Relevance of the Catholyte Mixing Method for Solid‐State Composite Cathodes

Abstract

The significant impact of the process steps on the electrode performance is one of the least developed aspects in the field of solid‐state batteries despite being a key issue for the transference of lab‐scale developments to production scale. To demonstrate that the knowledge of production parameters is essential, a set of high active material loading solid‐state batteries with a lithium metal anode and a polymer electrolyte is fabricated using different mixing methods for the catholyte preparation. Depending on the shear rate of the mixer, the polymer molecular weight and consequently, the viscosity of the catholyte is affected and these differences are preserved during the slurry preparation and electrode coating. The electrochemical performance of each cathode is studied in full‐cell configuration obtaining high areal capacities (≈1 mAh cm−2) and high specific capacities (92%, 82%, and 95% of the theoretical capacity of LiFePO4). After 50 cycles, composite cathodes mixed with high‐shear‐rate techniques experience a capacity fade related with the larger degree of deagglomeration of the C65 occurring when less viscous catholytes are used. Low‐shear‐rate cathodes keep the starting capacity, revealing a protective role of the catholyte during the wet‐mixing process.