Berlin 2012 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 33: Polymer Dynamics
CPP 33.9: Talk
Thursday, March 29, 2012, 12:15–12:30, C 264
Lithium transport mechanism in ternary mixtures of polymer electrolytes and ionic liquids - a molecular dynamics simulation study — •Diddo Diddens1,2 and Andreas Heuer1,2 — 1Institut für physikalische Chemie, Westfälische Wilhelms-Universität Münster, Germany — 2Graduate School of Chemistry, Münster, Germany
Electrolytes based on mixtures of lithium salts and poly(ethylene oxide) (PEO) are important candidates for modern lithium ion batteries. Unfortunately, in case of the common binary electrolytes like PEO/lithium-bis(trifluoromethane sulfonimide) (LiTFSI), the ionic conductivity is still too low for an efficient technological use. Here, the incorporation of room temperature ionic liquids (RTILs) into these materials promises a significant improvement, as the ionic conductivity is increased about an order of magnitude at room temperature, thus making them an ideal compromise between solid and liquid electrolytes.
Motivated by these experimental findings, we study the underlying microscopic transport mechanisms of the lithium ions by means of MD simulations. We find that these mechanisms are qualitatively the same as already observed in a previous study for PEO/LiTFSI. When adding ionic liquid into the electrolyte, the characteristic time scale of one of the mechanisms, namely the cooperative motion with the PEO segments, is reduced significantly. Therefore, it is possible to describe the lithium dynamics by a Rouse-based analytical transport model that has been developed for binary polymer electrolytes.