Synergistic Enhancement of Energy Storage in <scp>HAP</scp> / <scp>PMMA</scp> / <scp>PVDF</scp> Ternary Composites via Dual‐Phase Modulation

ABSTRACT Growing global energy shortages necessitate advanced flexible energy storage devices. Although poly(vinylidene fluoride) (PVDF) is widely used in flexible energy storage materials, its inherently low energy density and high dielectric loss limit its practical applications. To address these issues, we developed a novel ternary composite film by incorporating hydroxyapatite (HAP, ε r ~ 48) to enhance dielectric polarization and poly(methyl methacrylate) (PMMA) to improve breakdown strength and suppress dielectric loss. Innovatively, HAP nanoparticles serve as nucleating agents that optimize crystalline domains, while PMMA restricts charge carrier mobility in amorphous regions through molecular chain entanglement and hydrogen bonding. Through this synergistic dual‐phase modulation, the composite achieves a high energy density of 9.96 J/cm 3 at 440 kV/mm, representing a 44.56% enhancement over pure PVDF, along with significantly reduced dielectric loss. Furthermore, this composite film exhibits excellent flexibility, offering a novel and effective strategy for preparing flexible energy storage films with superior energy density.