Dielectric polymers for emerging energy applications

Nanostructure Engineering Significantly Enhances Capacitive Energy Storage Performance in All-Polymer Dielectrics at Elevated Temperatures

The growing demand for electrostatic capacitors in high-temperature environments requires dielectric polymers capable of withstanding both elevated temperatures and high electric fields. Here, we investigate all-polymer nanodielectrics (PNDs) fabricated through polymerization-induced microphase separation (PIMS) in thermoplastic/thermoset blends, focusing on the role of thermoset resins in high-temperature capacitive performance. Two BMI monomers, 2,2-bis(4-(4-maleimidophenoxy)phenylpropane) (BMP) and 4,4'-bismaleimidodiphenylmethane (BDM), form cross-linked domains of different sizes in a polysulfone (PSU) matrix, creating deeper charge traps. While trap depths are similar, PSU/BMP PNDs exhibit higher trap density owing to smaller BMP domains resulting from enhanced compatibility with PSU. This reduces current density at high temperatures compared to PSU/BDM and pristine PSU. Consequently, PSU/BMP PNDs demonstrate superior capacitive energy storage at elevated temperatures. These findings emphasize the importance of interfacial area in determining high-temperature electrical properties and provide insights for designing nanostructured all-polymer dielectrics for advanced applications.

Linear Dielectric Polymers with Ferroelectric-Like Crystals for High-Temperature Capacitive Energy Storage

Achieving optimal capacitive energy storage performance necessitates the integration of high energy storage density, typical of ferroelectric dielectrics, with the low polarization loss associated with linear dielectrics. However, combining these characteristics in a single dielectric material is challenging due to the inherent contradictions between the spontaneous polarization of ferroelectric dielectrics and the adaptability of linear dielectrics to changes in the electric field. To address this issue, a linear isotactic sulfonylated polynorbornene dielectric characterized by ferroelectric-like crystals has been developed. The sulfonyl dipoles in the ferroelectric-like crystals are oriented in the same direction, thereby enabling this polymer to exhibit a considerable dielectric constant (7.5) at room temperature. Notably, when the operating temperature surpasses the polymer's glass transition temperature (Tg ≈ 140 °C), its dielectric constant rises to 12 with just minor changes in the dissipation factor. At 150 °C, 90% efficiency of the discharge energy density reaches as high as 6.76 J cm-1 under a low electric field of 320 MV m-1, which is ten times that of the state-of-the-art, high-temperature, capacitor-grade polyetherimide. The enhancement of high-temperature capacitive performance, achieved by utilizing the crystallinity of isotactic polymers to form a polar structure, presents a new perspective for the design of high-temperature dielectric polymers.

High dielectric energy storage properties of chitin matrix composites regulated by SiO2

High-performance polymer-based dielectric materials have attracted much attention in the field of energy storage due to high breakdown field strength and low cost. However, partial polymer-based materials are derived from traditional fossil energy derivatives, which are characterized by non-renewable and low dielectric constants, which are not conducive to the improvement of energy storage. In this paper, dissolved chitin through alkali/urea system is composited with SiO2 prepared by electrostatic spinning. The maximum discharge energy density of the fiber composite film reaches 4.34 J cm-3, which is 1.6 times higher than that of the micron particle composite film (2.8 J cm-3) and 1.9 times higher than that of the pure chitin film. The high aspect ratio and low concentration of silica filler effectively improved the breakdown field strength. In addition, the thermal stability was improved. This study paves the way for the application of bio-based materials in high-performance dielectrics.

Improved Energy Storage Performance of Composite Films Based on Linear/Ferroelectric Polarization Characteristics

The development and integration of high-performance electronic devices are critical in advancing energy storage with dielectric capacitors. Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVTC), as an energy storage polymer, exhibits high-intensity polarization in low electric strength fields. However, a hysteresis effect can result in significant residual polarization, leading to a severe energy loss, which impacts the resultant energy storage density and charge/discharge efficiency. In order to modify the polarization properties of the polymer, a biaxially oriented polypropylene (BOPP) film with linear characteristics has been selected as an insulating layer and combined with the PVTC ferroelectric polarization layer to construct PVTC/BOPP bilayer films. The hetero-structure and polarization characteristics of the bilayer film have been systematically studied. Adjusting the BOPP volume content to 67% resulted in a discharge energy density of 10.1 J/cm3 and an energy storage efficiency of 80.9%. The results of this study have established the mechanism for a composite structure regulation of macroscopic energy storage performance. These findings can provide a basis for the effective application of ferroelectric polymer-based composites in dielectric energy storage.

Aromatic-Free Polymers Based All-Organic Dielectrics with Breakdown Self-Healing for High-Temperature Capacitive Energy Storage

High-temperature dielectric polymers are becoming increasingly desirable for capacitive energy storage in renewable energy utilization, electrified transportation, and pulse power systems. Current dielectric polymers typically require robust aromatic molecular frameworks to ensure structural thermal stability at elevated temperatures. Nevertheless, the introduction of aromatic units compromises electrical insulation owing to pronounced π─π interactions that facilitate electron transport and eliminate the breakdown self-healing property owing to their high carbon content. Herein, an aromatic-free polynorborne copolymer exhibiting electrical conductivity-two orders of magnitude lower than that of state-of-the-art polyetherimide-at elevated temperatures and high electric fields owing to its large bandgap (≈4.64 eV) and short hopping conduction distance (≈0.63 nm) is described. Density functional theory calculations demonstrate that the copolymer can effectively suppress the excitation of high-field valence electrons. Furthermore, the incorporation of trace semiconductors results in high discharge density (3.73 J cm-3 ) and charge-discharge efficiency (95% at 150 °C), outperforming existing high-temperature dielectric polymers. The excellent electrical breakdown self-healing capability of the copolymer film at elevated temperatures further demonstrates its potential for use in dielectric capacitors capable of continuous operation under extreme conditions.