Stretching Aligned Hydrogen Bonding Network to Evoke Mechanically Robust and High‐Energy‐Density P(VDF‐HFP) Dielectric Film Capacitors

Abstract Polymer‐based dielectric film capacitors are essential energy storage components in electronic and power systems due to their ultrahigh power density and ultra‐fast charge storage/release capability. Nonetheless, their relatively low energy density does not fully meet the requirements of power electronics and pulsed power systems. Herein, a scalable composite dielectric film based on a ferroelectric polymer with edge hydroxylated boron nitride nanosheets (BNNS‐OH) is fabricated via the construction of a hydrogen bonding network and stretching orientation strategy. The presence of hydroxyl groups on boron nitride aids in forming a robust hydrogen bonding network within the ferroelectric polymer, leading to a significant increase in Young's modulus and superior dielectric performance. Furthermore, the stretching process aligns the BNNS‐OH and the hydrogen bonding network along the drawing direction via covalent and hydrogen bonding interaction, resulting in a remarkable tensile strength (109 MPa), breakdown strength (688 MV m −1 ), and energy density (28.2 J cm −3 ), outperforming mostrepresentative polymer‐based dielectric films. In combining the advantages of a simple preparation process, extraordinary energy storage performance, and low‐cost raw materials, this strategy is viable for large‐scale production of polymer‐based dielectric films with high mechanical and dielectric performance and opens a new path for the development of next‐generation energy storage applications.