Perfluoropolyether (PFPE) polymers potentially improve the thermodynamic stability, compatibility, and ionic conductivity of sulfide-based solid-state electrolyte (SSE)/Li-metal interfaces. However, ion-transport kinetics of PFPE polymers remain inadequately understood. Using molecular dynamics, we characterized the coordination structures and diffusion in PFPEs terminated with hydroxyl or carboxyl moieties and poly(ethylene oxide) (PEO) embedded with lithium and bis(trifluoromethylsulfonyl)imide ions. The mechanism underlying Li⁺ diffusion in the PFPE polymers was found to differ from that in PEO, and their respective ion–polymer contact strengths and durations were analyzed. Furthermore, the terminal structure of PFPE polymers was shown to significantly alter the cation–polymer and anion–polymer coordination structures, which in turn accounts for the different extents of the Li⁺ coordination strength in PFPE-diol and PFPE-dimethylcarbonate (DMC). Finally, PFPE-DMC favors longer durations of contact with cations and shorter ones with anions, whereas this relationship is reversed in PFPE-diol. Thus, we provide a novel way to explain experimentally the observed differences in their ionic conductivities, and we illustrate a general principle for increasing Li⁺ diffusivity in PFPE polymers, providing an avenue for understanding ionic migration in PFPE–SSE composite electrolytes.

中文翻译：

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全氟聚醚聚合物中锂离子传输机制的计算研究

全氟聚醚 (PFP​​E) 聚合物可能提高硫化物基固态电解质 (SSE)/锂金属界面的热力学稳定性、相容性和离子电导率。然而，PFPE 聚合物的离子传输动力学仍未得到充分了解。使用分子动力学，我们表征了以羟基或羧基部分封端的 PFPE 中的配位结构和扩散，以及嵌入锂和双（三氟甲基磺酰基）亚胺离子的聚（环氧乙烷）（PEO）。^{Li +}的潜在机制发现 PFPE 聚合物中的扩散与 PEO 中的不同，并分析了它们各自的离子-聚合物接触强度和持续时间。此外，PFPE 聚合物的末端结构显着改变了阳离子-聚合物和阴离子-聚合物的配位结构，这反过来又解释了PFPE-二醇和 PFPE-碳酸二甲酯 (DMC) 中Li ^{+配位强度的不同程度。}最后，PFPE-DMC 倾向于与阳离子接触的时间更长，而与阴离子的接触时间更短，而这种关系在 PFPE-二醇中是相反的。因此，我们提供了一种新的方法来通过实验解释观察到的离子电导率差异，并说明了增加 Li ⁺PFPE 聚合物中的扩散率，为理解 PFPE-SSE 复合电解质中的离子迁移提供了途径。