Effect of Lithium Precursor on the Crystal Structure and Ionic Conductivity of Li₇La₃Zr₂O₁₂ Oxide Electrolyte

The garnet-structured solid electrolyte Li₇La₃Zr₂O₁₂ (LLZO) has attracted attention as a solid electrolyte for all-solid-state batteries due to its wide electrochemical window and high ionic conductivity. However, the formation of impurity phases and tetragonal LLZO during synthesis can rapidly reduce lithium-ion conductivity, and the low stability in air and water can lead to lithium loss. The effect of lithium sources including Li2CO3, LiOH and LiNO3 on the crystal structure, microstructure, and ionic conductivity of LLZO was investigated. X-ray diffraction (XRD) analysis was performed to confirm the crystallization and phase formation of the synthesized LLZO and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) was used to analyze the microstructure and chemical composition. Electrochemical impedance spectroscopy (EIS) was also used to confirm the ionic conductivity. As a result, LLZO prepared with LiOH as the source was confirmed to be cubic without impurities or intermediate phases, compared to solid electrolytes prepared with Li₂CO₃ and LiNO₃. In addition, a uniform particle size and distribution of less than 2 μm and an ionic conductivity of 1.311 × 10^-4 S cm^-1 at room temperature were confirmed. These results suggest that the choice of lithium source can significantly affect the properties of LLZO, and that LiOH is a promising lithium source for the preparation of high-performance LLZO solid electrolytes. In future studies, the effect of lithium sources on the properties of LLZO should be investigated in more detail and new methods should be developed to fabricate high-performance LLZO solid electrolytes.