Three-Dimensional Graphene Sponge with Hierarchically Porous Structure for Electrochemical Supercapacitors

Abstract

Supercapacitors is an electrochemical energy storage device typically used as sustainable power supply (such as electric vehicles and mobile electronic devices) due to their higher power density than batteries, higher energy density than conventional dielectric capacitors, and long life cycles. [1,2] Graphene, a two-dimensional (2D) one-atom-thick single layer of sp2-bonded carbon, is considered as an ideal electrode material in supercapacitors because of its superior electrical conductivity and exceptionally large specific surface area. Graphene sheets, unless well separated from each other, tend to form irreversible agglomerates through strong π-π stacking and van der Waals interaction.[3] Meanwhile, the electrochemical binders and additives are normally required to make graphene-based electrodes, which would have an adverse effect on the specific capacitance of the resulting electrodes. To tackle these challenges, three dimensional (3D) graphene networks with highly electrical conductivity and large specific surface area, short diffusion pathways for electrolyte ions and fast transport channels for electrons are very promising supercapacitor materials. To these aims, we have developed ways to synthesize a novel macroporous/nanoporous graphene sponge with tunable pore sizes. This 3D porous graphene sponge has i) an interconnected electrolyte-filled macroporous network that enables increase of contact surface between 3D network and electrolytic solution, and rapid ion transport, ii) short ion and electron transport lengths due to nanoporous structures, iii) a large electrode specific surface area and (iv) high electron conductivity in the electrode assembly. The structure characterization and capacitive properties of the 3D macroporous/nanoporous graphene sponge was investigated and discussed, indicating 3D porous graphene sponge as an ideal electrode materials for supercapacitors. Keywords：Graphene, 3D porous materials, supercapacitors, electrochemical energy