Structure and conductivity in polydioxolane/LiCF 3SO 3 electrolytes

Abstract

Thermal transition ( T g and T m), ionic association and ionic conductivity have been measured as a function of LiCF 3SO 3 concentration in polydioxolane (CH 2OCH 2CH 2O) n -based electrolytes. DSC and X-ray diffraction measurements were performed on samples with wt% between 2 and 58 wt% ( n=O:Li ratio between 207 and 3), as well as on the pure polymer. Ionic association in the electrolytes was investigated by micro-Raman spectroscopy at room temperature. Conductivity isotherms at 300, 323 and 345 K were obtained. It was found that: (a) T g increases from −69 to −44°C with increasing salt concentration; (b) the electrolyte is completely amorphous between 22 and 30 wt%; (c) the relative areas of the Raman peaks associated with different ionic species indicate the appearance of a new peak for a crystalline polymer/salt complex, also identified by the X-ray diffractograms; and (d) the ionic conductivity at 300 K shows a large maximum value of 7×10 −5 S cm −1 between 12 and 48 wt%.