Compaction of Separator and Composite Cathode Sheets for Sulfide-based All-solid-state Batteries

Summary:

Increasing the sustainability of energy storage systems is one of the main challenges of the 21st century. The efforts to address this issue have led to a high level of attention for electrochemical storage solutions. As a result, conventional lithium-ion batteries developed rapidly in recent years and their maximum energy density will be reached soon. Therefore, research around the world focuses on new storage technologies. Among these, all-solid-state batteries are particularly promising since they not only allow a significant increase in energy density but also improve characteristics such as long-term stability and safety.
Therefore, we are looking at a wet chemical production process for sulfidic separators and composite cathodes that is suitable for upscaling. The question that has emerged is whether it is possible to reach the indispensable density by uniaxial pressing at room temperature. Thereby it is important to examine the contact areas between particles.
Two types of particle contact exist in the components of the sulfidic all-solid-state battery. Contact type 1 is the contact between the solid electrolyte particles. Contact type 2 is the contact between the solid electrolyte particles and the cathode active material particles. Our research goal is the analysis of the influence of the compaction process on the particle contacts for both slurry-coated solid electrolyte separators as well as composite cathodes.
A SEM top view of a separator sheet reveals little contact between the solid electrolyte particles after the coating process. However, their high deformability enables densification of the coating after compression.
The microstructural analysis of the composite cathode shows that the particle contacts are barely present before the compression step. However, during compression, predominately the solid electrolyte deforms, resulting in improved contact between the particles.
In summary, uniaxial pressing at room temperature seems to be suitable for the densification of sulfidic cell components and is largely determined by the deformation of the solid electrolyte.