Traditionally the pathways and products of electrolyte decomposition processes were analyzed with the basic presumption of pristine Li-metal surface for simplicity. The challenge is to predict the chemical, structural and topographical heterogeneity of SEI layer arising from multitude of interfacial constituents. However, the extreme reactivity of Li-metal with the electrolyte leads to solid electrolyte interphase (SEI) layer which often impedes the Li + transport across the interface. Lithium metal is an ideal anode for rechargeable lithium battery technology. In addition, we find that the presence of different oxygen functional groups at the surface of graphite dictates the oligomerization products and the LiF formation mechanism in the SEI. Including FEC as an additive is thus able to suppress alkoxide regeneration and results in a smaller and thinner SEI layer that is more flexible toward lithium intercalation during the charging/discharging process. In contrast, FEC prefers to decompose through an S1 pathway, which does not promote alkoxide regeneration. However, decomposition of EC through a nucleophilic attack on a carbonyl carbon (C C) site (S1 mechanism) results in alkoxide species regeneration that is responsible for continual oligomerization along the graphitic surface. Texas A & M Engineering Experiment Station Sponsoring Org.: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V) OSTI Identifier: 1430652 Grant/Contract Number: EE0007766 Resource Type: Accepted Manuscript Journal Name: Journal of the Electrochemical Society Additional Journal Information: Journal Volume: 164 Journal Issue: 11 Journal ID: ISSN 0013-4651 Publisher: The Electrochemical Society Country of Publication: United States Language: English Subject: 25 ENERGY STORAGE 36 MATERIALS SCIENCE diffusion LAMMPS Li-ion Battery molecular dynamics nanotechnology = 0$$) edge facet through a nucleophilic attack on an ethylene carbon site (C E) of an EC molecule (S2 mechanism) is spontaneous during the initial charging process of LIBs. Publication Date: Wed May 17 00:00: Research Org.: Texas A & M Univ., College Station, TX (United States). Department of Chemical Engineering, Department of Electrical and Computer Engineering, and Department of Materials Science and Engineering Texas A & M Univ., College Station, TX (United States).Department of Chemical Engineering and Department of Electrical and Computer Engineering Moreover, we also evaluated the effect of applied electric fields in the diffusion of Li-ions at room temperature. We observed that the predominant mechanisms of Li-ion diffusion included vacancy assisted and knock-off diffusion in LiF, direct exchange in Li 2O, and vacancy and knock-off in Li 2CO 3. We find a slight increase in the diffusivity as the temperature increases and since diffusion is noticeable at high temperatures, Li-ion diffusion in the range of 130 to 1800 K was also studied and the diffusion mechanisms involved in each SEI compound were analyzed.

We studied the lithium ion diffusivity in the main components of the SEI found in LIB with silicon anodes and performed classical molecular dynamics (MD) simulations on lithium fluoride (LiF), lithium oxide (Li 2O) and lithium carbonate (Li 2CO 3) in order to provide insights and to calculate the diffusion coefficients of Li-ions at temperatures in the range of 250 K to 400 K, which is within the LIB operating temperature range. Understanding the transport properties of the solid electrolyte interface (SEI) is a critical piece in the development of lithium ion batteries (LIB) with better performance.

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