Abstract The lithium ion conducting solid lithium phosphorous nitride (LiPON) has been sputtered on the water-stable NASICON-type lithium ion conducting solid electrolyte Li 1+ x + y Al x Ti 2− x P 3− y Si y O 12 (LATP). The stability and the interface resistance of the Li–Al/LiPON/LATP/LiPON/Li–Al cell have been examined. It is shown that the LiPON film protects LATP from reacting with the Li–Al alloy. The impedance of the Li–Al/LiPON/LATP/LiPON/Li–Al cell has been measured in the temperature range 25–80 °C. The total cell resistance is about 8600 Ω cm 2 at room temperature and 360 Ω cm 2 at 80 °C. The analysis of the impedance profiles suggests that the Li–Al/LiPON interface resistance is dominant at lower temperatures. The LATP plate immersed in water for 1 month shows only a slight degradation in the conductivity.