This paper presents the results of research of behavior of phonon subsystem in ultrathin coatings that are applied on electrodes in Li-ion batteries and that increase the efficiency of ion transport. Using the method of Green functions it was demonstrated that in ultrathin films, increased mechanical oscillating of crystalline lattice and forming of standing waves occur, while, thermal capacitiveness and conduction of the overall coating decreases. With their increased oscillating, phonons release the ions captured on and within electrodes, and thus influence an increase in efficiency of ion conductivity.