Nanoporous Versus Nanoparticulate Carbon‐Based Materials for Capacitive Charge Storage
Yao Chen, Xiaoyue Hao, George Z. Chen
Abstract
This article reviews recent progresses in the preparation and supercapacitor applications of selected nanoporous and nanoparticulate carbon‐based materials, namely activated carbons, graphenes and carbon nanotubes and their composites with redox materials. Simplified processing steps and graphitization are crucial for making activated carbons. Progressive liquid processing and furnace technology are mainly used in graphene preparation, including curlization, electrolyte incorporation, self‐propagating high‐temperature synthesis, molten salt technology, and flash Joule heating. Redox deposition and new dispersion methods open better routes to making carbon nanotube composites of high charge capacity. Charge storage mechanisms are compared with attention to the facts that activated carbons store ionic charges largely in desirable nanopores, while the ion‐accessible external surfaces of nanoparticulates affect the storage performance of graphenes and composites of carbon nanotubes. Especially, it is explained that pseudocapacitance can result from partial (or zone) delocalization of electrons in graphenes caused by hetero atoms, oxygen in particular. A highlight of this review is on novel molten salt densified holey graphene that has enabled a high specific energy of 618 Wh kg −1 in supercapattery.