graphene foam is an emerging material for energy storage applications, owing to its high conductivity and hierarchical structure that facilitate efficient ion and electron transport. It is also light, flexible, and mechanically strong compared to the Ni electrode commonly used in Lithium-Ion batteries.
The unique properties of 3D graphene have allowed its integration into anode and cathode materials in energy storage devices. The 3D graphene scaffold provides the flexibility to support electro-active metals, oxides, sulfides, and semiconductors in various dimensions and morphologies. Moreover, 3D graphene is suitable to function as current collector due to its reversible capacity and excellent rate capability, without the need for binder and conducting agent.
As a result, several research groups have developed hybrids of 3D graphene with different transition metals, sulfides, and semiconductors for use in batteries. The 3D graphene architecture ensures good ion and electron transport within the battery electrode, resulting in a high volumetric and surface electric double layer capacitance.
An asymmetric supercapacitor with mesoporous flower-like NiCo2O4 and crosslinked MnO2 on GF prepared by CVD was demonstrated by Zang and collaborators . The composites have a high specific gravimetric capacity of 2577 Fg-1 to 1 Ag-1, and retain a reversible capacity of 975.4 mAhg-1 after 150 cycles at 200 mAg-1.
Soft-templated metallic templates (SMMTs) such as copper, nickel, and iron were used to grow macroporous GFs with a controlled pore size. By tuning the metal salt concentration, a controlled pore size of the monoliths was obtained with a pore diameter an order of magnitude smaller than commercial nickel foam. After evaporation of the metal template, free-standing GFs with high pore density and excellent mechanical properties were obtained without collapsing.