Atomic‐Layer‐Deposited ZnF ₂ on Aluminum Enabling In Situ NaF/Na–Zn Interphase for Robust Anode‐Free Sodium Batteries

ABSTRACT Achieving high‐energy‐density “anode‐free” sodium batteries remains a daunting challenge due to rapid capacity decay caused by poor reversibility and uncontrolled dendritic growth on bare current collectors. To overcome these limitations, we propose a potent interfacial engineering strategy: an aluminum current collector modified with a precisely engineered atomic‐layer‐deposited ultrathin ZnF 2 layer. We demonstrate that the ZnF 2 coating undergoes in situ electrochemical transformation during initial sodiation, forming a dense and conformal NaF/Na–Zn interphase. The sodiophilic Na–Zn alloy markedly lowers the nucleation overpotential, promoting highly uniform Na plating across the interface. Working synergistically, the NaF component stabilizes the solid‐electrolyte interphase by regulating Na + flux. Enabled by this dual‐functioning framework, the ZnF 2 ‐modified aluminum current collector achieves an exceptionally high average Coulombic efficiency of ∼99.76% under aggressive plating/stripping conditions (0.5 mA cm −2 , 1.0 mAh cm −2 ). Furthermore, anode‐free full cells pairing this modified current collector with high‐mass‐loading Na 3 V 2 (PO 4 ) 3 cathodes (11.6–14.3 mg cm −2 ) exhibit significantly improved cycling stability. This work establishes, to the best of our knowledge, the first example of atomic‐layer‐deposited ZnF 2 on aluminum deliberately converted into a NaF/Na–Zn interphase for anode‐free sodium batteries, providing a simple and scalable strategy for high‐performance sodium‐based energy storage systems.