Multilayer heterogeneous dielectric films with simultaneously improved dielectric constant and breakdown strength

Due to the development of the microelectronics industry, there is a great demand for flexible polymer dielectrics with simultaneously excellent permittivity and dielectric breakdown strength, so as to realize the prominent dielectric energy storage capability. Here, we prepare sandwich-structure films with ferroelectric dielectric Polyvinylidene Fluoride (PVDF) acting as the top layer, 2D Boron Nitride nanosheets (BNNS) as the middle layer and linear dielectric Polyimide (PI) as the bottom layer. In the films the PVDF ferroelectric layer provides high polarization, the PI linear layer enhances the dielectric breakdown strength and decreases dielectric loss, and the 2D sheet BNNS layer further strengthens the dielectric breakdown insulation. The permittivity of the multilayer films is in the range of 5.0–6.3 and dielectric loss are all below 0.03 at 100 Hz. And the sandwich-structure film with 3 mg/mL BNNS can achieve a highest dielectric energy storage of 4.35 J/cm³ at 417.6 kV/mm, surpassing that of the currently commercial BOPP by about 360 % (≈1.2 J/ cm³ under the electric field of 640 kV/mm). In addition, the multilayer films exhibit satisfactory thermal stability and mechanical properties. The multicomponent heterogeneous layered materials with simultaneously enhanced permittivity and dielectric insulating strength demonstrate a wide application prospect in the field of dielectric energy storage.