Unveiling Incompatibility of High Nickel Cathode With p‐xylene Solvent for Facile Wet‐Slurry Process in All‐Solid‐State Batteries

All-solid-state batteries (ASSBs) are considered one of the most promising next-generation batteries due to their outstanding safety and superior energy density. For the commercial success of ASSBs, developing a scalable wet-slurry-based electrode manufacturing process is essential. In this regard, non-polar solvents have been generally used in the wet-slurry process with sulfide-based solid electrolytes (SEs) to avoid their chemical crosstalk. Although many studies on the chemical compatibility between sulfide-based SEs and non-polar solvents have been conducted, to the best of the knowledge, an in-depth understanding of the interfacial chemistry between those solvents and active materials is not fully elucidated. In this study, the chemical incompatibility of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) cathode with p-xylene, a representative non-polar solvent, through in-depth analyses of cation mixing, Ni dissolution, and surface reconstruction is revealed. Contrary to expectations, severe interfacial challenges arise from the side reactions between NCM and p-xylene, resulting in poor electrochemical properties in ASSBs. The origin of the decrease in electrochemical performances of the wet-slurry-based electrodes in ASSBs is unveiled, which can be addressed by employing a surface protective coating layer on NCM cathodes.