Review of garnet-type Li₇La₃Zr₂O₁₂ solid electrolyte: materials and interface issues

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) solid electrolytes for solid-state lithium batteries have garnered significant research interest due to their excellent lithium-ion conductivity and wide electrochemical stable window. However, the LLZO-based electrolytes still face challenges in practical applications, such as instability in solid–solid contact, surface defects, and the presence of contaminants, which lead to interface failure between the electrolyte and the electrodes. This review article presents a comprehensive overview of the LLZO-based solid electrolytes, focusing on its materials properties and interface issues. The review begins with an introduction to the crystal structure of LLZO and its Li-ion conductivity and delves into the interface between LLZO and lithium anodes, discussing physical, chemical, and electrochemical stability, as well as strategies for interface regulation. The interface between LLZO and the cathode is also examined, including interface stability and engineering. Finally, the review summarizes the current understanding of LLZO and provides an outlook for future research directions.