Supercapacitors are also called electrochemical capacitors. Its performance is between ordinary capacitors and batteries. It has excellent pulse charge and discharge performance and high-power energy storage performance. Because of its large stored energy, light weight, and multiple charge and discharge A new type of energy storage device. At present, there are many kinds of super capacitor and capacitor products, but most of them are based on a similar electric double layer structure. Super capacitors are very similar in structure to electrolytic capacitors. Their main difference is the electrode material, as shown in Figure 1. shown.
The electrode materials used in supercapacitors include activated carbon, metal oxides, conductive polymers, etc. The electrolytes are divided into two types: aqueous solvents and non-aqueous solvents. The former has good conductivity, while the latter has a wide range of available voltages. When the practical application requires high current and short-term charging and discharging, supercapacitors will be an ideal choice. It can be used together with other types of batteries and play a complementary role.
According to the different electrodes used, supercapacitors can be divided into the following categories: ① carbon electrode capacitors; ② noble metal oxide electrode capacitors; ③ conductive polymer capacitors. According to the different mechanisms of storing electric energy, supercapacitors can be divided into two types: one is “electric double layer capacitor”, and its capacitance is mainly based on the electric double layer capacitance generated by the separation of charges on the electrode/electrolyte, such as carbon Electrode capacitor; the other is called “Faraday quasi-capacitor”, which is composed of noble metal and noble metal oxide electrodes, etc. The generation of capacitance is based on the underpotential deposition of electroactive ions on the surface of noble metal electrodes, or on noble metal oxide electrodes. The adsorption capacitance generated by the redox reaction on the surface and in the bulk phase is different from that of the electric double layer capacitance, and it usually has a larger specific capacitance with the occurrence of the charge transfer process. Its structure and principle are as follows: shown in Figure 2.
The maximum usable voltage of a supercapacitor is determined by the breakdown voltage of the electrolyte. The electrolyte can be an aqueous solution (such as a strong acid or strong base solution) or an organic solution (such as a salt in an aprotic solvent). High power and high specific power can be obtained with the aqueous system.
Combining supercapacitors with high-energy-density substances such as fuel cells, supercapacitors can provide rapid energy release to meet high power demands, allowing fuel cells to be used only as an energy source. Currently, the energy density of supercapacitors can be as high as 20kW/kg. Supercapacitors have a low ESR (equivalent impedance) value, allowing them to source large currents as well as absorb large currents quickly. Compared with the chemical charging principle, the working principle of the supercapacitor makes the performance of this product more stable, so the life of the supercapacitor is longer. Supercapacitors are an ideal power source for devices that require fast charging, such as power tools and toys.
The stored electrical energy of supercapacitors is 20 to 1000 times that of ordinary capacitors. It improves energy storage by using a porous electrolyte and increasing the area of the bipolar plates. supercapacitor
Conventional capacitors have the advantages of high power density and high charging energy density, fast charging and discharging, long service life, and not easy to age. The disadvantage is still that it is expensive and the energy is not large enough. However, it can be expected that the supercapacitor battery will be one of the most promising power storage devices in the photovoltaic power generation system in the future.