Coordination and interactions in a Li-salt doped ionic liquid
Journal article, 2015

We report on the coordination and interactions in the LiTFSI doped ionic liquid PyR14TFSI over a large concentration range, 0.01 <= x <= 0.4, using Raman spectroscopy. We find that the concentration dependence of the average number of TFSI anions coordinating to one Li-ion (N-TFSI/Li) can be divided into three regimes. For low concentrations, x <= 0.05, we find that a large number TFSI anions coordinate each Li-ion, N > 2. The number decreases with increasing salt concentration and the interaction between the Li-ion and the TFSI anions is rather weak in this concentration range. At intermediate concentrations, 0.1 <= x <= 0.2, the number of TFSI anions coordinating each Li-ion (N-TFSI/Li) is similar to 2 pointing towards the formation of [Li(TFSI)(2)](-) ionic clusters. At higher concentrations, x> 0.2, N-TFSI/Li decreases further indicating the transition to more complex structures with Li-ions bridging TFSI anions. We also show that the evolution of the microscopic structure as a function of Li-salt concentration is mirrored in the behaviour of macroscopic properties such as the ionic conductivity and the glass transition temperature, which also show a crossover in the same concentration range.

Li-ion coordination

Raman spectroscopy

Ionic liquid

Author

Jagath Pitawala

Chalmers, Applied Physics, Condensed Matter Physics

Anna Martinelli

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Applied Surface Chemistry

Patrik Johansson

Chalmers, Applied Physics, Condensed Matter Physics

Per Jacobsson

Chalmers, Applied Physics, Condensed Matter Physics

Aleksandar Matic

Chalmers, Applied Physics, Condensed Matter Physics

Journal of Non-Crystalline Solids

0022-3093 (ISSN)

Vol. 407 318-323

Areas of Advance

Energy

Materials Science

Subject Categories

Materials Chemistry

DOI

10.1016/j.jnoncrysol.2014.08.043

More information

Created

10/8/2017