Dense freeze-cast Li7La3Zr2O12 solid electrolytes with oriented open porosity and contiguous ceramic scaffold

Freeze casting is used for the first time to prepare solid electrolyte scaffolds with oriented porosity and dense ceramic walls made of Li7La3Zr2O12 (LLZO), one of the most promising candidates for solid-state battery electrolytes. Processing parameterssuch as solvent solidification rate, solvent type, and ceramic particle sizeare investigated, focusing on their influence on porosity and ceramic wall density. Dendrite-like porosity is obtained when using cyclohexane and dioxane as solvents. Lamellar porosity is observed in aqueous slurries resulting in a structure with the highest apparent porosity and densest ceramic scaffold but weakest mechanical properties due to the lack of interlamellar support. The use of smaller LLZO particle size in the slurries resulted in lower porosity and denser ceramic walls. The intrinsic ionic conductivity of the oriented LLZ ceramic scaffold is unaffected by the freeze casting technique, providing a promising ceramic scaffold for polymer infill in view of designing new types of ceramic-polymer composites.