skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Abstract

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:
; ; ; ; ORCiD logo; ;
Publication Date:
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)
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
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

Citation Formats

Wan, Chuan, Hu, Mary Y., Borodin, Oleg, Qian, Jiangfeng, Qin, Zhaohai, Zhang, Ji-Guang, and Hu, Jian Zhi. Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes. United States: N. p., 2016. Web. doi:10.1016/j.jpowsour.2015.12.120.
Wan, Chuan, Hu, Mary Y., Borodin, Oleg, Qian, Jiangfeng, Qin, Zhaohai, Zhang, Ji-Guang, & Hu, Jian Zhi. Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes. United States. doi:10.1016/j.jpowsour.2015.12.120.
Wan, Chuan, Hu, Mary Y., Borodin, Oleg, Qian, Jiangfeng, Qin, Zhaohai, Zhang, Ji-Guang, and Hu, Jian Zhi. Tue . "Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes". United States. doi:10.1016/j.jpowsour.2015.12.120.
@article{osti_1243217,
title = {Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes},
author = {Wan, Chuan and Hu, Mary Y. and Borodin, Oleg and Qian, Jiangfeng and Qin, Zhaohai and Zhang, Ji-Guang and Hu, Jian Zhi},
abstractNote = {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.},
doi = {10.1016/j.jpowsour.2015.12.120},
journal = {Journal of Power Sources},
number = ,
volume = 307,
place = {United States},
year = {Tue Mar 01 00:00:00 EST 2016},
month = {Tue Mar 01 00:00:00 EST 2016}
}
  • Natural abundance 17O NMR measurements were conducted on electrolyte solutions consisting of Li[CF3SO2NSO2CF3] (LiTFSI) dissolved in the solvents of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and their mixtures at various concentrations. It was observed that 17O chemical shifts of solvent molecules change with the concentration of LiTFSI. The chemical shift displacements of carbonyl oxygen are evidently greater than those of ethereal oxygen, strongly indicating that Li+ ion is coordinated with carbonyl oxygen rather than ethereal oxygen. To understand the detailed molecular interaction, computational modeling of 17O chemical shifts was carried out on proposed solvation structures. Bymore » comparing the predicted chemical shifts with the experimental values, it is found that a Li+ ion is coordinated with four double bond oxygen atoms from EC, PC, EMC and TFSI- anion. In the case of excessive amount of solvents of EC, PC and EMC the Li+ coordinated solvent molecules are undergoing quick exchange with bulk solvent molecules, resulting in average 17O chemical shifts. Several kinds of solvation structures are identified, where the proportion of each structure in the liquid electrolytes investigated depends on the concentration of LiTFSI.« less
  • Electrolytes with the salt lithium bis(fluorosulfonyl)imide (LiFSI) have been evaluated relative to comparable electrolytes with other lithium salts. Acetonitrile (AN) has been used as a model electrolyte solvent. The information obtained from the thermal phase behavior, solvation/ionic association interactions, quantum chemical (QC) calculations and molecular dynamics (MD) simulations (with an APPLE&P many-body polarizable force field for the LiFSI salt) of the (AN)n-LiFSI mixtures provides detailed insight into the coordination interactions of the FSI- anions and the wide variability noted in the electrolyte transport property (i.e., viscosity and ionic conductivity).
  • Complexes of U(BH/sub 3/CH/sub 3/)/sub 4/ with CH/sub 3/OCH/sub 2/CH/sub 2/OCH/sub 3/, (CH/sub 3/)/sub 2/NCH/sub 2/CH/sub 2/N(CH/sub 3/)/sub 2/, and CH/sub 3/SCH/sub 2/CH/sub 2/SCH/sub 3/ have been synthesized and their molecular structures determined by single-crystal X-ray diffraction. U(BH/sub 3/CH/sub 3/)/sub 4/ x CH/sub 3/OCH/sub 2/CH/sub 2/OCH/sub 3/ is tetragonal, P4/n, with a = 21.822 (8) A, c = 7.681 (5) A, Z = 8, d = 1.61 g/cm/sup 3/, and R = 0.028 (F/sup 2/ > 3sigma(F/sup 2/)); U(BH/sub 3/CH/sub 3/)/sub 4/ x (CH/sub 3/)/sub 2/NCH/sub 2/CH/sub 2/N(CH/sub 3/)/sub 2/ is monoclinic, P2/sub 1//n, with a = 10.206 (4) A,more » b = 15.436 (6) A, c = 12.880 (5) A, ..beta.. = 92.25 (3)/sup 0/, Z = 4, d = 1.54 g/cm/sup 3/, and R = 0.029 (F/sup 2/ > 3sigma(F/sup 2/)); U(BH/sub 3/CH/sub 3/)/sub 4/ x CH/sub 3/SCH/sub 2/CH/sub 2/SCH/sub 3/ is triclinic, P anti 1, with a = 8.937 (4) A, b = 13.692 (4) A, c = 8.186 (3) A, ..cap alpha.. = 96.46 (4)/sup 0/, ..beta.. = 97.64 (4)/sup 0/, ..gamma.. = 74.07 (4)/sup 0/, Z = 2, d = 1.66 g/cm/sup 3/, and R = 0.023 (F/sup 2/ > 2sigma(F/sup 2/)). With one exception, all BH/sub 3/CH/sub 3/ groups are coordinated to the uranium atoms by tridentate hydrogen bridges with a U-B bond distance of 2.55 +/- 0.02 A. For the (CH/sub 3/)/sub 2/NCH/sub 2/CH/sub 2/N(CH/sub 3/)/sub 2/ complex one B atom is coordinated to the uranium atom through a bidentate hydrogen bridge with a U-B distance of 2.72 (2) A and a U-B-C angle of 142 (2)/sup 0/. Uranium is coordinated to the O, N, and S atoms of the respective ligands with U-O, U-N, and U-S average distances of 2.58 +/- 0.04, 2.73 +/- 0.01, and 3.07 +/- 0.04 A, respectively.« less