Unraveling the Lithium Hydroxide Formation Reaction Mechanism in Lithium-O2 Batteries: A Theoretical Study

Abstract

It is important to identify the electronic factors that might enhance or hinder the formation of discharge/charge products or parasitic species within the complex electrolytic media of a lithium air battery. Although some reaction mechanisms have been proposed, the underlying reaction process by which LiOH formation occurs in the presence of LiI and water is not well understood. Similarly, the chemical decomposition reaction of LiOH, which leads toward molecular oxygen evolution still remains unknown. Herein is presented a theoretical study of the chemical reactions that may take place in the electrolytic media of a Li/O2 battery with dimethoxyethane (DME) solvent in the presence of water and the additive LiI. The results show that water is the most energetically accessible source of protons to obtain LiOH. The catalytic effect of iodide in the O-O peroxide bond scission could be ascribed to a halogen-bond interaction between the iodine atom and an oxygen nucleophilic site. The reaction pathway involving hydrogen peroxide was found to be a viable route accounting for the lithium hydroxide decomposition. Finally, the results for Li2O2 reactive species and a (Li2O2)4 cluster model were both compared.