Critical role of dynamic structure on ion migration in H2V2O5 cathode material for rechargeable batteries

Understanding ionic migration mechanisms in solid-state materials is of paramount importance for advancing rechargeable batteries technologies. Combining first-principle calculations and ab initio molecular dynamics (MD) simulations, we reveal a novel mechanism of ionic migration in 3D tunnel-type H2V2O5, a newly developed cathode material formed by proton pre-intercalated α-V2O5, where hydrogen bonds dynamic play a critical regulatory role. We demonstrate the rotation behavior of -OH groups and the synergistic coupling between the -OH rotation and divalent ion migration in H2V2O5. The paddle-wheel mechanism, as we referred to here, enables ultralow migration barriers (Eb) of 0.56 eV for Zn2+ and 0.44 eV for Mg2+. In a sharp contrast, this mechanism was not observed for monovalent cations (such as Li+) using the climbing image nudged elastic band (NEB) method, which yields Eb of 0.57 eV. However, by MD simulations, we obtained the activation energy Ea of 0.23 eV for Li+ migration. The discrepancy was found to lie in the paddle-wheel mechanism, which needs to be activated at elevated temperature (≥150 K) for Li+ migration and, therefore, cannot be captured in NEB calculation at 0 K. Our results thus highlight the importance of understanding the paddle-wheel mechanism, meanwhile, the potential of proton pre-intercalated α-V2O5 for cathode materials of both monovalent and divalent ion batteries.