Seki Shiro, Susan Md Abu Bin Hasan, Kaneko Taketo, Tokuda Hiroyuki, Noda Akihiro, Watanabe Masayoshi
Department of Chemistry and Biotechnology, Yokohama National University and CREST-JST, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
J Phys Chem B. 2005 Mar 10;109(9):3886-92. doi: 10.1021/jp045328j.
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.
两种不同的电解质盐，双（三氟甲烷磺酰）亚胺锂（LiTFSI），以及一种室温离子液体，1-乙基-3-甲基咪唑双（三氟甲烷磺酰）亚胺（EMITFSI），被掺入网络聚合物中以获得离子导电聚合物电解质。分别选择聚（环氧乙烷-共-环氧丙烷）（P(EO/PO)）和聚甲基丙烯酸甲酯（PMMA）的网络聚合物作为LiTFSI和EMITFSI的基质。两种聚合物电解质均为单相材料且完全无定形。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）。两个体系的电导率的阿伦尼乌斯图均呈现正曲率曲线，并且可以很好地拟合Vogel-Tamman-Fulcher（VTF）方程。在室温下，PMMA/EMITFSI电解质的电导率比LiTFSI/P(EO/PO)电解质的电导率最多高3个数量级。当将理想玻璃化转变温度T0（VTF拟合参数之一）与Tg进行比较时，在这些体系中离子传导的差异很明显。在P(EO/PO)/LiTFSI电解质中，T0和Tg随盐浓度平行增加，且T0比Tg低约50℃。相反，在PMMA/EMITFSI电解质中T0和Tg之间的差异随PMMA含量的增加而增大，在所研究的浓度范围内观察到的差异高达约100℃。LiTFSI/P(EO/PO)电解质在Tg时的电导率σ(Tg)约为10^(-14)-10^(-13) S cm^(-1)，并随盐浓度的增加而增加，而当PMMA浓度较高时，PMMA/EMITFSI聚合物电解质的电导率达到10^(-7) S cm^(-1)。根据两种不同聚合物电解质的耦合/解耦和强/弱概念讨论了离子传输机制。
