Architecting 3D carbon networks: A binder-free route to high-performance energy storage

Abstract

Achieving high capacitance, fast charge-discharge capability, and cycle stability simultaneously in supercapacitor electrodes remains a critical challenge for next-generation energy storage. Here, we present a three-dimensional (3D) reduced graphene hydrogel (RGH) architecture directly bonded to nickel foam (NF) via an optimized simple reduction process without the use of a binder. The resulting RGH/NF electrode exhibits the highest specific surface area (2424.5 m² g⁻¹) reported to date for graphene-based systems, forming interconnected ion channels and a continuous conductive network at the RGH-NF interface. This unique structure provides a record-breaking specific capacitance of 1.208 F/g at 5 mV s⁻¹, significantly outperforming conventional graphene electrodes. It demonstrates exceptional durability with a capacitance retention rate of 94.6 % after 10.000 cycles at 3 A g⁻¹. When configured as a symmetric supercapacitor, the device achieves an unprecedented combination of energy density (145 Wh kg⁻¹) and power density (1.09 kW/kg), outperforming most reported carbon-based systems. These results position 3D RGH, which grows directly on metal frameworks, as a scalable and highly effective strategy for high-performance energy storage technologies.