Elucidating Oligomer-Surface and Oligomer-Oligomer Interactions at a Lithiated Silicon Surface. (1st December 2016)

• Record Type: Journal Article
• Authors: Soto, Fernando A.; Balbuena, Perla B.
• Is Part Of: Electrochimica acta. Volume 220(2016)
• Page Start: 312
• Page End: 321
• Publication Date: 2016-12-01
• Subjects: Density functional theory -- Ab initio molecular dynamics -- Solid electrolyte interphase -- Silicon anodes -- Li-ion batteries; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2016.10.082
• Languages: English
• ISSNs: 0013-4686

Abstract

Graphical abstract: Abstract: 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 Li13 Si4 (010) surface and a Li13 Si4 (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/nm 2 and once this coverage is reached, oligomer-oligomer interactions dominate the stabilization of the porous block. Regarding association, lithium ethylene dicarbonate (Li2 EDC) 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 (Li2 VDC)'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.