Sodium superionic conductor (NASICON)-type compounds have been regarded as promising cathodes for sodium-ion batteries (SIBs) due to their favorable ionic conductivity and robust structural stability. However, their high cost and relatively low energy density restrict their further practical application, which can be tailored by widening the operating voltages with earth-abundant elements such as Mn. Here, we propose a rational strategy of infusing Mn element in NASICON frameworks with sufficiently mobile sodium ions that enhances the redox voltage and ionic migration activity. The optimized structure of Na_3.5Mn_0.5V_1.5(PO₄)₃/C is achieved and investigated systematically to be a durable cathode (76.6% capacity retention over 5,000 cycles at 20 C) for SIBs, which exhibits high reversible capacity (113.1 mAh·g^-1 at 0.5 C) with relatively low volume change (7.6%). Importantly, its high-areal-loading and temperature-resistant sodium ion storage properties are evaluated, and the full-cell configuration is demonstrated. This work indicates that this Na_3.5Mn_0.5V_1.5(PO₄)₃/C composite could be a promising cathode candidate for SIBs.

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.