A Facile and Scalable Strategy for Fabrication of Superior Bifunctional Freestanding Air Electrodes for Flexible Zinc–Air Batteries

Abstract The large‐scale fabrication of efficient and inexpensive bifunctional catalysts is highly desirable but very challenging for oxygen reduction reaction and oxygen evolution reaction (ORR–OER) in metal–air batteries. Here, a facile and scalable approach for the fabrication of hierarchically porous air electrode consisting of cobalt nanoparticles embedded in bamboo‐like nitrogen‐rich carbon nanotubes (Co/N@CNTs), which are in situ grown onto the surface of carbon nanotube macrofilm (CNMF) through a catalytic growth of crosslinked carbon nanotubes is reported. The resulting hybrid macrofilm (Co/N@CNTs@CNMF) can be directly used as a freestanding air electrode without adding any binder or addivities. More importantly, when incorporated in a zinc–air battery (ZAB), the Co/N@CNTs@CNMF electrode demonstrates drastically enhanced ORR and OER activity while maintaining excellent durability during cycling. Further, when it is used to assemble an all‐solid‐state ZAB, the cell also displays excellent mechanical flexibility, implying promising perspectives as power sources for wearable electronics.