Effect of thickness and uniformity of LiNbO3-coated layer on LiNi0.5Co0.2Mn0.3O2 cathode material on enhancement of cycle performance of full-cell sulfide-based all-solid-state batteries

Abstract

Although LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode active material (CAM) is considered to have application potential in sulfide-based all-solid-state batteries (ASSBs), CAM/solid electrolyte interfacial instability remains a significant limiting factor. To effectively improve the interfacial stability and long-term cycling performance, NCM523 cathode material was coated with LiNbO3 layers of different thicknesses and uniformity. As a result, the cycle performance was greatly enhanced by increasing the thickness and uniformity of the LiNbO3-coated layer. Our findings further demonstrate that a thick (≥9 nm) and uniform coated layer (surface without uncoated area) displays outstanding electrochemical performance, especially cycle stability (capacity retention of 85.1% after 300 cycles at 60 °C), indicating that this strategy is very effective for constructing high-performance NCM cathodes for sulfide-based ASSBs. Moreover, the performance improvement mechanism was investigated by electrochemical impedance spectroscopy (EIS) combined with XPS and TEM-EDX analysis. The findings reveal that controlling the thickness and uniformity of the coating material plays a crucial role in the effective suppression of interface side reactions and resultant performance degradation in NCM cathodes.