One of the most promising technologies for increasing the safety and durability of solid-state batteries (SSB) is nano-coating between electrodes and electrolytes. The paper presents the results of a detailed microscopic and electrochemical analysis of multilayer thin films. The investigated multilayer structures consist of a two-layer system of an amorphous Li-O layer and a Ta-O layer obtained by atomic-layer deposition on Si and steel substrate. The results show that the growth rate of the films is 0.21 nm/supercycle, which corresponds to the theoretical one under the given synthesis conditions. The X-ray diffraction pattern shows that the Li-O and Ta-O layers are X-ray amorphous with a small content of Ta2O5 nanocrystallites. The ratio of the Ta:O components in the films obtained was 1:4, which is close to the theoretical LiTaO3. However, no mixed oxides of the Li-Ta-O system were found, which indicates that the film is multilayered. Analysis of cyclic voltammograms showed no interaction with liquid electrolyte in the range of cathode potentials (4.3–3.0 V). In addition, the coatings do not significantly contribute to the electrochemical capacity so that they can be used as a functional layer between solid electrolytes and electrodes in SSB.