All Polymer Dielectric Films for Achieving High Energy Density Film Capacitors by Blending Poly(Vinylidene Fluoride-Trifluoroethylene-Chlorofluoroethylene) with Aromatic Polythiourea

Chengwei Li,Chengguang Zhang,Wenyao Yang,Xiali Li,Yajie Yang,Yujiu Zhou,Liuwei Shi

doi:10.1186/s11671-020-3270-x

Abstract

Construct dielectric films with high energy density and efficiency are the key factor to fabricate high-performance dielectric film capacitors. In this paper, an all organic composite film was constructed based on high dielectric polymer and linear dielectric polymer. After the optimized polycondensation reaction of a linear dielectric polymer aromatic polythiourea (ArPTU), the proper molecular weight ArPTU was obtained, which was introduced into poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) terpolymer for a composite dielectrics. The results indicate that the addition of ArPTU molecules reduces the dielectric loss and improves the breakdown field strength of the PVDF-TrFE-CFE effectively. For the PVDF-TrFE-CFE/ArPTU (90/10) composite film, the maximum energy density about 22.06 J/cm3 at 407.57 MV/m was achieved, and high discharge efficiency about 72% was presented. This composite material can be casted on flexible substrate easily, and PVDF-TrFE-CFE/ArPTU organic composite films having high energy density, high breakdown field strength, low dielectric loss, and higher discharge efficiency are obtained. This is an unreported exploration about high energy density organic dielectric films based on PVDF-TrFE-CFE matrix and linear polymer dielectrics, and the findings of this research can provide a simple and scalable method for producing flexible high energy density materials for energy storage devices.

Highlights

Dielectric film capacitors with high energy density, low dielectric loss, and high efficiency are required for compact and reliable power systems [1,2,3,4,5,6,7]
By controlling the polycondensation reaction conditions, especially the ratio of the two monomers, aromatic polythiourea (ArPTU) with different molecular weight were synthesized, as shown in Table 1 (A, B, and C are polythioureas synthesized by the molar ratio phenylene diisothiocyanate (PDTC)/ MDA (1/1), PDTC/MDA (0.95/1), and PDTC/MDA (1.05/1))
This is because the ArPTU molecule has a polar group-thiourea group, and the dipoles turning polarization in molecules contribute a lot to the dielectric constant

Summary

Introduction

Dielectric film capacitors with high energy density, low dielectric loss, and high efficiency are required for compact and reliable power systems [1,2,3,4,5,6,7]. Among the available electrical energy storage technologies, dielectric film capacitors have the highest power density because of their ultra-fast charge and discharge capability [8, 9]. Li et al Nanoscale Research Letters (2020) 15:36 cases, the recombination of the two materials results in aggregation and interfacial adhesion due to the difference in compatibility between the two ingredients, resulting in high dielectric loss. To this end, new dielectric materials need to be sought and designed to further increase the energy density of the films and related devices. PVDF terpolymers exhibit high dielectric loss under high electric field [22]

Methods

Results

Conclusion