Sebastian Jeremias

A Combined Theoretical and Experimental Study of the Influence of Different Anion Ratios on Lithium Ion Dynamics in Ionic Liquids

In this paper, we investigate via experimental and simulation techniques the transport properties, in terms of total ionic conductivity and ion diffusion coefficients, of ionic liquids doped with lithium salts. They are composed of two anions, bis(fluorosulfonyl)imide (FSI) and bis(trifluoromethanesulfonyl)imide (TFSI), and two cations, N-ethyl-N-methylimidazolium (emim) and lithium ions. The comparison of the experimental results with the simulations shows very good agreement over a wide temperature range and a broad range of compositions. The addition of TFSI gives rise to the formation of lithium dimers (Li(+)-TFSI(-)-Li(+)). A closer analysis of such dimers shows that involved lithium ions move nearly as fast as single lithium ions, although they have a different coordination and much slower TFSI exchange rates.

A joint theoretical/experimental study of the structure, dynamics, and Li+ transport in bis([tri]fluoro[methane]sulfonyl)imide [T]FSI-based ionic liquids.

The structure and dynamics of N-butyl-N-methyl pyrrolidinium(+) bis([tri]fluoro[methane]sulfonyl)imide(-) (PYR14(+)-[T]FSI(-)) ionic liquids doped with Li(T)FSI are investigated by combining experimental measurements to molecular dynamics simulations. The polarizable force field calculations indicate that the lithium cations are coordinated by (T)FSI anion oxygens forming lithium adducts stabilized over a large temperature range by strong Li-O bonds. Lithium aggregation is found to be negligible at the doping level considered here (10% mole fraction), and Li(+) diffusion occurs primarily by exchanging the (T)FSI anions in their first coordination shell. The resulting calculated transport properties are in good agreement with the corresponding nuclear magnetic resonance data.

Polymerizable ionic liquid with state of the art transport properties.

The physicochemical properties of diallyldimethylammonium-bis(trifluoromethanesulfonyl)imide (DADMATFSI) and its binary mixture with LiTFSI are presented herein, also showing this novel compound as a polymerizable room temperature ionic liquid with excellent transport properties for Li(+) ions. In particular, results of pulsed field gradient (PFG)-NMR diffusion experiments and impedance measurements show that DADMATFSI exhibits state of the art properties of ionic liquids. Similar ionic diffusion coefficients and a similarly high conductivity as seen in the benchmark compound N-butyl-N-methylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (PYR14TFSI) are observed. In accordance, the Li transference number in the binary mixture matches the trend seen for PYR14TFSI-LiTFSI mixtures. In addition to these impressive properties as ionic liquid, DADMATFSI was polymerized by UV treatment. The polymerization is demonstrated and the ion conducting properties of the resulting gel polymer electrolyte are investigated, showing that DADMATFSI can be transformed into an ionogel and may have applications where polymerization is desirable.