jp6b10774_si_001.pdf (3.09 MB)
Effects of High and Low Salt Concentration in Electrolytes at Lithium–Metal Anode Surfaces
journal contribution
posted on 2016-12-16, 00:00 authored by Luis E. Camacho-Forero, Taylor W. Smith, Perla B. BalbuenaThe
use of high-concentration salts in electrolyte solutions of
lithium–sulfur (Li–S) batteries has been shown to be
beneficial for mitigating some effects such as polysulfide shuttle
and dendrite growth at the Li metal anode. Such complex solutions
have structural-, dynamical-, and reactivity-associated issues that
need to be analyzed for a better understanding of the reasons behind
such beneficial effects. A passivation interfacial layer known as
solid–electrolyte interphase (SEI) is generated during battery
cycling as a result of electron transfer from the metal anode causing
electrolyte decomposition. Here, using density functional theory and
ab initio molecular dynamics simulations, we investigate the salt
decomposition, solvation effects, interactions among intermediate
products and other species, and potential components of the SEI layer
as a function of chemical nature and concentration of the salt for
lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide
(LiFSI) at 1 and 4 M concentrations in dimethoxyethane. It is found
that LiTFSI undergoes a less complete reduction and facilitates charge
transfer from the anode, whereas LiFSI shows a more complete decomposition
forming LiF as one of the main SEI products. In addition, the specific
decomposition mechanisms of each salt clearly point to the initial
SEI components and the potential main products derived from them.
Very complex networks are found among the salt and solvent molecules
in their attempt to maximize Li ion solvation that is quantified through
the determination of coordination numbers.
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Keywords
LiFSIchemical naturecharge transferpolysulfide shuttlemetal anodeSEI layerbielectrolyte solutionselectron transferLi ion solvation4 M concentrationshigh-concentration saltsbattery cyclingelectrolyte decompositionSEI componentsSEI productsreactivity-associated issuesLi metal anodecoordination numberssalt decompositiondecomposition mechanismsLiTFSIdendrite growthLow Salt Concentrationlithiumab initiodynamics simulationssolvation effects
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