A Minimalist Design Principle of Fluorine‐Integrated Monolithic Current Collectors Enabling Stable Anode‐Free Sodium Metal Batteries

ABSTRACT The advancement of anode‐free sodium metal batteries (AFSMBs) is hindered by unstable solid‐electrolyte interphases (SEIs) and heterogeneous sodium deposition on conventional current collectors. Although three‐dimensional sodiophilic hosts can improve performance, their intricate compositions, often incorporating multiple dopants and hierarchical pores, obscure fundamental stabilization mechanisms. Herein, we adopt a minimalist design principle using a pristine carbon nanotube framework (CNF) as a well‐defined platform. Solvothermal fluorination chemically reconstitutes CNF into a fluorine‐integrated monolithic conductor (FCNF), introducing semi‐ionic C─F bonds, expanding the interlayer spacing, and generating a uniform fluorine‐rich interface. FCNF isolates the role of lattice‐integrated fluorine, which simultaneously enhances sodiophilicity and supports the formation of a thin NaF‐rich SEI (≈10 nm). Consequently, FCNF enables highly reversible sodium plating/stripping with >99.9% Coulombic efficiency over 800 cycles at 3 mA cm −2 /3 mAh cm −2 . Anode‐free FCNF||Na 3 V 2 (PO 4 ) 3 full cells deliver a stack‐level gravimetric energy density of 356.3 Wh kg −1 (active‐stack basis) with 89% capacity retention over 300 cycles. Scaling to a practical pouch cell format demonstrates viability, delivering an areal capacity of ≈1.6 mAh cm −2 with 94.2% retention over 150 cycles. This work establishes lattice‐level chemical reconstitution of a conductive scaffold as a foundational design principle for durable metal anodes, moving beyond the paradigm of complex multicomponent composites.