Metal-organic framework-derived porous shuttle-like vanadium oxides for sodium-ion battery application

Vanadium oxides with a layered structure are promising candidates for both lithium-ion batteries and sodium-ion batteries (SIBs). The self-template approach, which involves a transformation from metal-organic frameworks (MOFs) into porous metal oxides, is a novel and effective way to achieve desirable electrochemical performance. In this study, porous shuttle-like vanadium oxides (i.e., V₂O₅, V₂O₃/C) were successfully prepared by using MIL-88B (Ⅴ) as precursors with a specific calcination process. As a proof-of-concept application, the asprepared porous shuttle-like V₂O₃/C was used as an anode material for SIBs. The porous shuttle-like V₂O₃/C, which had an inherent layered structure with metallic behavior, exhibited excellent electrochemical properties. Remarkable rate capacities of 417, 247, 202, 176, 164, and 149 mAh·g^-1 were achieved at current densities of 50, 100, 200, 500, 1, 000, and 2, 000 mA·g^-1, respectively. Under cycling at 2 A·g^-1, the specific discharge capacity reached 181 mAh·g^-1, with a low capacity fading rate of 0.032% per cycle after 1, 000 cycles. Density functional theory calculation results indicated that Na ions preferred to occupy the interlamination rather than the inside of each layer in the V₂O₃. Interestingly, the special layered structure with a skeleton of dumbbell-like V–V bonds and metallic behavior was maintained after the insertion of Na ions, which was beneficial for the cycle performance. We consider that the MOF precursor of MIL-88B (Ⅴ) can be used to synthesize other porous V-based materials for various applications.