In this work, the possibility of modifying poly(ethylene oxide) (PEO) with poly(ethylene glycol) polyhedral oligomeric silsesquioxane (PEG-POSS) was investigated for the purpose of reducing the crystalline phase of the polymer or improving his ionic conductivity. For this purpose, samples were prepared in which PEO was modified with 5, 10 and 15 % PEO-POSS and samples in which lithium bis(oxalate) borate salt was also added in the ratio of oxygen from PEO and lithium from salt 8:1. The samples were prepared by the dynamic method from the melt in a twin screw extruder, which ensures good dispersion of the filler and salt in polymer matrix, and the obtained results were compared with the results of the research of these samples prepared by mixing from the melt using the static method. It was found that the addition of PEG-POSS does not significantly affect the phase transition temperatures of PEO, as well as the proportion of the crystalline phase. PEG-POSS does not affect the thermal stability of PEO. Therefore, these results are not attributed to the poor dispersibility of the filler, which was assumed in the static preparation of the samples, but it is concluded that PEG-POSS does not affect either the thermal properties of PEO or the formation of the crystalline phase of PEO. It was also found that the LiBOB salt completely destroys the crystalline phase of PEO and that it increases the temperature of the beginning of PEO decomposition by 13 °C, while the value of the glass transition increases by ten degrees. Nevertheless, the results of electrochemical impedance spectroscopy show that the addition of PEG-POSS has an effect on ionic conductivity. The sample to which 15% of PEG-POSS and Li salt were added shows the highest values of ionic conductivity.