First principle study of the surface reactivity of layered lithium oxides LiMO2 (M = Ni, Mn, Co)

Abstract

LiNixMnyCo1−x−yO2 compounds (NMC) are layered oxides widely used in commercial lithium-ion batteries at the positive electrode. Nevertheless surface reactivity of this material is still not well known. As a first step, based on first principle calculations, this study deals with the electronic properties and the surface reactivity of LiMO2 (M = Co, Ni, Mn) compounds, considering the behavior of each transition metal separately in the same α-NaFeO2-type structure, the one of LiCoO2 and NMC. For each compound, after a brief description of the bare slab electronic properties, we explored the acido-basic and redox properties of the (110) and (104) surfaces by considering the adsorption of a gaseous probe. The chemisorption of SO2 produces both sulfite or sulfate species associated respectively to an acido-basic or a reduction process. These processes are localized on the transition metals of the first two layers of the surface. Although sulfate species are globally favored, a different behavior is obtained depending on both the surface and the transition metal considered. We conclude with a simple scheme which describes the reduction processes on the both surfaces in terms of formal oxidation degrees of transition metals.

Vallverdu, G.; Minvielle, M.; Andreu, N.; Gonbeau, D.; Baraille, I. First Principle Study of the Surface Reactivity of Layered Lithium Oxides LiMO2 (M = Ni, Mn, Co). Surface Science 2016, 649, 46–55.

doi:10.1016/j.susc.2016.01.004

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