Electrochemically Dissociated Highly Compact Porous Carbon as a High-Capacity Capacitive Cathode for Lithium-Ion Capacitors

Lithium-ion capacitors are promising candidates in future large-scale energy storage, but their practical application has long been restricted by the performance mismatches between the battery-type anode and capacitive cathode, especially the unsatisfactory charge storage capacity of the capacitive cathode. Herein, we demonstrate a novel capacitive cathode that is prepared by electrochemically dissociating a graphene-based highly compact porous carbon via anion intercalation chemistry. Comprehensive in situ characterizations reveal that under substantial electromigration forces, the anions in electrolyte can effectively intercalate into and dissociate the tightly stacked graphene nanosheets, thereby boosting the charge storage capacity. Remarkably, when used as the capacitive cathode of the lithium-ion capacitor, the activated material delivers an ultrahigh specific capacity of 390 mA h g^-1 or 585 mA h cm^-3, much outperforming those of state-of-the-art capacitive materials and even some advanced battery-type materials, thus taking a significant step in developing high-capacity capacitive cathode for applicable lithium-ion capacitors.