Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers...

Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

High-Energy-Density Ferroelectric Polymer Nanocomposites for Capacitive Energy Storage: Enhanced Breakdown Strength and Improved Discharge Efficiency

Much effort has been invested for nearly five decades to identify and develop new polymer capacitor dielectrics for higher than ambient temperature applications. Simultaneous demands of processability, dielectric permittivity, thermal conductivity, and dielectric breakdown strength dictated by increasing high power performance criteria limit the number of available materials. The present review first explains the advantages of metallized polymer film capacitors over the film-foil, ceramic, and electrolytic counterparts and then presents a comprehensive review on both past developmental effort of commercial resins and recent research progress on new polymers targeted for operating temperature above 150 °C. Some historical background and discussion on the limitation of the commercially available polymer film dielectrics for high temperature applications are also given. In many cases, further development of promising polymers that appear to possess all or most of the important criteria is limited by lack of large scale market incentives but could be of great value to niche applications in the military or aerospace realm.

Polymer Capacitor Dielectrics for High Temperature Applications.

Recent developments in various technologies, such as hybrid electric vehicles and pulsed power systems, have challenged researchers to discover affordable, compact, and super-functioning electric energy storage devices. Among the existing energy storage devices, polymer nanocomposite film capacitors are a preferred choice due to their high power density, fast charge and discharge speed, high operation voltage, and long service lifetime. In the past several years, they have been extensively researched worldwide, with 0D, 1D, and 2D nanofillers being incorporated into various polymer matrixes. However, 1D nanofillers appeared to be the most effective in producing large dipole moments, which leads to a considerably enhanced dielectric permittivity and energy density of the nanocomposite. As such, this Review focuses on recent advances in polymer matrix nanocomposites using various types of 1D nanofillers, i.e., linear, ferroelectric, paraelectric, and relaxor-ferroelectric for energy storage applications. Correspondingly, the latest developments in the nanocomposite dielectrics with highly oriented, surface-coated, and surface-decorated 1D nanofillers are presented. Special attention has been paid to identifying the underlying mechanisms of maximizing dielectric displacement, increasing dielectric breakdown strength, and enhancing the energy density. This Review also presents some suggestions for future research in low-loss, high energy storage devices.

Polymer Matrix Nanocomposites with 1D Ceramic Nanofillers for Energy Storage Capacitor Applications.

Polymer nanocomposite dielectrics with high energy density and low loss are major enablers for a number of applications in modern electronic and electrical industry. Conventional fabrication of nanocomposites by solution routes involves equilibrium process, which is slow and results in structural imperfections, hence high leakage current and compromised reliability of the nanocomposites. We propose and demonstrate that a nonequilibrium process, which synergistically integrates electrospinning, hot-pressing and thermal quenching, is capable of yielding nanocomposites of very high quality. In the nonequilibrium nanocomposites of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and BaTiO3 nanoparticles (BTO_nps), an ultrahigh Weibull modulus β of ∼30 is achieved, which is comparable to the quality of the bench-mark biaxially oriented polypropylene (BOPP) fabricated with melt-extrusion process by much more sophisticated and expensive industrial apparatus. Favorable phase composition and small cry...

Tuning Phase Composition of Polymer Nanocomposites toward High Energy Density and High Discharge Efficiency by Nonequilibrium Processing

Pulsed power capacitors are one of the key components the pulsed power systems for applications in mobile platforms including vehicles, ships and airplanes. The advances of capacitor technology have evolved slowly but steadily in the past 25 years. The energy density of large format millisecond discharge capacitors in >50 kJ sizes has been increased from 0.7 J/cc in the early 1990s to >2.4 J/cc in the 2010s with lifetimes over 10,000 shots. The energy density of microsecond discharge capacitors has been increased from 0.7 J/cc with a DC life less than 100 hours in early 1990s to 1.3 J/cc with a DC life of 2000 hours. The self-healing electrode has been the key to achieving higher energy density capacitors. The fault tolerance provided by these electrodes enables reliable operation near intrinsic breakdown strengths. In addition, the availability of higher quality and thinner biaxially oriented polypropylene (BOPP) film starting 2000s has contributed significantly by increasing the intrinsic breakdown strength of the films themselves. Coupled with design improvements, capacitors based on BOPP film have had significant, order-of-magnitude scale improvements in peak energy densities and peak power densities. The unfortunate consequence of this development is that these technologies have reached a point of diminishing returns, leading to significant efforts to develop new films to replace BOPP. We take this opportunity to review the advances and reflect what works so far to think about the future path.

Pulsed power capacitor development and outlook

Despite a great number of reports on high-energy density dielectric materials, very little attention is paid to determining realistic energy densities of larger scale devices made of these materials. These materials are typically evaluated with very short duration voltage withstand tests on very small sample areas, typically on the order of a few seconds and a few cm2. Conversely, full-scale devices require very long operational lifetimes on the order of years, and dielectric areas as large as several hundreds of m2. Practical components must also include additional material such as major insulation and packaging, resulting in volumetric efficiencies much less than 100%. Increases in total dielectric area, operating time, and packaging inefficiencies reduce practical energy densities by one to two orders of magnitude. Here we highlight the limitations of scaling up such results to high energy density capacitors as well as demonstrate the effect of self-healing and its necessity in high-energy-density, high-total-energy devices.

Electrical breakdown in capacitor dielectric films: Scaling laws and the role of self-healing

As an enabling technology, the state-of-the-art for wound film capacitors is continuously being driven towards higher temperature, higher energy density, and longer life to support the development of tomorrow's advanced systems Progress in high temperature capacitors, defined in this work as a capacitor operating at temperatures at or above 100°C, is particularly important as system developers seek to reduce weight and size by removing cooling equipment for electronic components This temperature regime is extremely strenuous for polymer wound film capacitors since all but the most expensive and specialized dielectric materials are greatly weakened electrically and mechanically Capacitors designed to operate under high frequency (30 kHz) and high RMS current values undergo even more strenuous conditions and require special consideration in their design In addition to ambient temperature, the heat generated by high frequency operation can decrease the lifetime of the unit and is of concern to both the designer of the component and the system it is used in This work investigates the thermal behavior of high temperature, high frequency capacitors with the intent of assisting both component and system designers

Thermal modeling of high temperature power conversion capacitors

Certain military and commercial applications require capacitors that can operate at high temperatures, high energy density, with long lifetimes. This paper describes life testing of capacitors with energy densities as high as 0.2 J/cc at >125°C. Capacitors using the same dielectrics but with a higher packing factor design can achieve the same performance but with energy densities >0.3 J/cc at 100°C. Data on dissipation factor, energy density, ripple current capability, lifetime, and other performance parameters are presented. This work was sponsored by the US Army Research Laboratory.

https://ieeexplore.ieee.org/iel7/6516158/6518655/06518867.pdf

Development and performance of high temperature power conversion capacitors

Summary form only given. There is a significant need for high temperature capacitors for a variety of operating conditions including pulse power, and high frequency power conditioning applications at temperatures between 125°C and 200°C. Here we cover several new developments in high temperature capacitor technologies presenting results on thin film capacitors useful for long life, high energy density, and high reliability. Additionally, results are presented on an improved very-high temperature film (200°C and higher) with more reliable self-healing, longer lifetime, and higher energy densities. Results from metallized film capacitors with improved termination demonstrating drastic improvements in current carrying capabilities in both CW RMS current and peak pulse current regimes are also presented. Finally, a theoretical high temperature capacitor utilizing a combination of these technologies is discussed and compared to existing COTS and SOTA capacitors.

M. C. Schalnat

Papers

Pulsed power capacitor development and outlook

Electrical breakdown in capacitor dielectric films: Scaling laws and the role of self-healing

Thermal modeling of high temperature power conversion capacitors

Development and performance of high temperature power conversion capacitors

High current, high temperature capacitors: Recent developments and future prospects