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Effect of Fluoroethylene Carbonate Additive on the Initial Formation of Solid Electrolyte Interphase on Oxygen Functionalized Graphitic Anode in Lithium Ion Batteries

preprint
submitted on 24.10.2020, 23:54 and posted on 27.10.2020, 11:18 by Nadia Intan, Jim Pfaendtner
The formation of a solid electrolyte interphase (SEI) at the electrode/electrolyte interface substantially affects the stability and lifetime of lithium-ion batteries (LIBs). One of the methods to improve the lifetime of LIBs is by the inclusion of additive molecules to stabilize the SEI. To understand the effect of additive molecules on the initial stage of SEI formation, we compare the decomposition and oligomerization reactions of a fluoroethylene carbonate (FEC) additive on a range of oxygen functionalized graphitic anode to those of an ethylene carbonate (EC) organic electrolyte. A series of density functional theory (DFT) calculations augmented by ab-initio molecular dynamics (AIMD) simulations reveal that EC decomposition on an oxygen functionalized graphitic (1120) edge facet through an SN2 mechanism is spontaneous, even in an uncharged cell. Decomposition of EC through an SN2 reaction pathway results in alkoxide species regeneration which is responsible for continual oligomerization along the graphitic surface. In contrast, FEC prefers to decompose through an SN1 pathway, which does not promote alkoxide regeneration. The ability of FEC as an additive to suppress alkoxide regeneration results in a smaller and thinner SEI layer that is more flexible towards lithium intercalation during the charging/discharging process. In addition, the presence of different oxygen functional groups at the surface of graphite dictates the oligomerization products and LiF formation in the SEI.

Funding

Understanding Molecular Scale Chemical Transformations at Solid-Liquid Interfaces ¿ Computational Investigation of Interfacial Chemistry in Electrolytes and Charged Interfaces

Basic Energy Sciences

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History

Email Address of Submitting Author

jpfaendt@uw.edu

Institution

University of Washington

Country

United States

ORCID For Submitting Author

https://orcid.org/0000-0001-6727-2957

Declaration of Conflict of Interest

There are no conflicts to declare

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