Multilayered ferroelectric polymer composites with high energy density at elevated temperature

Ferroelectric polymers have been widely explored for film capacitor applications due to their high energy storage densities that are almost an order of magnitude greater than those of the commercial capacitor dielectrics. However, the existing ferroelectric polymers are designed exclusively for room-temperature operation, and suffer from poor capacitive performance at elevated temperature, which falls short of the need in the emerging harsh-environment applications. In this paper, we report multilayered ferroelectric polymer composites exhibiting simultaneous high energy density and high discharge efficiency at elevated temperature. The multilayered composites consist of two copolymers of polyvinylidene fluoride (PVDF) with similar chemical structures but distinct dielectric properties, where one contributes to high electrical polarization and the other offers high thermal stability and suppresses charge injection. More importantly, we demonstrate that the critical issue of charge conduction at elevated temperature in ferroelectric polymers is well tackled by the established highly miscible interlayer interfaces in the multilayered structure set up between the two electrically dissimilar phases. At 70 °C, the maximum discharged energy density above 80% discharge efficiency of the multilayered composites reaches 15.5 J/cm3, far outperforming all the existing ferroelectric polymers. This work sheds light on the design of high-energy-density ferroelectric polymers for high temperature capacitive energy storage.