Effect of surface carbonates on the cyclability of LiNbO$_{3}$-coated NCM622 in all-solid-state batteries with lithium thiophosphate electrolytes

While still premature as an energy storage technology, bulk solid-state batteries are attracting much attention in the academic and industrial communities lately. In particular, layered lithium metal oxides and lithium thiophosphates hold promise as cathode materials and superionic solid electrolytes, respectively. However, interfacial side reactions between the individual components during battery operation usually result in accelerated performance degradation. Hence, effective surface coatings are required to mitigate or ideally prevent detrimental reactions from occurring and having an impact on the cyclability. In the present work, we examine how surface carbonates incorporated into the sol–gel-derived LiNbO$_{3}$ protective coating on NCM622 [Li$_{1+x}$(Ni$_{0.6}$Co$_{0.2}$Mn$_{0.2}$)$_{1-x}$O2] cathode material affect the efficiency and rate capability of pellet-stack solid-state battery cells with β-Li$_{3}$PS$_{4}$ or argyrodite Li$_{6}$PS$_{5}$Cl solid electrolyte and a Li$_{4}$Ti$_{5}$O$_{12}$ anode. Our research data indicate that a hybrid coating may in fact be beneficial to the kinetics and the cycling performance strongly depends on the solid electrolyte used.