Free Volume Mediated Decoupling of Ionic Conduction from Segmental Relaxation Leading to Enhancement in Ionic Conductivity of Polymer Electrolytes at Low Temperatures,ACS Macro Letters

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Free Volume Mediated Decoupling of Ionic Conduction from Segmental Relaxation Leading to Enhancement in Ionic Conductivity of Polymer Electrolytes at Low Temperatures
ACS Macro Letters ( IF 5.1 ) Pub Date : 2024-09-03 , DOI: 10.1021/acsmacrolett.4c00467
S K Sharma _{1,

2} , J Mor _{1,

2}

Affiliation

Coupling between segmental relaxation and ionic conduction has limited the ionic conductivity of flexible polymers like poly(ethylene oxide), PEO, based electrolytes especially at low temperatures where segmental relaxation becomes extremely slow. In the present study, we show that ionic conduction becomes decoupled from segmental relaxation in PEO-based electrolytes simply by loading succinonitrile (SN). As a result of SN interactions induced rigid chain packing of PEO, the semicrystalline morphology of PEO is completely altered along with the enhancement in number density of free volumes having smaller size and narrower size distribution. These free volumes provide additional pathways for ionic diffusion independent of segmental relaxations of PEO leading to decoupling of ionic diffusion from the segmental relaxation process. The decoupling finally leads to nearly two orders higher ionic conductivity (∼10^–11 Scm^–1)at glass transition temperature (T_g ∼ 210 K), than what is expected in the case of complete coupling.

中文翻译：

自由体积介导的离子传导与片段弛豫的解耦导致低温下聚合物电解质离子电导率的增强

链段弛豫和离子传导之间的耦合限制了柔性聚合物（如聚环氧乙烷、PEO）的离子电导率，尤其是在链段弛豫变得极其缓慢的低温下。在本研究中，我们表明，只需加载丁二腈（SN），离子传导就可以与基于 PEO 的电解质中的片段弛豫脱钩。由于SN相互作用诱导PEO的刚性链堆积，PEO的半晶形貌完全改变，同时具有更小尺寸和更窄尺寸分布的自由体积的数密度增强。这些自由体积提供了独立于 PEO 片段弛豫的离子扩散的额外途径，导致离子扩散与片段弛豫过程的解耦。去耦合最终导致在玻璃化转变温度（ T _g ∼ 210 K）下的离子电导率（∼10 ^–11 Scm ^–1 ）比完全耦合情况下的预期高出近两个数量级。

更新日期：2024-09-03

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