Ball-flower-like carbon microspheres via a three-dimensional replication strategy as a high-capacity cathode in lithium-oxygen batteries

The robust porous architectures of active materials are highly desired for oxygen electrodes in lithium-oxygen batteries to enable high capacities and excellent reversibility. Herein, we report a novel three-dimensional replication strategy to fabricate three-dimensional architecture of porous carbon for oxygen electrodes in lithium-oxygen batteries. As a demonstration, ball-flower-like carbon microspheres assembled with tortuous hollow carbon nanosheets are successfully prepared by completely replicating the morphology of the nanostructured zinc oxide template and utilizing the polydopamine coating layer as the carbon source. When used as the active material for oxygen electrodes, the three-dimensional porous architecture of the prepared ball-flower-like carbon microspheres can accommodate the discharge product lithium peroxide and simultaneously maintain the ions and gas diffusion paths. Moreover, their high degrees of defectiveness by nitrogen doping provide sufficient active sites for oxygen reduction/evolution reaction. Thus the prepared ball-flower-like carbon microspheres demonstrate a high capacity of 9,163.7 mA h g(-1) and excellent reversibility. This work presents an effective way to prepare three-dimensional architectures of porous carbon by replicating the controllable nanostructures of transition metal oxide templates for energy storage and conversion applications.