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A supercapacitor is a type of capacitor that can store a large amount of energy, typically 10 to 100 times more energy per unit mass or volume compared to electrolytic capacitors. It is preferred to batteries owing to its faster and simpler charging, and faster delivery of charge.
A supercapacitor is also known as ultracapacitor or double-layer electrolytic capacitor.
A supercapacitor is similar to a capacitor except for the bigger area of its plates and the smaller distance between these plates. The plates are metallic and are soaked in electrolytes and are separated by a very thin insulator. An electric double layer is created in the supercapacitor as opposite charges are formed on both sides of the separator when the plates are charged. This results in a supercapacitor with greater capacitance. In other words, the combination of plates and the larger effective surface area enables a supercapacitor to have greater capacitance and higher energy density. Unlike a battery, a supercapacitor has an unlimited life cycle, with little wear and tear on long-term use. Thus, it can be charged and discharged an unlimited number of times.
A supercapacitor has many advantages. It can deliver high power and enable high load currents owing to its low resistance. Its charging mechanism is simple and fast and is not subject to overcharging. Compared to a battery, a supercapacitor has excellent high- and low-temperature charge and discharge performance. It is also highly reliable and has low impedance.
A supercapacitor has certain limitations including its high cost and the high self-discharge involved. Moreover, unlike a regular battery, it has low specific energy and its use of the full energy spectrum is hindered by linear discharge voltage.
Because of their properties, supercapacitors are used in many applications. They are widely deployed to deliver power and bridge power gaps. They are a replacement for batteries in certain settings such as in battery-free devices.