- The structure and working principle of supercapacitor
Supercapacitors have a much larger capacity than normal capacitors. Because of its large capacity and the same external performance as the battery, it is also called “capacitor battery” or “golden battery”. The structure of supercapacitors is no longer a flat electrode with a dielectric material in between (capacitors separate electrodes with dielectrics, most of which are plastic, paper, or thin-film ceramics). Supercapacitor batteries belong to electric double layer capacitors. The basic principle is the same as other types of electric double layer capacitors. The electric double layer structure composed of activated carbon porous electrodes and electrolytes is used to obtain super large capacity.
What all supercapacitors have in common is that they contain a positive electrode, a negative electrode, and a separator between the two electrodes, and the electrolyte fills the two pores separated by the two electrodes and the separator. The internal structure of the supercapacitor is shown in the figure below.
Supercapacitors are made of activated carbon materials as porous electrodes, and an electrolyte solution is filled between the opposite carbon porous electrodes. When a voltage is applied at both ends, positive and negative electrons are collected on the opposite porous electrodes respectively, and the positive and negative ions in the electrolyte solution will Due to the action of the electric field, the two collector layers are formed on the interfaces opposite the positive and negative plates respectively, which is equivalent to two capacitors connected in series. Since the activated carbon material has an ultra-high specific surface area (that is, a large electrode area A is obtained) , and the interface distance between the electrolyte and the porous electrode is less than 1 nm (that is, a very small dielectric thickness d is obtained), because the capacitance of the capacitor increases with the increase of the plate area, and with the decrease of the dielectric thickness Therefore, the capacitance value of this electric double layer capacitor is much larger than that of the traditional physical capacitor, and the specific capacity can be increased by more than 100 times, so that the capacitance per unit mass can reach 100F/g, and the internal resistance of the capacitor is also It can be kept at a very low level. Carbon materials also have the advantages of low cost and mature technology, which makes it possible to use capacitors to store large amounts of energy. In actual use, the output voltage or current can be increased by series or parallel connection.
- Characteristics of supercapacitors
① The charging speed is fast. It can reach more than 95% of its rated capacity as long as it is charged for tens of seconds to a few minutes, and it usually takes several hours to charge the lead-acid battery with the largest area.
② Long cycle life, deep charge and discharge cycles can reach 500,000 times, if the supercapacitor is charged and discharged 20 times a day, it can be used continuously for 68 years, and there is no “memory effect”.
③The high-current discharge capacity is super strong, the energy conversion efficiency is high, the process loss is small, and the high-current energy cycle efficiency is 90%.
④ High power density, up to 300-5000W/kg, which is equivalent to dozens of times that of ordinary batteries; the specific energy is greatly improved, and lead-acid batteries can generally only reach 0.02kW h/kg, while the current research and development of super capacitors has reached 10kW ·h/kg.
⑤ The raw material composition, production, use, storage and dismantling process of the product are all pollution-free, and it is an ideal green power source.
⑥ The charging and discharging circuit is simple, no charging circuit like a rechargeable battery is needed, the safety factor is high, and the long-term use is maintenance-free.
⑦It has good ultra-low temperature characteristics, and the ambient temperature range is as wide as -40 to 70 °C.
⑧It is convenient to detect, and the remaining power can be directly read out.
⑨ The monomer capacity range is usually 0.1 to 1000F.