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.