Materials For Electrochemical Capacitors

The aim of this chapter is threefold. First of all, we will attempt to briefly highlight the differences between batteries and electrochemical capacitors (ECs), describe the general types of ECs (symmetric and asymmetric configurations), and present the electrochemical tools that are available to characterize these systems. Second, an EC is a complex device with many components (current collector, separator, active materials, external management electronics) and design features that ultimately determine the device characteristics. However, the advances in performance for future ECs that will be required for their broader implementation as an energy-storage technology will largely depend on new developments in electrode materials and electrolytes, which will be the focus of this chapter. Thus, this chapter will attempt to present a critical assessment of the materials that are currently being used and developed for hybrid ECs. Third, some current applications of ECs will be described in details and will clearly demonstrate that hybrid ECs are no longer a scientific curiosity and that they have found their place as energy-storage systems due to their unique characteristics. Finally, this chapter will be concluded by a section that presents the major role ECs will be playing in the field of energy storage and conservation.