Electrolytes made up of poly(ethylene oxide) (PEO), sol-gel silica and LiClO4 were prepared. Poly(ethylene oxide-g-dimethylsiloxane) (SEO) was used as a compatibilizer. Two groups of samples were investigated: in group A, the PEO content relative to the tetraethoxysilane, SEO and LiClO4 changed from 2.6 to 10 wt.%; in group B it varied from 35 to 69 wt.%. Electrolytes with conductivity in the range of 10(-6)-10(-4) S/cm (25 degreesC) were obtained. In group A, transparent gels, transparent and flexible films and white powders were obtained. Differential scanning calorimetry (DSC) and light microscopy showed that all these samples are amorphous. On the other hand, all samples of group B were translucent films, showing typical spherulites of the PEO crystalline fraction. In the DSC analysis, an endothermic peak near 70 degreesC, assigned to the PEO crystalline fraction melting, was observed. Most of the samples of both groups A and B were thermally stable up to 200 degreesC.