Surface-crumpled graphene hydrogels with macro- and microporous structures for ultrahigh-volumetric energy storage

Abstract

Recent research has focused on three-dimensional graphene hydrogels with macroporous structure effectively applied for power supply. Here we report a novel surface-crumpled reduced graphene oxide hydrogel with hierarchical pores, through adjusting the temperature and time of hydrothermal reaction with the addition of 2-butanol molecules. Large amounts of micropores in the interior of the macroporous hydrogel skeleton, are attributed to the crispation on the edge of graphene sheets, forming the uniform tubes with the inner diameter of 1.74 nm confirmed by transmission electron microscopy. The pressed hydrogel electrode can provide an outstanding specific capacitance of 549 F cm-3 at 1.14 A cm−3 and high rate capability of 62.2% from 1.14 A cm−3 to 114 A cm−3. The assembled symmetric device can deliver a volumetric specific capacitance of 517 F cm-3 at 1.14 A cm−3, energy density of 71.9 Wh L−1 at 0.57 kW L−1, excellent cycling stability (98.6%) and coulomb efficiency (97.3%). The achievement of such remarkable performances can open up an exciting route to the hierarchically porous structure of graphene-based networks for highly efficient capacitive energy storage.