An Encapsulation‐Based Sodium Storage via Zn‐Single‐Atom Implanted Carbon Nanotubes

Abstract The properties of high theoretical capacity, low cost, and large potential of metallic sodium (Na) has strongly promoted the development of rechargeable sodium‐based batteries. However, the issues of infinite volume variation, unstable solid electrolyte interphase (SEI), and dendritic sodium causes a rapid decline in performance and notorious safety hazards. Herein, a highly reversible encapsulation‐based sodium storage by designing a functional hollow carbon nanotube with Zn single atom sites embedded in the carbon shell (Zn_SA‐HCNT) is achieved. The appropriate tube space can encapsulate bulk sodium inside; the inner enriched Zn_SA sites provide abundant sodiophilic sites, which can evidently reduce the nucleation barrier of Na deposition. Moreover, the carbon shell derived from ZIF‐8 provides geometric constraints and excellent ion/electron transport channels for the rapid transfer of Na⁺ due to its pore‐rich shell, which can be revealed by in situ transmission electron microscopy (TEM). As expected, Na@Zn_SA‐HCNT anodes present steady long‐term performance in symmetrical battery (>900 h at 10 mA cm⁻²). Moreover, superior electrochemical performance of Na@Zn_SA‐HCNT||PB full cells can be delivered. This work develops a new strategy based on carbon nanotube encapsulation of metallic sodium, which improves the safety and cycling performance of sodium metal anode.