Ultrahigh Temperature Lead-Free Film Capacitors via Strain and Dielectric Constant Double Gradient Design

Enhanced Energy Storage Properties of Highly Polarized BMT-Based Thin Films through the Multiscale Structure Synergistic Regulation Strategy

For solving the trade-off relationship of the polarization and breakdown electric field, ferroelectric films with high polarization are playing a critical role in energy storage capacitor applications, especially at moderate/low electric fields. In this work, we propose a multiscale structure (including defect, domain, and grain structures) synergetic optimization strategy to optimize the polarization behavior and energy storage performances of BiMg0.5Ti0.5O3 (BMT) ferroelectric films by introducing Sr0.7La0.2TiO3 (SLT) without compromising the breakdown strength. At a moderate electric field of 2917 kV/cm, a high discharge density of 72.2 J/cm3 has been achieved in 0.9BMT-0.1SLT films, together with good frequency, thermal, and cycle stabilities for energy storage. Importantly, the phase difference Δφ is utilized to quantitatively evaluate the polarization switching mobility of the ferroelectric domain/PNRs at an external electric field stimulation. This research demonstrates that a multiscale structure optimization strategy could effectively regulate the energy storage performance, and ecofriendly BMT-based materials are promising candidates for next-generation energy storage capacitors, especially at moderate/low electric fields.

Metadielectrics for high-temperature energy storage capacitors

Dielectric capacitors are highly desired for electronic systems owing to their high-power density and ultrafast charge/discharge capability. However, the current dielectric capacitors suffer severely from the thermal instabilities, with sharp deterioration of energy storage performance at elevated temperatures. Here, guided by phase-field simulations, we conceived and fabricated the self-assembled metadielectric nanostructure with HfO2 as second-phase in BaHf0.17Ti0.83O3 relaxor ferroelectric matrix. The metadielectric structure can not only effectively increase breakdown strength, but also broaden the working temperature to 400 oC due to the enhanced relaxation behavior and substantially reduced conduction loss. The energy storage density of the metadielectric film capacitors can achieve to 85 joules per cubic centimeter with energy efficiency exceeding 81% in the temperature range from 25 °C to 400 °C. This work shows the fabrication of capacitors with potential applications in high-temperature electric power systems and provides a strategy for designing advanced electrostatic capacitors through a metadielectric strategy.

Significantly enhanced high-temperature capacitive energy storage in cyclic olefin copolymer dielectric films via ultraviolet irradiation

Polymer dielectrics with high operation temperature (∼150 °C) and excellent capacitive energy storage performance are vital for electric power systems and advanced electronic devices. Here, a very convenient and competitive strategy by preparing ultraviolet-irradiated cyclic olefin copolymer films is demonstrated to be effective in improving the energy storage performance at high temperatures. Compared with the unirradiated film, irradiated films exhibit a higher dielectric constant, higher breakdown strength and stronger mechanical properties as a result of the emergence of the carbonyl group and cross-linking network. Consequently, with a high efficiency above 95%, a superior discharged energy density of ∼3.34 J cm^-3 is achieved at 150 °C, surpassing the current dielectric polymers and polymer nanocomposites. In particular, the energy storage performance remains highly reliable over 20 000 cycles under actual operating conditions (200 MV m^-1 at 150 °C) in hybrid electric vehicles. This research offers a valuable pathway to build high-energy-density polymer-based capacitor devices working under harsh environments.