Dielectric and energy storage properties of all-organic sandwich-structured films used for high-temperature film capacitors

Dielectric polymers with ultrahigh power density are widely utilized in the fields of modern electronics and power systems. This article proposes the all-organic sandwich-structured films with ferroelectric polymer poly (vinylidene fluoride-hexafluoropropylene) and linear polymer poly (ethylene terephthalate) (PET) as the energy storage dielectrics for film capacitors. The morphological characterizations, thermal, dielectric, and energy storage performances have been investigated to evaluate the comprehensive properties of the sandwich-structured films. Excellent interlaminar interfaces are observed between poly(vinylidene fluoride-hexafluoropropylene) and PET layers. Compared with pure PET films, the sandwich-structured films exhibit improved thermal stability and dielectric constant, but some degradation in loss factor and breakdown strength. With the increase of ambient temperature, the sandwich-structured films still show improved and stable dielectric properties and insulating strength up to 125 °C. The sandwiched all-organic film shows an improved energy density ( U d ) as high as 8.2 J/cm 3 and concurrently an immense charge-discharge efficiency of 86.4%. This strategy offers a feasible idea to enhance the thermal, dielectric, and energy storage capability of dielectric films with a layered architecture, which facilitates the evolution of flexible film capacitors. • All-organic sandwich-structured films consisting poly(ethylene terephthalate) and poly(vinylidene fluoride-hexafluoropropylene) are fabricated. • An excellent energy density of 8.2 J/cm 3 and efficiency of 86.4% can be achieved. • The sandwich-structured films show improved and stable insulating strength up to 125 °C.