Abstract Development of efficient and robust electrode materials is significant for sodium-ion batteries (SIBs). Metallic selenides have been widely investigated as a promising anode material based on their relatively high theoretical capacity. However, rapid capacity fading and huge volume changes greatly hinder their practical application. Herein, for the first time, uniform yolk-shell Fe7Se8@C/N nanoboxes (Fe7Se8@C/N NBs) with the Fe7Se8 cores completely embedded by a thin and robust carbon shell are prepared using a strategy of facile etching method combined with selenization for advanced anode materials for SIBs. Benefiting from the unique structural merits, the Fe7Se8@C/N NBs electrodes for Na-ion half cells exhibit high Na-ion storage capacity (385.5 mAh g−1 at 0.1 A g−1) and superior rate performance (316.0 mAh g−1 at 5 A g−1) as well as impressive cyclability with no capacity decay over 1000 cycles. The sodium storage mechanism of Fe7Se8@C/N NBs electrode is systematically studied with the aid of ex-situ X-ray diffraction and transmission electron microscopy. Finally, the assembled full cells coupled with the lab-made high-voltage Na3V2(PO4)2O2F cathode and Fe7Se8@C/N NBs anode materials show superior energy-storage performance.

中文翻译：

---

合理设计的掺氮蛋黄-壳 Fe7Se8/碳纳米盒在半/全电池中具有增强的钠储存

摘要 开发高效耐用的电极材料对于钠离子电池（SIBs）具有重要意义。基于其相对较高的理论容量，金属硒化物作为一种有前途的负极材料已被广泛研究。然而，快速的容量衰减和巨大的体积变化极大地阻碍了它们的实际应用。在此，首次使用简易蚀刻法结合硒化策略制备了均匀的蛋黄壳 Fe7Se8@C/N 纳米盒（Fe7Se8@C/N NBs），其中 Fe7Se8 核完全嵌入薄而坚固的碳壳中用于 SIB 的高级负极材料。受益于独特的结构优点，用于钠离子半电池的 Fe7Se8@C/N NBs 电极表现出高钠离子存储容量（0.1 A g-1 时为 385.5 mAh g-1）和优异的倍率性能（316. 0 mAh g-1 at 5 A g-1) 以及令人印象深刻的循环性能，在 1000 次循环中没有容量衰减。借助非原位X射线衍射和透射电子显微镜系统研究了Fe7Se8@C/N NBs电极的储钠机制。最后，组装的全电池与实验室制造的高压 Na3V2(PO4)2O2F 阴极和 Fe7Se8@C/N NBs 阳极材料相结合，显示出优异的储能性能。