This paper investigates and analyzes the crystalline reversible arrow amorphous transition in the PEO:LiX-Al2O3 composite electrolyte system using differential scanning calorimetric and conductivity measurements. The usage of nanosize Al2O3, a mixture of lithium salts, and a thermal treatment at 175 degreesC have been determined to be effective means of influencing the transition and stabilizing the amorphous structure.