Effect of Macroscopic Crystallization Modification on the Energy Storage Performance of Poly(Vinylidene Fluoride-Hexafluoropropylene)

The application prospects of dielectric materials such as polyvinylidene fluoride polymers in the field of energy storage have stimulated extensive research, and the performances are mainly affected by crystallization. However, most of them are focused on the influences of single-layer crystalline rather than macroscopic structures. In this study, a unique sandwich structure is proposed by combining layer-by-layer casting and multi-step thermal processing methods to control the macroscopic crystallization in each layer. Four heating temperatures were first set, and it was found that as the drying temperature increases, the films present different crystallization, which results in different dielectric performances. According to this feature, a sandwich structure was proposed for modification of macroscopic crystallization and the influences on energy storage performance were studied. After macroscopic modification of the crystallization, a low loss [Formula: see text], high energy density (7.12[Formula: see text]J/cc) with the highest charge-discharging efficiency was obtained, which presents the advantages of this methods, and the related mechanisms were discussed.