Studies on the application of aluminum alkoxycarboxylates (containing oxyethylene substituents) as additives to solid and gel polymeric electrolytes obtained on the basis of poly(ethylene oxide) (PEO) and inorganic lithium salts have been carried out. The solid composites obtained have a homogeneous structure and show conductivity of the order of 10(-5) S/cm at 60 - 80 degreesC. The aluminum carboxylates applied assure good mechanical properties both of solid as well as of gel electrolytes also at elevated temperature due to the formation of a physical net with the polymer chains. The active role in the conduction process of the carboxylates used and their effect on the mechanical properties have been discussed on the basis of differential scanning calorimetry (DSC) and conductivity studies.