The Role of Ion-Polaron Electrostatic Attraction on Zn2+ Migration in α-V2O5 for Zinc Ion Battery: Insights from First-Principles Calculations

The migration of Zn²⁺ ions is significantly more challenging compared to that of Li⁺ ions within the same crystalline framework, leading to poor rate performance of zinc-ion batteries (ZIBs). Compared to Li⁺, the slower migration rate of Zn²⁺ is vaguely attributed to the stronger electrostatic interaction induced by Zn²⁺. Herein, the rule of how the size of the migration channel and electrostatic interaction affect Zn²⁺ and Li⁺ migration in α-V₂O₅ has been systematically investigated by first-principle calculations. It is found that expanding the layer spacing can facilitate Zn²⁺ migration. Once the layer spacing surpasses a certain threshold, further expansion does not lead to a continued reduction in the migration barrier. The local structure distortions caused by electron small polarons would lead to a decrease in migration channel size, which should have increased the energy barrier for Li⁺ and Zn²⁺ migration. However, interestingly, the electron small polarons decrease the energy barriers, which would be attributed to the ion-polaron electrostatic attraction. The higher activation barriers for the migration of Zn²⁺ ions compared to those of Li⁺ ions can be rationalized by the specific ion-polaron electrostatic attraction for Zn²⁺. Moreover, the comparative strength of the polaron-ion electrostatic attraction for alkali and alkaline earth metal ions is unveiled. Overall, this study provides theoretical insights into the role of ion-polaron electrostatic attraction on ion migration.