凯发

Compared with lithium-ion batteries, supercapacitors exhibit several advantages, such as long cycle life, short charging time, light weight, and high power density. Graphene and/or graphene oxide-based carbon materials, as newly discovered members of carbon family, have drawn extensive interests on various research areas including as electrode materials for supercapacitors, because of their own high specific area, exceptional electric-conductivity, facile synthesis, etc. 

In this presentation, I am going to discuss our recent progresses in the development of solid-state supercapacitors from reduced graphene oxides (RGO) and our understandings on the charge storage mechanisms of the assembled supercapacitors. As well-known, substantial differences in charge storage mechanisms exist between dielectric capacitors (DC) and electrochemical capacitors (EC), resulting in orders of magnitude difference of stored charge density in them. However, if ionic diffusion, the major charge transport mechanism in ECs is confined within nanoscale dimensions such as the spacing between graphene oxide layers, the Helmholtz layers and diffusion layers will overlap, resulting in dismissible ionic diffusion. An interesting contradiction between appreciable energy density and unrecognizable ionic diffusion are observed in solid-state ECs made from reduced graphene oxide films that challenge the fundamental charge storage mechanisms proposed in such devices. A new capacitive model is therefore proposed, which combines the two distinct charge storage mechanisms of DCs and ECs, to explain the contradiction, of high storage capacity yet poor ionic diffusion, seen in graphene oxide based supercapacitors.