Composition-Controlled Cathode Protective Layer via Powder-Atomic Layer Deposition for All-Solid-State Batteries

Controlling the ionic and electronic conductivities of the protective layers on cathode active materials (CAMs) is critical for interface stabilization with sulfide-based solid electrolytes in all-solid-state batteries (ASSBs). In this study, lithium zirconium oxide layers with varying compositions are grown on LiNi_0.8Co_0.1Mn_0.1O₂ using an O₃-based atomic layer deposition process. The ionic conductivity reaches 2.20 × 10^-7 S cm^-1 at 25 °C, and the electronic conductivity ranges from 10^-10 to 10^-7 S cm^-1 depending on composition. These composition-dependent transport properties directly affect electrochemical performance, leading to a 4.5% difference in initial Coulombic efficiency and a 37% difference in long-term retention. Compared to their uncoated counterparts, the coated CAMs exhibited 6.7% and 43% increases in initial efficiency and capacity retention of the cells, respectively. This study establishes a quantitative correlation between the protective layer's composition and battery performance, emphasizing that composition control is a key strategy for interfacial engineering in sulfide-based ASSBs.