(718b) Modeling the Effect of Charged Lithium-Metal Anode on Electrolyte Decomposition

The increasing demand of high-performance energy storage devices for commercial applications has accelerated the search for the next generation of battery systems. One of the most promising candidates to replace the conventional lithium-ion battery, which is approaching its limits, is the Lithium-Sulfur (Li-S) technology, where the lithium-metal anode is an essential component of the cell. Although Li-metal is considered an ideal candidate for anode materials due to its low density, extremely high theoretical specific capacity (3860 mA h g^−1), and very low negative electrochemical potential (−3.04 V vs. SHE), several challenges have stopped Li-metal anodes from becoming feasible to be used in commercial batteries. These issues are mainly related to the continuous decomposition of the electrolyte as a result of contact with the Li surface. These reaction products play an important role in the formation of the solid-electrolyte interphase (SEI). Thus, a rigorous understanding of the electrolyte stability as well as the reaction mechanisms that can occur on it may help us elucidate improvements in performance of the Li-S system and provide some guidelines for enhanced materials to extend battery life. Recent studies have shown that nature and composition of the electrolyte may improve the battery performance. In addition, computational studies have revealed new insight on electrolyte decomposition at Li-metal anode. However, the effect of charged electrode has not been incorporated yet. In this work, we use density functional theory (DFT) and ab initio molecular dynamics (AIMD) methods in order to model and investigate the effect of charged electrode-electrolyte interface on electrolyte mixtures composed by 1, 2-dimethoxyethane (DME) and salt. Here, two different salts: LiFSI (Lithium bis(fluorosulfonyl)) and LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide) are studied at 1 M concentration. The dynamics, reaction pathways, structure of the products, and charge distribution are examined and characterized in detail. Finally, some insights on thermodynamics and kinetics of the reactions are presented.