Multilayer Polymer Composites for High Energy Density Capacitors

Dear Colleagues,

Multilayer polymer composites are emerging as promising dielectric materials for next generation capacitors, where very fast charge/discharge speeds, low dielectric loss, and a high deliverable energy density are required. The increased energy density of these composites will allow for the fabrication of smaller and lighter capacitors with potential use in electric vehicles, defibrillators, and various pulsed power applications, such as high-power lasers, particle accelerators, and electromagnetic weaponry.

The bulk dielectric properties (such as dielectric constant and loss, breakdown strength, and energy density) of multilayer films can be tailored by the judicious choice of the source polymers, coupled with an intimate control over their relative volumetric composition and individual layer thicknesses. In certain compositions, the layer structure can impart a Barrier Effect that impedes the path of destructive high field breakdown trees through the thickness of the film, delaying the onset of breakdown to a higher field. The Barrier Effect yields an enhancement in breakdown strength, while also increasing the energy storage density, as the energy density is proportional to the square of the applied field.

Extensive research efforts are currently underway in order to establish a better fundamental understanding of the electrical breakdown and energy storage mechanisms in multilayer capacitor films, and to design new composite structures with optimized breakdown strength, operational lifetime, and energy density.

This Special Issues focuses on the development of multilayer films as the active dielectric material in high energy density capacitors. Topics of interest include, but are not limited to, the following:

• Screening of source polymers for dielectric, mechanical, and rheological properties suitable for use in multilayer capacitor films;
• Novel approaches for the fabrication of multilayer polymer capacitor films;
• Identification of structure/function relationships that describe how layer structure and polymer volumetric composition affect dielectric properties;
• Elucidation of dielectric loss mechanisms in multilayer capacitor films;
• Effects of post-processing techniques, such as biaxial stretching and annealing, on dielectric properties;
• Characterization techniques for the evaluation of breakdown strength and operational lifetime in multilayer capacitor films;
• New techniques to measure high field effects such as thermal conductivity, polarization hysteresis, interfacial polarization, and electromechanical strain/deformation;
• Novel techniques for layer structure verification and interface imaging;
• Evaluation of electrical breakdown mechanism in multilayer films, including the observation or verification of the Barrier Effect, or alternative breakdown pathways.
• Modeling of internal electric field distributions on a layer-by-layer basis, and relation to high field electrical breakdown;
• Inclusion of “composite” layers containing high dielectric constant dopants embedded within multilayer films.

Dr. Mason A. Wolak
Guest Editor

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• capacitor
• multilayer
• composite
• electrical breakdown
• energy density
• dielectric constant
• polymer film