Processing of Sulfide Solid Electrolytes for All-Solid-State Battery Electrodes. A Scalable Composite Cathode Manufacturing Approach

All-solid-state batteries (ASSB) exhibit significant benefits in gravimetric and volumetric energy density, operating temperature range, and safety in comparison to conventional liquid electrolyte based systems. While fundamental research at the level of materials has made considerable progress in recent years, the scalable production of components and cells for ASSB has hardly been addressed so far. The present work focusses on the processing of sulfide solid electrolytes. This class of material exhibits high ionic conductivities > 1 mS/cm and allows processing at room temperature. At IKTS a scalable processing of sulfide electrolytes as solid electrolyte separator (SES) and ion conducting phase in composite electrodes (anode, cathode) is investigated. For the manufacturing of slurry based SES, the sulfide electrolyte is first dispersed in a binder solution and then casted using a doctor blade. To prepare composite electrodes, the sulfide electrolyte, the active material and an optional electron conducting phase are dispersed in a binder solution. These slurries are directly coated on current collector foils. The microstructure, homogeneity and electrochemical properties of the composite electrodes and the SES are analyzed and compared to pristine, cold-plastically compressed reference materials. The processing conditions have been varied to achieve high ionic conductivities for the slurry based manufacturing, while exhibiting significantly higher scalability potential when compared to the cold-plastic reference process. Based on these developments, advanced sulfide-based composite electrodes are prepared with blended active materials that exhibit a protective coating. Following systematic studies on the impact of design, composition and reactivity against the sulfide electrolyte, blends with favorable processability , improved energy and power density and enhanced cycling performance are designed, serving as input specifications for the electrode processing.