Gudla Harish, Zhang Chao, Brandell Daniel
Department of Chemistry-Ångström Laboratory, Uppsala University, Lägerhyddsvägen 1, Box 538, 75121 Uppsala, Sweden.
J Phys Chem B. 2020 Sep 17;124(37):8124-8131. doi: 10.1021/acs.jpcb.0c05108. Epub 2020 Sep 4.
We herein report an all-atom molecular dynamics study on the role of solvent polarity for Li diffusion in polymer electrolytes using PEO-LiTFSI (poly(ethylene oxide)-lithium bis(trifluoromethane)sulfonimide) as a model system. By separating the effect of and the effect of solvent polarity in our simulations, we show that the maximum in the diffusion coefficient of Li with respect to the dielectric constant of polymer solvent ε is due to transitions in the transport mechanism. In particular, it is found that the frequent interchain hopping involves the coordination of both PEO and TFSI. This optimal solvating ability of PEO at an intermediate value of ε leads to the fast ion conduction. These findings highlight the synergetic effect of solvent polarity and bond polarity on Li-ion diffusion in solid polymer electrolytes.
我们在此报告一项全原子分子动力学研究，该研究以聚环氧乙烷-双（三氟甲烷）磺酰亚胺锂（PEO-LiTFSI）为模型体系，探讨溶剂极性对聚合物电解质中锂扩散的作用。通过在模拟中分离离子-离子相互作用和溶剂极性的影响，我们表明，锂扩散系数相对于聚合物溶剂介电常数ε的最大值是由于传输机制的转变。具体而言，发现频繁的链间跳跃涉及PEO和TFSI两者的配位。PEO在ε的中间值处的这种最佳溶剂化能力导致了快速离子传导。这些发现突出了溶剂极性和键极性对固体聚合物电解质中锂离子扩散的协同作用。
