In order to achieve a high energy density, Ni-rich polycrystalline materials have been explored as cathode materials for application in ASSLB applying sulfide solid electrolyte. However, the interaction between the electrode and the solid electrolyte comes with severe problems, such as a poor solid electrolyte interface and interfacial stress fracturing during the charge-discharge process. To alleviate the side reaction and the interfacial resistance, a coating layer between the cathode and sulfide electrolyte has since been proposed and developed. However, the inner surface of the primary particles in the polycrystalline can also be a form of coating layer, which does not meet the solid electrolyte and it is hence an inefficient coating mechanism for an ASSLB where the cathode/electrolyte interface occurs purely at the cathode outer surface. Here, we report a new coating strategy for Ni-rich polycrystalline cathode materials using a sol-gel process that focusses on improving the cathode/electrolyte interface of ASSLB. Commercial polycrystalline LiNi0.8Co0.1Mn0.1O2 was coated with 1 wt% lithium and cobalt acetate precursor with different coating coverage being achieved via control of the stirring speed (200 and 600 rpm). The coating materials, which uniformly coated on the inner and outer surfaces of the polycrystalline (I-NCM), showed effectively improved electrochemical performance with the structural stability in LIB, where the liquid electrolyte has contact with inner surface of polycrystalline materials. However, the cathode material, which was mainly coated on the outer surface of polycrystalline materials (ONCM), exhibited improved performance in the ASSLB, which only has contact with the electrolyte at the surface of the active material polycrystalline. The physical properties of the coated cathode material were analyzed using SEM and XRD, and the electrochemical performance was investigated through initial charge/discharge capacity and cycle stability in both LIB and ASSLB simultaneously. This concept of intentionally surface coating the polycrystalline material can be applied as a new coating strategy to realize improvements in both electrochemical properties and electrode structural stability of ASSLB.

All-solid-state Batteries Polycrystalline Ni-rich Cathode Materials Precursor Coverage Control Sulfide Electrolytes Surface Modification Coating