Electric double-layer capacitors also known as supercapacitors or ultra capacitors are charge storage devices for electrical energy. The formation of an electric double-layer capacitor is composed of carbon electrodes or derivatives of higher electrostatic double-layer capacitance, an electrolyte, and a separator. The cations and anions of an electrolyte form the Helmholtz double layer.

Hybrid capacitors has a combination of electrostatically and electrochemically charge storage. The charge storage for these capacitors are at the surface of the electrodes instead of within the electrodes and store up to 115% more energy than conventional supercapacitors.

Designed for battery supported applications, flat-style supercapacitors were developed to overcome the shortfall of mobile instruments when it came to typical supercapacitors. Design production for a flat-style supercapacitor usually consists of a rectangular or square shape, thin, and encapsulated in an aluminum foil packet or rigid metal shell. They can be surface mounted or stood on ends.