Hexagonal boron nitride nanosheets (BNNSs) are two-dimensional nanomaterials with graphitic-like layered nanostructures, high surface areas, and large aspect ratios. Owing to their excellent thermal conductivity, electrical and mechanical strengths, BNNSs are emerging as multifunctional fillers in polymer dielectrics. In this article, the authors review the recent progress in the BN-containing polymer nanocomposites designed for high-performance film capacitors. While general synthetic approaches to BNNSs and polymer/BNNS nanocomposites are summarized, particular attention is placed on structure-property correlation and rational structural design of the composites with optimized dielectric properties and capacitive performances. In stark contrast to the polymer composites employing high dielectric constant fillers to enhance the electric displacement, a new design concept based on the utilization of BNNSs with a wide bandgap to impede electrical conduction and consequently improve breakdown strength and charge-discharge efficiency of the polymer composites, is highlighted. The significance of developing dielectric capacitors with desirable thermal conductivity and thermal stability to ensure their robust and efficient operation is emphasized. The merits and challenges regarding the existing polymer dielectrics containing BNNSs for energy storage are identified. An outlook for future research opportunities and engineering applications is also presented in this review.

The development of advanced dielectric materials with high breakdown strength, high dischargeable energy densities, and great efficiencies is imperative to meet the ever-increasing demand of modern power systems and electronic devices. Herein, we present the layer-by-layer solution prepared bilayer-structured nanocomposite films with much enhanced capacitive performance via resolving the typical paradox between dielectric constant and breakdown strength in dielectric materials. The bilayered nanocomposite films are composed of Al2O3 dispersed in polystyrene as the interfacial barrier layer to inhibit electrical conduction and the polystyrene layer with TiO2 to enhance dielectric constant. The resulting layered film exhibits a discharged energy density of 4.43 J/cm3 along with ultrahigh charge−discharge efficiencies of >90%, which is among the highest energy densities ever achieved in the polystyrene-based dielectric polymer nanocomposites. In addition, the composite films show outstanding cyclic stability under high electric fields, which would enable the long-term efficient operation of film capacitors. This contribution represents an efficient route to high-energy-density dielectric composite materials by using interfacial barrier architectures.

Polymers are the preferred materials for dielectrics in high-energy-density capacitors. The electrification of transport and growing demand for advanced electronics require polymer dielectrics capable of operating efficiently at high temperatures. In this review, we critically analyze the most recent development in the dielectric polymers for high-temperature capacitive energy storage applications. While general design considerations are discussed, emphasis is placed on the elucidation of the structural dependence of the high-field dielectric and electrical properties and the capacitive performance, including discharged energy density, charge-discharge efficiency and cyclability, of dielectric polymers at high temperatures. Advantages and limitations of current approaches to high-temperature dielectric polymers are summarized. Challenges along with future research opportunities are highlighted at the end of this article.

The electrification of transport requires dielectric materials capable of operating efficiently at high temperatures to meet the increasing demand of electrical energy storage at extreme conditions. Current high-temperature dielectric polymers rely on the incorporation of wide bandgap inorganic fillers to restrain electrical conduction and achieve high efficiencies at elevated temperatures. Here, we report a new class of all-polymer based high-temperature dielectric materials prepared from crosslinking of melt-processable fluoropolymers. The crosslinked polymers exhibit larger discharged energy densities and greater charge-discharge efficiencies along with excellent breakdown strength and cyclic stability at elevated temperatures when compared to the current dielectric polymers. The origins of the marked improvement in the high-temperature capacitive performance are traced to efficient charge-trapping by a range of the molecular trapping centers resulting from the crosslinked structures. In addition, the implementation of melt-extrudable polymers would enable scalable processing that is compatible with the current fabrication techniques used for polymer dielectrics, which is in sharp contrast to the dielectric polymer composites with inorganic fillers.

Modern electronics and electrical systems demand efficient operation of dielectric polymer-based capacitors at high electric fields and elevated temperatures. Here, polyimide (PI) dielectric composites prepared from in situ polymerization in the presence of inorganic nanofillers are reported. The systematic manipulation of the dielectric constant and bandgap of the inorganic fillers, including Al2O3, HfO2, TiO2, and boron nitride nanosheets, reveals the dominant role of the bandgap of the fillers in determining and improving the high-temperature capacitive performance of the polymer composites, which is very different from the design principle of the dielectric polymer composites operating at ambient temperature. The Al2O3- and HfO2-based PI composites with concomitantly large bandgap and moderate dielectric constants exhibit substantial improvement in the breakdown strength, discharged energy density, and charge–discharge efficiency when compared to the state-of-the-art dielectric polymers. The work provides a design paradigm for high-performance dielectric polymer nanocomposites for electrical energy storage at elevated temperatures.

Polymer dielectrics are preferred materials for high-energy-density capacitive energy storage. In particular, high-temperature dielectrics that can withstand harsh conditions, e.g., ≥150 °C, is of crucial importance for advanced electronics and electrical power systems. Herein, high-temperature dielectric polymer composites composed of polyetherimide (PEI) matrix and hafnium oxide (HfO2) nanoparticles are presented. It is found that the incorporation of HfO2 with a moderate dielectric constant and a wide bandgap improves the dielectric constant and simultaneously reduces the high-field leakage current density of the PEI nanocomposites. As a result, the PEI/HfO2 composites exhibit superior energy storage performance to the current high-temperature engineering polymers at elevated temperatures. Specifically, the nanocomposite with 3 vol% HfO2 displays a discharged energy density of 2.82 J/cm3 at 150 °C, which is 77% higher than neat PEI. This work demonstrates the effectiveness of incorporation of the nanofiller with a medium dielectric constant into the polymer on the improvement of high-temperature capacitive properties of the polymer composites.

Cytosolic RNA/DNA sensing elicits primary defense against viral pathogens. Interferon regulatory factor 3 (IRF3), a key signal mediator/transcriptional factor of the antiviral-sensing pathway, is indispensible for interferon production and antiviral defense. However, how the status of IRF3 activation is controlled remains elusive. Through a functional screen of the human kinome, we found that mammalian sterile 20-like kinase 1 (Mst1), but not Mst2, profoundly inhibited cytosolic nucleic acid sensing. Mst1 associated with IRF3 and directly phosphorylated IRF3 at Thr75 and Thr253. This Mst1-mediated phosphorylation abolished activated IRF3 homodimerization, its occupancy on chromatin, and subsequent IRF3-mediated transcriptional responses. In addition, Mst1 also impeded virus-induced activation of TANK-binding kinase 1 (TBK1), further attenuating IRF3 activation. As a result, Mst1 depletion or ablation enabled an enhanced antiviral response and defense in cells and mice. Therefore, the identification of Mst1 as a novel physiological negative regulator of IRF3 activation provides mechanistic insights into innate antiviral defense and potential antiviral prevention strategies.