Ceramic solid state-electrolytes attract significant attention due to their intrinsic safety and, in case of the garnet type Li_6.45Al_0.05La₃Zr_1.6Ta_0.4O₁₂ (LLZO), the possibility to use Li-metal anodes to provide high energy densities on cell and battery level. However, the widespread application of all solid-state cells depends both on the development of scalable manufacturing processes and the increase of cell capacity.

One key factor for the fabrication of LLZO containing cell components via solvent based production routes is the sensitivity of LLZO to air and protic solvents due to the Li⁺/H⁺-exchange and its influence on the reproducibility and the electrochemical properties of the component. Only a new mechanistic understanding allowed for the development of a new, tailored tape-casting process for LLZO components. Thin, free-standing LLZO separators with a total Li-ion conductivity of 3.90 ∙ 10^-4 S cm^-1 and a critical current density of over 300 µA cm^-2 can now be fabricated.

Additionally, the fundamental understanding of the process allowed for the development of all-ceramic free-standing LiCoO₂/LLZO mixed cathodes. The obtained free-standing cathodes have sufficient mechanical stability to allow the application of hybrid and ultra-thin separators to further increase the energy density on the full cell level to industrially relevant levels. Further morphology engineering by introduction of a sequential layer casting enabled the production of mixed cathodes resulting with opposite concentration gradients for the active material and the electrolyte over the thickness of the cathode. With this optimized microstructure, the discharge capacity of the mixed cathodes was increased to 2.8 mAh cm^-2 utilizing 99% of the theoretical capacity.