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Title: Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes

Natural abundance 17O and 6Li NMR experiments, quantum chemistry and molecular dynamics studies were employed to investigate the solvation structures of Li+ at various concentrations of LiFSI in DME electrolytes in an effort to solve this puzzle. It was found that the chemical shifts of both 17O and 6Li changed with the concentration of LiFSI, indicating the changes of solvation structures with concentration. For the quantum chemistry calculations, the coordinated cluster LiFSI(DME)2 forms at first, and its relative ratio increases with increasing LiFSI concentration to 1 M. Then the solvation structure LiFSI(DME) become the dominant component. As a result, the coordination of forming contact ion pairs between Li+ and FSI- ion increases, but the association between Li+ and DME molecule decreases. Furthermore, at LiFSI concentration of 4 M the solvation structures associated with Li+(FSI-)2(DME), Li+2(FSI-)(DME)4 and (LiFSI)2(DME)3 become the dominant components. For the molecular dynamics simulation, with increasing concentration, the association between DME and Li+ decreases, and the coordinated number of FSI- increases, which is in perfect accord with the DFT results. These results provide more insight on the fundamental mechanism on the very high CE of Li deposition in these electrolytes, especially at high current density conditions.
Authors:
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Publication Date:
OSTI Identifier:
1243217
Report Number(s):
PNNL-SA-113087
Journal ID: ISSN 0378-7753; 44591; KC0208010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Power Sources; Journal Volume: 307
Publisher:
Elsevier
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Electricity Delivery and Energy Reliability (OE); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
Natural abundance 17O and 6Li NMR; molecular modeling studies; electrolytes; lithium bis(fluorosulfonyl)imide; 1,2-dimethoxyethane; solvation structure.; Environmental Molecular Sciences Laboratory