Development of Redox mediators for high energy density and high efficiency lithium oxygen batteries Introduction Exploring a Novel Redox Mediator Inspired By Biological System Investigation on the Kinetic Property of Redox Addressing Shuttle Phenomena: Anchored Redox Mediator for Sustainable Redox Mediation Conclusion. This thesis addresses the introduction of redox mediator into lithium oxygen batteries to improve their electrochemical performance especially in terms of practical energy density and round trip efficiency. In chapter 1 basic electrochemistry regarding lithium oxygen batteries and redox mediators are introduced. In chapter 2 to 4 comprehensive researches including the discovery of a new redox mediator inspired by biological system the investigation on kinetic property of redox mediator and the prevention of shuttle phenomenon are introduced followed by chapter 5 summarizing the contents. This thesis is targeted to students and researchers interested in electrochemistry and energy storage systems.