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

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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.