Hierarchical architecture: A novel, facile and cost-efficient strategy to boost electrochemical performance of Li-O-2 battery cathodes

The sluggish performance of cathodes, which is eagerly awaiting optimal design, is a major impediment to the practical implementation of lithium-oxygen batteries (LOBs). We present the meticulous design and synthesis of hierarchical porous graphene foam (HPGF) cathodes with various pore size architectures. A novel and facile method was proposed to prepare highly porous Ni foam from which graphene foam with a surface area increase of more than ten times was derived. To enable the transportation of Li+ and O2 species through graphene sheet thickness, Ni(NO3)2 was used as an ignition source to generate adjustable holes in graphene layers, resulting in a tri-continuous passage of electrons, ions, and oxygen. As a result, superior electrochemical performances such as high capacity, good rate capability, and cycling stability (5 percent degradation in 2500 h) were achieved. A pouch-type battery demonstrated good flexibility and a broad application perspective by operating directly in ambient air.