A Simple and Low-Cost Method to Fabricate Beta-Alumina Solid Electrolyte (BASE) for Na Battery Applications

Abstract

βʺ-Al2O3 has been the dominated choice for the electrolyte materials of sodium batteries because of its high ionic conductivity, excellent stability with the electrode materials, satisfactory mechanical strength, and low material cost. To achieve adequate electrical and mechanical performance, sintering of βʺ-Al2O3 is typically carried out at temperatures above 1600°C with deliberate efforts on controlling the phase, composition, and microstructure. Here, we reported a simple method to fabricate βʺ-Al2O3 /YSZ electrolyte at relatively lower temperatures. With the starting material of boehmite, single phase of βʺ-Al2O3 can be achieved at as low as 1200°C. It was found that TiO2 was extremely effective as a sintering aid for the densification of βʺ-Al2O3 and similar behavior was observed with MnO2 for YSZ. With the addition of 2 mol% TiO2 and 5 mol% MnO2, the βʺ-Al2O3 /YSZ composite was able to be densified at as low as 1400°C with a fine microstructure and good electrical/mechanical performance. This study demonstrated a new approach of synthesis and sintering of βʺ-Al2O3 /YSZ composite, which represented a simple and low-cost method for fabrication of high-performance βʺ-Al2O3 /YSZ electrolyte.