While the incorporation of the inorganic fillers into polymers is envisioned to improve the properties of polymers, the organic–inorganic interface in the nanocomposite plays a prominent role in the modulation of the electrical, mechanical and thermal properties. Here, the epoxy chain-grafted silica nanoparticles were prepared and utilized as the fillers in epoxy matrix. The multiple physical properties such as the tensile strength, the elongation at break, the glass transition temperature, the dielectric strength of the nanocomposites with epoxy chain-grafted silica are simultaneously improved in comparison with those of the neat epoxy and the nanocomposites with unmodified silica. Moreover, substantial reductions in the water absorption ratio, dielectric loss and electric conductivity are obtained in the nanocomposites filled with epoxy-grafted silica even at relatively low filler loadings. These results verify the critical role of the chemically-bonded interface between organic and inorganic phases in determining the mechanical and dielectric strength of the polymer nanocomposites. The interaction zone models for the interface between nanoparticle and polymer matrix have been proposed to rationalize the experimental results.

The introduction of inorganic components into a polymer matrix to form polymer composites is an emerging and promising approach to dielectric materials for capacitive energy storage. Ferroelectric polymers are particularly attractive as matrices for dielectric polymer composites owing to their highest dielectric constant (≥10) among the known polymers. Here, the important aspects and recent advances in the development of the ferroelectric-polymer-based dielectric polymer composites for high-energy-density capacitor applications are summarized. The preparation methods of ferroelectric-polymer composites with 0D, 1D, and 2D nanostructured fillers, surface-modified nanofillers, and hierarchically structured fillers, and their comprehensive impacts on the dielectric properties, breakdown strength, and energy density of the resulting composites are described. The most recent progress on the incorporation of multiple nanofillers with complementary functionalities into ferroelectric polymers and the design of layer-structured ferroelectric-polymer composites is also highlighted. A discussion of the scientific and technological issues that remain to be addressed and an outlook for the future of ferroelectric polymer-based dielectric composites are also presented.

As the transmission capacity of gas insulated transmission line (GIL) increases, the synergistic improvement in dielectric and mechanical strengths of GIL insulators is urgently needed for the development of advanced power systems. Mechanical defects in power equipment are prone to induce discharges during high voltage operations, which need to be mitigated. In this paper, the strains on the GIL insulator surface are measured by fiber Bragg grating (FBG) strain sensors during hydrostatic tests. An abnormal change of strain is detected near the interface between center conductor and the spacer. The numerical results of stress distributions of GIL insulator during manufacturing and high-voltage operation are calculated by the finite element method. The results indicate that the mechanical stresses are concentrated at the interface, which lead to the development of conductor-spacer interface separation. In addition, based on the hydrostatic test and the FEM calculations, the dielectric interfacial strength, including the electric field distribution, and flashover are investigated by a combination of numerical and experimental studies. The results indicate that the air gaps generated by the separated interface distort the electric field at the tip of the gap, which is likely to cause discharges and reduce the gas-solid interfacial flashover strength of the insulator, placing concerns of insulation failure and even operating failures of GIL. This work sheds light on the importance of interfacial structure of power equipment and will guide the design and the manufacture of GIL insulator.

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.

Poly(vinylidene fluoride)-based terpolymers, known for having the largest dielectric constant among the existing dielectric polymers, are attractive materials for electrostatic film capacitors used in lightweight electrification systems. However, the potential of these terpolymers in film capacitor applications remains constrained by their low electrical insulating and mechanical strengths. To address these limitations, we introduced rigid covalent organic framework (COF) nanospheres into the thin films of soft terpolymers via in situ synthesis and a facile layer-by-layer solution casting method, whereby multilayer films consisting of two polymer outer layers and a COF-containing middle layer were readily obtained. The resultant all-organic thin films exhibit simultaneously high dielectric constant, enhanced breakdown strength, superior energy density (∼25 J cm–3) at efficiencies over 80%, along with greatly improved mechanical self-supporting capability and excellent mechanical flexibility. This work demonstrates the unprecedented use of COF for electrostatic energy storage, uncovering its potential for flexible electronic applications operating under high electric fields.

High capacity polymer dielectrics that operate with high efficiencies under harsh electrification conditions are essential components for advanced electronics and power systems. It is, however, fundamentally challenging to design polymer dielectrics that can reliably withstand demanding temperatures and electric fields, which necessitate the balance of key electronic, electrical and thermal parameters. Herein, we demonstrate that polysulfates, synthesized by sulfur(VI) fluoride exchange (SuFEx) catalysis, another near-perfect click chemistry reaction, serve as high-performing dielectric polymers that overcome such bottlenecks. Free-standing polysulfate thin films from convenient solution processes exhibit superior insulating properties and dielectric stability at elevated temperatures, which are further enhanced when ultrathin (~5 nm) oxide coatings are deposited by atomic layer deposition. The corresponding electrostatic film capacitors display high breakdown strength (>700 MV m^-1) and discharged energy density of 8.64 J cm^-3 at 150 °C, outperforming state-of-the-art free-standing capacitor films based on commercial and synthetic dielectric polymers and nanocomposites.