Stable performance for pouch-type all-solid-state batteries enabled by current collector with optimized primer layer

Sulfide-based all-solid-state batteries (ASSBs) are advancing beyond solid electrolyte development to focus on composite electrode design and scalability for commercialization. Scaling from laboratory prototypes to pilot-scale production of large cells with high-energy density and high-performance ASSBs introduces new challenges. Large-scale electrode development necessitates selection of suitable polymeric binders that are compatible with sulfide electrolytes and exhibit strong binding forces for enhanced longevity. In this regard, we used rubber- and styrene-based polymeric binders in ASSBs and introduced a primer layer on the current collector, combining carbon conductive agents and polyvinylidene fluoride, to improve adhesion to the current collector. This primer layer reduces the binder content, which is an inactive component in the electrode, thereby diversifying Li-ion and electron conduction pathways and enhancing the ionic and electronic conductivity of the composite electrode. Furthermore, the primer layer not only prevents direct contact between the sulfide-based solid electrolyte and the Cu current collector but also blocks interactions between the Cu current collector and vaporized sulfur. By acting as a passivation layer, it effectively suppresses Cu corrosion. Consequently, a pouch-type full cell incorporating a primer layer demonstrated improved initial capacity and higher Coulombic efficiency under non-pressurized conditions. Specifically, the cell retained 80.7 % of its capacity after 100 cycles, demonstrating improved performance compared to uncoated full cells (64.8 %).