Redefining polymer binders: enabling ion transport and interfacial stability in sulfide-based all-solid-state lithium batteries

Abstract

Research on sulfide-based all-solid-state lithium batteries (ASSLBs) has predominantly focused on primary components such as active materials, solid electrolytes, and conductive carbons. In contrast, polymer binders have received relatively little attention, despite their critical influence on cell performance. The lack of systematic understanding and rational design strategies for binder materials hinders their effective contribution to the practical development of ASSLBs. While previous studies have primarily emphasized the binders' mechanical integrity and processability, their potential contribution to ionic conductivity and interfacial stability remains largely unexplored. Departing from this traditional focus, this review highlights the essential role of polymer binders in enhancing interfacial adhesion and maintaining continuous Li+ ion conductive pathways within electrodes and solid electrolyte sheets. Binder design should aim to integrate mechanical robustness with ionic functionality to promote uninterrupted ion transport. From this perspective, polymer binders are redefined as essential design elements that not only provide mechanical cohesion but also compensate for ion transport limitations and stabilize internal interfaces. Their strategic integration at the film level is anticipated to be a decisive factor in advancing ASSLBs technologies.