Elucidating Oligomer-Surface and Oligomer-Oligomer Interactions at a Lithiated Silicon Surface

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• 作者：Fernando A. Soto^a ; Perla B. Balbuena^a ; ^b ; ^{balbuena@tamu.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Density functional theory ; Ab initio molecular dynamics ; Solid electrolyte interphase ; Silicon anodes ; Li-ion batteries
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：1 December 2016
• 年：2016
• 卷：220
• 期：Complete
• 页码：312-321
• 全文大小：2874 K

文摘

Solid-electrolyte interphase (SEI) layers are multicomponent films formed at the surface of electrodes in Li-ion batteries due to electrochemical instability of the electrolyte components. The properties of this film significantly affect the lifetime of the battery. Here we study the interaction of some electrolyte reduction products (oligomers) with a bare Li₁₃Si₄ (010) surface and a Li₁₃Si₄ (010) surface partially covered with lithium fluoride (LiF) using classical Monte Carlo and density functional theory-based methods The adsorption, charge transfer, and association of oligomers on the surface are reported. Overall, the oligomers attach firmly to the surface. Our findings indicate that the surface-oligomer interaction dominates the stabilization of the system up to a coverage of approximately 1 oligomer/nm² and once this coverage is reached, oligomer-oligomer interactions dominate the stabilization of the porous block. Regarding association, lithium ethylene dicarbonate (Li₂EDC) tends to associate with the bare and partially covered surface through O.Li.O bridges. However, the association mechanism varies depending on the existing nucleating products at the surface. In contrast, lithium vinylene dicarbonate (Li₂VDC)’s backbone is closer to the surface and exhibits a more flexible structure than the Li2EDC oligomer. This difference may further affect the compactness of the SEI layer. Aligned with our previous studies, we also found oligomer decomposition on the surface. Our calculations offer critical information regarding the structure of electrolyte decomposition products over silicon electrodes.