Quantifying Single-Ion Transport in Percolated Ionic Aggregates of Polymer Melts,ACS Macro Letters

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Quantifying Single-Ion Transport in Percolated Ionic Aggregates of Polymer Melts
ACS Macro Letters ( IF 5.1 ) Pub Date : 2020-04-02 , DOI: 10.1021/acsmacrolett.0c00139
Jonathan A Bollinger ₁ , Mark J Stevens ₁ , Amalie L Frischknecht ₁

Affiliation

Single-ion conducting polymers such as ionomers are promising battery electrolyte materials, but it is critical to understand how rates and mechanisms of free cation transport depend on the nanoscale aggregation of cations and polymer-bound anions. We perform coarse-grained molecular dynamics simulations of ionomer melts to understand cation mobility as a function of polymer architecture, background relative permittivity, and corresponding ionic aggregate morphology. In systems exhibiting percolated ionic aggregates, cations diffuse via stepping motions along the ionic aggregates. These diffusivities can be quantitatively predicted by calculating the lifetimes of continuous association between oppositely charged ions, which equal the time scales of the stepping (diffusive) motions. In contrast, predicting cation diffusivity for systems with isolated ionic aggregates requires another time scale. Our results suggest that to improve conductivity the Coulombic interaction strength should be strong enough to favor percolated aggregates but weak enough to facilitate ion dissociation.

中文翻译：

量化聚合物熔体的渗透离子聚集体中的单离子传输

离子聚合物等单离子导电聚合物是很有前途的电池电解质材料，但了解游离阳离子传输的速率和机制如何依赖于阳离子和聚合物结合阴离子的纳米级聚集至关重要。我们对离聚物熔体进行粗粒度分子动力学模拟，以了解作为聚合物结构、背景相对介电常数和相应离子聚集体形态函数的阳离子迁移率。在表现出渗透离子聚集体的系统中，阳离子通过沿着离子聚集体的步进运动扩散。这些扩散率可以通过计算带相反电荷的离子之间连续结合的寿命来定量预测，这等于步进（扩散）运动的时间尺度。相比之下，预测具有孤立离子聚集体的系统的阳离子扩散率需要另一个时间尺度。我们的结果表明，为了提高电导率，库仑相互作用强度应该足够强以有利于渗透聚集体，但足够弱以促进离子解离。

更新日期：2020-04-23

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