Loo Whitney S, Faraone Antonio, Grundy Lorena S, Gao Kevin W, Balsara Nitash P
Department of Chemical and Biomolecular Engineering, University of California-Berkeley, Berkeley, California 94720, United States.
National Institute of Standards and Technology Center for Neutron Research, Gaithersburg, Maryland 20899, United States.
ACS Macro Lett. 2020 May 19;9(5):639-645. doi: 10.1021/acsmacrolett.0c00236. Epub 2020 Apr 15.
Polymer chain dynamics of a nanostructured block copolymer electrolyte, polystyrene--poly(ethylene oxide) (SEO) mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, are investigated by neutron spin echo (NSE) spectroscopy on the 0.1-100 ns time scale and analyzed using the Rouse model at short times ( ≤ 10 ns) and the reptation tube model at long times ( ≥ 50 ns). In the Rouse regime, the monomeric friction coefficient increases with increasing salt concentration, as seen previously in homopolymer electrolytes. In the reptation regime, the tube diameters, which represent entanglement constraints, decrease with increasing salt concentration. The normalized longest molecular relaxation time, calculated from the NSE results, increases with increasing salt concentration. We argue that quantifying chain motion in the presence of ions is essential for predicting the behavior of polymer-electrolyte-based batteries operating at large currents.
通过中子自旋回波（NSE）光谱在0.1 - 100纳秒时间尺度上研究了与双（三氟甲磺酰）亚胺锂（LiTFSI）盐混合的纳米结构嵌段共聚物电解质聚苯乙烯 - 聚环氧乙烷（SEO）的聚合物链动力学，并在短时间（≤10纳秒）使用Rouse模型以及在长时间（≥50纳秒）使用蛇行管模型进行分析。在Rouse区域，单体摩擦系数随盐浓度增加而增大，这与之前在均聚物电解质中观察到的情况相同。在蛇行区域，代表缠结约束的管径随盐浓度增加而减小。根据NSE结果计算得到的归一化最长分子弛豫时间随盐浓度增加而增大。我们认为，在存在离子的情况下量化链运动对于预测基于聚合物电解质的大电流运行电池的行为至关重要。
