Effect of Sn or Ta doping on the microstructure and total conductivity of perovskite Li0.24La0.587TiO3 solid electrolyte

Abstract Perovskite-structured Sn- or Ta-doped Li0.24–(q–4)xLa0.587Ti1–xMxO3 (LLTMxO, M = Sn or Ta, q is equal to the valence of M, x = 0, 0.02, 0.04, 0.06, 0.08) solid electrolytes are prepared by the pressureless sintering method for Li ion batteries. The phase composition, microstructure and electrical performance as a function of the type of doping elements and the amounts corresponding are studied by XRD, Raman spectrometer, SEM and electrochemical impedance spectroscopy. The LLTMxO pellets sintered at 1350 °C for 12 h have high relative densities (96.2%–97.9%) and high conductivities, where the total conductivity of LLTTa0.04O and LLTSn0.02O reach 4.09 × 10−4 S cm−1 and 2.98 × 10−4 S cm−1 at room temperature (RT) respectively. Compared with the pure specimen (1.52 × 10−4 S cm−1), the total conductivities of the doped specimens are more than doubled. In addition, Sn or Ta doping can significantly reduce the activation energy, with LLTTa0.04O exhibiting the low activation energy of 0.31 eV. The improvement in the total conductivity is attributed to the expansion of the Li ion transmission channels, the improvement of the relative density and the rise in the Li ion vacancy concentration, which are all resulted from the effect of dopant.