Optimized hydrogel electrodes for supercapacitors from high-concentration aqueous graphene nanoplatelet dispersions

In the present work, high-concentration aqueous dispersions of graphene nanoplatelets, stabilized by small amounts of graphene oxide, are investigated as graphene hydrogel precursors. Experiments with varying graphene hydrogel synthesis parameters are performed to determine their influence on specific surface area and dynamic shear modulus. Correlations are generated which allow for the formulation of an "optimized" graphene hydrogel. The optimized hydrogels are characterized in terms of material and electrochemical properties. A volumetric capacitance of 14.4 F cm−3 at 1 A g−1 (23.8 F cm−3 at 1 mV s−1) is achieved when the optimized hydrogels are used as a supercapacitor electrode material. This is more than 360% higher than a conventional graphene hydrogel electrode made from aqueous graphene oxide dispersions alone. Therefore, we suggest that aqueous dispersions of graphene nanoplatelets provide a high-performing and binder-free electrode precursor that serves as a cost-effective and improved alternative to graphene oxide dispersions.