Magnetron Sputtering Preparation of Nitrogen-Incorporated Lithium-Aluminum-Titanium Phosphate Based Thin Film Electrolytes for All-Solid-State Lithium Ion Batteries

We report for the first time a new lithium ion conducting Li-Al-Ti-P-O-N thin film solid electrolyte for all-solid-state lithium ion batteries. It was prepared by radio frequency (RF) magnetron sputtering deposition using a NASICON structural Li-Al-Ti-P-O target in a N-2 atmosphere at various temperatures. XRD and SEM test results showed that the thin film was composed of an amorphous structure and that its surface was smooth, dense, and homogeneous. FTIR and XPS analyses indicated that nitrogen atoms were actually incorporated into the Li-Al-Ti-P-O matrix framework. The substitution of nitrogen for oxygen in the thin film created more abundant cross-linking structures and decreased the electrostatic energy, which favored the higher mobility of lithium ions. A high Li ionic conductivity of 1.22 X 10(-6) S/cm was obtained for the thin film deposited at room temperature. Moreover, the higher value of 1.22 X 10(-5) S/cm for the thin film deposited at 500 degrees C indicated that some crystallites in the amorphous film might be beneficial in improving Li ionic conductivity. Therefore, different conductivity values are correlated with structural differences. The temperature dependence of the ionic conductivities fit the Arrhenius relation and the thin film deposited at 500 degrees C possessed of the lowest activation energy. Electrochemical analyses suggest that the high Li ionic conductivity is attributed to the reduced activation energy by the control of composition and structure. These properties make this thin film electrolyte a promising candidate material for use in all-solid-state thin film lithium ion batteries.