Design of densified nickel-rich layered composite cathode via the dry-film process for sulfide-based solid-state batteries

Solid-state batteries (SSBs) based on sulfide solid electrolytes are expected to replace flammable liquid electrolytes in conventional lithium-ion batteries, potentially improving safety and energy density. However, widespread research on SSBs is hampered by several challenges, such as improving the interparticle connection and standardizing electrode formats to enhance the utilization of active materials throughout the composite cathode process. This study investigated the relationship between the microstructures of different electrode compositions and the electrochemical performance of densified composite cathodes prepared via a solvent-free dry-film process. Composite cathodes consisting of LiNi0.8Co0.15Al0.05O2 (NCA), Li6PS5Cl (LPSCl), Super-C65, and polytetrafluoroethylene (PTFE) particles were fabricated with respect to the content of NCA (75-85 wt%), and its microstructure, cycle performance, and charge transport kinetics were analysed using electrochemical impedance spectroscopy (EIS) and DC polarization measurements. The balance of ionic and electronic conductivity of the composite cathode with 80 wt% NCA significantly increased the capacity retention and rate capability. EIS measurements on cycled SSBs indicated that a balanced charge transport lowered the complex resistance in the composite cathode. Our findings imply that establishing a balanced conduction path in the composite cathode is the most important design/manufacturing criteria for high-performance SSB electrodes.