Structural and conductivity investigations of composite polymer electrolytes based on poly(oxyethylene)

The scope of this paper is to study in detail the influence of inorganic fillers on the structure of composite polymeric electrolytes based on high-molecular weight poly(oxyethylene). It was mostly driven by large discrepancies between results reported by different authors as well as lack of detailed and complete information on the properties of composite electrolytes in the numerous articles published in the last 30 years. To enhance the transport properties-annealing steps were applied. First just below the melting point of the crystalline poly(oxyethylene) phase-at 60 degrees C, and then at 80 degrees C, 100 degrees C and 120 degrees C. They led to a dramatic increase of the ionic conductivities, for both-reference, and composite electrolytes; however, the effect was most pronounced for micron-sized fillers. On the other hand, nano-powders filled samples exhibited the best mechanical stability. To study the mechanism of the conductivity enhancement, combined X-ray diffraction (XRD) and differential scanning calorimetry (DSC) studies were conducted. Appearance, disappearance, and changes in relative volume of different phases present in the electrolytes were observed. These are the first-reported results showing such changes upon annealing. Since these are multiphase systems and no obvious space groups can be applied to study the changes in the diffractograms, correlation analysis was employed to investigate this phenomenon.