Tailoring Interphasial Na + Flux by Fluorinated Covalent Organic Frameworks Toward Robust Anode‐Less Na Metal Batteries

Abstract Developing Na metal batteries offers great promise for high energy density and low cost energy storage, yet their practical application is severely limited by interphase instability and uncontrollable Na dendrite growth. Here fluorinated covalent organic framework (F‐COF) is rationally employed to homogenize and accelerate the interphasial Na + flux to regulate homogeneous Na metal deposition, while the in situ generated NaF‐rich interphase can effectively inhibits dendritic Na growth. As a result, the Na symmetric cells exhibit high rate capability (10 mA cm −2 ) and exceptional long‐term cycling stability (2600 h). The Na||Na 3 V 2 (PO 4 ) 3 (NVP) cell demonstrates an ultralong lifespan stable cycling over 5000 cycles even at 20 C, with an extremely low capacity decay of ≈0.0018% per cycle. Furthermore, the anode‐less Na||NVP pouch cell with a high areal capacity of 2.3 mAh cm −2 still delivers a remarkable stable cycling over 150 cycles, even enduring harsh cycling conditions of a low negative‐to‐positive‐capacity ratio of 1.4 and a lean electrolyte of 6.5 g Ah −1 . This work presents a new pathway of manipulating the interphasial properties toward high performance anode‐less Na metal batteries.