Solid Electrolyte Interphase Formation at the Ionic Liquid Electrolyte—Lithium-Metal Interface Using an Ab Initio Molecular Dynamics Approach

<p>An interfacial study is performed using ab initio molecular dynamics (AIMD) simulations to elucidate the electrochemical interfacial stability of an ionic liquid (IL) as component of an electrolyte in contact with a Li-metal anode when an additive, vinylene carbonate (VC), is added to the electrolyte. The IL electrolyte is composed of 1-butyl-1-methylpyrrolidinium bis(fluoro-sulfonyl)-imide (PYR14⁺FSI⁻) with lithium bis(trifluoromethane-sulfonyl)imide salt (Li⁺TFSI⁻) in a 8:2 concentration ratio. Reactions observed at the interface electrolyte/Li-metal during the AIMD simulations are verified by electronic structure calculations using density functional theory calculations considering a continuum solvent model. We found that the addition of VC to the IL prevents further reduction of the counter-ion TFSI⁻and retards reduction of FSI⁻in comparison to the case when the additive VC is absent. The PYR14⁺reduction is never observed with or without the additive. The 1st, 2nd, and 3rd electron affinities of the PYR14⁺are −0.08, −0.36 and −3.65 eV, indicating little to large repulsive behavior against electrons. The opposite is observed for the two negative ions, FSI⁻and TFSI⁻, which yield 1st electron affinities of 1.73 and 1.83 eV, respectively. Reactions obtained under open circuit conditions. Dissociation mechanisms are presented for all IL components reduced at the IL/Li-metal interface.</p>. Authors: Galvez-Aranda, Diego; Seminario, Jorge (ORCID:0000000153979281). DOE Contract: AC05-76RL01830; AC02-06CH11357. Subjects: Electrochemistry; Materials Science