Density Optimization of Lithium Lanthanum Titanate Ceramics for Lightweight Lithium-Air Batteries

The US Army has an urgent need for robust, high-energy-density, lightweight energy storage devices, and the lithium (Li)-air battery is one promising solution due to its high-energy density and lower weight compared with Li-ion batteries. The ceramic electrolytic membrane is currently the bottleneck for successful implementation of Li-air batteries. The density of the electrolytic membrane material, Li0.35La0.57TiO3 (LLTO), must be optimized for LLTO to attain its maximum ionic conductivity because previous work done by the US Army Research Laboratory has demonstrated a relationship between density and conductivity in LLTO. The sintering behavior of LLTO requires comprehensive study to synthesize dense ceramics with high ionic conductivity. Therefore, the sintering temperature was varied from 1,100 C to 1,350 C, and the density of LLTO pellets was measured using 3 different techniques X-ray diffraction, optical microscopy, and scanning electron microscopy, which were also used to determine the phases, crystal structure, crystallite size, and microstructure of the sintered LLTO pellets. It was found that sintering at 1,200 C produced tetragonal LLTO ceramics with the highest density more than 95% of the theoretical density. Lower sintering temperatures yielded LLTO samples with lower densities and smaller crystallite sizes. Sintering at 1,300 C produced concave pellets with slight preferred crystallographic orientation.
The original document contains color images. Prepared in collaboration with the Department of Chemistry, Rochester Institute of Technology, Rochester, NY.