Analysis of Super Capacitor

In principle, supercapacitors can be thought of as a rechargeable battery. It can store charges that are proportional to its capacity and release them when the discharge is required. The biggest difference between super capacitors and electrolytic capacitors is their electronic bilayer structure, which can achieve higher capacity.

The standard capacitance is structured as a dielectric layer between two electrodes attached to the metal plate (fig. 1). Depending on the type of capacitance, the dielectric can be alumina, tantalum tetroxide, barium oxide or polypropylene polyester. Different materials determine different capacity and voltage characteristics (Fig. 2). The amount of dielectric and the distance between the plates will also affect the capacitance. However, the maximum allowable distance between plates limits the number of dielectrics.

In this monolayer structure, it is usually feasible to increase the capacity by increasing the number of dielectric. There are three methods: increasing the package width and plate size, increasing the package length and increasing the distance between the plates or the combination of the two methods. All three methods will result in the volume of capacitors becoming larger, which is a sacrifice that must be made to increase the capacity of capacitors.

The EDLC (double layer Capacitor) solves the above problem as literally, adding a second dielectric layer in the same package, which works in parallel with the first layer on both sides of the intermediate isolation (Fig. 3). EDLC also uses porous dielectric, such as activated carbon, carbon nanotubes, carbon black gel, and the selection of conductive polymers, its storage capacity is much higher than the standard electrolytic materials. This combination of extra layers and more efficient dielectric materials can increase the capacitance by nearly four orders of magnitude.

However, voltage capability is a weak link in supercapacitors and is rooted in dielectric materials. . However, these thin layers do not have the ideal insulation characteristics of traditional dielectric, so they require lower working voltage.