Inorganic-organic polymer electrolytes based on PEG400 and Al[OCH(CH3)(2)](3) II. Morphology, thermal stability, and conductivity mechanism

This report presents detailed studies on the morphology, thermal stability, and electrical spectroscopy of 11 aluminum-containing hybrid inorganic-organic polymer electrolytes with the general formula $Al@O~CH2CH2O)8.7]r /(LiClO4)z%n , where 1.85 < r < 2.24 and 0 < z < 1.06. Scanning electron microscopy showed a solid-plastic appearance and a smooth texture on the surface of the bulk materials. Thermogravimetric investigations indicated that the hybrid polymer electrolytes are thermally stable up to ;260°C. Furthermore, a detailed study of the mechanism of ion conduction in these systems was carried out by impedance spectroscopy in the 20 Hz to 1 MHz range and at temperatures varying from 18 to 80°C. It was demonstrated that the $Al@O~CH2CH2O)8.7]r /(LiClO4)z%n materials conduct ionically by a charge-transfer mechanism mainly regulated by segmental motion and fast ion-hopping processes between equivalent coordination sites distributed along polyether chains. The ‘‘anion trapping’’ ability of the aluminum atoms toward perchlorate contributes greatly to the conductivity performance of the $Al@O~CH2CH2O)8.7]r /(LiClO4)z%n networks. Finally, the best conductivity observed in these materials is 1.66 3 1025 S cm21 at 25°C.