Carbon Nanocomposites in Electrochemical Capacitor Applications

Carbon has been widely used as electrode material due to its high electrical conductivity, chemical stability, high surface area, various carbon sources, and so on. However, the theoretical capacitance of carbon materials is relatively low compared with pseudoactive materials. Moreover, carbon materials such as graphene, carbon nanotube, and so on are easy to agglomerate, which dramatically decreases the effective surface area that can be utilized for charge storage and hinders electrolyte diffusion. To further improve the electrochemical performance of carbon materials, different carbon-based nanocomposites including carbon/carbon, carbon/metal oxide, and carbon/conductive polymers have been developed over the past decades and demonstrated superior electrochemical energy storage performance. In carbon/carbon nanocomposite, one carbon could act as a spacer to prevent agglomeration of the other. While in carbon/metal oxide and carbon/conductive polymer nanocomposites, additional pseudocapacitance can be introduced through the incorporation of pseudoactive metal oxide and conductive polymers. In this chapter, a brief introduction was provided on the fundamentals of electrochemical capacitors, including working principles of electric double layer capacitor and pseudocapacitor, methods to prepare electrode, principles of electrolyte selection, evaluation of electrochemical energy storage performance, and design guidelines of advanced electrodes. Meanwhile, a detailed overview was provided on the most recent progress of electrochemical energy storage performance with innovative carbon-based nanocomposites.