Introduction to the hottest supercapacitor

2022-08-11
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With the development of social economy, people pay more and more attention to green energy and ecological environment. As a new type of energy storage device, supercapacitor has attracted more and more attention because of its irreplaceable advantages. In some designs that require high-power and high-efficiency solutions, engineers have begun to replace traditional batteries with supercapacitors that do not have a great impact on the cutting force due to the cutting rate in drilling

defects of battery technology

li ion, NiMH and other new batteries can provide a reliable energy storage scheme, and have been widely used in many fields. As we all know, chemical batteries store charge by generating Faraday charge transfer through electrochemical reaction. They have short service life and are greatly affected by temperature, which is also the difficulty faced by designers who use lead-acid batteries (batteries). At the same time, high current will directly affect the life of these batteries. Therefore, for some applications requiring long life and high reliability, these batteries based on chemical reaction show various deficiencies

characteristics and advantages of supercapacitors

the principle of supercapacitors is not a new technology. Most common supercapacitors are electric double layer structures. Compared with electrolytic capacitors, this kind of supercapacitors has very high energy density and power density. Compared with traditional capacitors and secondary batteries, supercapacitors have higher charge storage capacity than ordinary capacitors, and have the characteristics of fast charge and discharge, high efficiency, no pollution to the environment, long cycle life, wide temperature range and high safety

in addition to being able to charge and discharge quickly, another major feature of supercapacitors is their low impedance. Therefore, when a supercapacitor is fully discharged, it will show a small resistance characteristic and complete all the research content. If there is no limit, it will pull the possible source current. Therefore, constant current or constant voltage chargers must be used

10 years ago, supercapacitors could only be sold in small quantities every year, and the price was very expensive, about $1-2/farad. Now, supercapacitors have been supplied to the market in large quantities as standard products, and the price has also been greatly reduced, with an average of $0.01-0.02/farad. In recent years, supercapacitors have begun to enter many application fields, such as consumer electronics, industry, transportation and other fields

Figure 1 super capacitors have long cycle life and high power density, safety and efficiency

structure of super capacitors

although there are many super capacitor manufacturers around the world that can provide many kinds of super capacitor products, most products are based on a similar double-layer structure, and super capacitors are very similar to electrolytic capacitors in structure, The main difference between them is the electrode material, as shown in Figure 2

Figure 2 in terms of structure, the main difference between supercapacitors and batteries or electrolytic capacitors is the electrode material

the electrode of early supercapacitors uses carbon. The surface area of carbon electrode material is large, and the size of capacitance depends on the surface area and the distance between electrodes. The large surface area of this carbon electrode plus a small electrode distance makes the capacitance of supercapacitors very large, and most supercapacitors can achieve farad level, The general capacity range is 1 ~ 5000f

using supercapacitors

supercapacitors have a wide range of applications. Combined with high energy density substances such as fuel cells, supercapacitors can provide rapid energy release and meet high power requirements, so that fuel cells can only be used as energy sources. At present, the energy density of supercapacitors can be as high as 20kw/kg, which has begun to seize this part of the market between traditional capacitors and batteries

in those applications that require high reliability but do not require high energy, supercapacitors can be used to replace batteries, or supercapacitors can be combined with batteries to be used in occasions that require high energy, so smaller and more economical batteries can be used

the ESR value of super capacitor is very low, so it can output large current and absorb large current quickly. Compared with the chemical charging principle, the working principle of super capacitor makes the performance of this product more stable, so the service life of super capacitor is longer. For devices like power tools and toys that need fast charging, supercapacitors are undoubtedly an ideal power supply

some products are suitable for the hybrid system of battery/super capacitor. The use of super capacitor can avoid using large batteries in order to obtain more energy. For example, digital cameras in consumer electronics are an example. The use of supercapacitors enables digital cameras to use cheap alkaline batteries (rather than expensive Li ion batteries)

the rated voltage range of the supercapacitor unit (cell) is 2 5 ~ 2.7V, so many applications need to use multiple supercapacitor units. When these units are connected in series, the design engineer needs to consider the balance and charging between the units

any super capacitor will discharge through the internal parallel resistance when it is powered on. This discharge current is called leakage current, which will affect the self discharge of the super capacitor unit. Similar to some secondary battery technologies, the voltage of supercapacitors needs to be balanced when used in series, because there is leakage current, and the internal parallel resistance will determine the voltage distribution on the supercapacitor units in series. When the voltage on the supercapacitor is stable, the voltage on each unit will change with the leakage current, while the non condensing experiment will change with the capacitance. The larger the leakage current is, the smaller the rated voltage is. On the contrary, the common problems of leakage current joint research are small, and the rated voltage is high. This is because the leakage current will cause the discharge of the supercapacitor unit and reduce the voltage, which will then affect the voltage of other units connected in series with it (it is assumed that these units in series use the same constant voltage for power supply)

in order to compensate for the change of leakage current, a resistor is often connected in parallel next to each unit to control the leakage current of the whole unit. This method effectively reduces the change of the corresponding parallel resistance between the units

another recommended method is active cell balancing. With this method, each cell will be actively monitored. When there is a voltage change, it will balance each other. This method can reduce any additional load on the unit and make the work efficiency higher

if the voltage exceeds the rated voltage of the unit, the service life of the unit will be shortened. For high reliability supercapacitors, how to maintain the voltage within the required range is the key point. The charging voltage must be controlled to ensure that it cannot exceed the rated voltage of each unit. (end)

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