Effect of a conformal lithium titanate buffer layer deposited via powder atomic layer deposition on the performance of sulfide-based all-solid-state batteries

Abstract

The capacity degradation mechanisms that occur during cycling in sulfide-based all-solid-state batteries employing high-Ni-content cathode active materials are systematically identified and mitigated by introducing a lithium titanate (LTO) coating layer on the cathode surface. Uniform and conformal LTO coatings with varying thicknesses were successfully formed on the surfaces of spherical cathode particles via powder atomic layer deposition. Detailed analysis reveals that uncoated NCA (LiNixCoyAlzO2) suffers from rapid capacity fading in the early cycling stages due to chemical instability at the cathode–electrolyte interface, while in the later stages, structural degradation caused by irreversible phase transitions becomes dominant. The LTO coating effectively suppresses both interfacial side reactions and structural phase transitions by serving as a chemically and structurally stabilizing interlayer, thereby enhancing the long-term performance and stability of the cell. As a result of the LTO coating, cells comprising (Li[sbnd]In)|LPSCl (Li6PS5Cl)|cathode composite with LTO-coated NCA achieve a markedly improved electrochemical performance, retaining 74 % of the capacity after 100 cycles—significantly outperforming uncoated NCA cells, which show only 48 % retention.