Poly(ethylene oxide) (PEO)-based solvent-free electrolytes may be used for applications above room temperature, e.g. in batteries for electric vehicles. The system PEO-LiPF6 has to date received only scarce attention because of the poor thermal stability and hygroscopicity of the lithium salt. However, for applications above the melting of PEO crystalline phase, it is possible to consider films with relatively low salt content, which can overcome the above-mentioned problem. In this paper, we perform a thermal and transport characterisation of the system PEO-LiPF6. We show that conductivity values above 10(-4) Ohm (-1) cm(-1) can be reached at 70 degreesC for n = EO/Li = 30. The addition of nanoscale silica is shown to influence the thermal decomposition of the salt.