The first-principles study of alkali halides dispersed in polyethylene chains is performed, the dispersion of salts modifies the bond lengths of atoms, bending of polymer chains is occurred, and Li/Na cations are found to be attracted towards oxygen anions; it causes to the reduction in crystallinity. Charge density analysis exhibits partially ionic and covalent bonds between C and O atoms of all PEO systems, and ionic bonds between Li and O and between Na and O atoms. There issphybridization in all polymer systems; the forbidden energy gap reduces gradually by increasing dispersed salt molecules and is smaller in PEO10-4NaI. The formation of the concentration of Na cations is higher than Li cations in polymer salts. The stability of PEO10-4LiI is larger and that of PEO5-LiI is smaller, and the bond breaking energy is higher in PEO10-4NaI and lower in PEO10-2NaI. Graphic abstract