More Like this

1. Intrinsic Polymer Dielectrics for High Energy Density and Low Loss Electric Energy Storage

   Wei, Junji; Zhu, Lei (July 2020, Progress in polymer science)

   High energy density, high temperature, and low loss polymer dielectrics are highly desirable for electric energy storage, e.g., film capacitors in the power electronics of electric vehicles and high-speed trains. Fundamentally, high polarization and low dielectric loss are two conflicting physical properties, because more polarization processes will involve more loss mechanisms. As such, we can only achieve a delicate balance between high dielectric constant and reasonably low loss. This review focuses on achieving low dielectric loss while trying to enhance dielectric constants for dielectric polymers, which can be divided into two categories: extrinsic and intrinsic. For extrinsic dielectric systems, the working mechanisms include dipolar (e.g., nanodielectrics) and space charge (e.g., ion gels) interfacial polarizations. These polarizations do not increase the intrinsic dielectric constants, but cause decreased breakdown strength and increased dielectric loss for polymers. For intrinsic dielectric polymers, the dielectric constant originates from electronic, atomic (or vibrational), and orientational polarizations, which are intrinsic to the polymers themselves. Because of the nature of molecular bonding for organic polymers, the dielectric constant from electronic and atomic polarizations is limited to 2-5 for hydrocarbon-based insulators (i.e., band gap > 4 eV). It is possible to use orientational polarization to enhance intrinsic dielectric constant while keeping reasonably low loss. However, nonlinear ferroelectric switching in ferroelectric polymers must be avoided. Meanwhile, paraelectric polymers often exhibit high electronic conduction due to large chain motion in the paraelectric phase. In this sense, dipolar glass polymers are more attractive for low loss dielectrics, because frozen chain dynamics enables deep traps to prevent electronic conduction. Both side-chain and main-chain dipolar glass polymers are promising candidates. Furthermore, it is possible to combine intrinsic and extrinsic dielectric properties synergistically in multilayer films to enhance breakdown strength and further reduce dielectric loss for high dielectric constant polar polymers. At last, future research directions are briefly discussed for the ultimate realization of next generation polymer film capacitors. 

   more » « less
2. Enhancing the Dielectric Breakdown Strength of Solid-State Polymer Capacitors by Chain End Manipulations

   Singh, Maninderjeet; Wu, Wenjie; Dong, Mei; Tran, David; Wooley, Karen L.; Pradhan, Nihar; Raghavan, Dharmaraj; Karim, Alamgir (March 2020, Bulletin of the American Physical Society)

   The need for high power density, flexible and light weight energy storage devices requires the use of polymer film-based dielectric capacitors. Theoretically, it has been shown that chain ends contribute adversely to electrical breakdown, resulting in low energy density in polymer capacitors. In this work, we enhanced the energy density of polymer capacitor by using well-ordered high molecular weight block copolymer (BCP), in which the chain ends are segregated to narrow zones. Cyclic homopolymers (no chain ends) and linear homopolymers having chemistry-controlled chain ends also show enhanced breakdown strength, resulting in higher energy density as compared to the linear counterparts. These novel insights into manipulating chain end distribution such as in BCPs and with molecular topology to increase the energy density of polymers will be helpful for fulfilling next-generation energy demands. 

   more » « less
3. Polarity-dependence of the nonlinear dielectric response in interfacial water

   https://doi.org/10.1063/5.0142483  

   Mulpuri, Nagaraju; Bratko, Dusan (March 2023, The Journal of Chemical Physics)

   Molecular dynamics simulations are used to study nonlinear dielectric responses of a confined aqueous film in a planar nanopore under perpendicular electric fields at varied voltages between confining graphene sheets. Dielectric saturation reminiscent of the bulk phase behavior is prevalent at very strong fields, whereas we observe a nonmonotonic permittivity dependence on electric field at intermediate strengths where field-alignment and spontaneous polarization of interfacial water are of comparable magnitudes. The coupling between the two effects results in distinct dielectric responses at opposite confinement walls. The normal component of both the differential dielectric constant and dielectric difference constant tensors averaged over the region closer to the wall under incoming electric field (field pointing from the liquid to the solid phase) initially increases with the strength of the imposed field. The differential permittivity peaks at a field strength previously shown to offset the surface-induced orientation bias of hydration molecules at this wall. Further strengthening of the field results in conventional saturation behavior. At the opposite wall (subject to outgoing field) and in the central region of water slab, the nonlinear dielectric response resembles bulklike saturation. The conditions at the permittivity extremum coincide with the window of accelerated reorientation rates of interfacial water molecules under incoming field uncovered in earlier molecular dynamics analyses. 

   more » « less
4. Enhancing corona resistance in Kapton with self-assembled two-dimensional montmorillonite nanocoatings

   https://doi.org/10.1039/D2MA00205A  

   Ren, Ming; Wang, Yifei; Liu, Jingjing; Wu, Chao; Hou, Zaili; Konstantinou, Antigoni; Zhou, Jierui; Nguyen, Hiep; Davis-Amendola, Kerry; Sun, Luyi; et al (May 2022, Materials Advances)

   Polymer dielectrics have been widely used in electrical and electronic systems for capacitive energy storage and electrical insulation. However, emerging applications such as electric vehicles and hybrid electric aircraft demand improved polymer dielectrics for operation not only under high electric fields and high temperatures, but also extreme conditions, for example, low pressures at high altitudes, with largely increased likelihood of electrical partial discharges. To meet these stringent requirements of grand electrifications for payload efficiency, polymers with enhanced discharge resistance are highly desired. Here, we present a surface-engineering approach for Kapton® coated with self-assembled two-dimensional montmorillonite nanosheets. By suppressing the magnitude of the high-field partial discharges, this nanocoating endows polymers with improved discharge resistance, with satisfactory discharge endurance life of 200 hours at a high electric field of 46 kV mm −1 while maintaining the surface morphology of the polymer. Moreover, the MMT nanocoating can also improve the thermal stability of Kapton®, with significantly suppressed temperature coefficients for both the dielectric constant and dielectric loss over a wide temperature range from 25 to 205 °C. This work provides a practical method of surface nanocoating to explore high-discharge-resistant polymers for harsh condition electrification. 

   more » « less
5. Enhancements of electric field and afterglow of non-equilibrium plasma by Pb(ZrxTi1−x)O3 ferroelectric electrode

   https://doi.org/10.1038/s41467-024-47230-7  

   Xu, Yijie; Liu, Ning; Lin, Ying; Mao, Xingqian; Zhong, Hongtao; Chang, Ziqiao; Shneider, Mikhail N; Ju, Yiguang (December 2024, Nature Communications)

   Abstract Manipulating surface charge, electric field, and plasma afterglow in a non-equilibrium plasma is critical to control plasma-surface interaction for plasma catalysis and manufacturing. Here, we show enhancements of surface charge, electric field during breakdown, and afterglow by ferroelectric barrier discharge. The results show that the ferroelectrics manifest spontaneous electric polarization to increase the surface charge by two orders of magnitude compared to discharge with an alumina barrier. Time-resolved in-situ electric field measurements reveal that the fast polarization of ferroelectrics enhances the electric field during the breakdown in streamer discharge and doubles the electric field compared to the dielectric barrier discharge. Moreover, due to the existence of surface charge, the ferroelectric electrode extends the afterglow time and makes discharge sustained longer when alternating the external electric field polarity. The present results show that ferroelectric barrier discharge offers a promising technique to tune plasma properties for efficient plasma catalysis and electrified manufacturing. 

   more » « less