LLZO separator sheets manufactured by a tape casting process and their electrochemical characterization

In terms of developing components for All Solid State Batteries, plenty of research focused on optimization of solid electrolyte properties. Garnet materials, especially LLZO, are considered as one very promising class of solid electrolytes due to their high reported Lithium ion conductivity in the range of 10-4 S/cm [1, 2], as well as their capability to use metallic lithium as anode. Nonetheless, scientific research mainly focusses on material properties and characterization. Until now very little research is focusing on the development of scalable technologies for the manufacturing of All Solid State Batteries. Within the project 'Artemys', funded by the German Federal Ministry of Education and Research - BMBF, a complete process chain for All Solid State Batteries shall be developed. One goal in this project is the development of a tape casting process for LLZO electrolyte-separator sheets. A suitable slurry recipe has been developed and process parameters for the casting as well as drying have been adapted. A sintering profile with a debinding step has been optimized to obtain dense and flat substrates. The properties of the separators were evaluated, using scanning electron microscopy and electrochemical methods. For evaluating the lithium ion conductivity, impedance spectroscopy measurements were conducted on samples with ion blocking Au electrodes as well as non-blocking lithium electrodes. The morphological and electrochemical properties of the casted and sintered LLZO sheets were compared to sintered pellets of the same powder. The correlation between sheet manufacturing parameters and the electrolyte-separator properties were investigated and will be shown in this contribution.[1] S. Ohta et al., J. Power Sources, 196 (2011), 332[2] Y. Li et al., J. Mater. Chem., 22 (2012), 15357