Polymer electrolytes based on low molecular weight poly(ethylene glycol)s doped with LiClO4 (0.1–1 mol kg PEG) and containing up to 10 mass% of AlBr3 additive were synthesized and characterized by impedance spectroscopy, FT-IR, DSC and rheological techniques. It has been found that addition of small amount (up to 5 mass%) of AlBr3 increases electrolytes conductivity in comparison with pure PEG–LiClO4 electrolytes for samples containing 1 mol of LiClO4 per kg PEG. Room temperature conductivity as high as 3×10−4 S/cm was measured. For higher AlBr3 concentrations stiffening of the polymer organic electrolyte was observed which results in a decrease in the ionic conductivity. The systematic studies of the interfacial phenomena performed in the symmetrical cell comprising two lithium electrodes separated by PEG–LiClO4–AlBr3 electrolyte allow us to postulate different rate of SEI (solid electrolyte interface) formation and limitation of its growth in the presence of AlBr3 interface thus enhancing the effectiveness of lithium cells.