Atomic Layer Deposited Lithium Silicates as Solid-State Electrolytes for All-Solid-State Batteries.

Development of solid-state electrolyte (SSE) thin films is a key toward the fabrication of all-solid-state batteries (ASSBs). However, it is challenging for conventional deposition techniques to deposit uniform and conformal SSE thin films in a well-controlled fashion. In this study, atomic layer deposition (ALD) was used to fabricate lithium silicate thin films as a potential SSE for ASSBs. Lithium silicates thin films were deposited by combining ALD LiO and SiO subcycles using lithium tert-butoxide, tetraethylorthosilane, and HO as precursors. Uniform and self-limiting growth was achieved at temperatures between 225 and 300 °C. X-ray absorption spectroscopy analysis disclosed that the as-deposited lithium silicates were composed of SiO tetrahedron structure and lithium oxide as the network modifier. X-ray photoelectron spectroscopy confirmed the chemical states of Li in the thin films were the same with that in standard lithium silicate. With one to one subcycle of LiO and SiO the thin films had a composition close to LiSiO whereas one more subcycle of LiO delivered a higher lithium content. The lithium silicate thin film prepared at 250 °C exhibited an ionic conductivity of 1.45× 10 S cm at 373 K. The high ionic conductivity of lithium silicate was due to the higher lithium concentration and lower activation energy.