Dielectric and Energy Storage Properties of Coupling Agent Modification of BT-PVDF Nanocomposite Films

Ceramic–polymer nanocomposites are widely used in various applications, such as medicine, aerospace, optoelectronic devices, and energy storage devices, owing to their impressive mechanical, thermal, optical, and electrical properties. Due to an excellent capability to combine a high dielectric constant of ceramics and a high breakdown strength of polymers, the preparation of ceramic–polymer dielectric nanocomposites is a promising and widely accepted approach to develop capacitors with high energy density, low dielectric loss, and good flexibility. In this paper, poly(vinylidene fluoride) (PVDF) was used as the polymer matrix. Silane coupling agent, KH550, with different contents (3 wt.%, 6 wt.%, 9 wt.%, 12 wt.%, 15 wt.%, 18 wt.%) was added to modify the surface of BaTiO3 ceramic particles to improve the compatibility between BaTiO3 and PVDF using a film processing technique of spin coating. By comparison between the unmodified and modified ceramic–polymer nanocomposites by the addition of the silane coupling agent, KH550, the dielectric constant, breakdown strength, and energy storage density were studied. It was found that the addition of the silane coupling agent did not change the crystal structure of BaTiO3. Moreover, the changing trends of dielectric constant and dielectric loss of the BaTiO3/PVDF/KH550 and the unmodified nanocomposites in sweeping frequency were studied. In addition, KH550 can improve the compatibility of the BaTiO3 nanoparticles and the PVDF matrix, and also increase the breakdown strength (by 55.6%), and energy storage density (by 56%), of BaTiO3/PVDF nanocomposites compared with unmodified ones.