Recent Advances in Polymer‐Based Dielectric Composites

ABSTRACT With the continued miniaturization, integration, and lightweighting of electronic devices, polymer‐based dielectric materials have attracted extensive attention, particularly for capacitive energy storage and high‐voltage insulation. Compared with conventional ceramic dielectrics, polymer matrices offer advantages such as low density, excellent flexibility, ease of processing, and good mechanical integrity. However, their practical implementation is still limited by several intrinsic drawbacks, including relatively low dielectric constant, insufficient breakdown strength, poor thermal stability, and the difficulty of simultaneously achieving low dielectric loss and high energy density. In recent years, extensive efforts have been devoted to overcoming these limitations through the incorporation of functional fillers, interfacial engineering, multiscale structural design, and advanced fabrication strategies. This review systematically summarizes recent advances in polymer‐based dielectric composites from multiple perspectives. In particular, the paper primarily focuses on polymer‐based dielectric composites for capacitive energy storage, while high‐voltage insulation is discussed as a secondary application context. The discussion mainly centers on dielectric composites for capacitive energy storage, with emphasis on simultaneously achieving high dielectric constant, high breakdown strength, low dielectric loss, and thermal stability. First, the types, characteristics, and modification strategies of common fillers, including metallic, carbon‐based, ceramic, and polymeric fillers, are discussed. Then, representative interfacial engineering approaches such as surface treatment, coupling agents, plasma modification, and core‐shell architectures are analyzed, with emphasis on their roles in reducing interfacial defects and regulating charge transport. Next, the polarization mechanisms governing dielectric behavior, including electronic polarization, dipolar polarization, and interfacial polarization, are reviewed in detail. Fourth, major fabrication methods, such as solution casting, solution blending, in situ polymerization, and 3D printing, are summarized in terms of their effects on microstructure and performance. In addition, emerging topics including numerical simulation, machine learning‐assisted design, and sustainability‐oriented material development are highlighted. Overall, the key to improving polymer‐based dielectric composites lies in the coordinated optimization of filler selection, interfacial structure, and multiscale architecture. Finally, this review outlines the current bottlenecks and future directions for developing high‐performance, low‐loss, thermally stable, and scalable dielectric composites for next‐generation energy storage and electronic systems.