Here, we report our recent findings in exploration of new electrolytes and oxygen cathodes in order to develop Li-Air batteries with sustainable, high-energy density. We investigated the performance of Li-O2 batteries using various porous carbon materials, electrolytes based on both organic and ionic liquids, and additives such as redox mediators. Various carbon substrates (such as Super-P, CNT, graphene and Ketjen black, Figure 1) were used to construct a porous cathode structure. It appears that their electrochemical properties (relevant to Li-Air batteries) are different due to their dissimilar morphology and surface area. We also conducted experiments with various electrolytes including some additives (LiNO3, LiI, etc.) as shown in Figure 2. Ionic liquids are promising electrolytes owing to relatively high electrochemical and chemical stabilities, along with safety benefits and environmental friendliness. Recently, the use of redox mediators has been identified as a promising route for reducing the overpotentials of the charge process. Based on these studies, we also investigated the effects (nature and concentration) of solvents (ionic liquids, ethers, and their mixtures) and redox mediators in electrolytes on the charging potential and reversibility of oxygen cathodes. Furthermore, we have used different porous carbon fiber papers as both a current collector and gas diffusion media. It appears that the physical oxygen diffusion property is closely linked to the capacity and cycling performance of Li-Air batteries due to the different sizes and connectivity of pores in different gas diffusion media. Electrochemical characterization techniques were combined with microanalysis (SEM, XRD) to optimize the electrode structures and performance. It is hoped that this study will provide some useful insights to the design criteria for high-performance Li-Air batteries. 
