Tailoring Binder Molecular Weight to Enhance Slurry‐Cast <scp>NMC</scp> Cathodes for Sulfide Solid‐State Batteries

We demonstrate for the first time the critical influence of binder molecular weight on the performance of slurry‐cast lithium nickel manganese cobalt oxide (NMC) cathodes in sulfide‐based all‐solid‐state batteries (SSBs). SSBs are increasingly recognized as a safer and potentially more efficient alternative to traditional Li‐ion batteries, owing to the superior ionic conductivities and inherent safety features of sulfide solid electrolytes. However, the integration of high‐voltage NMC cathodes with sheet‐type sulfide solid electrolytes presents significant fabrication challenges. Our findings reveal that higher molecular weight binders not only enhance the discharge capacity and cycle life of these cathodes but also ensure robust adhesion and structural integrity. By optimizing binder molecular weights, we effectively shield the active materials from degradation and mechanical stress, significantly boosting the functionality and longevity of SSBs. These results underscore the paramount importance of binder properties in advancing the practical application of high‐performance all‐solid‐state batteries.