Preparation, Characterization and Properties of New Ion-Conducting Ormolytes

Abstract

Two families of hybrid organic-inorganic composites exhibiting ionic conduction properties, so called ORMOLYTES (organically modified electrolytes), have been prepared by the sol-gel process. The first family has been prepared from a mixture of 3-isocyanatopropyltriethoxysilane (IsoTrEOS), O,O′ Bis (2-aminopropyl)polyethyleneglycol and lithium salt. These materials present chemical bonds between the organic (polymer) and the inorganic (silica) phases. The second family has been prepared by an ultrasonic method from a mixture of tetraethoxysilane (TEOS), polyethyleneglycol and lithium salt. The organic and inorganic phases are not chemically bonded. The Li+ ionic conductivity has been studied by AC impedance spectroscopy up to 100 °C. Values of aσ up to 10−4 Scm−1 have been found at room temperature. The conduction properties have been related to the materials structure using linewidth and relaxation times NMR measurements of 7Li between −100 °C and 90 °C. A systematic study has been done changing the lithium concentration, the polymer chain length and the polymer to silica weight ratio. The structures and the ionic conduction properties of both families are compared with emphasis on the nature of the bonds between the organic and inorganic components.