Enhancing high-temperature energy storage in all-organic composites through the polyfluorine effect

The extensive utilization of electrostatic capacitors across diverse sectors and extreme environments necessitates materials with high breakdown strength (E-b), substantial energy storage density (U-e) and exceptional toughness at high temperatures. Herein, all-organic composite films fluorinated-polyimide/polyvinylidenefluoride-hexafluoropropylene (F-PI/PVDF-HFP) were synthesized via in-situ compounding and multilayer casting. Experimental and theoretical calculations reveal that doping F-atoms in PI reduces dielectric loss and broadens the bandgap, while the introduction of the ferroelectric polymer PVDF-HFP enhances the high-temperature toughness and insulation of the composites through the polyfluorine effect, effectively suppressing carrier transport and preventing premature thermal/electrical breakdown. Consequently, the F-PI/PVDF-HFP achieves exceptional high-temperature energy storage performance (E-b similar to 500 MV/m, U-e similar to 5.2 J/cm(3), eta similar to 80 %) alongside robust toughness at 120 degrees C, surpassing most polymer dielectrics even at 150 degrees C (U-e similar to 2.91 J/cm(3), eta similar to 75 %@423 MV/m). This investigation unveils novel strategy leveraging the polyfluorine effect to advance the high-temperature energy storage performance and processing characteristics of PI-based dielectrics.