Preparation of sodium beta″-alumina electrolyte thin film by electrophoretic deposition using Taguchi experimental design approach

With the desire to lowering the working temperature of Na-β″- Al₂O₃ solid electrolyte (BASE) based batteries, electrophoretic deposition process is employed to fabricate 300 μm thick Na-β″-Al₂O₃ sheet with densification microstructure and high ionic conductivity. Taguchi design of experiment approach with signal to noise ratio analysis is utilized to optimize the operation parameters. The results show that the TiO₂ content in the precursor powders is critical to determine the ionic conductivity of the resulting electrolyte. X-Ray diffraction analysis and X-ray photoelectron spectroscopy examination point out that Ti⁴⁺ can enter the crystal lattice of Na-β″-Al₂O₃, which results in the variation of lattice parameters, densifies the microstructure and improves both β″ phase content and ionic conductivity of the resulting sample. The thin Na-β″-Al₂O₃ disk obtained under the optimized conditions Exhibit 97% β″ phase content and relatively high ionic conductivity. Moreover, a Daniell-typed cell built with this optimized sample disk, using copper/zinc redox couples as electrodes and 1 M NaBF ₄ in DMSO as the secondary electrolyte, shows reversible charge and discharge behaviors at relatively low temperature, 100 °C.