A universal method to fabricating porous carbon for Li-O2 battery

The main bottleneck in the application of biomass-based carbon material in energy field is the development of an economical, nanoscale controllable and universal fabrication method. Herein, we demonstrate that a biomassderived carbon consisting of loose carbon nanosphere clusters could serve as an ideal cathode material for high performance Li-O-2 batteries. The carbon nanomaterial can be prepared from both biomass derivatives and crude biomass by a low cost, facile and nanoscale controllable method. The open slit-shaped hierarchical pore structure endows the electrode sufficient active surface sites and mass transport channels that are not easily asphyxiated by the discharge products. The concentration of oxygenic groups and structure defects on the surface of obtained carbon materials is very low, which minimizes the side reactions associated with carbon decomposition. The unique pore structure and surface properties of the carbon electrode give rise to a superhigh specific capacity of 20,300 mA h g(-1) and an extremely long cycle life which a cyclic capacity retention of 100% is maintained for 543 cycles with current density of 0.2 mA cm(-2) at controlled discharge-charge depths of 500 mA h g(-1).