A 50 µm-Thick Fiber-Reinforced Fluorinated Polymer Plastic Crystal Electrolyte Enabling High Ionic Conductivity and Voltage Stability for Advanced Solid-State Sodium Batteries

Low room-temperature conductivity, narrow electrochemical stability window, and insufficient mechanical strength restrict the further application of solid polymer electrolytes in solid-state sodium metal batteries (SMBs). Here, we reported a 50 µm-thick fiber-reinforced fluorinated polymer plastic crystal electrolyte (PPCE) prepared via in-situ polymerization. The fluorinated polymer effectively disrupts the ordered structure of the plastic crystal, thus increasing the proportion of amorphous phase that provides rapid Na + transport pathways. Meanwhile, the fluorohydrocarbon and ether units within polymer weaken its binding energy with Na + , which facilitates Na + dissociation and achieves high room-temperature conductivity (2.34 mS cm − 1 ). Furthermore, the fluorine-rich groups enhance PPCE's oxidation resistance and deliver a robust, inorganic F-rich interphase, which stabilize the electrode/electrolyte interface and extend high-voltage tolerance (4.83 V). The integration of a 34 µm-thick polyethylene fiber-reinforced substrate (tensile strength: 8.50 MPa) and the copolymer skeleton provides critical mechanical support. When paired with various cathodes, including Na 3 V 4 (PO 4 ) 3 , Prussian white, Na 3 V 2 (PO 4 ) 2 F 3 , or NaNi 0.33 Fe 0.33 Mn 0.33 O 2 , the cells deliver high capacity, stable cyclability, and excellent rate performance. This work demonstrates a highly compatible and robust PPCE design, highlighting its broad application prospects in advanced solid-state sodium batteries.