Exploring the use of butadiene rubbers as a binder in composite cathodes for all-solid-state lithium batteries

Among the various next-generation battery systems, all-solid-state lithium batteries (ASSLBs) employing sulfide-based solid electrolytes have garnered considerable attention because of their high energy density and enhanced safety compared to conventional lithium-ion batteries (LIBs) with liquid electrolytes. The fabrication of composite cathodes for ASSLBs by the wet-slurry process is highly desirable, because it can be scaled into a large sheet and be applied to the established slurry-processed electrode manufacturing technology of LIBs. A polymer binder in the composite cathode is an important component for maintaining good interfacial contacts among the electrode components (active material, solid electrolyte, and conducting carbon) during charge and discharge cycles. In this study, we used polybutadiene and acrylonitrile-butadiene rubbers (NBR) with different acrylonitrile (AN) contents as a polymer binder in the composite cathode. Our results demonstrated that a composite cathode employing NBR with 25 wt.% AN (NBR25) showed good elastic properties and superior adhesion without the large deterioration of interfacial contacts during cycling. The solid-state Li-In/Li6PS5Cl/LiNi0.7Co0.1Mn0.2O2 cell assembled with the composite cathode employing NBR25 exhibited an initial discharge capacity of 149.0 mAh g−1 with good capacity retention at 0.2 C and 25 °C.