A Facile Synthesis of Bulk LIPON in Solution for Solid-State Electrolytes

We present a facile, solution-based approach to prepare bulk lithium phosphorus oxynitride (LiPON) utilizing a stepwise reduction between lithium tert-butoxide (LiO^tBu) and a phosphazene base, diethyl phosphoramidate (DEPA), which are also precursors used in LiPON synthesis by atomic layer deposition (ALD). The study finds that the two ALD LiPON precursors can readily react upon mixing in THF at room temperature, which yields an ionically conductive solid powder that may be used as a solid-state electrolyte in solid-state batteries or as a material for surface coating. We conducted comprehensive characterization studies using solid-state nuclear magnetic resonance (SSNMR) spectroscopy, cryogenic transmission electron microscopy (cryo-TEM), matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS) to study the structure of this bulk LiPON material, which exhibits a composition closely resembling LiPO₂N. We propose a reaction mechanism of this bulk synthesized LiPON in a solution system.