Characterization of the Calendering Process for Sulfide-Based Solid-Electrolyte Separators

Industrializing solid-state batteries is crucial for advancing energy storage technologies, as solid-state batteries offer a promising alternative to conventional lithium-ion batteries with increased energy densities and improved safety. Reducing the porosity and enhancing the particle-to-particle contact between particles of the solid-electrolyte separator has been shown to improve the performance of solid-state batteries. This study investigates calendering as a scalable process to achieve a homogeneous densification of solid-electrolyte separators. The influence of key process parameters on the solid-electrolyte separator’s properties is examined using a pilot-scale calender for the processing of both sheet-based and coil-based materials. Interactions between the parameters and the resulting microstructural, mechanical, and electrochemical properties of the solid-electrolyte separators are analyzed. The findings of this work demonstrate that calendering significantly reduces the porosity of solid-electrolyte separators, creating mechanically robust, flexible free-standing separators. This enables roll-to-roll processing and thus provides a scalable alternative to the predominantly used uniaxial pressing technique for producing solid-electrolyte separators.