What is super capacitor?
Supercapacitor, also known as Farad capacitor, gold capacitor, electrochemical capacitor, double layer capacitor, is different from traditional chemical power supply, it is a kind of power supply with special performance between traditional capacitor and battery, which mainly relies on double layer and redox pseudo capacitive charge to store electric energy. However, no chemical reaction occurs in the process of energy storage, and this process is reversible, because of which supercapacitors can be charged and discharged hundreds of thousands of times repeatedly.
How to charge the supercapacitor?
Supercapacitor charging is very simple, as long as it does not exceed its spike voltage, as for supercapacitor discharging, the voltage is decreasing, and the current is determined according to the load, generally the resistance of the back-end load is changing, not constant, if it is constant, the current is also decreasing.
Introduction of knowledge about supercapacitors.
The specific details on supercapacitor construction depend on the application and use of the supercapacitor. These materials may vary slightly due to the manufacturer or the needs of a particular application. Common to all supercapacitors is that they all contain a positive electrode, a negative electrode, and a diaphragm between these two electrodes, with the electrolyte filling the pores of the two separated by the two electrodes and the diaphragm.
The components of an ultracapacitor can vary from product to product. This is determined by the geometry of the supercapacitor package. For the placement of prismatic or square package product parts, the internal structure is based on the setup of the internal parts, i.e. the internal collectors are extruded from the stack of each electrode. These collector pads will be soldered to the terminals, thus extending the current path outside the capacitor.
For round or cylindrical packages, the electrodes are cut in a spooled configuration. Finally, the electrode foil is soldered to the terminals, allowing the external capacitor current path to be extended.
The basic principle is the same as that of other types of double layer capacitors, which use a double layer structure consisting of activated carbon porous electrodes and electrolyte to obtain a very large capacity.
The outstanding advantages are high power density, short charging and discharging time, long cycle life and wide working temperature range, and it is the largest capacity among the double layer capacitors that have been put into mass production in the world.
According to the different energy storage mechanism, it can be divided into the following two categories.
1、Double layer capacitor: It is generated at the electrode/solution interface by the confrontation of charges caused by the directional arrangement of electrons or ions. For an electrode/solution system, a bilayer is formed at the interface between the electron-conducting electrode and the ion-conducting electrolyte solution. When an electric field is applied to the two electrodes, the anions and cations in the solution migrate to the positive and negative electrodes respectively, forming a double layer on the electrode surface; when the electric field is withdrawn, the positive and negative charges on the electrodes are attracted to the oppositely charged ions in the solution and the double layer is stabilized, producing a relatively stable potential difference between the positive and negative electrodes. At this time, for a certain electrode, an opposite ion charge equal to the charge on the electrode will be generated within a certain distance (dispersion layer) to keep it electrically neutral; when the two poles are connected to the external circuit, the charge on the electrode migrates and generates current in the external circuit, and the ions in the solution migrate to the solution to be electrically neutral, which is the charging and discharging principle of the double layer capacitance.
2. Faraday quasi-capacitance: The theoretical model was first proposed by Conway, which is a two-dimensional or quasi-two-dimensional space on the electrode surface and near the surface or in the bulk phase, where electroactive substances are deposited under potential and highly reversible chemical adsorption and desorption and redox reactions occur to produce capacitance related to the electrode charging potential. For Faraday quasi-capacitors, the process of storing charge includes not only storage on the bilayer, but also redox reactions between electrolyte ions and electrode active material. When ions in the electrolyte (e.g. H+, OH-, K+ or Li+) diffuse from the solution to the electrode/solution interface in the presence of an applied electric field, they enter the bulk phase of the active oxide on the electrode surface through redox reactions at the interface, thus allowing a large amount of charge to be stored in the electrode. When discharged, these ions entering the oxide will return to the electrolyte through the reverse reaction of the above redox reaction, and the stored charge will be released through the external circuit, which is the charging and discharging mechanism of Faraday quasi-capacitor.
The characteristics of supercapacitor.
1) Fast charging speed, charging for 10 seconds to 10 minutes can reach more than 95% of its rated capacity.
2) Long cycle life, the number of cycles of deep charging and discharging can be 1~500,000 times, no "memory effect".
(3) high-current discharge capacity, high energy conversion efficiency, small process loss, high-current energy cycle efficiency ≥ 90%.
(4) high power density, up to 300W/KG ~ 5000W/KG, equivalent to 5 to 10 times the battery.
(5) product raw material composition, production, use, storage and disassembly process are not polluted, is the ideal green power supply.
6) simple charging and discharging lines, no need for charging circuits like rechargeable batteries, high safety factor, maintenance-free for long-term use.
7) good ultra-low temperature characteristics, wide temperature range -40℃～+70℃.
8) easy to detect, the remaining power can be read out directly.
9) Capacity range is usually 0.1F--1000F.
Advantages of supercapacitor.
Farad level capacity in a very small volume.
No need for special charging circuit and controlled discharging circuit.
Overcharging and overdischarging do not negatively affect their lifetime compared to batteries.
It is a green energy source from an environmental point of view.
Supercapacitors are solderable and thus do not have problems such as poor contact with batteries.
Disadvantages of supercapacitors.
It can cause phenomena such as electrolyte leakage if used improperly.
Compared with aluminum electrolytic capacitors, it has a higher internal resistance and thus cannot be used in AC circuits.
Unit introduction edit
Farad, abbreviated as "Far", symbolized as F.
1 farad is the potential difference between the two plates when the capacitor stores 1 coulomb of charge, 1 volt 1F = 1C/1V.
1 coulomb is the amount of power transported by 1A current in 1s, i.e. 1C = 1A-S.
1 coulomb = 1 ampere-second.
1 farad = 1 ampere-second per volt.
The discharge of the battery (battery) 12 volts 14 amp-hours = 14 * 3600 * 1/12 = 4200 Farad (F), (Note: 12 volts 14 amp-hours battery is from 2v14 amp-hours 6 pieces in series, if changed to 6 fast parallel, it is equal to 2v84 amp-hours, converted to 1v is 168 amp-hours). The capacitance value of the earth is only about 1-2F.
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