Nanostructured Activated Carbons for Supercapacitors

Electrochemical capacitors (also called supercapacitors) store energy by ion adsorption or redox reactions in the vicinity of an electrode/electrolyte interface. Activated carbon (AC) is one of the most frequently applied electrode materials for supercapacitors, especially for electrical double-layer capacitors (EDLCs), for its many advantages, such as high specific surface area, low cost, low toxicity, excellent mechanical and chemical stabilities, to name a few. Recently, with the successful synthesis and application of nanostructured ACs with finely tuned porosity, the performance of AC-based supercapacitors has been notably improved. In this chapter, we discuss the structure-property-performance relationships in nanostructured ACs for supercapacitors. We first review synthesis strategies of nanostructured ACs. Then, we summarize key factors determining the performance of nanostructured ACs-based EDLCs, including the porous texture of the ACs, their electrical and ionic conductivity and the electrolyte selection and discuss each in detail, respectively. Lastly, we discuss the self-discharge of ACs-based supercapacitors induced by electrode surface functionalities, impurities, electrolyte decompositions, and side reactions. The discussions in this chapter serve as guidance for future efforts in research, development, and production of novel carbon materials for advanced supercapacitors with improved performance characteristics.