High-volumetric-capacitance graphene supercapacitors via DEGDE-mediated GO clay process

A refined and facile strategy is reported for preparing high-volumetric-capacitance graphene supercapacitor electrodes via a diethylene glycol dimethyl ether (DEGDE)-mediated graphene oxide (GO) clay process. Building upon the GO "pottery" concept from our previous work, this method addresses the critical limitation of solvent evaporation and loss of workability by employing DEGDE-a high-boiling-point, high-molecular-weight organic solvent-as a processing aid. This modification preserves the plasticity and uniformity of the GO clay during calendering and thermal reduction, enabling the direct production of dense, self-supporting reduced graphene oxide (rGO) electrode sheets without binders, conductive additives, or extensive purification. The resulting rGO electrodes exhibit a well-defined layered graphene architecture with high packing density. In a symmetric two-electrode configuration with 5 M KOH electrolyte, the electrode delivers a gravimetric specific capacitance of 119.4 ± 4.4 F g^‒1 and a volumetric specific capacitance of 84.0 ± 3.1 F cm^‒3 at 1 mA cm^‒2, with stable performance across varying currents and excellent reproducibility. This work provides a practical and cost-effective route for high-density graphene electrodes with competitive volumetric performance for compact energy storage applications.