Transition metal oxides (TMOs) are a popular choice for cathode materials in secondary batteries and often exist as layered structures. Intercalation of ions between these layers can result in drastic volume changes, though this is primarily due to change in interlayer spacing which is dictated by weak van der Waals forces. This volumetric flexibility also allows for the intercalation of multivalent ions which can be much larger than lithium ions. One avenue to completely bypass this issue is by utilizing single layers, resulting in two-dimensional materials with high surface-to-mass ratios with their entire surface being accessible to ions. However, it is not clear yet how the properties of the single layers differ from those of their layered counterparts. We have carried out dispersion-corrected density functional theory (DFT) calculations to address this question for several layered TMOs as potential cathodes for multivalent ion batteries. These include the layered structures of: MnO2, TiS2, TiSe2, V2O5, as well as P3-Ni0.25Mn0.75O2, and their single-layer versions. We consider the voltage associated with intercalating/adsorbing various ions (e.g. Li, Na, Mg, Ca, Al) in/on these TMOs, the electronic structures as calculated from their density of states, changes in lattice constants, and ion diffusion barriers. This computational work will not only advance development of 2D battery materials but also help better understand layered systems.

2D transition metal oxides for multivalent ion cathodes

2019 Fall National Meeting

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