Phase Composition, Density, and Ionic Conductivity of the Li₇La₃Zr₂O₁₂-Based Composites with LiPO₃ Glass Addition

The glass-ceramic composite electrolytes based on tetragonal Li₇La₃Zr₂O₁₂ (t-LLZ) and cubic Al-doped Li₇La₃Zr₂O₁₂ (c-LLZ) with the LiPO₃ glass additive have been prepared. The electrical conductivity and microstructure of the t-LLZ/LiPO₃ and c-LLZ/LiPO₃ composites have been investigated. The phase evolution of electrolytes has been studied using XRD, SEM, and Raman spectroscopy. It was indicated that the impurities formation depends on the composition of the composite. The phase composition of the solid electrolytes determines their thermal properties, which have been studied by the DSC method. The relative density of the obtained composite electrolytes was established to be higher than one of the sintered t-LLZ and c-LLZ. The Li⁺ conductivity of the t-LLZ-based composites gradually increased from 4.6 × 10^-7 S cm^-1 (undoped t-LLZ) to 2.5 × 10^-6 S cm^-1 (t-LLZ/5 wt % LiPO₃ composite) at 25 °C. The highest total conductivity of the c-LLZ/LiPO₃ composites has been achieved by introducing 1 wt % additive (0.11 mS cm^-1 at room temperature), whereas further doping resulted in the impurities formation.