The cell performance of lithium oxygen batteries using nitrogen doped graphene as a catalytic cathode has been validated in recent research, but the cathode reaction mechanism of lithium and oxygen still remains unclear. Since the oxygen reduction reaction (ORR) mechanism by ionic lithium and catalytic surface is predicted to be distinct for different defective sites such as graphitic, pyridinic, and pyrrolic, it is necessary to observe the behavior of ionic lithium and oxygen gas at each defective site in nitrogen doped graphene. In this study, density functional theory (DFT) calculations are adopted to analyze at an atomic scale how effectively each defective site acts as a catalytic cathode. Interestingly, unlike pyridinic or pyrrolic N is known to be the most effective catalytic site for ORR in fuel cells. Among the other defective sites, it is found that the graphitic N site is the most effective catalytic media activating ORR by ionic lithium in lithium-oxygen batteries due to the electron accepting the reaction of Li-O formation by the graphitic N site. (C) 2014 Elsevier B.V. All rights reserved.