Nitrogen-Doped Carbon-Confined\nNi<sub>0.6</sub>Fe<sub>0.4</sub>Se<sub>2</sub> Nanoboxes Bridged by\nCarbon Nanotube Networks\nfor Efficient Sodium-Ion Batteries

The reasonable design of effective anode materials while\nsimultaneously\nachieving rapid rate capacity and satisfied long lifespan is urgently\nrequired yet still challenging for sodium-ion batteries (SIBs). Herein,\nwe design and build Ni<sub>0.6</sub>Fe<sub>0.4</sub>Se<sub>2</sub> nanoboxes confined by a nitrogen-doped carbon layer and bridged\nby carbon nanotube networks (Ni<sub>0.6</sub>Fe<sub>0.4</sub>Se<sub>2</sub>@NC/CNTs) via a precipitation method combined with a carbonization\nand selenylation process to suitable anode materials toward efficient\nSIBs. The obtained Ni<sub>0.6</sub>Fe<sub>0.4</sub>Se<sub>2</sub>@NC/CNTs\ncombines multiple merits of ample ion/electron active sites of hierarchical\nstructure, enhanced ability to mitigate substantial volume expansion\nof nitrogen-doped carbon sheet layers, and fast electron- and Na<sup>+</sup>-transfer kinetics induced by high conductivity of the interconnected\ncarbon nanotube networks. As expected, the optimized Ni<sub>0.6</sub>Fe<sub>0.4</sub>Se<sub>2</sub>@NC/CNTs render a prominent sodium\nstorage performance with an exceptional reversible capacity (564.3\nmAh g<sup>–1</sup> after 100 cycles at 0.1 A g<sup>–1</sup>) and a superior prolonged cycle lifespan (401.1 mAh g<sup>–1</sup> at 5.0 A g<sup>–1</sup> over 1000 long-term cycles), surpassing\nmost previously reported NiFe-based electrodes to our knowledge. This\nwork hereby highlights a practical strategy for engineering advanced\nanode materials for high-efficiency SIBs.