Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany.
J Chem Phys. 2017 Sep 14;147(10):104502. doi: 10.1063/1.5001946.
Ionically conducting plastic crystals (PCs) are possible candidates for solid-state electrolytes in energy-storage devices. Interestingly, the admixture of larger molecules to the most prominent molecular PC electrolyte, succinonitrile, was shown to drastically enhance its ionic conductivity. Therefore, binary mixtures seem to be a promising way to tune the conductivity of such solid-state electrolytes. However, to elucidate the general mechanisms of ionic charge transport in plastic crystals and the influence of mixing, a much broader database is needed. In the present work, we investigate mixtures of two well-known plastic-crystalline systems, cyclohexanol and cyclooctanol, to which 1 mol. % of Li ions were added. Applying differential scanning calorimetry and dielectric spectroscopy, we present a thorough investigation of the phase behavior and the ionic and dipolar dynamics of this system. All mixtures reveal plastic-crystalline phases with corresponding orientational glass-transitions. Moreover, their conductivity seems to be dominated by the "revolving-door" mechanism, implying a close coupling between the ionic translational and the molecular reorientational dynamics of the surrounding plastic-crystalline matrix. In contrast to succinonitrile-based mixtures, there is no strong variation of this coupling with the mixing ratio.
离子导电塑料晶体（PCs）是储能器件中固态电解质的候选材料。有趣的是，向最著名的分子 PC 电解质琥珀腈中添加较大分子的混合物，会显著提高其离子电导率。因此，二元混合物似乎是调节此类固态电解质电导率的一种很有前途的方法。然而，为了阐明塑料晶体中离子电荷输运的一般机制以及混合的影响，需要更广泛的数据库。在本工作中，我们研究了两种著名的塑料晶体体系环己醇和环辛醇的混合物，其中加入了 1mol%的锂离子。通过差示扫描量热法和介电谱，我们对该体系的相行为以及离子和偶极子动力学进行了全面研究。所有混合物均呈现出具有相应取向玻璃化转变的塑料晶体相。此外，它们的电导率似乎由“旋转门”机制主导，这意味着离子的平移和周围塑料晶体基质的分子重排动力学之间存在紧密耦合。与基于琥珀腈的混合物不同，这种耦合随混合比的变化不大。
