INVESTIGATION OF ZNBR2-PEO POLYMER ELECTROLYTE CHARACTERISTICS

The PEO(n):ZnBr2 polymer electrolyte system, where n = 1.5-19, has been studied using x-ray absorption fine structure (EXAFS) by phase diagram construction and conductivity measurements. The electrolytes have been prepared using either water or ethanol/acetonitrile as the casting solvent. With adequate drying both casting solvents produce electrolytes with very similar properties. The phase diagram indicates that at room temperature, below a mole fraction of 0.2, only two phases exist: a crystalline PEO phase and a crystalline intermediate compound. EXAFS from this region show that surrounding each zinc atom there are on average two bromine atoms. However for many reasons it is difficult to determine the precise number of surrounding oxygens. All samples within the same area of the phase diagram have very similar conductivity values.