PVDF ‐Based Sandwich‐Structured Dielectrics Synergistically Constructed With High‐Breakdown‐Strength and High‐Polarization Layers

This study fabricated Ti 3 C 2 T x MXene/poly(vinylidene fluoride) (PVDF) (MXP) films, polydopamine (PDA)‐modified MXene/PVDF (PMP) films, and sandwich‐structured (APA) composite films via spin‐coating, with poly(methyl methacrylate) (PMMA)/PVDF as the outer layers and PMP as the intermediate layer. Conductive MXene nanosheets formed percolation networks or microcapacitors, significantly improving the dielectric constant ( ε r ) of composites at low loading. At 1.0 wt% MXene, MXP exhibited an ε r of 19.648, a 240% increase compared to pure PVDF, but with reduced breakdown strength. To address this trade‐off, PDA surface‐modified MXene was used to prepare PMP nanodielectrics, simultaneously enhancing ε r and breakdown strength. PMP‐0.1 showed an ε r of 9.5 (16% improvement), breakdown strength of 442.4 MV/m (9.3% improvement), and energy storage density of 5.37 J/cm 3 (34.9% improvement) vs. PVDF, with lower dielectric loss than MXP. APA‐0.1 achieved an energy storage density of 7.33 J/cm 3 , representing increases of approximately 84% and 36.5% compared with PVDF and PMP‐0.1, respectively. PMMA and PDA reduced film loss and improved charge–discharge efficiency, providing a convenient method for high‐performance polymer‐based dielectric composites.