What are Supercapacitor and its Characteristics?
A supercapacitor (Supercapacitor, Ultracapacitor) is known as an electric double-layer capacitor (EDLC), an electrochemical capacitor (EC). It is also known as Gold capacitor, Farad capacitor, and many other terms.
A supercapacitor is an electrical element with an electrochemical principle. Its theoretical basis is the electric double layer theory proposed by the German physicist Hermann von Helmholtz. In this sense, a supercapacitor is a brand-new type of capacitor, including physical and chemical elements. When a metal electrode is inserted into the electrolytic solution, its surface will produce an opposite excess charge. If you continue to apply a voltage that is less than the electrolyte, the positive and negative ions in the electrolyte will quickly move to the two poles, forming a tight layer on the electrode surface, which is known as the electric double layer.
Although it is called an electrochemical element, it does not undergo any chemical reactions when it is used and during energy storage. The supercapacitors are not unilaterally energy-dissipating compare to the traditional batteries. On the contrary, they can not only release energy but the process of storing energy is also reversible. It is precise because this supercapacitor can be repeatedly charged and discharged hundreds of thousands of times (10E6 or more).
Supercapacitors not only have the characteristics of rapid charge and discharge with large current but have the characteristics of battery storage like a battery plus a much longer lifespan. When discharging, the electrons between the moving conductors are used to discharge the current (without relying on chemical reactions) to provide power for the device.
Since the charging and discharging process of the supercapacitor will not produce a chemical reaction, it will shape the characteristics and increase the advantages of the supercapacitor:
1. Small in size and large capacity
- Due to the characteristics of the structured porous electrode, the charge of the adsorbed electrolyte increases. Therefore, the capacity can be very large.
2. Strong charge and discharge ability
- When voltage is applied to the electrodes at both ends, the ions are attracted to the double-layer electrical surface and start to charge. The charging speed is extremely fast, and it can reach more than 95% of its rated capacity in only a few tens of seconds to a few minutes. The traditional battery charging process goes through chemical reactions. Once charged too fast, it will produce other chemical reaction substances, which will affect battery life.
- The high current discharge ability is super strong, the energy conversion efficiency is high, and the process loss is small. Its discharge process is just that the electrons run from one side of the capacitor to the other side. Since there is no chemical reaction, the high current discharge will not affect its lifespan.
3. Ultra-long lifespan, charge, and discharge repeatedly over hundreds of thousands of times (10E6 or above).
4. Extreme low-temperature resistance
- Supercapacitors have phenomenal temperature resistance, the lowest is -40C, and the working range is generally between -40C~+70C.
5. The circuit becomes open when a failure occurs. The supercapacitor does not breakdown when there is an influx of volts going through the machine. Perfectly safe from overvoltage and reliable.
The Energy and Differences Between Supercapacitor and Battery
The energy density of supercapacitors can reach 10KWh/KG. By following this energy density standard, plus the mechanical conversion efficiency, each KG is equivalent to 1 liter of gasoline. By comparing the energy density of 0.05~0.18KWh/Kg for chemical batteries, supercapacitors have far superior advantages. The principle of the battery is the movement of electrons. Lithium batteries provide electrons from the hydrogen of the negative electrode, and the positive electrode obtains electrons from materials such as lithium cobalt oxide or lithium iron phosphate, thereby forming a current. A large number of materials such as hydrogen storage materials, electrolytes, and the material of the positive electrode are to make the hydrogen electrons move. Therefore, most of the weight of the traditional battery has already done the auxiliary work. The hydrogen electrons are the most effective within the supercapacitor. The principle of the supercapacitor is the two materials. By giving it a voltage, the electrons will run aside. When discharging, the electrons on the piece of material with more electrons will run on the one with fewer electrons to form a current. So in theory, all the weight of the supercapacitor can participate in the flow of electrons, which results that its energy density will be much greater than that of chemical batteries.
1. Ultra-low series equivalent resistance (LOW ESR), and power density are more than tens of times than lithium-ion batteries. The supercapacitor is suitable for large current discharge.
2. Supercapacitors can charge and discharge for more than 500,000 times. It is 500 times more than the Lithium-ion battery. 1000 more times than NiMH and Ni-Cd battery. The supercapacitor can charge and discharge 20 times a day and can be used continuously for 68 years.
3. Short charging and discharging time, simple charging circuit requirements, no memory effect.
4. The temperature of the working range for supercapacitors is generally between -40C~+70C. For general battery, it is -20C~60C. When the temperature starts to decrease from 0C~-20C, the output energy decreases accordingly, and the highest attenuation energy can reach more than 20%.
So the supercapacitor not only has the characteristics of capacitance but also the characteristics of the battery. It is very vivid to say that it is a "charge and discharge integrated" battery.
The Major Materials of Supercapacitor and its Environmental Effect
Supercapacitors are double-layer capacitors. It is the largest type of double-layer capacitors that have been put into mass production in the world. Its basic principle is the same as other types of double-layer capacitors. They are electric double layers composed of activated carbon porous electrodes and electrolytes. The structure gains a huge capacity. In terms of specific energy and power, the supercapacitor is located between the battery and the traditional capacitor. Its life cycles and charge and discharge efficiency are much higher than the battery. Due to the long lifespan, it usually exceeds the life of the equipment that utilizes it. Therefore, supercapacitors do not require maintenance for life. Plus, the supercapacitor is non-polluting after use and is also called green energy, meaning it is environmentally friendly, whereas chemical batteries cause pollutions to the environment during and after use. Supercapacitors can reduce oil consumption and effectively reduce lithium batteries and lead-acid batteries pollution. Other than that, the relative cost is low. Although the price of supercapacitors is higher than general batteries, the lifespan of supercapacitors is 100 times higher than all chemical batteries. Overall, the operating cost of supercapacitors is much lower than the chemical batteries.
In the automotive field, it can be used as a starting power supply for automobiles. It can provide power during peak power transmission, which is better than traditional battery power supplies. In UPS uninterruptible power supplies, supercapacitors can be used to provide instantaneous power output, as a backup power supply, a laser pulse energy and storage energy of other equipment. It can also be used as an auxiliary battery in portable devices to extend battery life, etc.
Disadvantages and Use of Supercapacitors
At present, the pressure resistance of supercapacitors is not too high, and the overvoltage protection circuit is indispensable in actual use. If the voltage exceeds the rated voltage of the unit, the lifespan of the unit will be shortened. For a high-reliability supercapacitor, it is necessary and vital to maintain the voltage within the required range. The charging voltage must be controlled on the control circuit to ensure that it cannot exceed the rated voltage of each unit.
Product design often uses two or more supercapacitors in series or in parallel. Since the self-discharge of the capacitor and the error value of the capacitor unit are not the same, it is easy to cause local unit damage after multiple charges and discharges in the following period. The solution is the active cell-balancing method. With this method, each cell will be actively monitored. When there is a voltage change, they will be balanced with each other. This method can reduce the extra load, which can greatly improve efficiency and avoid damage.
Future Development of Supercapacitors
Supercapacitors have incomparable advantages over traditional batteries, but supercapacitors still have many shortcomings. Therefore, they cannot be used on a large scale. It does not require a long time to improve these shortcomings, perhaps one or two years, because this technology has an extremely broad application prospect. We can imagine what will happen once this technology is mature and can be used on a large scale. When it comes to an electric car, it can be charged within 20 minutes at once. It can run for more than 500 kilometers after charging. Not only that, but the battery can also be used for decades. For a mobile phone, it only takes 5 minutes to be fully charged and can be used for the whole day. Imagine having electric cars and mobile phones invented with the supercapacitor, the sales of gasoline, traditional battery raw material manufacturers will be affected significantly. The social economy may also cause different degrees of impact. (Taking gasoline and traditional batteries as an example) Power source equipment and products will be replaced by power sources from one after another, and an industrial revolution in the application of new materials will follow.)