Interphase/interface modification on the dielectric properties of polycarbonate/poly(vinylidene fluoride‐co‐hexafluoropropylene) multilayer films for high‐energy density capacitors

Abstract

Unique three-component multilayer films with ATB-TATBTA configuration were fabricated using forced assembly multilayer coextrusion for novel dielectric systems. The dielectric breakdown strength, displacement-electric field hysteresis, and dielectric spectroscopy of 65-layer polycarbonate (PC)/tie/ poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) were investigated with various tie materials. Three different tie materials, poly(methyl methacrylate) (PMMA), styrene-co-acrylonitrile copolymer with 30% acrylonitrile content (SAN30), and poly(ethylene terephthalate-co-1,4-cycohexanedimethylene terephthalate) (PETG) were chosen owing to their various degrees of interaction with either P(VDF-HFP) or PC. The 65-layer PC/ PMMA/P(VDF-HFP) films exhibited a 25% enhancement in breakdown properties, 50% higher energy density, 40% smaller hysteresis loop areas, and orders of magnitude slower ion migration relative to the 33-layer PC/P(VDF-HFP) control. These property improvements are mainly attributed to the localized interactions at PMMA/P(VDF-HFP) and PMMA/PC interfaces, forming interphase regions. The modified PMMA/P(VDF-HFP) interphase region can effectively hinder the migration of impurity ions in P(VDF-HFP), reducing their mobility within the layer. Additionally, a small fraction of PMMA can lead to slightly increased dielectric constant of the composite films owing to strong interaction between PMMA and P(VDF-HFP). The other two systems with PETG and SAN30 as tie layers exhibited marginal improvements in dielectric properties owing to their weaker interactions with the P(VDF-HFP) layers. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 978-991

Review of Polymer‐Based Nanodielectric Exploration and Film Scale‐Up for Advanced Capacitors

“…In this case, a similar interfacial region is also created between two distinct polar polymers that exhibit 2–2 composites with a more structured ordering. A representative example is the coextruded multilayer film that consists of alternating layers of polar PVDF and PC polymers, which was demonstrated by Baer and Zhu's research groups . It was conjectured that the existence of multiple interfaces plays a critical role in blocking charge migration, thereby enhancing the breakdown strength.…”

“…After demonstrating the advantage of laminating hundreds of nanometer layers of dissimilar polymers, the researchers improved the coextrusion process and produced higher‐quality nanolaminate films. More information is available in several publications …”

The search for enhanced dielectric strength of polymer‐based dielectrics: A focused review on polymer nanocomposites

“…The challenges are associated with low dielectric strength, mechanical strength, and scale‐up of composite films. [ 59–63 ] Therefore, the choice of dielectric materials with excellent overall properties and processes is minimal, considering the requirements in dielectric loss, dielectric strength, harmful solvents, heat shrinkage, and film‐forming ability, etc. Better ideas are highly needed to fulfill high dielectric strength, low dielectric loss, and innovative material processes.…”

Rational Co‐Design of Polymer Dielectrics for Energy Storage

“…Biaxially oriented polypropylene (BOPP), with a high breakdown field of about 700 MV m −1 and a dielectric constant of about 2.2, is the current state‐of‐the‐art polymer dielectric in high‐energy‐density (metalized) film capacitors. Attempts to improve upon BOPP have been based on poly(vinylidene fluoride) (PVDF) and its copolymers, polymer nanocomposites, multilayers, and so on. All such potential replacements have suffered from one or another weakness, like high loss or low parallel‐plate breakdown field.…”