Multilevel‐Interface‐Structured Polymer Dielectrics by Direct Gas Fluorination Reaction for Significantly Enhanced Capacitive Energy Storage

Abstract Polymer dielectrics in electronics still suffer from low energy density, hindering miniaturization of electrical systems. Fluorine with the maximal electronegativity can forcefully restrict electron transport, and formed fluorine‐containing groups also possess excellent stability owing to high bond energy. Here we demonstrated a one‐step, high‐throughput and high‐efficiency gas fluorination reaction on capacitor film, which enables an extraordinarily high discharge energy density of 9.24 J cm −3 at 750 kV mm −1 compared with that of pristine film (3.88 J cm −3 at 500 kV mm) at an efficiency exceeding 95%, which presents obvious preponderance in this field. Meanwhile, the charge–discharge life of fluorinated film also has an obvious enhancement over 200%. We demonstrated that the special fluorination diffusion reaction fabricates surface fluorination layer with enough thickness to avoid tunnelling effect and further offers deep electron traps at the interface between fluorination layer and interior film. Moreover, it also enhances charge dissipation ability of film surface and interfacial compatibility with electrode, further restricting electron injection and accumulation. Such multilevel‐interface‐structure fabrication by fluorination strengthening strategy is applicable for other capacitor films. This work reveals advanced process strategy, distinctive property and broader applicability of gas fluorination reaction on polymer dielectrics that is compatible with the assembly lines of film capacitors.