New polymer gel electrolytes containing ionic liquids were developed for modern chemical power sources—supercapacitors and lithium-ion batteries. Ternary systems polymer–ionic liquid–aprotic solvent as well as materials containing also lithium salts (LiClO4 or LiPF6) were prepared by direct, thermally initiated polymerisation. Poly(2-ethoxyethyl methacrylate) PEOEMA was combined with various ionic liquids based on 1-methylimidazole. Only 1-butyl-3-methylimidazolium hexafluorophosphate BMIPF6 formed a homogenous and slightly translucent polymer electrolyte, where aprotic solvents—propylene carbonate and ethylene carbonates were used as plasticisers. Materials were studied using the electrochemical and thermogravimetric methods and exhibit high ionic conductivity up to 0.94mScm−1 at 25°C together with high electrochemical stability: the accessible potential window on the glassy carbon was found ca. 4.3V. Prepared non-volatile materials are long-term and thermally stable up to 150°C.