Manipulating Interfacial Renovation via In Situ Formed Metal Fluoride Heterogeneous Protective Layer toward Exceptional Durable Sodium Metal Anodes

Abstract Sodium metal is regarded as an optimal anode material for high‐energy‐density sodium‐ion batteries (SIBs). However, during the processes of sodium deposition and stripping, the failure of the solid electrolyte interphase (SEI) film leads to the continuous accumulation of inactive sodium, thereby compromising the cycling reversibility of the battery. Here, a novel metal fluoride heterointerface layer is generated and constructed through in situ manipulation of the continuous reaction between TiF₄ and metal Na. The reconstructed NaF/TiF₃ interface layer, which tightly anchors the sodium metal, effectively suppresses the formation of sodium dendrites during the charge‐discharge process. The highly sodium‐philic TiF₃ component exhibits strong binding with Na ions, while NaF reduces the Na⁺ diffusion energy barrier, significantly enhancing the reaction kinetics. Due to the successful artificial construction of this interface layer, the Na/TiF₄ composite electrode demonstrates an exceptional ultra‐long cycling stability of 2370 h in symmetric cells (0.5 mAh cm⁻²). Density functional theory (DFT) calculations further validate the functionality of each component in the Na/TiF₄ protective layer. When paired with NaNi_1/3Fe_1/3Mn_1/3O₂ cathode in a pouch cell, it exhibits stability up to 2000 cycles at current densities of 2 C and 4 C, with a maximum energy density output of 483.1 Wh kg⁻¹ (power density: 320.8 W kg⁻¹).