Crystal Facet Energies and Surface Reconstructions in Spinel MgV₂O₄ Nanocrystals

Spinel vanadium oxides are promising candidate material for multivalent ion battery cathodes. In MgV₂O₄, the spinel framework provides ionic pathways for the migration and reintroduction of Mg²⁺ upon electrochemical cycling. These pathways are highly directional, in the case of spinels oriented parrallel to [110] and symmetric surface types, thus the overall crystal shape and size play an important role in cathode design.

In this contribution, we will present a study of MgV₂O₄ nanocrystal using conventional and scanning transmission electron microscopy (TEM/STEM) to determine the preferred facet growths, as well as provide an atomic-scale determination of the surface reconstructions observed along different orientations. We will report that crystals preferentially grow [111] followed by [001] surface types. We will also show that higher energy surfaces, such as [110] undergo surface reconstructions resulting in a step-like terrace formation.