The densification of separators for solid-state batteries is significant to achieve high energy density, improved ionic conductivity, and a defined microstructure. In this study, fundamental investigations for the densification of Li3PS4-based separators by uniaxial pressing were conducted. Separator slurries based on p-xylene as solvent and two different contents of hydrogenated nitrile butadiene rubber type as binder were produced using a dissolver and were coated on a substrate foil by doctor blading for further analysis.

The ionic conductivity and density of the separators were evaluated as a function of fabrication pressures up to 200 MPa, as well as a stepwise compaction up to 1.5 GPa stack pressure for the binder-based separators. To assess the influence of the binder, the same measurements were also conducted for pure electrolyte powder. Moreover, pressure-induced strain, the cell setup for electrochemical impedance spectroscopy, as well as elastic recovery after pressure release were taken into account. The results emphasize the importance of a suitable binder system for the production of sulfide-based solid-state batteries, particularly concerning scalability, as well as important information for potential optimizations are provided.