Synergistic Enhancement of Energy Storage Performance in Ternary Composite Films by Photo‐Crosslinking and Fluorine Effect

The advancement of flexible electronics demands dielectric materials beyond single‐mechanism regulation. This study introduces a synergistic dual‐regulation strategy combining photo‐crosslinking and fluorine effects to concurrently suppress relaxation and conduction losses. We fabricated cross‐linked hexafluorobutyl methacrylate (HFMA)/β‐cyclodextrin (β‐CD)/poly(vinylidene fluoride) (PVDF) ternary composite films via ultraviolet (UV)‐induced in situ polymerization. Fluorine incorporation effectively inhibited relaxation loss and leakage current, reducing its density from 6.19 × 10 −6 μC/cm 3 (1 wt% β‐CD/PVDF) to 1.79 × 10 −6 μC/cm 3 (30 wt% HFMA composite), thereby mitigating thermal/electrical breakdown risks. Simultaneously, the photo‐crosslinked structure restricted chain segment mobility, enhancing breakdown strength from 364.35 MV/m (PVDF) to 545.16 MV/m. The synergistic effect significantly improved energy storage performance, achieving a maximum energy density of 7.21 J/cm 3 at 20 wt% HFMA loading—156% of the value for PVDF. This work provides a new design pathway for high‐performance flexible polymer dielectrics featuring low loss, high breakdown strength, and superior energy storage density.