Epoxy Fiber Derived All‐Polymer Films for High Performance Electrostatic Energy Storage Dielectrics

Dielectric films with high discharged energy density are highly desired in electrical and electronic systems. Adding inorganic nanoparticles, especially for 1D inorganic fillers, in polymer films is recognized as one of the most effective methods to improve the electric breakdown strength, which is a key parameter of energy storage. However, 1D inorganic fillers added into thin films will undoubtedly introduce many defects and reduce the electric insulation performance. Herein, homogeneous epoxy fiber derived all‐polymer films are fabricated by electrospinning, laminating, and curing in sequence. The existing 1D structure of the epoxy films significantly enhance the dielectric constant and electric breakdown strength, resulting in a very high enhancement of 2.7 times the discharged energy storage density at 25 °C, up to 9.6 J cm−3. Assisted by the simulation analysis, the enhanced dipole polarization and reduced current density are found to be the main reasons for the improved energy storage performances. Preparing all‐polymer films with fiber structure has proved to be an effective way to find advanced energy storage dielectric films. The epoxy fiber films fabricated by electrospinning and hot‐pressing achieve significantly enhances dielectric energy storage density. The dielectric permittivity and electric breakdown strength could reach 6.89 at 1 kHz and 654 kV cm−1 at room temperature, leading to a high energy density of 9.55 J cm−3. At the same time, the energy discharge efficiency could maintain over 90% at room temperature.