Mechanical properties of the solid electrolyte Al-substituted Li7La3Zr2O12 (LLZO) by utilizing micro-pillar indentation splitting test

Garnet structured Al-substituted Li₇La₃Zr₂O₁₂ (Al:LLZO) is a promising candidate as electrolyte in all-solid-state Li-ion batteries due to its chemical stability against Li-metal and high voltage cathode materials. In order to ensure long-term stable operation, electrolyte crack growth induced and/or the volume change of the active material on the cathode side needs to be avoided, requiring in particular knowledge of local and global mechanical properties of the electrolyte material. Micro-pillar splitting test was used for the first time on this material to determine the microscopic fracture toughness of single grains and compare it with conventional Vickers indentation fracture toughness (VIF), which represents macroscopic fracture toughness. Both methods yielded comparative results. In conclusion, the micro-pillar splitting test can be used as an advanced locally resolved characterization method that can open up new experimental directions for characterizing and understanding battery materials and enable a targeted approach for material improvements.