Supercapacitor

A supercapacitor, also called an ultracapacitor, is a high capacity electrical energy storage device that stores far more energy per unit mass than an ordinary capacitor, ten to a hundred times more, while charging and discharging much faster and enduring many more cycles than a rechargeable battery. It stores charge electrostatically at the interface between electrode and electrolyte, across a layer only a fraction of a nanometer thick, and in many designs also stores additional charge through fast reversible surface reactions called pseudocapacitance. H. Becker built the first prototype with porous carbon electrodes in 1957, and NEC brought the technology to market in 1978 under the name supercapacitor, initially for backing up computer memory. Because they deliver and absorb power in rapid bursts, supercapacitors are used today for regenerative braking in vehicles, buses and trains, and for buffering and stabilizing voltage on electrical grids.