Gudla Harish, Hockmann Anne, Brandell Daniel, Mindemark Jonas
Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden.
Institute of Physical Chemistry, University of Münster, Corrensstrasse 28/30, 48149 Münster, Germany.
ACS Appl Polym Mater. 2025 Apr 15;7(8):4716-4724. doi: 10.1021/acsapm.4c03724. eCollection 2025 Apr 25.
Although the basic modes of ion transport in solid polymer electrolytes (SPEs) are already classified and well-described, their distribution in typical polymer electrolytes is not clear and neither are the effects on the distribution by different degrees of ion-ion and ion-polymer interactions. Here, the ion-transport mechanisms in poly(ethylene oxide) are studied along with poly(ε-caprolactone) at different molecular weights and LiTFSI salt concentrations using molecular dynamics simulations. Through tracking of the cation coordination changes, three transport mechanisms are categorized, i.e., ion hopping, continuous motion (successive exchange of the coordination sphere), and vehicular transport. The observed dominant transport mechanism is in all cases continuous motion, which changes from polymer-mediated to anion-mediated with increasing salt concentration, while polymer-mediated vehicular transport is not observed to be a major contributor to cation transport. In both systems, ion hopping is also essentially absent, as can be expected in systems with strong ion-polymer interactions. The results illustrate how the usual description of ion transport in polymer electrolytes as coupled to segmental motions is too simplistic to catch the full essence of the ion-transport phenomena, whereas the frequently used notion of "ion hopping" in the majority of cases is incorrect for SPEs.
尽管固体聚合物电解质（SPEs）中离子传输的基本模式已被分类且描述详尽，但其在典型聚合物电解质中的分布尚不清楚，不同程度的离子 - 离子和离子 - 聚合物相互作用对其分布的影响也不明确。在此，利用分子动力学模拟研究了聚环氧乙烷以及不同分子量和LiTFSI盐浓度的聚己内酯中的离子传输机制。通过追踪阳离子配位变化，可将三种传输机制分类，即离子跳跃、连续运动（配位球的连续交换）和载流子传输。在所有情况下观察到的主要传输机制都是连续运动，随着盐浓度的增加，其从聚合物介导转变为阴离子介导，而聚合物介导的载流子传输并非阳离子传输的主要贡献因素。在这两个体系中，离子跳跃也基本不存在，这在具有强离子 - 聚合物相互作用的体系中是可以预期的。结果表明，将聚合物电解质中的离子传输通常描述为与链段运动相关过于简单，无法捕捉离子传输现象的全部本质，而在大多数情况下，常用的“离子跳跃”概念对于固体聚合物电解质是不正确的。
