Electrochemical sodium storage properties in monolayer VOPO4: A density functional theory prediction

The unique structural properties of two-dimensional materials make them promising for energy storage applications. This work theoretically predicts for the first time that Monolayer VOPO₄ (MNL VOPO₄), exfoliated from the delithiated phase of tetragonal LiVOPO₄, is stable at room temperature, exhibiting excellent thermodynamic and kinetic stability, thus making it a promising high-capacity anode material for sodium-ion batteries (SIBs). Compared to bulk VOPO₄, the monolayer structure significantly reduces the sodium ion migration energy barrier from 1.006 to 0.0795 eV, thereby markedly enhancing sodium ion migration kinetics. MNL VOPO₄ can adsorb up to 32 sodium ions, corresponding to a theoretical capacity of 634.88 mA h g⁻¹ and an energy density of 895.18 Wh kg⁻¹. Furthermore, the excellent structural stability of MNL VOPO₄ favors its cycling performance during charge and discharge processes. This work provides theoretical insights for better utilizing and developing multi-atomic phosphate compounds as electrode materials for secondary batteries.