The Influence of Oxygen Dissolved in the Liquid Electrolyte on Lithium Metal Anodes

Abstract

Due to the need for high energy density storage, Li–O2 batteries and Li metal anodes (LMA) are in the focus of research. As safe operation of the LMA is yet not possible, more knowledge about factors influencing the stability of the solid electrolyte interphase (SEI) is necessary to utilize the LMA. Especially concerning the influence of O2 dissolved in the electrolyte, there are still many unanswered questions, and there are conflicting opinions reported. In this work, plating/stripping experiments are used to show that the Coulomb efficiency is increased by dissolving O2 in the electrolyte. SEM and XPS analysis of the SEI shows that reaction of the conducting salt with Li metal is the cause of the poor reversibility of the LMA in cells without O2. The improved stability in the presence of O2 can be attributed to a protective Li2O and Li2CO3 rich SEI that prevents degradation. In addition, the SEI on freshly deposited Li is compared to that on a commercial Li foil. The reactivity of the native passivation layer formed on the Li foil during storage differs significantly from that of plated Li regarding the influence of O2, which can explain the different results and conclusions in literature.