Crosslinked PVDF Terpolymers and Nanocomposites
Abstract
ABSTRACT:The demand for high-performance energy-storage devices is rapidly growing thanks to increasing deployments of advanced electronics, electric vehicles, and power systems. Among the various electrical energy-storage devices, polymer thin-film capacitors possess the combined advantages of high power density, mechanical flexibility, and low-cost large-area processability.They are already used in certain electronic devices and power systems. The state-of-the-art capacitor films represented by bi-axially oriented polypropylene exhibit high charge-discharge efficiency. However, its energy density is rather low, limited by the low dielectric constants of the polymers. Since capacitors can take up more than 25% of the volume and weight of electric power systems, increasing the energy density of the thin-film capacitors would directly translate into reduction of the volume and weight of the power systems.Poly(vinylidene difluoride)-based polymers, are among the best known polymers with high dielectric constants. Relaxor ferroelectric poly(vinylidene difluoride) terpolymers are particularly interesting for high-energy-density thin-film capacitors thanks to their relatively low polarization hysteresis and dielectric loss. Moreover, these polymers have also been suggested for otherimportant applications including solid state cooling, non-volatile memory, and electromechanical transduction. However, the terpolymers also exhibit critical problems including a low glasstransition temperature which leads to high dielectric loss and rapid failure at elevated temperatures.Nanocomposites incorporating high dielectric nanoparticles have been extensively investigated to further increase the dielectric constant and thus energy density of the terpolymers. However, the increased dielectric loss and diminished breakdown field strength often overwhelm the gain in dielectric constant.We propose an integrative approach to synthesizing poly(vinylidene difluoride) terpolymer nanocomposite with chemically modified polymer matrix and uniformly dispersed nanoparticles.The introduction of chemical modification to the polymer structure will facilitate spontaneous polarization to lower the hysteresis loss of the polymer matrix. It also enhances the thermal stability of the polymer and lowers the dielectric loss at elevated temperatures. The nanoparticle fillers will be introduced using an innovative chemical approach to effect uniform dispersion of the nanoparticles at high loading content and suppress aggregation-induced dielectric loss anddielectric breakdown. The project aims to demonstrate dielectric nanocomposite films with high dielectric constant, high breakdown field strength, low charging/discharging loss across a broad temperature range, and high energy density.The project will also investigate electrode materials that can be applied over large areas of the nanocomposite films at low cost, can enhance fault tolerance to increase the long term operational stability of the thin film capacitors. The new materials will be further investigated and modified as necessary for other DoD-important applications including thermal and electromechanical devices.The proposed research should lay the scientific foundation for the synthesis of dielectric composites with high-volume loading and uniform-distribution of nanoparticles. It will experimentally validate the synthetic approach to provide a new generation of dielectric materials for high density energy storage and high-power discharging. The scientific approach could be adapted for the development of new composites with far reaching applications for the national security and defense.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 23, 2019
- Source ID
- N000141912212
Entities
People
- Qibing Pei
Organizations
- Office of Naval Research
- United States Navy
- University of California, Los Angeles