Atomic Layer Deposition of Lithium Niobium Oxides as Potential Solid-State Electrolytes for Lithium-Ion Batteries

The development of solid-state electrolytes by atomic layer deposition (ALD) holds unparalleled advantages toward the fabrication of next-generation solid-state batteries. Lithium niobium oxide (LNO) thin films with well-controlled film thickness and composition were successfully deposited by ALD at a deposition temperature of 235 °C using lithium tert-butoxide and niobium ethoxide as Li and Nb sources, respectively. Furthermore, incorporation of higher Li content was achieved by increasing the Li-to-Nb subcycle ratio. In addition, detailed X-ray absorption near edge structure studies of the amorphous LNO thin films on the Nb L-edge revealed the existence of Nb as Nb⁵⁺ in a distorted octahedral structure. The octahedrons in niobium oxide thin films experienced severe distortions, which could be gradually alleviated upon the introduction of Li atoms into the thin films. The ionic conductivities of the as-prepared LNO thin films were also measured, with the highest value achieving 6.39 × 10^-8 S cm^-1 at 303 K with an activation energy of 0.62 eV.