Experimental and DFT study of the structural, electronic, and thermoelectrical properties of Li3xLa2/3-xTiO3 (x = 0.125) ceramic leads free for battery applications

Abstract

We synthesized Li 3x La 2/3−x TiO 3 (LLTO, x = 0.125) via solid-state sintering, yielding a structurally stable orthorhombic perovskite with high environmental compatibility. The resulting material was characterized experimentally through X-ray diffraction (XRD), dielectric measurements (permittivity and loss), complex impedance analysis, and electrical conductivity testing. In parallel, first-principles computations using the BoltzTraP program and Density Functional Theory (DFT) were performed to determine the structural, electronic, and thermoelectric properties. Experimental results reveal a very high dielectric constant at low frequencies and high temperatures, with moderate dielectric loss behavior typical of ion-conducting perovskites. Nyquist plots demonstrate a significant decrease in impedance with increasing temperature, indicating enhanced mobility of Li + ions. Electrical conductivity increases with temperature, exceeding 10 −2 S/m at 800 °C, and the ionic conduction activation energy is estimated to be ≈ 1.45 eV. Complementarily, DFT confirms structural stability and a 1.65 eV semiconducting band gap. BoltzTraP simulations highlight outstanding thermoelectric performance, with a Seebeck coefficient up to 4.5 µV/K at 500 K and ZT figure of merit approaching 1, increasing steadily with temperature—ideal for thermal-to-electric conversion. This work emphasizes ionic conductivity's crucial role in solid-state electrolytes: it directly impacts Li + transport efficiency, thermal stability, and solid-state battery technologies' overall performance. Thus, LLTO's synergy of high ionic conductivity, mechanical/thermal stability, enhanced dielectric properties, and commendable thermoelectric positions it as a versatile material for next-generation solid-state Li-ion batteries and thermoelectric devices, as supported by recent research.