Abstract The present work reports the Raman spectroscopic characterization of solvent-cast and hot-pressed P(EO) 20LiN(SO 2CF 2CF 3) 2 (LiBETI) polymer electrolytes containing nanosized (7 and 12 nm) SiO 2 and micro-sized γ-LiAlO 2. The Raman spectra showed slight changes, including peak shifting and new peaks, in the low frequency region that are likely due to the interaction between the filler and the polymer. However, no significant differences in the BETI − anion modes in filler-free and filler-containing P(EO) 20LiBETI polymer electrolytes were detected. This indicates that the presence of the nanometric SiO 2 ceramic filler in the P(EO) 20LiBETI polymer electrolyte may have little influence on the ionic interactions. In addition, solvent-cast polymer electrolytes showed only slight changes in very weak vibrational modes.