Transport properties of alkali/alkaline earth cations in ionic-liquid based electrolytes

NMR investigation of multi-scale dynamics in ionic liquids containing Li+ and La3+: from vehicular to hopping transport mechanism

“…The decrease of both cholinium and TFSI D/D 0 upon salt addition is notably stronger with La 3+ than those with Li + . This is consistent with the stronger increase of viscosity upon adding multivalent cation than adding monovalent cation [4,10]. As expected, the TFSI diffusion is more affected than cholinium one (note that it was not possible to measure the self-diffusion coefficient of lanthanum by PFG NMR).…”

“…Such decrease when adding lithium salt in ionic liquids has been observed, along with an increase of the viscosity, for all the studied systems: imidazolium type with LiTFSI [3,4,[44][45][46][47], LiBF 4 [48][49][50] or LiPF 6 [44], pyrrolidinium kind with LiTFSI [51][52][53] or LiPF 6 , ammonium kind [54,55], and other less common ionic liquids [46]. The density of the liquid also often increases upon lithium salt addition.…”

“…In this regard, the effect of anion on transport in lithium/ionic liquids system has been more often investigated. The very symmetric BF 4 anion yields a very slow diffusion of Li + , despite D BF 4 remains close to the diffusion value of the ionic liquid cation [48][49][50], whereas for TFSI, the diffusion of lithium remains close to other ionic species [3,4,[44][45][46]. From this comparison emerges the picture of a strong solvation of lithium by the very symmetric BF 4 and a loose solvation by TFSI anion.…”

“…Both the structural and dynamical properties are modified upon the addition of a supplementary species. For instance, in the frequently studied IL, 1-butyl-3-methylimidazolium (C 4 mim) bis(trifluoromethanesulfonyl)imide (TFSI), the addition of water yields an increase of the diffusion and the systems tends to separate the molecular species much before the demixing concentration [2]; on the contrary, the addition of lithium cation induces a great decrease of the diffusion [3][4][5], that is due to the strong interaction of lithium with the TFSI anion [3,6]. In this paper, we have focused on this question from the dynamical point of view, and in the case where the supplementary species are monoatomic cations.…”

“…Surprisingly, there are very few studies on mixtures of ionic liquids and other monoatomic cation than lithium. The studies dealing with other cation mostly concerns other monovalent cation, in the aim of evaluating their interest for battery [4,10,11].…”