Box-shaped necklace-like Fe3O4/MoS2-CNFs composite nanofibers with confinement effect enhancing sodium storage performance

A nanofiber necklace with a box-shaped structure has been designed. The box-shaped template can introduce other transition metal compounds, effectively compensating for the intrinsic defects of electrode materials. α-Fe 2 O 3 nano cubes as the template mix with PAN to get α-Fe 2 O 3 /PAN. And then the α-Fe 2 O 3 nano cubes calcine to form Fe 3 O 4 with more valence state under high temperature, which get the box-shape necklace-like structure Fe 3 O 4 -CNFs. The confined space has formed by high concentrated HCl etching, the box-shaped necklace-like Fe 3 O 4 /MoS 2 carbon nanofibers (BN Fe 3 O 4 /MoS 2 -CNFs) anode material is obtained by hydrothermal method of confining growth of MoS 2 nanosheets. The mixed valence state of Fe 3 O 4 (Fe 3+ /Fe 2+ ) can effectively improve the conductivity of MoS 2 nanosheets. The box-shape necklace structure constructed by α-Fe 2 O 3 nanocube has mesoporous structure and confined space, which can alleviate the volume effect of electrode material. When the electrode material is applied to the SIBs, the reversible capacity is 354 mA h g −1 after 500 cycles at 0.5 A/g, and the specific capacity of 131.5 mA h g −1 can be maintained at 8 A/g. On the one hand, the heterogeneous structure in the confined space alleviates the volume effect of the material, thereby improving the long cycle performance, on the other hand, it effectively enhances the electrical conductivity and increases more lithium/sodium storage sites.