Preparation and electrochemical characterisation of (PEO)(n)LiAI(SO3Cl)(4) (n = 2-12) polymer electrolytes containing a mixture of plasticisers, i.e. propylene carbonate and 1,2-dimethoxyethane is reported. The effect of humidity on polymer electrolyte microstructural and electrical characteristics (degree of crystallinity, glass transition temperature, conductivity) is studied using X-ray powder diffractometer analysis, differential scanning calorimetry and impedance spectroscopy.