Reduced Graphene Oxide Hydrogels Deposited in Nickel Foam for Supercapacitor Applications: Toward High Volumetric Capacitance

Abstract

Graphene hydrogels have been considered as ideal materials for high-performance supercapacitors. However, their low volumetric capacitance significantly limits its real application. In this study, we report an environment-friendly and scalable method to prepare high packing density, electrochemically reduced graphene oxide hydrogels (ERGO) for supercapacitor application by the electrophoretic deposition of graphene oxide onto nickel foam, followed by the electrochemical reduction and hydraulic compression of the deposited materials. The as-prepared ERGO on nickel foam was hydraulic compressed up to 20 tons, resulting in an increase of the packing density of ERGO from 0.0098 to 1.32 g cm^–3. Consequently, the volumetric capacitance and volumetric energy density of ERGOs greatly increased from 1.58 F cm^–3 and 0.053 Wh cm^–3 (as-prepared ERGO) to 176.5 F cm^–3 and 6.02 Wh cm^–3 (ERGO compressed at 20 tons), respectively. The ERGOs also exhibited long-term electrochemical stability with a capacitance retention in the range of approximately 79–90% after 10 000 cycles. Lastly, we believe that these high packing density ERGOs are promising for real-world energy storage devices for which scalable, cost-effective manufacturing is of significance and for which space constraints are paramount.