Fragiadakis Daniel, Dou Shichen, Colby Ralph H, Runt James
Department of Materials Science and Engineering and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Chem Phys. 2009 Feb 14;130(6):064907. doi: 10.1063/1.3063659.
We investigate the segmental and local dynamics as well as the transport of Li(+) cations in a series of model poly(ethylene oxide)-based single-ion conductors with varying ion content, using dielectric relaxation spectroscopy. We observe a slowing down of segmental dynamics and an increase in glass transition temperature above a critical ion content, as well as the appearance of an additional relaxation process associated with rotation of ion pairs. Conductivity is strongly coupled to segmental relaxation. For a fixed segmental relaxation frequency, molar conductivity increases with increasing ion content. A physical model of electrode polarization is used to separate ionic conductivity into the contributions of mobile ion concentration and ion mobility, and a model for the conduction mechanism involving transient triple ions is proposed to rationalize the behavior of these quantities as a function of ion content and the measured dielectric constant.
我们使用介电弛豫光谱法，研究了一系列具有不同离子含量的基于聚环氧乙烷的模型单离子导体中Li(+)阳离子的链段和局部动力学以及传输情况。我们观察到，在临界离子含量以上，链段动力学减慢，玻璃化转变温度升高，同时出现了与离子对旋转相关的额外弛豫过程。电导率与链段弛豫密切相关。对于固定的链段弛豫频率，摩尔电导率随离子含量的增加而增加。我们使用电极极化的物理模型将离子电导率分离为移动离子浓度和离子迁移率的贡献，并提出了一个涉及瞬态三离子的传导机制模型，以解释这些量随离子含量和测量介电常数的变化行为。
