Paper actuality is based on growing need for non-combustible and safe batteries, which operate portable electronic devices and much more. Influence of lithium salts concentration on the electrical properties in ambient temperature of Polyethylene oxide (PEO) composite films was investigated. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements are made to determine composite’s crystallinity, thermal properties and thermal stability too. Different amounts of lithium chloride (LiCl) and lithium trifluoromethanesulfonate (LiCF3SO3) were added to the PEO polymer. The salts affected the crystallinity degree and thus electrical properties of the composite. Electric conductivity increased with respect to the enhancement of the filler, however 20 % amount of LiCF3SO3 caused the conductivity to decrease. This behavior was related to the different interactions between PEO and Lithium salts, as confirmed by DSC analysis. By increasing Lithium salt concentration in PEO composite, crystallinity decreased. TGA analysis show, that 5% of LiCl give maximum thermal resistance between pure PEO and PEO composites.