Conformational Dynamics in an Organic Ionic Plastic Crystal

Liyu Jin, Kate M. Nairn, Chris D. Ling, Haijin Zhu, Luke A O'Dell, Jiaye Li, Fangfang Chen, Adriano F. Pavan, Louis A Madsen, Patrick C. Howlett, Douglas R. Macfarlane, Maria Forsyth, Jennifer M. Pringle

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27 Citations (Scopus)


Understanding the short-range molecular motions of organic ionic plastic crystals is critical for the application of these materials as solid-state electrolytes in electrochemical devices such as lithium batteries. However, the theory of short-range-motions was originally developed for simple molecular plastic crystals and does not take account of strong interionic interactions that are present in organic ionic plastic crystals. Here we report a fundamental investigation of the dynamic behavior of an archetypal example triethyl(methyl)phosphonium bis(fluorosulfonyl)amide ([P1222][FSI]) through calorimetry, impedance spectroscopy, synchrotron X-ray diffraction, and solid-state NMR and Raman spectroscopies. For the first time, we show the presence of conformational dynamics in the solid state for the FSI anion. We relate the dynamics to a unique second-order displacive phase transition of [P1222][FSI]. This detailed analysis suggests a new disorder mechanism involving cooperative motion between the cation and FSI anion in the plastic crystal due to strong interionic interactions.

Original languageEnglish
Pages (from-to)5439-5446
Number of pages8
JournalJournal of Physical Chemistry B
Issue number21
Publication statusPublished - 1 Jun 2017

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