The mechanism and characteristics of supercapacitors

Due to the dual pressures of environmental pollution and oil crisis, electric vehicles have gradually become an important green means of transportation in people's lives. Power is the power of electric vehicles, but the current battery technology cannot fully meet the requirements of electric vehicles. A supercapacitor is an energy storage element between a battery and an electrostatic capacitor . Compared with batteries, it has higher energy density and higher power density. It is not only suitable for short-term power output sources, but also can be applied to its advantages of high specific power, large specific energy, and more energy storage at one time, effectively improving the movement characteristics during exercise. The electric car starts, accelerates and climbs. In addition, supercapacitors also have the following advantages: low internal resistance, high charge-discharge efficiency (over 90%), long cycle life (tens of thousands to 100,000 times), no pollution and other power components (initiators, batteries, fuels) batteries, etc.) can work together, which is an effective way to achieve energy recovery and reduce pollution, and a single charge can greatly increase the range of electric vehicles. Therefore, supercapacitors have broad application prospects in the field of electric vehicles, and will become one of the important directions for the development of electric vehicles in the future. 

1. The mechanism and characteristics of supercapacitors Supercapacitors are the most recently developed new energy storage elements. It is a physical auxiliary power supply with super power storage function, which can provide strong pulsating power. It is different from regular capacitors. Its capacity can reach tens of thousands of ways. . Supercapacitors are mainly divided into three categories according to the energy storage mechanism: (1) Electric double layer capacitors generated by separating the charges on the interface between carbon electrodes and electrolytes; (2) Using metal oxides as electrodes, which are formed by reversible chemical adsorption of the surface and the surface of Faraday capacitors . Oxidative recovery reaction on the body occurs; ③ a capacitor with conductive polymer as electrode and oxidative recovery response. 

Since the charging and discharging of electric double-layer capacitors are purely physical processes, the cycle times are high and the charging process is fast, making them more suitable for electric vehicles. Electric double-layer supercapacitors are a new class of energy storage devices that rely on polarized electrolytes to store electrical energy. Its principle structure is shown in Figure 1. When the electrode is charged, the surface charge of the electrode in the ideal electrode state will absorb the opposite ions in the surrounding electrolyte solution, and then these ions are attached to the surface of the electrode to form an electric double layer, which constitutes an electric double layer capacitor. Compared to conventional capacitors, supercapacitors have a larger area to store charge and a much smaller interval to block the charge. Therefore, the capacitance of the supercapacitor unit is as high as several to tens of thousands of ways. Due to the special process, the equivalent resistance of supercapacitors is very low, the capacitance is large, and the internal resistance is small. Supercapacitors can have very high peak currents, so they have very high specific powers, z as high as 50-100 times that of batteries, and can reach about 10kW/kg. This feature makes supercapacitors ideal for short-term high-power applications.

Supercapacitors have excellent charging and discharging capabilities. Within the extra voltage range, they can charge to any voltage value very quickly. When discharged, they are able to release all stored electrical energy without damaging the fast charging and discharging of the battery. question. In addition, supercapacitors also have the advantages of not polluting the environment, high mechanical strength, safety (fire and explosion-proof), maintenance-free during use, long service life (more than 10 years) and wide operating temperature range (-30 ° C ~ 45 ° C). Instantaneous high voltage, short-circuit high current and other advantages, and has a buffer function, the energy system is relatively stable.