Ionic Potential Regulation Coupled with Multiphase Sodium Storage Engineering for Advanced Cathode Materials

Currently, the intercalated MoSe2 acts as a heterogeneous engineering regulator to modulate the electronic structure of Na3V2(PO4)3 (NVP). By regulating the amount of MoO2 added, we effectively control the coating morphology of MoSe2 on the NVP surface, successfully preparing the flocculent NVP@MoSe2-2 sample. Ex situ XRD/XPS analysis elucidate that the decomposition of MoSe2 under high-voltage stimulation generates Mo4+ and Se2–. With the higher ionic potential of Mo4+ (6.15 Å–1 vs. 4.69 Å–1 of V3+), trace Mo4+ substitution for V3+ results in charge rearrangement, suggesting an increase in the electron-cloud density around Mo4+ and therefore the emergence of electronic delocalization effects of V3+. The modified V reveals stronger coordination properties and electrochemical activity, as confirmed by XAFS. Partial V4+ oxidizes Mo4+ to activate the extra redox couple of Mo4+/Mo5+, forming the second reversible discharge plateau at 3.9 V, further increasing the capacity and energy density. Meanwhile, the intercalated MoSe2 could provide rich reactive sites for Na+ to produce the intermediate solid-solution phase of NaxMoSe2, elevating reversible capacity. Furthermore, DFT calculations demonstrate that the NVP/MoSe2 heterostructure exhibits a zero-band-gap electronic structure and modified charge rearrangement, indicating its superior electronic structure. Finally, the modified NVP@MoSe2-2 delivers a high capacity value of 130.6 mAh g–1 at 0.1 C, and it maintains 95.1 and 87.9 mAh g–1 at 5 and 10 C after 1200 and 2000 cycles, corresponding to capacity retention rates of 97.1 and 94.1%.