ABSTRACT Polypropylene (PP) is widely used in high‐voltage capacitors due to its advantages in insulation performance, processability, degradability, and recyclability. During long‐term operation, space charges are easily injected from electrodes into the dielectric under a strong electric field, inducing material degradation and even breakdown. Space charge suppression has long been a key issue in engineering applications. Different from the traditional technology route of space charge suppression by nano‐doping, a kind of novel physical method of regulating the charge migration path inside the dielectric by Strontium ferrite Magnetic Nanoparticles (SrFe 12 O 19 ) was proposed. The experimental results show that the oriented magnetic field generated by SrFe 12 O 19 can inhibit the free charge movement, reduce leakage current, and improve breakdown strength. Furtherly, PP/SrFe 12 O 19 composite was used as a functional layer to suppress carrier injection, a three‐layer structure (referred to as SPS) was constructed. When the mass fraction of SrFe 12 O 19 is 0.5%, the breakdown strength of the SPS rises to 283 kV/mm, which is 36 kV/mm higher than that of the PP. The leakage current at 100 kV/mm is 2.17 × 10 −9 A, decreasing about 81.8%. This work provides a new idea to solve space charge accumulation and improve the breakdown strength of DC capacitors.

Dielectric capacitors are essential for high-power, fast-response electronics, but their performance is limited by trade-offs between high polarization, low hysteresis loss, and high breakdown strength. The urgent need for eco-friendly materials has spurred intense interest in lead-free oxide dielectrics. Recent advances in synthesis and advanced characterization have revealed that atomic- and nanoscale local structures exert a profound influence on energy-storage performance. Specifically, local polar nanoregions, chemical inhomogeneities, lattice distortions, and interfacial architectures play a pivotal role in regulating polarization configuration, leakage behavior, and breakdown pathways. This review systematically summarizes recent progress in lead-free dielectric oxides through local structural design. After a concise overview of dielectric energy-storage principles and classification, representative systems are discussed, with a focus on how specific local structural motifs correlate with macroscopic performance. The emerging strategies, such as local chemical framework design, high-entropy approaches, polar nanodomain engineering, local microstructure architectures, multiphase/heterogeneous interfaces, and local amorphous design, are summarized. By integrating key advances in this field, the review clarifies intrinsic structure-property relationships, identifies current challenges, and outlines opportunities for future breakthroughs, which could deliver timely guidance for designing high-performance and environmentally benign dielectric capacitors.

Ordered alkene-alkyne alternating conjugation in polyimides: A dual-strategy approach to ultralow dielectric constant and high thermal conductivity.

With the ongoing trend toward miniaturization in electronic devices and the concomitant increase in power density, the operational requirements for dielectric polymer films have extended beyond conventional room-temperature conditions. In this study, low mass fraction boron nitride nanodots (BNNDs) were incorporated into polyetherimide (PEI) films. The strong π-π interaction between BNNDs and PEI enables BNNDs to effectively intercalate between adjacent PEI molecular chains, thereby effectively weakening the interchain conjugation effects within the PEI matrix, successfully suppressing energy losses at high temperatures. Consequently, the composite film achieved an exceptional breakdown strength (Eb) of 549.4 MV m-1 at 200°C while maintaining discharge energy density (Ud) of 6.49 J cm-3 and efficiency (η) of 65%. Furthermore, the film demonstrated notable self-healing capability following dielectric breakdown, at 200°C and 500 MV m-1, the Ud values before and after breakdown were 4.88 and 4.24 J cm-3, respectively, with η of 85% and 82%. In summary, this study demonstrates the existence of strong π-π conjugated interactions between BNNDs and PEI molecular chains. Consequently, BNNDs can intercalate between PEI molecular chains, replacing the π-π conjugation between these chains, thereby enhancing the high-temperature performance of aromatic dielectric polymers.

High-temperature polymer dielectrics must meet the requirements of modern power electronic systems, particularly high energy storage density under elevated-temperature conditions. However, polyetherimide (PEI), one of the most promising candidate materials, suffers from significant deterioration in energy storage density due to high conductive loss under high temperatures. In this study, we designed a polymer alloy comprising PEI and semi-aromatic benzimidazole polyimide (SPBII), where intermolecular hydrogen bonding acts as a compatibilizer to stabilize a nanoscale microphase-separated structure. The SPBII polymer chains confined within nanoregions exhibit a nanoconfinement effect, substantially enhancing the thermal and mechanical properties of the polymer alloy, with Tg and Young's modulus of 50% SPBII reaching287.5°C and 5.32 GPa. Furthermore, the high positive electrostatic potential of SPBII introduces charge traps at the PEI/SPBII interface, effectively suppressing high-temperature conduction loss. As a result, the 50% SPBII polymer alloy demonstrates remarkable improvements in breakdown strength and energy storage density. For instance, at 200°C, it achieves an energy density of 4.53 J cm-3 with an efficiency of 90%, outperforming that ofpure PEI (1.71 J cm-3). This breakthrough provides a promising solution for achieving superior capacitive performance of dielectrics under high-temperature conditions, significantly advancing the applications of polyimide-based dielectric materials.

Abstract This study proposes a high-performance β-Ga₂O₃ trench-gate (TG) MOSFET employing a variable lateral doping (VLD) scheme to strengthen power-device capability. The analysis examines the impact of VLD engineering, high-κ HfO₂ and Al₂O₃ dielectrics, and field-plate structures on the electrical, thermal, and radio-frequency (RF) characteristics. HfO₂ demonstrates lower ON-resistance and higher transconductance than Al₂O₃, along with reduced temperature sensitivity. The β-Ga₂O₃ TG-MOSFET achieves picosecond-scale switching, with a turn-on delay of 31.6 ps and rise time of 33.2 ps, supported by low parasitic capacitances (Ciss = 126.1 fF/mm, Crss = 89.5 fF/mm). The turn-off transition (td(off) = 1.2 ns, tf = 7.7 ns) confirms suitability for high-frequency power and RF operation. Incorporating dual field plates raises the off-state breakdown voltage from 2058 V to 3045 V an increase of 48% by lowering peak electric fields and redistributing the lateral field profile. The results confirm that the synergy between trench-gate design, lateral doping engineering, and dielectric optimization in β-Ga₂O₃ markedly enhances switching behavior, heat management, and breakdown strength, making the proposed architecture a compelling solution for advanced high-power, high-temperature, and RF applications.

Achieving synchronously high permittivity and breakdown strength in Mo/PVDF dielectrics via engineering insulating MgO as interlayer

Excellent high-temperature breakdown and energy storage performances of polyetherimide dielectric film with silver/alumina nanosheets derived from sequential bimetallic ion exchange.

Dielectric breakdown strength and energy storage improvement of polyimide through environmentally benign reactive ion etching plasma surface modification

This study examined the effects of Sr(Ti0.85Zr0.15)O3 (STZ) additive and post-sintering treatments on the electrical and biological properties of lead-free (1 − x)[0.7(Bi0.5Na0.5)TiO3–0.3(Sr0.7Bi0.2)TiO3]–xSr(Ti0.85Zr0.15)O3 or ((1 − x)(BNT–SBT)–xSTZ) ceramics synthesized by solid-state reaction. All compositions showed coexistence of rhombohedral and tetragonal phases, with increased STZ promoting the rhombohedral phase. The x = 0.15 composition exhibited favorable results, featuring a broad temperature coefficient of capacitance (TCC) stability range (±15% from 38–310 °C), a 43% increase in energy storage density, 92.90% energy efficiency, strong breakdown strength (95 kV cm−1), and excellent thermal stability, with only 1.48% energy density variation between 25 and 125 °C. Its initial electrostrain of 0.06% was notably low. Post-sintering aging enhanced electrostrain to 0.33% representing a 450% increase and significantly improving electromechanical response. Cytotoxicity testing confirmed excellent cell viability, and bioactivity in simulated body fluid, initially moderate, was notably enhanced by β-tricalcium phosphate surface coating. These results highlight the biomedical potential of the optimized x = 0.15 ceramic composition.

Improved suppression of electrical breakdown strength variation during melting annealing by enhanced multiphase stability in long-chain branching polypropylene high-voltage insulation

Inspired by the hierarchical structure of the feathers of black swans at the Shaanxi University of Science and Technology (SUST), we developed compositionally graded cellulose-based composite films incorporating BCZT ceramic fillers with varying compositions into a cellulose/P(VDF-HFP) blend film (C8/PH2) for high-performance and sustainable dielectric capacitors. Three configurations-single-layer, down-graded trilayer (C8/PH2-BCZT-dg), and up-graded trilayer (C8/PH2-BCZT-ug)-were fabricated and systematically evaluated. The C8/PH2-BCZT-dg film achieved the highest recoverable energy storage density (Wrec = 38.73 J cm-3) and efficiency (η = 79.39%), attributed to the stable Schottky emission conduction across its interfaces, as revealed by current-voltage fitting and band-diagram analysis. In contrast, the C8/PH2-BCZT-ug film structure exhibited a conduction-mechanism transition to Ohmic contact, leading to reduced breakdown strength. Finite element simulations confirmed the experimental breakdown trends and highlighted the role of internal potential distribution. The C8/PH2-BCZT-dg film also demonstrated excellent frequency stability (10 Hz-10 kHz), cycling durability (106 cycles), and high-power performance, with rapid energy release (t0.9 = 41.97 ns) and a discharge energy density of 21.07 J cm-3 at 5.0 MV cm-1. Furthermore, combustion testing revealed the superior fire resistance of the film, underscoring its safety for long-term operations. These results establish hydrogen-bond-engineered, compositionally graded cellulose composites as promising eco-friendly alternatives to petroleum-based dielectric materials for advanced energy-storage applications.

The inherently low dielectric constant constrains the discharged energy density of polypropylene (PP)-based dielectrics, making it challenging to meet the growing demand for lightweight, efficient, and cost-effective dielectric capacitors. In this work, highly aligned polyamide 6 (PA6) submicron fibrils were in situ fabricated in the PP matrix via the "melt blending-hot stretching-quenching-annealing" technique, where the PA6 submicron fibrils could effectively serve as the heterogeneous nucleation sites for promoting the formation of PP crystals. As a result, the well-defined PA6 submicron fibrils and PP crystalline structure not only provided extensive interfacial areas to increase the interfacial polarization, but also significantly increased the propagation path of electric trees to improve the breakdown strength. The PP/PA6 dielectric films exhibited a remarkable maximum discharged energy density of 5.8 J cm- 3 with a high energy efficiency of 88.9% at 700 MV m-1. This work demonstrates that heterogeneous interface engineering provides a viable route to simultaneously achieve high energy density and high efficiency in PP-based dielectric films, thereby promoting the scalable fabrication of high-performance all-organic dielectric capacitors.

Polymer dielectric composites have garnered growing attention due to their ability to combine properties of both polymers and ceramic fillers. However, the relatively low energy storage density still limits their application in continuously updating electronic capacitors. Herein, we present copper calcium titanate nanorods (CCTONRs) and polyetherimide (PEI) based dielectric composites with an enhanced energy storage density through orientating of CCTONRs achieved by hot stretching. First, 1D structured CCTONRs are synthesized and surface-modified using carboxylated polyetherimide (cPEI), offering cPEI@CCTONRs. The cPEI@CCTONRs are then incorporated into PEI matrix, followed by hot stretching, resulting cPEI@CCTONRs/PEI-HS composites. Due to the surface modification of CCTONRs, cPEI@CCTONRs are homogeneously dispersed in PEI matrix. Additionally, an 100% hot stretching ratio leads to an orientation degree of 18.4% of cPEI@CCTONRs within the composite. As a result, the dielectric constant of the hot stretched composite film with 15 wt% cPEI@CCTONRs reaches 10.14, with its breakdown strength remaining at a high level of 467.4 MV·m-1. Therefore, the discharged energy density of this composite can be up to 10.1 J·cm-3, which is 2.52 times to that of pure PEI. This work is highly feasible for the development of outstanding performance energy storage materials for film capacitor with high-density energy storage.

To achieve further optimization of dielectric capacitors for modern advanced electronic devices and power systems, the overall improvement of the energy storage density and energy storage efficiency remains a great challenge. We implemented a strategy that leverages the self-assembled insulating network structures of the Bi-O layer unit to simultaneously optimize both the energy storage density and efficiency. Using the introduction of relaxation ferroelectric block of SrTiO3 with trace Mn elements, the periodic tunability of the perovskite layer of the Bi4Ti3O12 structure is realized through reducing the interlayer coupling force, from 3 to 8 layers, which induces the random distribution of the Bi-O layer, resulting in the insulating network structure. The structure of the Bi-O network was clearly observed using spherical aberration-corrected transmission electron microscope, which effectively improves the multidimensional insulating properties of the film, thus greatly improving the high voltage resistance, while maintaining high polarization disorder. The simultaneous enhancement of spontaneous polarization (80 μC·cm-2) and breakdown strength (5.1 MV·cm-1) in the present thin films leads to a Wrec of 140 Joules per cubic centimeter and efficiencies as high as ∼76%. The proposed strategy provides valuable design ideas for high-performance dielectrics.

Adding tiny amounts of tungsten (W) and graphene (Gr) in traditional Cu-Cr contact efficiently enhances the mechanical strength and breakdown strength of vacuum circuit breakers (VCBs). However, anodes made of W or W-alloy are acknowledged to harm the interruption performance of VCBs through impeding the post-arc recovery of vacuum gap by stronger surface emission. To investigate into the influence of W/Gr addition with a small mass ratio in Cu-Cr contact, this study employs molecular dynamics method to simulate anode behaviours during arcing and post-arc processes. Through the simulations, surface temperature and surface atom emission of the anode, which are perceived as the key phenomena affecting the post-arc recovery of vacuum, are used to assess the influence of material modifications on the interruption performance of VCBs. As a result, the existence of additional phases and the resulted interfaces are shown inevitably affecting the thermal processes of anode. Furthermore, this influence relates to the position, thickness, and orientation of the additional phases, and could be mitigated by limiting the size of the additional phases. Simulation results are validated by experiences of W usage in VCBs, as well as theoretical analysis of thermal processes of anode. Based on the simulation, suggestions on the material preparation of material modifications are provided to mitigate their influences on the interruption performance of VCBs.

In modern electronics and power systems, high-performance dielectric capacitors with metallized films are indispensable for efficient energy storage and power delivery. However, commercially available polymers like BOPP and PVDF are limited by inherent structural defects, restricting their ability to achieve high energy density and low energy loss. Glassy polymers, which offer a promising balance between these attributes, are severely restricted by their brittleness, complicating film casting and coil winding processes crucial for capacitor applications. To address these challenges, we introduced non-polar hydroxyl-terminated polybutadiene monomers into glassy polymers to construct distinct sea-island structures. This approach enhances the dielectric constant through interface polarization and significantly improves material toughness. These structures concentrate stress, enable plastic deformation, inhibit crack propagation, and demonstrate self-healing capabilities. Additionally, the reverse electric field generated by interface polarization traps charges, preventing further electron migration and delaying the decline in breakdown strength. Our results show a releasing efficiency of 89.5%, a discharge energy of 10.48 J/cm3 at 550 MV m-1, and a fracture elongation of 27.3%. This study pioneers a novel strategy to decouple the trade-offs between high energy density, low energy loss, and enhanced toughness through the strategic construction of sea-island structures, opening new avenues for advanced dielectric materials.

The rapid advancement of electric vehicles, renewable energy integration, and next-generation power electronics has intensified the demand for high-performance dielectric capacitors capable of operating reliably under high temperatures and electric fields. In this study, we develop an all-polymer dielectric (APD) system with superior high-temperature capacitive performance achieved through strategically designed heterogeneous interfaces that introduce high electron barriers. These interfaces are constructed via in situ polymerization and cross-linking of a commercial bismaleimide (MIR) monomer within a fluorinated polyimide (FPI) matrix. The pronounced band structure mismatch between FPI and MIR domains generates substantial interfacial electron barriers, which effectively suppress high-temperature leakage currents while concurrently enhancing breakdown strength, charge-discharge efficiency, and energy density. The optimized FPI/MIR APD achieves outstanding discharged energy densities of 5.8 J/cm3 at 150 °C and 3.0 J/cm3 at 200 °C with high efficiency (η > 90%), as well as excellent cycling endurance (>50000 cycles at 150 °C). Moreover, the material exhibits intrinsic self-healing capability, exceptional scalability, and large-area uniformity. The straightforward and cost-effective fabrication process further underscores its potential for scalable production of high-temperature polymer dielectrics.

ABSTRACT Polymer dielectrics are crucial for high‐energy‐density electrostatic capacitors yet suffer from severe high‐temperature performance degradation due to escalated conduction loss and diminished breakdown strength. While conventional construction of nanoscale inorganic surface layers on dielectric polymer films can partially suppress conduction losses at elevated temperatures, poor interfacial adhesion coupled with complex, expensive fabrication technology hinders industrial scalability. Herein, we develop a solution‐processed nanoscale inorganic covalent surface barrier (SNICS) strategy. Specifically, scalable ultrathin SiO x barrier layers featuring covalently bonded Si─C transition interphases are conformally fabricated on both surfaces of polyetherimide (PEI) films via facile ultrasonic spray‐coating (USC) of perhydropolysilazane (PHPS) precursor solution followed by room‐temperature ultraviolet (UV) irradiation. The SNICS architecture ensures robust interfacial cohesion while effectively suppressing conduction loss through: 1) substantial elevation of the Schottky emission barrier height; 2) introduction of deep charge traps by the high‐electron‐affinity Si─C interphase; and 3) enhanced thermal/mechanical stability from the covalent bonding, outperforming traditional magnetron‐sputtered counterparts. Consequently, SNICS‐engineered films with optimized 186 nm SNICS achieve an exceptional discharged energy density ( U d ) of 5.05 J cm −3 with 90 % efficiency at 200 °C, which is significantly higher than the reported values obtained in the composites fabricated with multilayered structures, with along siding excellent self‐healing capability and outstanding cyclability. This surface engineering presents a scalable pathway for high‐temperature high‐performance polymer capacitors.

Presently, polypropylene (PP), a type of thermoplastic polymer, becomes favorable for use in power cable insulation owing to its better electrical properties over the thermoset crosslinked polyethylene (XLPE). However, PP has a significant issue in term of mechanical properties. Specifically, standalone PP has high stiffness and brittleness. Therefore, adding copolymers into PP is an effective approach to tailor the flexibility of standalone PP. Nevertheless, this often comes with degraded dielectric strength of PP/copolymer blends, particularly with increasing loadings of copolymers. Therefore, this paper investigates the chemical structure and AC and DC breakdown performance of PP with 20 wt% of ethylene-based copolymer (EBC) and 20 wt% of propylene-based copolymer (PBC). The results reveal that the presence of methyl groups of PP/EBC is more pronounced compared to PP/PBC. Meanwhile, the AC breakdown strengths of PP with 20 wt% of EBC and 20 wt% of PBC are comparable at 151 kV/mm and 153 kV/mm respectively, compared to that of XLPE (148 kV/mm). Additionally, PP with 20 wt% of EBC has a comparable DC breakdown strength (317 kV/mm) to XLPE (324 kV/mm) while PP with 20 wt% of PBC has a higher DC breakdown strength (338 kV/mm) over XLPE. Therefore, both the AC and DC breakdown performance of PP with 20 wt% of EBC and 20 wt% of PBC are not inferior over XLPE. These suggest that 20 wt% of EBC and 20 wt% of PBC are appropriate for formulating PP/EBC blend and PP/PBC blend as alternatives to XLPE.