A supercapacitor is able to store and release energy very rapidly. By comparison, a capacitor can store and release energy quickly, but can’t store as much energy as a battery. A battery can store more energy, but can’t deliver it as quickly as a capacitor. Supercapacitors are in the middle and provide both qualities. A design engineer may choose a supercapacitor to improve battery performance when combined in hybrid power sources, or to provide an efficient and long-lasting means of energy storage when used on its own.