This paper describes the preparation and characterization of poly(ethylene oxide) (PEO)-lithium bis(perfluoroethylenesulfonyl)imide (LiBETI), LiN(SO2CF2CF3)(2) polymer electrolytes The structural properties of P(EO)(n)LiBETI electrolyte tapes, investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC), are correlated with their ionic conductivities. PEO-LiBETI complexes were found to have very high ionic conductivities due to their amorphous structure.