Nanostructured Garnet-type Li₇La₃Zr₂O₁₂: Synthesis, Properties, and Opportunities as Electrolytes for Li-ion Batteries

The garnet-type Li⁺ ion conductor Li₇La₃Zr₂O₁₂ (LLZO) is a promising candidate as a solid electrolyte for all-solid-state Li-ion batteries. Significant progress towards understanding the structure and properties of LLZO, conventionally synthesized using solid state reaction methods, has already been made in the last decade. The aim of this review is to summarize recent efforts on the synthesis of nanostructured LLZO, with a focus on electrospinning, cellulose templating, and low-temperature (< 900 °C) sol-gel based methods, as well as to highlight the unique properties of nano-sized LLZO. Further research is still needed to fully understand the potential benefits of using nanostructured LLZO in pellet-type, ceramic electrolytes, but a natural opportunity for nanostructured LLZO is in the role of ceramic filler within solid composite polymer electrolytes (CPEs). The current status of CPEs embedded with LLZO ceramic fillers is summarized, including the elucidation of Li⁺ transport pathways using nuclear magnetic resonance (NMR) spectroscopy.