Distinct difference in ionic transport behavior in polymer electrolytes depending on the matrix polymers and incorporated salts.
Distinct difference in ionic transport behavior in polymer electrolytes depending on the matrix polymers and incorporated salts.
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DOI：
10.1021/jp045328j
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发表时间：
2005-02
期刊：
影响因子：
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通讯作者：
S. Seki;M. A. B. H. Susan;Taketo Kaneko;H. Tokuda;Akihiro Noda;M. Watanabe
中科院分区：
文献类型：
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作者：
S. Seki;M. A. B. H. Susan;Taketo Kaneko;H. Tokuda;Akihiro Noda;M. Watanabe
将两种不同的电解质盐双(三氟甲磺酰亚胺)锂(LiTFSI)和室温离子液体1-乙基-3-甲基咪唑双(三氟甲磺酰亚胺)(EMITFSI)引入到网络聚合物中，得到了离子导电聚合物电解质。分别选择聚环氧乙烷-环氧丙烷(P(EO/PO))和聚甲基丙烯酸甲酯(PMMA)网络聚合物作为LiTFSI和EMITFSI的基质。这两种聚合物电解质都是单相材料，完全无定形。在很宽的温度范围内测量了聚合物电解质的离子电导率，最低温度接近或低于玻璃化转变温度(Tg)。两种体系的电导率Arrhenius曲线均为正曲线，符合Vogel-Tamman-Fulcher(VTF)方程。在室温下，PMMA/EMITFSI电解液的电导率最多比LiTFSI/P(EO/PO)电解液高3个数量级。当比较理想玻璃化转变温度T0(VTF拟合参数之一)和Tg时，这些体系的离子导电性有明显的差异。在P(EO/PO)/LiTFSI电解液中，T0和Tg随着盐浓度的增加而增加，T0比Tg低约50℃。相反，T0和Tg之间的差异随着PMMA/EMITFSI电解液中PMMA含量的增加而增大，所观察到的浓度范围的差异高达约100℃。LiTFSI/P(EO/PO)电解液在Tg，sigma(Tg)的数量级为10(-14-)10(-13)S厘米(-1)，并随着盐浓度的增加而增加，而当PMMA浓度较高时，PMMA/EMITFSI聚合物电解质的极化强度达到10(-7)S cm(-1)。根据耦合/解偶和强/脆的概念，讨论了两种不同聚合物电解质的离子输运机理。
Two different electrolyte salts, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI), were incorporated into network polymers to obtain ion-conductive polymer electrolytes. Network polymers of poly(ethylene oxide-co-propylene oxide) (P(EO/PO)) and poly(methyl methacrylate) (PMMA) were chosen as matrixes for LiTFSI and EMITFSI, respectively. Both of the polymer electrolytes were single-phase materials and were completely amorphous. Ionic conductivity of the polymer electrolytes was measured over a wide temperature range, with the lowest temperatures close to or below the glass transition temperatures (Tg). The Arrhenius plots of the conductivity for both of the systems exhibited positively curved profiles and could be well fit to the Vogel-Tamman-Fulcher (VTF) equation. The conductivity of the PMMA/EMITFSI electrolytes was higher at most by 3 orders of magnitude than that of the LiTFSI/P(EO/ PO) electrolytes at ambient temperature. When the ideal glass transition temperature, T0 (one of the VTF fitting parameters), was compared with the Tg, a difference in the ionic conduction was apparent in these systems. In the P(EO/PO)/LiTFSI electrolytes, the T0 and Tg increased in parallel with salt concentration and the T0 was lower than the Tg by ca. 50 degrees C. On the contrary, the difference between the T0 and the Tg increased with increasing content of PMMA in the PMMA/EMITFSI electrolytes, with the observed difference in the concentration range studied reaching up to ca. 100 degrees C. The conductivity at the Tg, sigma(Tg), for the LiTFSI/P(EO/PO) electrolytes was on the order of 10(-14-)10(-13) S cm(-1) and increased with increasing salt concentration, whereas that for the PMMA/EMITFSI polymer electrolytes reached 10(-7) S cm(-1) when the concentration of PMMA was high. The ion transport mechanism was discussed in terms of the concepts of coupling/decoupling and strong/fragile for the two different polymer electrolytes.