ATR infrared spectroscopy is used to study the structure of lithium metaborate-lithium fluoride composite thin films. The variation of the principal spectral characteristics of the composite is explained by the transformation of the tetra-coordinated in tri-coordinated boron groups. The ionic conductivity is found to vary along with the composition. The highest value corresponds to the molar fraction X(LiF) = 0.56 then decreases gradually due to the presence of non-bridging oxygen atoms which trap the Li+ ions in the covalent network reducing the mobility.