Practical development and challenges of garnet-structured Li₇La₃Zr₂O₁₂ electrolytes for all solid-state lithium-ion battery—A review

In order to achieve higher safety and higher energy density lithium-ion batteries, all solid-state lithium-ion batteries (ASSLIBs) have been widely studied. Recently, some review and experimental papers have focused on how to improve the ionic conductivity, stabilize the electrochemical performance and enhance the interface compatibility between the electrodes and the solid-state electrolytes (SSEs), including oxides, sulfides, composite electrolytes, gel electrolytes and so on. Among these SSEs, the garnet-structured Li₇La₃Zr₂O₁₂ (LLZO) is regarded as one of the most expected candidates for SSEs. However, numbers of challenges also exist for garnet-structured LLZO-based electrolytes, such as low ionic conductivity, indefinite cubic phase, poor interfacial compatibility with anodes/cathodes and so on, which urges us to explore effective solutions. Herein, we will review recent developments on garnet-structured LLZO and provide comprehensive insights to guide the development of garnet-structured LLZO electrolytes in this work. We will not only systematically and comprehensively discuss the following content, including preparation, element doping, the structure, stability, polymer-ceramic composite electrolytes (PCCEs) and interface improvement of LLZO, but also give a forward-looking perspective. We hope that it would provide meaningful guidance for the advanced solid garnet-electrolytes, and we think that the commercialization of ASSLIBs will be achieved in the near future.