Electrochemical supercapacitors: Operation, components and materials

Abstract

Supercapacitors are the best choice when there is a need to deliver high power to the consumer or to store energy. Hybrid supercapacitors with their beneficial characteristics can somewhat overcome the basic lack of batteries, that is the low power density, and when supercapacitors are combined with batteries, the current maximum power can be increased and the lifetime extended. The number of research studies on development of new materials and construction technologies for supercapacitors has been increasing steadily in recent years. As a result, production of commercial devices and their applications are constantly growing, with improved product properties. Here we present the current state of development of supercapacitors as highly promising energy storage systems by an overview of operation principles, main components and various electrode materials and electrolytes, as well as description of different modes of production. A special attention was paid to the need of a good match of the active material and electrolytes, in order to achieve high capacity of the device. The electrode/electrolyte phase optimization is the key to maximizing characteristics of a supercapacitor, especially the capacitance. In selecting the materials, requirements of the final application must be considered, such as the specific energy and power, energy and power density, and service life-time. In addition to material selection, design and optimization of the cell configuration provide new opportunities for development of hybrid battery/supercapacitor systems. Demand for such systems will increase in future, when using a battery or a supercapacitor alone will not be able to meet specific needs, such as the energy density, number of charge and discharge cycles or voltage. Finally, equally important as the development of materials and cells, are the electrode production technology and the cell construction, which need to be optimized in order to improve supercapacitor properties.