Dense Graphene Monolith Oxygen Cathodes for Ultrahigh Volumetric Energy Densities

A convenient strategy is developed to prepare template-assisted, high density, porous graphene monolith (THPGM) cathodes with high densities for compact Li-O-2 batteries. Graphene oxide is used as the primary building block to construct condensed carbon electrodes by self-assembly followed by capillary drying. SiO2 nanoparticles are incorporated onto the dense graphene monolith to function as sacrificial pore former. The bimodal pores of diameters ranging 1-6 and similar to 40 nm created in the close-grained graphene monolith facilitate ion transport and oxygen diffusion, while providing sufficient space to accommodate the discharge products. The oxygen cathodes made from THPGM possess the advantageous features of high volumetric densities, a fully-developed porous structure and a robust architecture, resulting in unprecedented volumetric energy densities and excellent cyclic stability for Li-O-2 batteries.