Pristine Graphene Inks for 3D Printed Supercapacitors with High Capacitance

Abstract

The 3D printing of 2D materials, such as graphene, transition metal dichalcogenides and M-Xenes, offers a cost-efficient and sustainable route for the fabrication of integrated electronics and advanced energy devices with arbitrarily complex architectures. In particular, the assembly of 2D materials into rationally designed three-dimensional electrodes can enhance the charge transport kinetic and increase the electrochemically-active surface area, resulting in superior electrochemical performance.Graphene has long been considered a promising active material for carbon-based supercapacitors, owing to its high intrinsic capacitance, superior mechanical strength and flexibility, and excellent electrical conductivity. However, because of the limited processability of pristine graphene in water, the 3D printing of graphene supercapacitors has either relied on inks containing high boiling solvents and electrochemically inactive binders, or on aqueous dispersions of graphene oxide, which must be thermally reduced at elevated temperatures (>1000°C) after printing.In this work we demonstrate a new class of 3D printed supercapacitors obtained from aqueous inks of pristine graphene, without the need of functional additives or high-temperature processing to achieve high capacitance. With an electrical conductivity of ~1370 S m-1 and rationally designed architectures, the symmetric supercapacitors can achieve an exceptional areal capacitance of 1.57 F cm-2 at 2 mA cm-2 which is retained over 72% after repeated voltage holding test. The areal power density (0.968 mW cm-2) and areal energy density (51.2 μWh cm-2) outperform many carbon-based supercapacitors previously reported, indicating the feasibility of this approach for the fabrication of efficient energy storage devices.