Lithium-Ion Cathode/Coating Pairs for Transition Metal Containment

Abstract

For many lithium-ion cathode materials, transition metal (TM) dissolution into the electrolyte contributes to cell degradation. Cathode coatings can limit TM dissolution by containing TMs in cathode materials. We perform density functional theory calculations to evaluate cathode/coating pairs for TM containment, specifically focusing on reactive stability of coating/cathode pairs as well as TM solubility in the coating materials. We consider stability and containment of materials at both synthesis and operating conditions. We find that many cathode/coating pairs are reactive when lithiated, while other cathode-coating pairs are stable when lithiated but become reactive following delithiation. Of all the coatings that we considered, Li3PO4 occupies a unique chemical position, in that its coatings on oxide cathode materials maintained equilibrium under both lithiated and delithiated conditions. Furthermore, for oxide cathode materials, the Li3PO4 coatings exhibit low TM solubilities across all cathode states of charge. Our results demonstrate that Li3PO4 is a promising candidate for stable coatings on oxide cathode materials to limit TM dissolution into the electrolyte.