Se-Regulated MnS Porous Nanocubes Encapsulated in Carbon Nanofibers as High-Performance Anode for Sodium-Ion...

Manganese-based chalcogenides have significant potential as anodes for sodium-ion batteries (SIBs) due to their high theoretical specific capacity, abundant natural reserves, and environmental friendliness. However, their application is hindered by poor cycling stability, resulting from severe volume changes during cycling and slow reaction kinetics due to their complex crystal structure. Here, an efficient and straightforward strategy was employed to in-situ encapsulate single-phase porous nanocubic MnS_0.5Se_0.5 into carbon nanofibers using electrospinning and the hard template method, thus forming a necklace-like porous MnS_0.5Se_0.5-carbon nanofiber composite (MnS_0.5Se_0.5@N-CNF). The introduction of Se significantly impacts both the composition and microstructure of MnS_0.5Se_0.5, including lattice distortion that generates additional defects, optimization of chemical bonds, and a nano-spatially confined design. In situ/ex-situ characterization and density functional theory calculations verified that this MnS_0.5Se_0.5@N-CNF alleviates the volume expansion and facilitates the transfer of Na⁺/electron. As expected, MnS_0.5Se_0.5@N-CNF anode demonstrates excellent sodium storage performance, characterized by high initial Coulombic efficiency (90.8%), high-rate capability (370.5 mAh g^-1 at 10 A g^-1) and long durability (over 5000 cycles at 5 A g^-1). The MnS_0.5Se_0.5@N-CNF //NVP@C full cell, assembled with MnS_0.5Se_0.5@N-CNF as anode and Na₃V₂(PO₄)₃@C as cathode, exhibits a high energy density of 254 Wh kg^-1 can be provided. This work presents a novel strategy to optimize the design of anode materials through structural engineering and Se substitution, while also elucidating the underlying reaction mechanisms.