Dry coating of active material particles with sulfide solid electrolytes for an all-solid-state lithium battery

In this study, we present a dry coating process to produce a core-shell composite particle for an all-solid-state lithium battery, where a single particle of the active material is coated with solid electrolytes. LiNi1/3 Co1/3Mn1/3O2 (NCM) and Li3PS4 (LPS), which are typical cathode active material and sulfide solid electrolyte, were used. A dry impact-blending device was employed for the dry coating process. We demonstrated that a single particle of NCM was uniformly coated with a continuous layer of LPS by the dry coating process without any breakage or attrition of NCM, to produce an NCM@LPS core-shell particle. The charge-discharge cycling tests showed that the rate and cycle performances of an all-solid-state half-cell prepared with the NCM@LPS core-shell particles significantly improved. The three-dimensional internal structure of the composite cathode was subsequently analyzed using FIB-SEM with an image reconstruction technique. The results revealed that the composite cathode prepared with the NCM@LPS core-shell particles had a (i) high interfacial contact area between NCM and LPS and (ii) well-percolated ion transport pathway. In conclusion, the core-shell composite particle contributed to the structure of the composite cathode, thus resulting in improved cell performance.