The Effect of Lithium Iodide in Li-O2 Batteries

Tuesday, October 13, 2015
West Hall 1 (Phoenix Convention Center)
S. H. Lee (Department of Energy Engineering, Hanyang University), H. M. Kim (Hanyang University), D. Hirshberg (Bar-Ilan University), D. Sharon, H. J. Shin (Department of Energy Engineering, Hanyang University), D. Aurbach (Bar-Ilan University), and Y. K. Sun (Hanyang University)
Non aqueous Li-O2 battery would seem to be a most promising energy storage and conversion battery system. However, it has practical challenges such as solvent and electrode stability, pronounced overvoltage for oxygen evolution reactions, limited cycle life and poor rate capability. One of the strategies is the use of electrocatalysts. These were used to facilitate oxygen reduction, and the oxidation of the Li2O2 precipitate.1-2 One of the approaches suggested to the fast oxidation of Li2O2 is the use of redox mediators such as iodine. Redox mediators in electrolyte can easily be electrochemically oxidized and transfer electrons to Li2O2.  The latter step considerably reduces the high over-voltage required to oxidize solid Li2O2. One of the redox mediators recently studied in Li-O2 batteries was iodine.3 Iodine and its reduced forms I3- and I- are soluble in polar aprotic solvent. Considering that upon oxidation iodide forms iodine which oxidation, which in turn catalyzes the oxidation of Li-peroxide, the development of Li–oxygen cells with LiI as an additive would look quite promising.4 At very low concentrations of LiI, the iodine formed serves as a redox mediator for Li2O2 oxidation, oxygen is reduced to Li2O2. However, in high concentrations of LiI, the presence of the salt promotes a side reaction that forms LiOH as a major product.




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