Solid electrolytes based on Li7La3Zr2O12 doped with Nb and Al were synthesized; Li6.6Al0.05La3Zr1.75Nb0.25O12 has the maximum lithium-ion conductivity at 25 °C – 6.3•10-4 S/cm. Al with various thicknesses - 10, 50, and 150 nm was deposited on solid electrolyte. It was established that the deposition of 150 nm Al leads to the resistance decrease at the interface between solid electrolyte and Li and to a more rapid formation of a stable interface at room and elevated temperatures.