Grain Boundary Engineering of Lithium-Ion-Conducting Lithium Lanthanum Titanate for Lithium-Air Batteries

Soldiers currently have 68 h worth of batteries to power all of their personal communication devices, which is currently limiting the mission operational time. To improve the mission time, current technology could be replaced with lithium (Li)-air batteries, which have higher energy densities and a porous cathode. Li-air battery performance is limited by the electrolytic membrane, which needs high Li-ionic conductivity. Lithium lanthanum titanate (Li3xLa(2/3)-xTiO3, or LLTO) is a promising electrolytic membrane material due to its high lattice conductivity; however, the total conductivity of LLTO is lowered by its grain boundaries. We aim to increase the grain boundary conductivity by introducing an intergranular film (IGF) through novel processing techniques such as room temperature ion exchange and magnetron sputtering on a fluidized powder bed. After incorporation of the IGF, the grain boundary conductivity increased by up to 60% while maintaining crystal structure, microstructure, and density of the sintered pellets. The results of this study indicate that if the best-performing materials from this report are incorporated into a battery and all of the Soldiers batteries were replaced, the Soldier would be able to stay on-task in a mission for approximately 340 h without replacing batteries.