Snapshots of the Hydrolysis of Lithium 4,5-Dicyanoimidazolate-Glyme Solvates. Impact of Water Molecules on Aggregation Processes in Lithium-Ion Battery Electrolytes

Maciej Dranka , Piotr Jankowski , Grażyna Żukowska

Abstract

Despite that 4,5-dicyano-2-(trifluoromethyl)imidazole lithium salt (LiTDI) exhibits several interesting features in aprotic solvents such as glymes or carbonate esters, little is known about its structural rearrangement after exposure to water. Since the LiTDI salt has been verified as an effective moisture scavenger able to suppress degradation of the LiPF6-based electrolyte, comprehensive knowledge of coordination modes in the LiTDI–H2O system, as well as information about the structure of formed hydrates, is desirable. In the present study, we report the impact of water on the LiTDI glyme-based electrolytes investigated by means of the single-crystal X-ray diffraction technique and Raman spectroscopy. We have found that the exposure of lithium 4,5-dicyanoimidazolate–glyme solvates to humid air gives rise to the hydrolysis products arising from stepwise addition of water molecules to the lithium coordination sphere. Several structural motifs have been distinguished as preferred coordination modes in the LiTDI–H2O system. A high number of available ether oxygen donor center water molecules cause dissociation of ionic contact pairs and aggregation of cationic species stabilized by crown ethers. Low O:Li molar ratio leads to the formation of LiTDI–glyme–water solvates and LiTDI hydrates. The air-stable LiTDI trihydrate comprises ionic pairs formed by a lithium cation coordinated to an imidazole nitrogen of TDI. A lithium cation coordinated via nitrile groups and bearing water molecules is a basic motif constituting dimeric species of formula [Li(H2O)2TDI]2 which are present in aggregated [Li(H2O)TDI]n chains making up the structure of a monohydrate. The discovered motifs have been proved to occur in both the solid and melted hydrated systems of LiTDI. They will be helpful for conducting molecular dynamic calculations and for obtaining information how to manipulate the structure of a Li+-solvation sheath in both hydrated and liquid aqueous electrolytes based on heterocyclic anions.
Publication typeOriginal work published as abstract
Author Maciej Dranka (FC / CICSST)
Maciej Dranka,,
- Chair Of Inorganic Chemistry And Solid State Technology
, Piotr Jankowski (FC / CICSST)
Piotr Jankowski,,
- Chair Of Inorganic Chemistry And Solid State Technology
, Grażyna Żukowska (FC / CICSST)
Grażyna Żukowska,,
- Chair Of Inorganic Chemistry And Solid State Technology
Journal seriesThe Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter, ISSN 1932-7447, (A 35 pkt)
Issue year2018
Vol122
No6
Pages3201-3210
Publication size in sheets0.5
DOIDOI:10.1021/acs.jpcc.7b11145
URL https://pubs.acs.org/doi/10.1021/acs.jpcc.7b11145
Languageen angielski
File
wdpb_publikacje_pliki_plik_publikacja_3426_org.pdf 3.21 MB
Score (nominal)35
ScoreMinisterial score = 35.0, 10-08-2018, ArticleFromJournal
Ministerial score (2013-2016) = 35.0, 10-08-2018, ArticleFromJournal
Publication indicators WoS Impact Factor: 2016 = 4.536 (2) - 2016=4.796 (5)
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