Metal-Electronegativity-Induced, Synchronously Formed Hetero- and Vacancy-Structures of Selenide Molybdenum for Non-Aqueous Sodium-Based Dual-Ion Storage

Sodium-based dual-ion batteries (SDIBs) have attracted increasing research interests in energy storage systems because of their advantages of high operating voltage and low cost. However, exploring desirable anode materials with high capacity and stable structures remains a great challenge. Here, an elaborate design is reported, starting from well-organized MoSe2 nanorods and introducing metal-organic frameworks, which simultaneously forms a bimetallic selenide/carbon composite with coaxial structure via electronegativity induction. By rationally adjusting the vacancy concentration and combining heterostructure engineering, the optimized MoSe2-x/ZnSe@C as anode material for Na-ion batteries achieves rapid electrochemical kinetics and satisfactory reversible capacities. The systematic electrochemical kinetic analyses combined with theoretical calculations further unveil the synergistic effect of Se-vacancies and heterostructure for the enhanced sodium storage, which not only induces more reversible Na+ storage sites but also improves the pseudocapacitance and reduce charge transfer resistance, thereby providing a great contribution to accelerating reaction kinetics. Furthermore, the as-constructed SDIB full cell based on the MoSe2-x/ZnSe@C anode and the expanded graphite cathode demonstrates impressively excellent rate performance (131 mAh g(-1) at 4.0 A g(-1)) and ultralong cycling life over 1000 cycles (100 mAh g(-1) at 1.0 A g(-1)), demonstrating its practical applicability in a wide range of sodium-based energy storage devices.