Lithium Salt Effects on the Liquid Structure of Choline Chloride–Urea Deep Eutectic Solvent
2022
Di Pietro, Maria Enrica | Goloviznina, Kateryna | van den Bruinhorst, Adriaan | de Araujo Lima e Souza, Giselle | Costa Gomes, Margarida | Padua, Agilio A. H. | Mele, Andrea
Deep eutectic solvents (DESs) added with lithium salts are emerging as alternative electrolytes for lithium-ion batteries (LIBs). Yet, to design, optimize, and develop efficient DES-based electrolytes for LIBs, an in-depth understanding of the role played by the lithium cations in the intermolecular interactions between all species in the mixture is crucial. A joint approach of experimental NMR techniques and polarizable molecular dynamics (MD) simulations is used here to gather a comprehensive picture of the structure and dynamics of the prototypical system composed of the DES choline chloride:urea (ChCl:U, xCₕCₗ = 0.33) and the lithium salt containing the same anion, LiCl. Strong coordination of lithium cations by chloride anions, resulting in the formation of LiCl₃²– units, is revealed. Other species (especially, urea) are present in the second coordination shell of lithium, creating an extensive hydrogen-bond network. The effect of small quantities of water, typically absorbed by DES from air moisture, on the studied properties is discussed.
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