Poly(vinylidene fluoride-hexafluoropropylene) based blend film for ultrahigh energy density capacitor applications

Abstract

In this paper, we investigated the blend film of poly(vinylidene fluoride-trifluoroethylene)/poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-TrFE)/P(VDF-HFP)) with various compositions for high energy density applications. After characterization using x-ray diffraction and transmission electron microscopy, it was found that the crystallinity and spherulite size of the material decreased with the increasing PVDF-HFP contents in the blend film. Furthermore, the blend film showed a maximum breakdown field of 820 MV m-1 and an energy density of 23.8 J cm-3 for the blend film with a 5:5 composition ratio (P(VDF-TrFE)/P(VDF-HFP)). Moreover, the mechanisms of the breakdown field associated with the spherulite size and the crystallinity of the blend film were investigated for the first time. It was revealed that for the materials with similar Young’s moduli, the breakdown field is greatly improved with the reduced spherulite size and decreased crystallinity of the P(VDF-TrFE)/P(VDF-HFP) blend film. This investigation shows an effective approach for improving the breakdown field of dielectric materials in high energy density capacitor applications.