, with the energy conservation, emission reduction and environmental products being favored by the majority citizens, Super capacitor, as the environmental and energy saving product, also received extensive attention of research workers.Super capacitor mainly include electrode, electrolyte and the diaphragm. However, the electrode material is the most core part of super capacitor, mainly including carbon materials, metal oxide and conducting polymers, etc. Carbon-based materials are the most mature electrode materials in the early research, including activated carbon, carbon fiber, carbon black, carbon aerogel, carbon nanotubes, and grapheme, etc. But in the present study, most of the carbon materials are still under the laboratory theoretical exploration stage. The cost of super capacitor is high, lacking of electrode material source in the actual production, plus the process of preparation is more complicated. In addition, the specific capacitance, specific energy, cycle life and other electrochemical performance remain to be further improved.The purpose of this paper is to reduce the super capacitor production cost, improving its electrochemical properties, such as specific capacitance and specific energy. In this paper, with the raw material of loofah, loofah activated carbon is acquired through carbonization and activation. Characterized by nitrogen adsorption and desorption, Loofah activated carbon’s specific surface is 2700m2/g, entrance is 1.3672cm3/g, the average pore size is 1.9588 nm. With loofah activated carbon as electrode materials, electrolyte are respectively 1M C8H20BF4N/PC、6M KOH、1M Na2SO4 and 1M Li2SO4, and diaphragm is polypropylene. Then assemble them to form button type super capacitor. Also the property of composite materials such as grapheme and Co3O4 which combines with activated carbon, are examined in the aqueous electrolyte, showing that loofah activated carbon as electrode is very excellent.Use Loofah activated carbon that of equal mass to assemble button symmetric super capacitor, with 6M KOH as the electrolyte. The working voltage is 1.2v under constant current charge-discharge test at the current density of 0.048A/g. Linear relation and symmetry of charging and discharging are good. Calculated by the formula, specific capacitance of the loofah activated carbon is as high as 356.77F/g, the energy density is 12.49wh/ kg. Under the big current, after 10000-cycle recharge, the capacitance of loofah activated carbon remains 86.3%. And after 8000 times, energy efficiency is around 83%, showing good circulation service life and energy utilization. Use Loofah activated carbon that of equal mass to assemble button symmetric super capacitor, with 1M C8H20BF4N/PC as the electrolyte. The working voltage is 2.7v under constant current charge-discharge test at the current density of 0.2A/g, and the specific energy is 16.395wh/kg. Assemble symmetry super capacitor to test by three electrodes, the specific capacitance reaches 338F/g at a currant density of 1A/g in 6M KOH, which is better than most of the specific capacitance of the activated carbon of biomass reported in literatures. In addition, we also did CV and EIS test by three electrodes. While the graph of CV is similar to rectangle, exhibiting a double layer electrochemical behavior. Potential window is-0.6~0.8V,which indicates it has large working voltage range.Composite materials is combined loofah activated carbon with graphene. Use composite materials that of equal mass to assemble button symmetric super capacitor, with 1M C8H20BF4N/PC as the electrolyte. when Co3O4’s weight is 5% of AC the capacitance of the composites is as high as 130.8F/g. The specific capacitance reaches 182.7F/g at a currant density of 35 m A/g in 6M KOH. Linear relation and symmetry of charging and discharging is good, showing the electrochemical behavior of symmetry super capacitor. But the capacitance is smaller than that of loofah activated carbon, showing that loofah activated carbon is a very excellent kind of electrode material. Under the big current, conduct charge-discharge test for 1000 times. The specific capacitance retention rate is 97%,showing that the composite of graphene and loofah activated carbon have a good cycle life. Tested by three electrodes in 6 MKOH, the graph of EIS showed that the transfer impedance and diffusion impedance of composite are small, which is helpful to improve the service life of the super capacitor and other electrochemical performance.Combined loofah activated carbon with Co3O4, composited Co3O4/AC is acquired by hydrothermal synthesis and coprecipitation. Use composite materials that of equal mass to assemble button symmetric super capacitor, with 6M KOH as the electrolyte.By the means of coprecipitation, when Co3O4’s weight is 30% of AC, the specific capacitance of composite reached 516.2F/g at the current density of 0.055 A/g, and the working voltage range is 1.2V. The linear relationship and symmetry of charging and discharging are poor, showing the constraint capacitor performance. Under high current density, the specific capacitance did not obviously attenuate after a 1500-cycle recharge. Specific capacitance retention rate reached 95.5%,showing good cycle life. Proceed constant current charge-discharge test by three electrodes in 6M KOH,when Co3O4:AC equals 3:10, the specific capacitance of composite is 603F/g at the current density of 1A/g, showing the excellent performance of capacitance.In this paper, super capacitor is acquired through loofah as raw material. On one hand, it reduces the production cost of super capacitor; On the other hand, it can improve the electrochemical performance of super capacitor. Furthermore the method is simple and easy to popularize. Not only it has provided ideas for scientific research in laboratory, but also has accelerated the industrialization of super capacitor. |
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