Thermally Stable Low-Loss Polymer Dielectrics Enabled by Attaching Cross-Linkable Antioxidant to Polypropylene

Synergistic Interaction of Sulfonyl-Containing Sulfanilamide/Sulfamide To Enhance the Dielectric and Mechanical Properties of Polyurethane Materials

High-performance dielectric materials have gained widespread attention, due to their great potential for various applications, such as flexible electronics and capacitive sensors. In this study, sulfamide (SA) and sulfanilamide (SAN), containing sulfonyl groups, were introduced into polyurethane (PU) as chain extenders. The polyurethane with the best performance was end-capped with 3-methylsulfonyl-1-propanol (3-MSP) to investigate the effects of the SAN/SA molar ratio and the capping agent on the microstructure, dielectric properties, and mechanical performance of the PU. The experimental results indicated that, at a frequency of 102 Hz, the polyurethane material with an SAN/SA molar ratio of 2:1 (sample PU-N2S1) exhibited the highest dielectric constant (15.65), representing a 144% increase, compared to sample PU-N0S0. Meanwhile, sample PU-N2S1 showed the highest degree of microphase separation. At a frequency of 1.26 × 105 Hz, its dielectric loss was 0.055. Notably, 3-MSP had a relatively large dipole moment (μ = 6.93 D). However, its incorporation into polyurethane significantly reduced the dielectric constant. The results demonstrated that the dielectric constant and dielectric loss of polyurethane were not only dependent on its dipole moment but were also closely related to its microstructure, including microphase separation and intermolecular interaction.

Recent Advances in Preparation and Application of BOPP Film for Energy Storage and Dielectric Capacitors

Energy storage polymers are critical to modern microelectronics, electric vehicles, and wearable devices. Capacitor energy storage devices are the focus of contemporary research, with film dielectric capacitors being the focus of mainstream research. Research on polymers-particularly polypropylene-has yielded numerous innovations, but their energy storage performance and breakdown resistance under extreme conditions remain unsatisfactory. Numerous reports have proposed various solutions, but systematic reviews, classifications, and investigations regarding the effects of processing on polypropylene films remain lacking. This study collects and organizes the latest research reports on dielectric-related polypropylene films with the aim of addressing this issue by providing a comprehensive review of the research on polypropylene thin film materials that exhibit high dielectric stability and high energy storage density under extreme conditions. These conditions include mixing and doping, surface modification, designing new molecular structures, and constructing multilayers. This study analyzes how polypropylene's dielectric properties can be enhanced. It reviews the impacts of processing on the dielectric properties of biaxially oriented polypropylene and the underlying mechanisms. The paper is concluded with a summary of the current research progress and shortcomings in industrial production and performance, as well as discussions of future prospects. It offers valuable references for enhancing the dielectric properties of biaxially oriented polypropylene films and optimizing film processing.

The Large-Scale Manufacturing of Polymer Dielectric Capacitors: Advancements and Challenges

Since the 18th century, capacitors have significantly advanced in theoretical research and industrial applications. With the increasing demand for high-performance capacitors, the focus on advanced materials and manufacturing techniques has become critical. This review aims to provide a comprehensive survey of polymer capacitors, emphasizing their manufacturing processes and the connection between theoretical research and practical applications. Beginning with the fundamental principles of dielectric materials and capacitor design, this review delves into key aspects such as material preparation, film fabrication, and capacitor assembly while addressing the challenges in scale-up manufacturing for practical usage. Special attention is given to the metallization and winding processes, as these are pivotal for ensuring high reliability and performance in polymer capacitors. Additionally, this review analyzes the growing market demand for capacitors with enhanced thermal stability and operational efficiency, identifying research directions to address current limitations. By integrating the latest advancements in high-temperature polymer dielectrics, this review aims to provide valuable insights for both academia and industry. Finally, a forward-looking perspective is provided on future development trends and the obstacles that lie ahead, emphasizing the necessity for stronger collaboration between research and industry to foster innovation in this vital field.

Effect of Temperature on Condensed State Structure and Conductivity Characteristics of Micron-Level Biaxially Oriented Polypropylene Films

Polymer-based dielectric films are increasingly demanded for devices under high electric fields used in new energy vehicles, photovoltaic grid connections, oil and gas exploration, and aerospace. However, leakage current is one of the significant factors limiting the improvement of the insulation performance. This paper tested the leakage current and condensed state structure characteristics of biaxially oriented polypropylene (BOPP) films and obtained the nonlinear characteristics of leakage current of BOPP films in the range of 40-440 V/μm and 40-110 °C. The conduction mechanisms of BOPP films are hopping conductivity within 40-120 V/μm and the Poole-Frenkel effect within 120-440 V/μm, and the threshold electric field of the two kinds conduction mechanisms decreases from 120 to 80 V/μm above 70 °C. The in situ FTIR results indicate that the structure of the BOPP films including band structure, amorphous phase, and isotacticity indices changes above 70 °C, corresponding to the threshold electric field of both conductivity mechanisms gradually decreasing from 120 to 80 V/μm at 70 °C. This study can provide guidance for the optimization design to suppress the leakage current of BOPP and improve its insulation performance.

Core@Double-Shell Engineering of Zn Particles toward Elevated Dielectric Properties: Multiple Polarization Mechanisms in Zn@Znch@PS/PVDF Composites

Flexible dielectrics with large dielectric constant (ε') coupled with low loss are highly pursued in many applications. To bolster the ε' of raw Zn (zinc)/poly(vinylidene fluoride, PVDF) while maintaining pimping dielectric loss, in this study, the core@double-shell structured Zn@zinc carbonate (ZnCH)@polystyrene (PS) particles are first synthesized through a suspension polymerization of styrene, and then composited with PVDF to elevate the ε' and keep low loss of the composites. By optimizing the PS shells' thickness and tailoring the electrical resistivity of Zn@ZnCH@PS particles, both the slow inter-particle polarization and fast intra-particle polarization in the composites can be decoupled and synergistically tuned, thus, the Zn@ZnCH@PS/PVDF achieves a much higher ε' and lower dielectric loss, simultaneously, which far exceed the unmodified Zn/PVDF. Both experiment and theoretic calculation reveal that the double-shell ZnCH@PS not only induces and promotes multiple polarizations enhancing the composites' ε', especially at the optimized PS's thickness, but also maintains suppressed loss and conductivity thanks to their obvious barrier effect on long-range charge migration. The core@double-shell filler design strategy facilitates the development of polymer composites with desirable dielectric properties for applications in electronic and electrical power systems.

Alicyclic polyimides with large band gaps exhibit superior high-temperature capacitive energy storage

Flexible polymer dielectrics for capacitive energy storage that can function well at elevated temperatures are increasingly in demand for continuously advancing and miniaturizing electrical devices. However, traditional high-resistance polymer dielectrics composed of aromatic backbones have a compromised band gap (E_g) and hence suffer from low breakdown strength and a huge loss at high temperatures. Here, based on the density functional theory (DFT) calculations, rigid and non-coplanar alicyclic segments are introduced into the polyimide backbone to overcome the incompatibility of a high glass transition temperature (T_g) and large E_g. Thanks to the large optical E_g (∼4.6 eV) and high T_g (∼277 °C), the all-alicyclic polyimide at 200 °C delivers a maximum discharge energy density (U_e) of 5.01 J cm^-3 with a charge-discharge efficiency (η) of 78.1% at 600 MV m^-1, and a record U_e of 2.55 J cm^-3 at η = 90%, which is 10-fold larger than that of the state-of-art commercial polyetherimides (PEIs). In addition, compared with aromatic polyimides, the all-alicyclic polyimide possesses a better self-clearing characteristic due to a smaller ratio of carbon to hydrogen and oxygen, which facilitates its long-term reliability in practical applications.

Toward Excellent Energy Storage Performance via Well-Aligned and Isolated Interfaces in Multicomponent Polypropylene-Based All-Organic Polymer Dielectric Films

Polypropylene (PP) serves as an excellent commercialized polymer dielectric film owing to its high breakdown strength, excellent self-healing ability, and flexibility. However, its low dielectric constant causes the large volume of the capacitor. Constructing multicomponent polypropylene-based all-organic polymer dielectric films is a facile strategy for achieving high energy density and efficiency simultaneously. Thereinto, the interfaces between the components become the key factors that determine the energy storage performance of the dielectric films. In this work, we propose to fabricate high-performance polyamide 513 (PA513)/PP all-organic polymer dielectric films via the construction of abundant well-aligned and isolated nanofibrillar interfaces. Laudably, a significant enhancement in the breakdown strength is achieved from 573.1 MV/m of pure PP to 692.3 MV/m with 5 wt % of PA513 nanofibrils. Besides, a maximum discharge energy density of about 4.4 J/cm² is realized with 20 wt % of PA513 nanofibrils, which is about 1.6-folds higher than pure PP. Simultaneously, the energy efficiency of samples with modulated interfaces maintains higher than 80% up to 600 MV/m, which is much higher than pure PP of about 40.7% at 550 MV/m. This work provides a new strategy to fabricate high-performance multicomponent all-organic polymer dielectric films on an industrial scale.

Combination of Polymer Gate Dielectric and Two-Dimensional Semiconductor for Emerging Field-Effect Transistors

Two-dimensional (2D) materials are considered attractive semiconducting layers for emerging field-effect transistors owing to their unique electronic and optoelectronic properties. Polymers have been utilized in combination with 2D semiconductors as gate dielectric layers in field-effect transistors (FETs). Despite their distinctive advantages, the applicability of polymer gate dielectric materials for 2D semiconductor FETs has rarely been discussed in a comprehensive manner. Therefore, this paper reviews recent progress relating to 2D semiconductor FETs based on a wide range of polymeric gate dielectric materials, including (1) solution-based polymer dielectrics, (2) vacuum-deposited polymer dielectrics, (3) ferroelectric polymers, and (4) ion gels. Exploiting appropriate materials and corresponding processes, polymer gate dielectrics have enhanced the performance of 2D semiconductor FETs and enabled the development of versatile device structures in energy-efficient ways. Furthermore, FET-based functional electronic devices, such as flash memory devices, photodetectors, ferroelectric memory devices, and flexible electronics, are highlighted in this review. This paper also outlines challenges and opportunities in order to help develop high-performance FETs based on 2D semiconductors and polymer gate dielectrics and realize their practical applications.

All-Organic PTFE Coated PVDF Composite Film Exhibiting Low Conduction Loss and High Breakdown Strength for Energy Storage Applications

Plastic film capacitors are widely used in pulse and energy storage applications because of their high breakdown strength, high power density, long lifetime, and excellent self-healing properties. Nowadays, the energy storage density of commercial biaxially oriented polypropylene (BOPP) is limited by its low dielectric constant (~2.2). Poly(vinylidene fluoride) (PVDF) exhibits a relatively high dielectric constant and breakdown strength, making it a candidate material for electrostatic capacitors. However, PVDF presents significant losses, generating a lot of waste heat. In this paper, under the guidance of the leakage mechanism, a high-insulation polytetrafluoroethylene (PTFE) coating is sprayed on the surface of a PVDF film. The potential barrier at the electrode-dielectric interface is raised by simply spraying PTFE and reducing the leakage current, and then the energy storage density is increased. After introducing the PTFE insulation coating, the high-field leakage current in the PVDF film shows an order of magnitude reduction. Moreover, the composite film presents a 30.8% improvement in breakdown strength, and a 70% enhancement in energy storage density is simultaneously achieved. The all-organic structure design provides a new idea for the application of PVDF in electrostatic capacitors.

Significantly Suppressed Dielectric Loss and Enhanced Breakdown Strength in Core@Shell Structured Ni@TiO2/PVDF Composites

An insulating shell on the surface of conductive particles is vital for restraining the dielectric loss and leakage current of polymer composites. So as to inhibit the enormous loss and conductivity of pristine nickel (Ni)/poly(vinylidene fluoride)(PVDF) composites but still harvest a high dielectric permittivity (ε_r) when filler loading approaches or exceeds the percolation threshold (f_c), pristine Ni particles were covered by a layer of titanium dioxide (TiO₂) shell via a sol-gel approach, and then they were composited with PVDF. The impacts of the TiO₂ coating on the dielectric performances of the Ni/PVDF composites were explored as a function of the filler concentration, the shell thickness and frequency. In addition, the dielectric performances were fitted using the Havriliak-Negami (H-N) equation in order to further understand the TiO₂ shell's effect on polarization mechanism in the composites. The Ni@TiO₂/PVDF composites exhibit high ε_r and enhanced breakdown strength (E_b) but remarkably suppressed loss and conductivity when compared with pristine Ni/PVDF because the TiO₂ shell can efficiently stop the direct contact between Ni particles thereby suppressing the long-range electron transportation. Further, the dielectric performances can be effectively tuned through finely adjusting the TiO₂ shell' thickness. The resulting Ni@TiO₂/PVDF composites with high ε_r and E_b but low loss show appealing applications in microelectronics and electrical fields.

High-Energy-Density and High Efficiency Polymer Dielectrics for High Temperature Electrostatic Energy Storage: A Review

Polymer dielectrics are key components for electrostatic capacitors in energy, transportation, military, and aerospace fields, where their operation temperature can be boosted beyond 125 °C. While most polymers bear poor thermal stability and severe dielectric loss at elevated temperatures, numerous linear polymers with linear D-E loops and low dielectric permittivity exhibit low loss and high thermal stability. Therefore, the broad prospect of electrostatic capacitors under extreme conditions is anticipated for linear polymers, along with intensive efforts to enhance their energy density with high efficiency in recent years. In this article, an overview of recent progress in linear polymers and their composites for high-energy-density electrostatic capacitors at elevated temperatures is presented. Three key factors determining energy storage performance, including polarization, breakdown strength, and thermal stability, and their couplings are discussed. Strategies including chain modulation, filler selection, and design of topological structure are summarized. Key parameters for electrical and thermal evaluations of polymer dielectrics are also introduced. At the end of this review, research challenges and future opportunities for better performance and industrialization of dielectrics based on linear polymers are concluded.

Ultrahigh energy storage performance of all-organic dielectrics at high-temperature by tuning the density and location of traps

Improving the tolerance of flexible polymers to extreme temperatures and electrical fields is critical to the development of advanced electrical and electronic systems. Suppressing carrier movement at high temperatures is one of the key methods to improve the high-temperature charging and discharging efficiency. In this work, a molecular semiconductor (ITIC) with high electron affinity energy is blended into the promising polymer polyetherimide (PEI). This molecular semiconductor will introduce traps in the dielectric that can trap carriers, thus achieving the effect of inhibiting carrier movement. Changing the concentration and position of the molecular semiconductor by electrospinning technology also means changing the density of the trap and the position of the trap layer. The effects of trap density and trap layer location on the high-temperature breakdown strength and energy storage properties of composite dielectrics are studied successively, and the structure of a composite with optimal high temperature energy storage properties is obtained. That is, the dielectric S-15-28 has an energy storage density (U) of 6.37 J cm^-3 at a temperature of 150 °C with a charge-discharge efficiency (η) of 90%; it also has a U of 4.3 J cm^-3 at a temperature of 180 °C with the η of 90%. A mechanism based on Mott and Gurney's law is proposed to explain the effect of trap parameters on leakage current. This work provides a new structural design idea to regulate the dielectric properties of all-organic dielectrics through trap distribution parameter optimization.

Controllable synthesis and structural design of novel all-organic polymers toward high energy storage dielectrics

As the core unit of energy storage equipment, high voltage pulse capacitor plays an indispensable role in the field of electric power system and electromagnetic energy related equipment. The mostly utilized polymer materials are metallized polymer thin films, which are represented by biaxially oriented polypropylene (BOPP) films, possessing the advantages including low cost, high breakdown strength, excellent processing ability, and self-healing performance. However, the low dielectric constant (εr < 3) of traditional BOPP films makes it impossible to meet the demand for increased high energy density. Controlled/living radical polymerization (CRP) and related techniques have become a powerful approach to tailor the chemical and physical properties of materials and have given rise to great advances in tuning the properties of polymer dielectrics. Although organic-inorganic composite dielectrics have received much attention in previous studies, all-organic polymer dielectrics have been proven to be the most promising choice because of its light weight and easy large-scale continuous processing. In this short review, we begin with some basic theory of polymer dielectrics and some theoretical considerations for the rational design of dielectric polymers with high performance. In the guidance of these theoretical considerations, we review recent progress toward all-organic polymer dielectrics based on two major approaches, one is to control the polymer chain structure, containing microscopic main-chain and side-chain structures, by the method of CRP and the other is macroscopic structure design of all-organic polymer dielectric films. And various chemistry and compositions are discussed within each approach.

Towards synchronously improving dielectric performances and thermal conductivity in Ni/PVDF by tailoring core-shell structured Ni@NiO particles

An insulating interlayer between conductive particles and polymer is crucial for preparing polymer dielectrics with high dielectric permittivity ( ε) but low loss and high breakdown strength ( E b). To restrain the large loss of raw nickel (Ni)/poly (vinylidene fluoride) (PVDF) composites when still maintaining a high- ε at the percolation threshold ( f c) of conductive fillers, in this work, nanoscale nickel oxide (NiO) shell with diverse thickness was coated around the surface of Ni particles via a facile thermal calcination at 650°C under air, and the gained Ni@NiO particles were composited with PVDF to produce morphology-controllable high- ε, low loss composites. The influences of the NiO shell and thickness on the dielectric performances and thermal conductivity (TC) of the composites were investigated in terms of filler loading and frequency. Compared with raw Ni/PVDF, the Ni@NiO/PVDF composites exhibit remarkably suppressed dielectric loss and enhanced E b and TC because the NiO interlayer not only prevents the Ni particles from direct contact and hinders the long-range electron migration thereby resulting in rather low leakage current, but also simultaneously suppresses thermal interfacial resistance and enhances interfacial compatibility between the fillers and the matrix subsequently resulting in improved TC. Therefore, the Ni@NiO/PVDF with high ε-low loss, heightened E b and TC present appealing potential applications in microelectronics and electrical industries.

The synthesis and properties research of functionalized polyolefins

This work demonstrated a tandem ROMP/hydrogenation approach for the preparation of functionalized polyolefins and their properties were investigated.