Interplay of Adsorbed and Free Polymer Governs Microstructure and Processability of Battery Slurries

Abstract In Li-ion battery anodes, sodium carboxymethyl cellulose (CMC) serves as an indispensable binder despite its minimal electrochemical contribution. Even at low concentrations, CMC imparts colloidal stability, ensures adequate flow during coating, and promotes uniform distribution of active materials. Within the slurry, CMC simultaneously exists in adsorbed and nonadsorbed (free) states, each interacting with active components through distinct mechanisms. This coexistence gives rise to a complexity that belies the apparent simplicity of binder chemistry, raising fundamental questions about how binders govern slurry microstructure and rheological behavior. In this study, we systematically vary CMC molecular weight and concentration to control the degree of intermolecular interactions between CMC and active components, and explicitly decouple the roles of adsorbed and free polymer f…