Tunable Surface Selenization on MoO2 -Based Carbon Substrate for Notably Enhanced Sodium-Ion Storage Properties.

Transition metal chalcogenides with high theoretical capacity are promising conversion-type anode materials for sodium ion batteries (SIBs), but often suffer from unsatisfied cycling stability (hundreds of cycles) caused by structural collapse and agglomerate. Herein, a rational strategy of tunable surface selenization on highly crystalline MoO2 -based carbon substrate is designed, where the sheet-like MoSe2 can be coated on the surface of bundle-like N-doped carbon/granular MoO2 substrate, realizing partial transformation from MoO2 to MoSe2 , and creating b-NC/g-MoO2 @s-MoSe2 -10 with robust hierarchical MoO2 @MoSe2 heterostructures and strong chemical couplings (MoC and MoN). Such well-designed architecture can provide signally improved reaction kinetics and reinforced structural integrity for fast and stable sodium-ion storage, as confirmed by the ex situ results and kinetic analyses as well as the density functional theory calculations. As expected, the b-NC/g-MoO2 @s-MoSe2 -10 delivers splendid rate capability and ultralong cycling stability (254.2 mAh g-1 reversible capacity at 5.0 A g-1 after 6000 cycles with ≈89.0% capacity retention). Therefore, the tunable surface strategy can provide new insights for designing and constructing heterostructures of transition metal chalcogenides toward high-performance SIBs.