Interfacial Stability of Layered LiNi_xMn_yCo_1–x–yO₂ Cathodes with Sulfide Solid Electrolytes in All-Solid-State Rechargeable Lithium-Ion Batteries from First-Principles Calculations

Among the key impediments to the practical application of all-solid-state lithium-ion batteries are the reactions occurring at the interfaces between the electrode active material, the solid electrolyte, and conductive additives such as carbon. Here, we provide in-depth insights into the relationship between composition and interfacial stability with sulfide solid electrolytes for the layered LiNixMnyCo1-x-yO2 (NMC) cathodes in wide-spread commercial applications today using density functional theory calculations. We show that increasing the Ni content and, to a lesser extent, increasing the Co content, has the effect of increasing reactivity with the Li6PS5Cl (LPSCl) solid electrolyte. This suggests that current efforts to reduce the Co content in cathodes may compromise potential application in all-solid-state architectures. However, we also find that common SEI phases such as Li2CO3, surface phases such as NiO, and oxide buffer layers such as LiNbO3 generally exhibit only limited reactivity with either LiMO2 or LPSCl. Hence, these phases, formed either in operando or added during synthesis, can potentially serve as effective barriers against further reaction, provided a uniform coating can be achieved.