Effects of Sodium Sources on Nonaqueous Precipitation Synthesis of β″-AlO and Formation Mechanism of Uniform Ionic Channels.

High-temperature and long-term sintering of β″-AlO solid electrolyte (Beta″ Alumina Solid Electrolyte, BASE) can easily cause NaO volatilization. It reduces the solid electrolyte (SE) quality, resulting in low ion conductivity of the electrolyte. It is also difficult to form uniform ionic channels. This work designs a simple nonaqueous precipitation through de-etherification heterogeneous polymerization reaction between optimal sodium source sodium ethoxide and aluminum isopropoxide to synthesize highly active precursor powders with Na-O-Al as the skeleton, effectively reducing the synthesis and sintering temperatures of β″-AlO solid electrolyte and minimizing the NaO volatilization. Importantly, residual organic groups and a low synthesis temperature of 1150 °C promote the formation of in situ carbon uniformly. In-situ carbon with a mass fraction of about 3.98% will form uniformly distributed ion transport channels with a diameter of 1-3 μm when sintering at 1580 °C. These channels ensure a migration rate of sodium ions and ion conductivity of β″-AlO solid electrolyte of 0.028 S/cm at 300 °C.