Structure and conductivity in polydioxolane/LiCF3SO3 electrolytes

Thermal transition (T, and T,,), ionic association and ionic conductivity have been measured as a function of LiCF3SO3 concentration in polydioxolane (-CH2OCH2CH2O-)(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. II was found that: (a) T,increases from - 69 to - 44 degreesC 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 x 10(-5) S cm(-1) between 12 and 48 wt%. (C) 2001 Elsevier Science Ltd. All rights reserved.