Ionic liquids (ILs), a class of compounds composed entirely of ions, are prominent candidates for battery electrolytes, as they allow for increased safety due to their negligible vapor pressure, non-flammability and high thermal and electrochemical stability. Another benefit of ILs is their tunable properties, including solvating power, polarity and surface tension. Those could be used to influence the SEI formation as well as modify the overpotential on the electrodes. This effect can be used in different metal-air batteries, where the use of IL-based electrolyte allows for high electrolyte stability combined with the use of a normal gas diffusion electrode. [1] Further advantages that ILs bring, especially in the context of lithium sulphur batteries are their ability to reduce the formation of soluble polysulfides and to reduce dendrite formation. [2] This feature can be also beneficial for other types of lithium metal batteries.

The major problem of using ILs as electrolytes - their high viscosity - can be overcome by using mixtures of selected ILs in specific ratios, thus reducing viscosity and increasing performance of the electrolyte. [3] In connection with that, our latest developments on use of ILs as electrolytes for different types of batteries will be presented. We will focus on physicochemical properties of selected ILs, their mixtures and possible additives, designed for specific batteries applications. The compatibility of the particular ILs with battery materials will be also discussed.

References:

[1] Liu, G. Pulletikurthi , A. Lahiri , T. Cui, F. Endres, Dalton Trans., 2016, 45, 8089.

[2] W. Park, K.Ueno, N. Tachikawa, K. Dokko, M. Watanabe, J. Phys. Chem. C. 117 , 20531–20541.

[3] A. Taige, D. Hilbert, T. J. S. Schubert Z. Phys. Chem. 226, 129.