Innovative Design for the Enhancement of Lithium Lanthanum Titanate Electrolytes

Abstract

The high ionic conductivity in lithium lanthanum titanate perovskite ceramics, Li3xLa(2/3)-xTiO3 (LLTO), is well-known for the x ≈ 0.11 lithium concentration. The grain conductivity is approximately 10–3 S·cm–1 at room temperature, which makes this compound one of the best candidates for the development of solid-state electrolytes. However, lower grain boundary conductivity (10–6 to 10–4 S·cm–1) blocks lithium diffusion. In order to increase the total conductivity of LLTO ceramics, single crystal fibers of lanthanum aluminate (LAO) were inserted into its green ceramic matrix. Our hypothesis is that single crystal fibers are capable of inducting LLTO abnormal grain growth, thus improving the overall electrical conductivity of the composite. The results show that LAO single crystals act like seeds, creating abnormal grain growth at the LaAlO3 fiber surface. The impedance spectroscopy shows that the new composites have a substantial relative enhancement of total ionic conductivity (more than 200%) in comparison with the monolithic ceramic samples. This result shows the possibility of developing a novel composite design as a candidate for solid electrolyte applications.