Speaker
Description
The development of lithium and lithium–air batteries increasingly relies on solid electrolytes and separators with high ionic conductivity. A promising material class for these applications is oxide ceramics based on lithium lanthanum titanate with a perovskite structure. However, practical implementation requires the fabrication of ultrathin, highly dense plates that ensure stable electrochemical performance. In this work, we aimed to identify synthesis and sintering parameters for Li3xLa2/3-xTiO3 ceramics that maximize densification and ionic conductivity.
Polycrystalline Li3xLa2/3-xTiO3 samples were prepared by a citrate–nitrate sol–gel route using titanyl nitrate and lithium and lanthanum salts. To stabilize titanium ions in solution, citric acid was added, followed by ethylene glycol; upon heating, gel formation proceeded via esterification and polymerization reactions. Thermal analysis/heat treatment indicated that crystallization of a single-phase perovskite product occurs in the 950–1000°C range. The primary crystallites formed after this heat treatment were 90–95 nm in size. Elemental composition control by atomic emission spectrometry confirmed that no lithium loss due to volatilization occurs up to 1200°C, which is essential for maintaining stoichiometry. The sol–gel approach provided high powder homogeneity and reactivity, enabling a reduction in the subsequent sintering temperature.
Sintering of pressed compacts at 1200–1300°C yielded ceramic pellets with a relative density of up to 95% of the theoretical (X-ray) density. Microstructural characterization revealed grains with a rectangular cross-section, consistent with tetragonal lattice symmetry. The highest ionic conductivity, measured by electrochemical impedance spectroscopy for samples sintered at 1300°C, reached 1.3 × 10-3 S cm-1. These conductivity values are comparable to those of known analogues and indicate the potential for scaling up the process. As a result, dense pellets with a thickness of 400–600 µm were obtained; due to the combination of high density and ionic conductivity on the order of ~1 mS cm-1, they can be used as separators for lithium–air batteries.