463413 Effect of Salt Concentration on the Reactivity and Dynamics of the Electrolyte at the Li Anode of Lithium/Sulfur Batteries

Wednesday, November 16, 2016: 3:55 PM
Mason (Hilton San Francisco Union Square)
Luis E. Camacho-Forero, Taylor Smith and Perla B. Balbuena, Chemical Engineering, Texas A&M University, College Station, TX

Due to the increasing number of commercial applications that require high performance energy storage devices such as electrical vehicles, the need for improvements in conventional lithium-ion batteries is arising very quickly. In the screening of alternative chemistries, the Lithium/Sulfur (Li/S) technology appears as one of the most promising candidates due to its high energy density, and reduced cost compared to traditional Li-ion systems. However, a number of technical challenges have prevented Li/S technology from becoming feasible for commercialization. One of them is the need for an electrolyte that exhibits stability even near the lithium-metal anode, and, in the case of decomposition, the formation of a solid-electrolyte interface (SEI) with beneficial properties for the cell is desired. Recent studies have shown that the nature and composition of the salt in the electrolyte may improve the battery performance. Therefore, a comprehensive understanding of the electrolyte stability far and near the Li-anode as well as the reaction mechanisms that can take place may help us to elucidate the improvements in performance of such system and provide some guidelines for enhanced electrolytes. In this work, we use density functional theory (DFT) and ab initio molecular dynamics (AIMD) methods in order to investigate the effect of salt concentration 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 both high (4M) and low (1M) concentrations near and relatively far from the anode. The reaction pathways, structure of fragments, distribution of charge, and structure of the SEI are examined and characterized in detail. Finally, some insights on the formation of an electrolyte coordinated network due to high salt concentration are provided.

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