Design, Synthesis, and Characterization of Polymer Precursors to LixPON and LixSiPON Glasses: Materials That Enable All-Solid-State Batteries (ASBs)

LiPON-like glasses that form lithium dendrite impenetrable interfaces between lithium battery components are enabling materials that may replace liquid electrolytes permitting production of all-solid-state batteries (ASBs). Unfortunately, to date, such materials are introduced only via gas-phase deposition. Here, we demonstrate the design and synthesis of easily scaled, low-temperature, low-cost, solution-processable inorganic polymers containing LiPON/LiSiPON elements. OPCl3 and hexachlorophosphazene [Cl2P═N]3 provide starting points for elaboration using MNH2 (M = Li/Na) or (Me3Si)NH followed by reaction with controlled amounts of LiNH2 to produce oligomers/polymers with molecular weights (MWs) ≈1–2 kDa characterized by multinuclear NMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (ToF) offering stabilities to 150–200 °C and ceramic yields (800 °C) of 50–60%. 7Li NMR suggests that precursor-bound Li+ dissociates easily, beneficial for electrochemical applications. XPS shows higher N/P ratios (1–3) than via gas-phase methods (<1) correlating N/P ratios, 7Li shifts, and Li+ conductivities. Li2SiPHN offers the highest ambient conductivity of 3 × 10–1 mS cm–1 at 400 °C/2 h/N2.