In Situ Interfacial Reconstruction Enables Sodiophilic and Ion‐Conductive Current Collectors for Anode‐Free Sodium Metal Batteries

ABSTRACT

Anode‐free sodium metal batteries (AFSMBs) are promising for high‐energy‐density storage but are limited by poor Na plating/stripping reversibility on conventional current collectors, where insufficient sodiophilicity and unstable interfacial chemistry induce uneven sodium deposition and rapid sodium inventory loss. Here, an in situ interfacial reconstruction strategy is developed on an Al current collector by introducing SnF ₂ into a PVDF‐HFP layer. A hot‐pressing‐induced redox reaction forms a prefabricated interfacial layer containing metallic Sn and AlF ₃ , which further evolves during initial sodiation into a NaF‐rich organic/inorganic composite interphase. The uniformly distributed metallic Sn sites markedly reduce the Na nucleation barrier and promote high‐density nucleation, while the fluorine‐rich interphase lowers the Na ⁺ transport barrier and stabilizes the anode interface. Through the coupled regulation of nucleation behavior, ion transport, and interfacial stability, the reconstructed current collector enables dense and highly reversible Na deposition. As a result, asymmetric cells achieve 450 cycles at 5 mAh cm ⁻² with an average CE of 99.91%, symmetric cells sustain stable cycling for over 1300 h at 90% depth of discharge, and AFSMBs deliver 84% capacity retention and 330 Wh kg ⁻¹ under a cathode loading of 35.17 mg cm ⁻² . This work offers an effective interfacial engineering strategy for practical AFSMBs.