Synthesis and integration of thin film solid state electrolytes for 3D Li-ion microbatteries

An essential element to realize lithium-ion microbatteries is an effective and conformal thin film solid state electrolyte over irregular or porous structures with specific composition and controlled elemental spatial distribution. Atomic layer deposition is a surface reaction based and non-line-of-sight technique that can rationally design an optimal electrolyte material, including high conductivity for lithium ions; adhesion to the substrate; uniformity over large area; thermal, mechanical, and electrical stability; and reproducibility required to integrate this deposition method into a manufacturing process. This review focuses on the current state-of-the-art development of a thin film solid state electrolyte, highlights the tunability of the electrical and electrochemical properties by controlling the composition and the microstructure of these materials, and discusses the future outlook in this technologically important area.