SnS2/NiS2 heterostructure confined in N-doped hollow carbon nanofibers as high-rate anode for sodium-ion batteries

Tin disulfide (SnS2) with its high capacity and suitable interlayer spacing, is a promising anode for sodium-ion batteries (SIBs), but its substantial volume expansion during sodium insertion and sluggish ion and electron transfer kinetics in bulk materials limit its broader application. Herein, SnS2/NiS2 particles are encapsulated in hollow nitrogen-doped carbon nanofibers (SnS2/NiS2@HCNFs) by the combination of coaxial electrostatic spinning and carbonization/sulfurization processes. The hollow channel structure of the carbon skeleton creates a three-dimensional pathway that facilitates rapid electron transmission and provides buffer space for volume changes, enhancing structural stability. Additionally, the interface electric field generated by the SnS2/NiS2 heterojunction accelerates Na+ transfer, as supported by findings from density functional theory (DFT) calculations and galvanostatic intermittent titration techniques (GITT). Together, the hollow structure and heterojunction contribute to improved reaction kinetics. As a result, the SnS2/NiS2@HCNFs composite exhibits outstanding cycling stability with a capacity of 315 mA h g-1 over 1000 cycles at 2 A g-1. Moreover, the assembled SnS2/NiS2@HCNFs//Na3V2(PO4)3 full-cell delivers a high reversible capacity of 186 mA h g-1 after 500 cycles at 1 A g-1. This study offers a valuable approach for the rational design of heterostructured anodes aimed at enhancing the efficiency of SIBs.