Microstructure Evolution in Dry‑Coated Sulfidic All-Solid-State Battery Cathodes: Investigating Core-Shell Particle Morphology.

This study investigates continuous extruder mixing and high‑shear batch mixing to promote the formation of core-shell-like particle coatings for enhanced interfacial contact in dry‑coated sulfidic all‑solid‑state battery cathodes containing 82 wt.% high-Ni NCM85 (LiNi0.85Co0.10Mn0.05O2, particle size D50 3.8 µm) cathode active material and 0.5 wt.% polytetrafluoroethylene (PTFE) binder. Particle morphology and electrode microstructure are analyzed by particle size measurements, electron microscopy, and X-ray characterization. Morphological observations indicate that extrusion yields a robust PTFE fibril network and a more homogeneous electrode surface, where deformed Li6PS5Cl solid electrolyte particles suggest a core-shell-like coating. Batch mixing resulted in reduced electrode quality, tensile strength, and microstructure homogeneity. Despite its dedicated mechanofusion process and higher specific mechanical energy input (∼ speed, time), a distinct core-shell-like coating is not evident for such a small-particle system. Charge transport features are analyzed in symmetric cells under blocking conditions. Batch‑mixed electrodes attain higher electronic conductivity, whereas extruder‑mixed electrodes achieve higher ionic conductivity. These differences likely arise from microstructural features. Electrochemical characterization of half‑cells demonstrates the enhanced performance of extruder‑mixed electrodes, including higher active material utilization, reduced overpotentials, and improved rate capability. Overall, extruder mixing provides a scalable and effective route for engineering the electrode microstructure.