Dielectric Relaxation Behavior of a Poly(ethylene carbonate)-Lithium Bis-(trifluoromethanesulfonyl) Imide Electrolyte
Dielectric Relaxation Behavior of a Poly(ethylene carbonate)-Lithium Bis-(trifluoromethanesulfonyl) Imide Electrolyte
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DOI：
10.1002/macp.201500125
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发表时间：
2015-08-01
影响因子：
2.5
通讯作者：
Tominaga, Yoichi
中科院分区：
文献类型：
--
作者：
Motomatsu, Joh;Kodama, Hidekazu;Tominaga, Yoichi
一种由聚碳酸乙烯（PEC）和金属盐组成的新型聚合物电解质，由于其优异的电解质性能，有望在全固态电池中得到应用。为了研究PEC基电解质的离子导电机理，采用宽带介电光谱法分析了40℃下PEC-双（三氟甲磺酰）亚胺锂电解质在宽盐浓度范围内（0-150 mol%）的介电弛豫与离子导电之间的关系。PEC体系有两种弛豫模式，分别与PEC链的节段运动和局部运动有关。随着盐浓度的增加，电导率呈指数增长，而在低盐浓度下，弛豫频率(f)随着强度（epsilon）的增加而降低，而在高于10 mol%的高盐浓度下，弛豫频率(f)随着epsilon饱和而增加。认为高浓度下PEC段的迁移率是由两个因素增强的。首先是分子间的相互作用减少，因为在解离离子高度集中的饱和PEC区域周围存在许多离子对和聚集离子。二是离子偶极相互作用降低了CO和CH2的分子内相互作用。
A new class of polymer electrolytes, consisting of poly(ethylene carbonate) (PEC) and metal salts, is expected to find application in all-solid-state batteries because of its excellent performance as an electrolyte. To study the ion-conductive mechanism in PEC-based electrolytes, broadband dielectric spectroscopy is used to analyze the correlation between dielectric relaxation and ionic conduction in PEC-lithium bis-(trifluoromethanesulfonyl) imide electrolytes over a broad range of salt concentration (0-150 mol%) at 40 degrees C. The PEC system has two relaxation modes, and , associated respectively with the segmental motion and the local motion of PEC chains. The conductivity increases exponentially with increasing salt concentration, while the relaxation frequency (f) decreases with increasing strength (epsilon) at low salt concentrations, whereas in contrast f increases with epsilon being saturated at high salt concentrations above 10 mol%. It is believed that the mobility of PEC segment at high concentration is enhanced by two factors. The first is that intermolecular interactions decrease, given the existence of many ion pairs and aggregated ions around saturated PEC domains where the dissociated ions are highly concentrated. The second is that intramolecular interactions between CO and CH2 are lowered by the ion-dipole interaction.