Effect of Sb ³⁺ doping on the structure and performance of lithium lanthanum titanate solid electrolytes

Abstract Lithium lanthanum titanate (Li _0.33 La _0.56 TiO ₃ , LLTO) solid electrolyte exhibits excellent Li ⁺ ionic conductivity with high conductivity at room temperature. However, its relatively high grain boundary resistance results in a lower overall ionic conductivity in practical applications (10 ⁻⁵ –10 ⁻⁶ S·cm ⁻¹ ). To improve the total ionic conductivity, the LLTO solid electrolyte was synthesized by introducing Sb ³⁺ with a large ionic radius to dope Ti ⁴⁺ by the solid phase method, and the effects of different doping amounts on the structure and properties of the LLTO solid electrolyte were studied. It was found that when the doping content was low, Sb ³⁺ could promote the growth of grains and increase the density, which was conducive to the conduction of Li ⁺ ions. However, excessive doping will change the morphology of the grains, resulting in a decrease in density, which is not conducive to the improvement of ionic conductivity. The total ionic conductivity of the undoped samples in this study is 0.82 × 10 ⁻⁵ S·cm ⁻¹ . When the doping content is 0.03 mol, the activation energy decreases to 0.243 eV, the maximum bulk density reaches 5.557 g/cm ³ , and the optimal ionic conductivity increases significantly to 4.55×10 ⁻⁵ S·cm ⁻¹ , showing a substantial improvement compared with the undoped sample.