polymorphs from first principles

V₂O₅ is a very promising battery electrode material that can intercalate not only Li, but also more abundant alkaline metals such as Na and K, and even multivalent ions such as Mg, Ca, Zn, and Al. V₂O₅ can occur in several polymorphs, with at least 7 different polymorphs observed. During intercalation phase transitions can take place, and such phase transitions can be detrimental to battery performance. Understanding these transitions requires knowledge of the energetics and structural properties of the various V₂O₅ polymorphs.
We provide such understanding by employing density functional theory (DFT) calculations based on hybrid functionals. Since several of the polymorphs are layered, van der Waals interactions are important. However, this interaction is not included in standard DFT calculations. We therefore tested several approaches to include these interactions in combination with hybrid functionals. Based on our results we discuss the structural and electronic properties of the various polymorphs, and show the role polarons play in electronic transport. The obtained insights can be used to optimize future V₂O₅-based battery electrodes.