Unlocking the structure and anion synergistic modulation of MoSe2 anode for ultra-stable and high-rate sodium-ion storage

The two-dimensional MoSe2 possesses a large interlayer spacing (0.65 nm) and a narrow bandgap (1.1 eV), showing potential in sodium-ion storage. However, it faces slow kinetics and volume stress during Na+ (de)intercalation process, thereby affecting the cycling stability and lifespan of sodium-ion batteries (SIBs). In this work, a novel approach involving anionic doping and structural design has been proposed, wherein a two-step in-situ selenization and surface thermal annealing doping process is applied to fabricate a novel configuration material of fluorine-doped MoSe2@nitrogen-doped carbon nanosheets (F-MoSe2@FNC). The obtained F-MoSe2@FNC, benefiting from the dual advantages of structure and F-doping, synergistically promotes and accelerates the stable (de)intercalation of Na+. Henceforth, F-MoSe2@FNC demonstrates notable characteristics in terms of reversible specific capacity, boasting a high initial coulombic efficiency of 76.97%, alongside remarkable rate capabilities and cyclic stability. The constructed F-MoSe2@FNC anode-based half cell manifests exceptional longevity, enduring up to 2550 cycles at 10 A<middle dot>g-1 with a specific capacity of 322.04 mAh<middle dot>g-1. Its electrochemical performance surpasses that of MoSe2@NC and Pure MoSe2, underscoring the significance of the proposed synergistic modulation. Through comprehensive kinetic analyses, encompassing in-situ electrochemical impedance spectroscopy (EIS), it is elucidated that the F-MoSe2@FNC electrode showcases elevated pseudo-capacitance and rapid diffusion attributes during charge and discharge processes. Furthermore, the assembled full-cell (F-MoSe2@FNC//Na3V2(PO4)3) attains a notable energy density of 166.94 Wh<middle dot>kg-1. This design provides insights for the optimization of MoSe2 electrodes and their applications in SIBs. (sic)(sic)(sic)(sic)MoSe2(sic)(sic)(sic)(sic)(sic)(sic)(sic) (0.65 nm) (sic)(sic)(sic)(sic)(sic) (1.1 eV) , (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)Na+ ((sic)(sic)) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)MoSe2(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (F-MoSe2@FNC) .(sic)(sic)F-MoSe2@FNC(sic)(sic)(sic)(sic)(sic)(sic)F(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)Na+(sic)(sic)(sic) ((sic)) (sic)(sic).(sic)(sic), F-MoSe2@FNC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)76.97%(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)F-MoSe2@FNC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)10 A<middle dot>g-1(sic)(sic)(sic)(sic)2550(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)322.04 mAh<middle dot>g-1.(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)MoSe2@NC(sic)(sic)MoSe2, (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (EIS) , (sic)(sic)(sic)F-MoSe2@FNC(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic) (F-MoSe2@FNC//Na3V2(PO4)3) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)166.94 Wh<middle dot>kg-1.(sic)(sic)(sic)(sic)MoSe2(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).