Ab initio investigations on bulk and monolayer V2O5 as cathode materials for Li-, Na-, K- and Mg-ion batteries

Abstract

First-principles computations based on density functional theory (DFT) were performed to investigate the performance of bulk and monolayer V₂O₅ as the cathode material for Li-, Na-, K- and Mg-ion batteries. Both the average voltage and ion migration barrier were studied. The results indicate that alkali metal ions with a large ionic radius (such as Na and K) have much lower migration barriers (0.44 and 0.39 eV for Na and K, respectively) on monolayer V₂O₅ than in bulk V₂O₅ (1.17 and 1.66 eV) without great voltage loss, while for Li polymorphs, the difference between monolayer and bulk V₂O₅ is minimal. However, the performance of monolayer V₂O₅ is not ideal enough as the cathode material for multivalent metal-ion (such as Mg) batteries. As a result, for Na- and K-ion batteries with a large ionic size, monolayer V₂O₅ is an attractive cathode material.