Dynamic Observation of Molecular Movement at Interface Between Electrode and Solid Polymer Electrolyte by Using In Situ FTIR Spectroscopy

固体聚合物电解质已被用作燃料电池、可充电锂电池和传感器的重要材料。在这项研究中，我们研究了固体聚合物电解质在固体电极和它们之间的界面上的动态行为。到目前为止，已经发展了许多仪器技术来观察这种由聚合物和金属电极组成的界面。原位FTIR测量是检测这类界面的物理化学变化的有用工具之一。在本项目前期，我们开发了具有内反射的原位FTIR测量系统。在第二阶段，研究了Nafion与铂电极界面的动态变化。研究结果如下：(1)研究了非水电解液中金属锂表面膜化学成分的动态变化，以验证本测量系统的可靠性。(2)考察了Nafion的模型化合物CF_3(CF_2)_7SO_3H的吸附行为。在铂电极上的吸附行为取决于电极电位和CF_3(CF_2)_7SO_3H的浓度。(3)将Nafion膜浇铸在铂电极上，然后用HClO_4水溶液浸泡。在这个过程中，用原位FTIR测量观察了Nafion与铂之间界面的动态行为。结果表明，这些处理改变了化学和物理状态。通过原子力显微镜和表面电位检测发现了Nafion膜的微相分离。

Solid polymer electrolytes have been studied as important materials used in fuel cells, rechargeable lithium batteries, and sensors. In this study, we investigated a dynamic behavior of solid polymer electrolytes at interfaces between a solid electrodes and them. So far, many instrumental techniques have been developed in order to observe such interfaces consisting of polymers and metal electrodes. An in situ FTIR measurement is one of useful tools for detection physical and chemical changes of such interfaces. In early state of this project, we developed the measurement system of in situ FTIR with an internal reflectance. At the secons stage, the interfacial dynamic change of Nafion and Pt electrode interface was investigated. The results obtained from this study were summarized as follows.(1)A dynamic change of chemical compositions of a surface film on lithium metal in nonaqueous electrolytes was investigated in order to confirm a reliability of our measurement system.(2)An adsorption behavior of CF_3(CF_2)_7SO_3H,which was used as a model compound of nafion, was examined. An adsorption behavior on the Pt electrode depended on the electrode potential and the concentration of CF_3(CF_2)_7SO_3H.(3)The Nafion film was casted on the Pt electrode and then it was soaked by HClO_4 aqueous electrolvte. In the course of these processes, the dynamic behavior of the interface between the Nafion and the Pt was observed by using in situ FTIR measurement. It was found that the chemical and physical states were changed by these treatments. Moreover, they were changed by the electrode potential.(4)A micro-phase separation of the Nafion membrane was detected by using an atomic force microscopy and a surface potential detection.