Dense graphene monolith oxygen cathodes for ultrahigh volumetric energy densities

The dense yet porous graphene-based material is fabricated via three-dimensional densification of graphene hydrogel and using a sacrificial pore former (SiO2) on the dense graphene monolith. The bimodal pores with diameters ranging 1-6 nm and 40 nm created in the graphene-based monolith facilitate ion transport and oxygen diffusion, while providing sufficient space to accommodate the discharge products. Benefiting from a developed pore structure and robust microstructure, it delivers an unprecedented volumetric energy density with excellent long-term stability for Li-O2 batteries.215