Energy Storage Properties of Blended Polymer Films with Normal Ferroelectric P(VDF-HFP) and Relaxor Ferroelectric P(VDF-TrFE-CFE)

Abstract

With the recent development of wearable/portable electronic devices, the power sources need to be flexible and miniaturized. As the power supply, a dielectric capacitor is used for systems requiring high power in a short time, which in turn necessitates dielectric materials with high energy density and fast discharging time for device miniaturization. In this study, we attempt to improve the energy density of organic materials by blending normal ferroelectric P(VDF-HFP), which offers high dielectric breakdown strength, and relaxor ferroelectric P(VDF-TrFE-CFE), which provides a high dielectric constant. The role of P(VDF-HFP) as a defect in the P(VDF-TrFE-CFE) crystallite improved the properties of the relaxor-ferroelectrics. Increasing the terpolymer content in the blended films reduced the normal ferroelectric β-phase, which revealed that non-polar phase was induced. The copolymer and terpolymer were blended in various weight ratios (10:0, 7:3, 5:5, 3:7, 1:9 and 0:10) and cast into films. The blends with a copolymer/terpolymer ratio of 1:9 showed reduced hysteresis and remnant polarization, compared to those of the pure terpolymer, and a higher maximum polarization (Pmax) value at an electric field of 250 MV/m, indicating a less saturated polarization at high electric field. To conclude, the PVDF-based copolymer/terpolymer (1:9 ratio) blends showed the highest energy density (6.58 J/cm3).