Molecular structure and ultrafast dynamics of sodium thiocyanate ion pairs formed in glymes of different lengths

文献情報

出版日 2018-12-06

DOI 10.1039/C8CP06869K

インパクトファクター 3.676

著者

Susith R. Galle Kankanamge, Daniel G. Kuroda

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要旨

Glyme-based electrolytes are one of the promising candidates in the development of sodium ion batteries due to their compatibility with conventional graphite electrodes. Recent studies have shown that the chelation effect significantly affects the ion pair formation in these sodium–glyme based electrolytes. However, the solvation structure and dynamics of the sodium–glyme complex have yet to be fully characterized. In this paper, the structure and the motions of the sodium–glyme complex are investigated by using the thiocyanate ion as a reporter of the structure. To this end, steady state and time resolved infrared spectroscopy in conjunction with computational simulations and numerical modeling are used. Overall, the experiments show that the anion is mostly associated with the cation forming contact ion-pairs in all solutions. Time resolved vibrational anisotropy shows a bi-exponential dynamics which is in agreement with the reorientational dynamics of the thiocyanate ion describing its restricted and the overall rotations in the ion-pair-glyme complex. In addition, two dimensional infrared spectroscopy with parallel polarization reveals two dynamical processes for the anion with time scales that increase as a function of glyme length. The molecular motions giving rise to the observed vibrational dynamics are derived by comparing the results with a model describing the restricted rotational diffusion of an axially symmetric particle. The simulated anisotropy shows a good agreement with the experimental measurement. However, to obtain a good agreement of the simulated decorrelation time of the frequency–frequency correlation function (FFCF) with the experiment, a loose tethered oscillator with large stochastic fluctuations is needed. The large stochastic motions are described in terms of the dynamics of the glyme end chains given the observed correlation between the dynamics of the FFCF and the glyme length.

掲載誌

Physical Chemistry Chemical Physics

CiteScore: 5.5

自己引用率: 10.3%

年間論文数: 3036

Physical Chemistry Chemical Physics (PCCP) is an international journal co-owned by 19 physical chemistry and physics societies from around the world. This journal publishes original, cutting-edge research in physical chemistry, chemical physics and biophysical chemistry. To be suitable for publication in PCCP, articles must include significant innovation and/or insight into physical chemistry; this is the most important criterion that reviewers and Editors will judge against when evaluating submissions. The journal has a broad scope and welcomes contributions spanning experiment, theory, computation and data science. Topical coverage includes spectroscopy, dynamics, kinetics, statistical mechanics, thermodynamics, electrochemistry, catalysis, surface science, quantum mechanics, quantum computing and machine learning. Interdisciplinary research areas such as polymers and soft matter, materials, nanoscience, energy, surfaces/interfaces, and biophysical chemistry are welcomed if they demonstrate significant innovation and/or insight into physical chemistry. Joined experimental/theoretical studies are particularly appreciated when complementary and based on up-to-date approaches.