Unraveling the Role of Hydrogen Insertion in Enhancing the Electrochemical Performance of the V2O5 Cathode for Mg-Ion Batteries: A First-Principles Study

• Published in: ACS applied energy materials 2023-09, Vol.6 (17), p.8666-8676
• Main Authors: Untarabut, Panupol, Singsen, Sirisak, Ngamwongwan, Lappawat, Fongkaew, Ittipon, Junkaew, Anchalee, Suthirakun, Suwit
• Format: Article
• Language: English
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.3c00830

Vanadium pentoxide, V2O5, is a promising candidate for Mg-ion batteries owing to its high theoretical capacity. But sluggish electron–ion conductivity and capacity fading limit its commercialization. Adding a small amount of water into the electrolyte greatly enhances the charge transport kinetics and increases the capacity of the V2O5 cathode. It is suggested that water could dissociate and provide H that could be inserted into the cathode, but the role of H insertion remains unclear. In this work, we carried out first-principles computations to explore the effect of H insertion on the electronic conductivity, Mg diffusion kinetics, and structural stability upon Mg intercalation. We find that H insertion at high concentrations greatly reduces the band gap and increases the electronic conductivity of the material. The inserted H could act as a charge carrier, which enhances the capacity of the cathode. The transport kinetics of H is much faster than that of Mg. It is expected that during discharge, the cathode contains a high content of H before Mg intercalation. The preinserted H structure hastens the Mg diffusion by lowering the diffusion barrier of Mg from 0.93 to 0.23 eV. In addition, the fully protonated V2O5 cathode greatly suppresses irreversible α to δ phase transition which is considered the main cause of capacity fading. The enhanced ion transport kinetics and suppression of phase transformation stem from the weakened electrostatic interaction between the Mg ion and the lattice oxygen upon the H insertion. These findings could be used to rationally design the strategy to improve the electrochemical performance of the V2O5 cathode of Mg-ion batteries.