Cubic phase behavior and lithium ion conductivity of Li7La3Zr2O12 prepared by co-precipitation synthesis for all-solid batteries

•Cubic phase LLZO powders were synthesized by a modified co-precipitation process.•The particle size was strongly dependent on the calcination temperature.•The ionic conductivity of the cubic LLZO pellet is 3.2 × 10−4 S cm−1 at 25 °C.•Calcination temperature is critical to obtain a sintered pellet with high density.

Li7La3Zr2O12 powders with cubic phase and high ionic conductivity were synthesized using co-precipitation process, in which the mixture precursors of La–Zr–(OH)x and Li source were calcined and sintered at different conditions. XRD analysis showed that cubic phase of garnet-type LLZO powder is formed as calcined at 700 and 800 °C, respectively. However, tetragonal phase is formed at above 900 °C. As these samples were sintered in the form of pellets at 1200 °C, LLZO powder calcined at 700 °C showed excellent ionic conductivity of 3.2 × 10−4 S cm−1 at 25 °C, indicating cubic structure of LLZO single phase and high relative density of above 90% that is different with LLZO powder calcined at 900 °C.

Graphical abstractFigure shows the cross-sectional SEM image of the LLZO pellets after calcination at 1200 °C for 5 h, which is showed a compact microstructure, resulting in the high ionic conductivity.Figure optionsDownload full-size imageDownload as PowerPoint slide