Synergistic effects of confined substitution and architecture engineering in CoTe2/Sb2Te3 heterostructures towards durable and fast sodium storage

Metal tellurides (MTes) with high volume-specific capacity are promising anode materials for sodium-ion batteries (SIBs), but they constantly suffer from capacity degradation and slow dynamics. Herein, we propose a hierarchical porous structure to address the aforementioned challenges by incorporating electrospinning and in-situ ion-substitution, in which ultrafine CoTe2/Sb2Te3 heterojunction particles are confined by dual-carbon layers (CoTe2/Sb2Te3@NCNFs). Specifically, the porous nanofiber network enhances electrolyte infiltration and constitutes a highway for electron transport. Interestingly, high-capacity Sb replaces part of the Co through an asymmetric ion-substitution reaction, which not only obtains more pores to alleviate volume stress and particle agglomeration during cycling, but also improves the reversible capacity by constructing heterostructures. Impressively, the CoTe2/Sb2Te3@NCNFs anode exhibits outstanding specific capacity (301.77 mAh g−1 after 500 cycles at 0.2 A g−1) and excellent rate performance (144.52 mAh g−1 at 5.0 A g−1) for sodium storage. Systematic in-situ testing reveals the highly reversible "conversion-alloy" storage mechanism, and the "battery-capacitor dual-mode" reaction process. Finally, a Na-ion full cell (P2-NaNMMT//CoTe2/Sb2Te3@NCNFs) is assembled and achieves excellent cycling performance and rate capability. This unique nanostructure design approach provides new insights into the design of advanced electrode materials for sodium-ion batteries.