Modified Li7La3Zr2O12 (LLZO) and LLZO-polymer composites for solid-state lithium batteries

The solid-state lithium battery (SSLB) is recognized as the most promising candidate for energy storage devices with good safety and high energy density. The solid-state electrolyte (SSE), as the most critical component of solid-state lithium batteries (SSLBs), largely leads the future battery development. To obtain the SSE with good overall performance is a significant prerequisite to realize the application of SSLBs. Garnet Li7La3Zr2O12 (LLZO) family solid-state electrolytes (SSEs) have great potential for SSLBs, owing to high ionic conductivity, wide electrochemical stability window and excellent stability against lithium metal. Achieving cubic modified LLZO of high quality is always an extremely important task in LLZO engineering. Numerous works on LLZO family SSEs and their extensions have been tried, and plenty of breakthrough results are achieved. However, these electrolytes and their SSLBs still suffer from quite a few pivotal problems for a real business. Herein, this review presents a systematic, special summary and discussion on modified LLZO, LLZO-polymer composite electrolyte and their SSLBs to better understand the progress and challenges. Notably, (i) effects of element doping, preparation techniques and storage stability of modified LLZO, (ii) fabrication, properties and lithium-ion conduction mechanism of LLZO-polymer composite electrolytes, and (iii) the direct LLZO ceramic and LLZO-polymer composite derived SSLBs are emphatically concentrated. Additionally, the instructive prospects on LLZO ceramic SSEs and LLZO-polymer composite electrolytes for SSLBs are proposed as well. We suggest that this review could enable readers to deepen their understanding of this field.