Principle of Super Capacitor1

1. The principle of supercapacitors

Supercapacitors are new types of components that store energy through the double layer of the interface formed between the electrode and the electrolyte. When the electrode is in contact with the electrolyte, due to the Coulomb force, the intermolecular force and the interatomic force, the solid-liquid interface has a stable and opposite sign double layer charge, which is called the interface double layer.

The electric double-layer supercapacitor is regarded as two inactive porous plates suspended in the electrolyte, and voltage is applied to the two plates. The electric potential applied to the positive plate attracts the negative ions in the electrolyte, and the negative plate attracts the positive ions, thereby forming an electric double layer capacitor on the surfaces of the two electrodes.

Electric double layer capacitors can be divided into carbon electrode double layer supercapacitors, metal oxide electrode supercapacitors and organic polymer electrode supercapacitors according to different electrode materials.

2. The characteristics of supercapacitors

Compared with batteries and traditional physical capacitors, the characteristics of supercapacitors are mainly reflected in:

(1) High power density. It can reach 102～104 W/kg, which is much higher than the power density level of batteries.

(2) Long cycle life. After a few seconds of high-speed deep charge and discharge cycles of 500,000 to 1 million times, the characteristics of the supercapacitor change very little, and the capacity and internal resistance are only reduced by 10% to 20%.

(3) Wide working temperature limit. Since the adsorption and desorption speed of ions in the supercapacitor does not change much in the low temperature state, its capacity change is much smaller than that of the battery. The operating temperature range of commercial supercapacitors can reach -40°C to +80°C.

(4) Maintenance-free. Supercapacitors have high charging and discharging efficiency, have a certain endurance to overcharge and overdischarge, and can be stably charged and discharged repeatedly, and theoretically, no maintenance is required.

(5) Green and environmental protection. Supercapacitors do not use heavy metals and other harmful chemicals in the production process and have a long lifespan. Therefore, they are a new type of green and environmentally friendly power supply.