Diddens Diddo, Heuer Andreas
Institut für Physikalische Chemie, Westfälische Wilhelms-Universität, Corrensstrasse 28/30, 48149 Münster, Germany.
Graduate School of Chemistry, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Strasse 10, 48149 Münster, Germany.
ACS Macro Lett. 2013 Apr 16;2(4):322-326. doi: 10.1021/mz3006457. Epub 2013 Apr 2.
The lithium transport mechanism in ternary polymer electrolytes, consisting of PEOLiTFSI and various fractions of the ionic liquid PYRTFSI, is investigated by means of MD simulations. This is motivated by recent experimental findings (Passerini et al. , , 330), which demonstrated that these materials display an enhanced lithium mobility relative to their binary counterpart PEOLiTFSI. In order to grasp the underlying microscopic scenario giving rise to these observations, we employ an analytical, Rouse-based cation transport model (Maitra et al. , , 227802), which has originally been devised for conventional polymer electrolytes. This model describes the cation transport via three different mechanisms, each characterized by an individual time scale. It turns out that also in the ternary electrolytes essentially all lithium ions are coordinated by PEO chains, thus, ruling out a transport mechanism enhanced by the presence of ionic-liquid molecules. Rather, the plasticizing effect of the ionic liquid contributes to the increased lithium mobility by enhancing the dynamics of the PEO chains and consequently also the motion of the attached ions. Additional focus is laid on the prediction of lithium diffusion coefficients from the simulation data for various chain lengths and the comparison with experimental data, thus demonstrating the broad applicability of our approach.
通过分子动力学模拟研究了由聚环氧乙烷锂双（三氟甲基磺酰）亚胺（PEOLiTFSI）和不同比例的离子液体吡啶双（三氟甲基磺酰）亚胺（PYRTFSI）组成的三元聚合物电解质中的锂传输机制。这是受近期实验结果（帕塞里尼等人，，330）的推动，这些结果表明这些材料相对于其二元对应物PEOLiTFSI表现出增强的锂迁移率。为了理解导致这些观察结果的潜在微观情况，我们采用了一种基于分析的、基于劳斯模型的阳离子传输模型（梅特拉等人，，227802），该模型最初是为传统聚合物电解质设计的。该模型通过三种不同的机制描述阳离子传输，每种机制都有各自的时间尺度。结果表明，在三元电解质中，基本上所有锂离子也都由聚环氧乙烷（PEO）链配位，因此排除了由离子液体分子的存在增强的传输机制。相反，离子液体的增塑作用通过增强PEO链的动力学以及因此也增强附着离子的运动，有助于提高锂迁移率。还额外关注从模拟数据预测各种链长的锂扩散系数，并与实验数据进行比较，从而证明了我们方法的广泛适用性。
