Supercapacitors for Short‐term, High Power Energy Storage

Abstract

Supercapacitors, also known as electrochemical capacitors, are promising energy storage devices for applications where short term (seconds to minutes), high power energy uptake and delivery are required. Supercapacitors store electric charges either by electric double layer capacitance or fast faradic redox reactions occur at the surface or sub-surface of the electrode material. In spite of the merits of high power and long cycle life, supercapacitors suffer from relatively low energy density. Research efforts have been mainly been devoted to the improvement of energy density by developing electrode materials of high specific capacitance and devices with a higher cell voltage. Over the last 30 years, the development of electrode materials, including carbons, conducting polymers, metal oxides, together with the latest reported metal sulphides, selenides, and phosphides, has pushed the limits of capacitance per unit weight and volume. By coupling these electrode materials with suitable electrolytes and matching their electrochemical potential window, supercapacitor devices with increased working voltage have been developed. This contribution presents recent advances in the development of electrode materials and devices, indicating strategies to improve the performance of supercapacitors via modification of the electrode/electrolyte interface, identification of new materials and design of high voltage, asymmetric devices.