Lithium Halides As Redox Mediators in Lithium Oxygen Battery

Abstract

In case of soluble electrolyte catalysts for Li-O2 batteries as a redox mediator, they were utilized to facilitate the exchange of electron and lithium ion, which can help formation and decomposition of discharge product. Although further researches are needed for finding proper catalysts, there is a promising approach fortunately, using lithium halides as a redox mediator in Li-O2 batteries. Related researches have been progressed vigorously. Previous paper reported in our group demonstrated the reaction mechanism and effect of the lithium iodide (LiI) in Li-O2 battery.1 Lim et al. exhibited the superior performance of Li-O2 battery using LiI additive.2 Recently, Liu et al. developed this concept and exhibited Li-O2 battery having better performance with LiOH as a discharge product by adapting more advanced electrodes.3 However, further research with LiI is necessary for clear comprehension because there is no accurate elucidation on the reaction mechanism which can be activated gradationally in Li-O2 battery system yet. Therefore, here in, we has progressed comparing and contrasting researches using LiI and lithium bromide (LiBr) for clearly understanding the role of lithium halide materials in Li-O2 battery system. As a redox mediator, LiBr catalyzes the reversible formation and decomposition of lithium peroxide (Li2O2), but hygroscopic LiI generated the side reaction making lithium hydroxide (LiOH) as a byproduct. Especially, when Li-O2 batteries are operated with LiBr and LiI until enough amount of capacities for practical using, LiOH made by LiI included electrolyte couldn’t be reversible compared to Li2O2 made by LiBr included electrolyte. Therefore, in our research, LiBr is much reliable redox mediator to operate the Li-O2 battery system. References Kwak, W.-J. et al. J. Mater. Chem. A 3, 8855–8864 (2015).Lim, H. et al. Angew. Chem. Int. Ed. Engl. 53, 3926–31 (2014)T. Liu. et al. Science, 350, 6260, 530-533 (2015).