Functional Pillared Graphene Frameworks for Ultrahigh Volumetric Performance Supercapacitors

Supercapacitors, also known as electrochemical capacitors, can provide much faster charge-discharge, greater power density, and cyclability than batteries, but they are still limited by lower energy densities (or the amount of energy stored per unit volume). Here, a novel strategy for the synthesis of functional pillared graphene frameworks, in which graphene fragments in-between graphene sheets, through simple thermal-treatment of ozone (O-3)-treated graphene oxide at very low temperature of 200 degrees C is reported. Due to its high packing density, high content of stable oxygen species, and continues ion transport network in-between graphene sheets, the functional pillared-graphene framework delivers not only high gravimetric capacitance (353 F g(-1) based on the mass of the active material) and ultrahigh volumetric capacitance (400 F cm(-3) based on total mass of electrode material) in aqueous electrolyte but also excellent cyclic stability with 104% of its initial capacitance retention after 10 000 cycles. Moreover, the assembled symmetric supercapacitor achieves as high as 27 Wh L-1 of volumetric energy density at a power density of 272 W L-1. This novel strategy holds great promise for future design of high volumetric capacitance supercapacitors.