Recent Progress and Future Prospects on All-Organic Polymer Dielectrics for Energy Storage Capacitors

Unveiling Synergistic Interface Effects on Charge Trapping Regulation in Polymer Composite Dielectrics through Multiscale Modeling

Interface design is a promising strategy to enhance the dielectric strength in polymer composites through regulating the charge transport process. However, the targeted exploitation of interface effects is limited due to a lack of fundamental understanding of the underlying mechanisms involving elementary electronic processes and details of the intricate interplay of characteristics of molecular building blocks and the interfacial morphology - details that cannot fully be resolved with experimental methods or commonly used band transport models. Here, we instead build a proper theoretical framework for polymer dielectrics based on charge hopping and employ a multiscale modeling approach linking the quantum properties of the charge carriers with nano- and mesoscale structural details of complex interfaces. Applied to a prototypical application-proven cellulose-oil interface system, this approach demonstrates that charges are trapped in the disordered region. Specifically, it unveils this trapping as a synergistic effect of two transport-regulating interface mechanisms: back-transfer to the oil region is suppressed by energetic factors, while forward-transfer to the crystalline cellulose is suppressed by low electronic coupling. The insight into the molecular origins of interface effects via dual-interface regulation in the framework of charge hopping offers new development paths for developing advanced energy materials with tailored electrical properties.

Sharply Improved Electrical Insulation of Polyimide Dielectrics at Elevated Temperatures by Charge Reassignment Engineering

The electrical insulation of traditional polyimides (PI) dielectrics for capacitive energy storage will be significantly destroyed at elevated temperatures due to enhanced conductive loss caused by strong conjugated effect and charge transfer (CT) interactions. To address this issue, novel PI dielectrics are designed and synthesized based on charge reassignment engineering. Beneficial from non-planar dianhydride and poor conjugated diamine, the main chain of synthesized PI (semi-aromatic NA2-alt-OB1) significantly reduces the conjugated effect. Alicyclic dianhydride structural unit endows NA2-alt-OB1 with a large bandgap width of 5.22 eV and a high LUMO energy level (-0.79 eV), making the polymer resistant to both excited and injected electrons. More importantly, this work intelligently combines trifluoromethyl and dicyclohexyl to achieve weak charge reassignment on donor-acceptor electron sites in the polymer chain, effectively decreasing CT effect. Consequently, a super-high Weibull breakdown strength value of 862 and 691 MV m-1 at room temperature and 230 °C respectively is achieved. Semi-aromatic NA2-alt-OB1 obtains a high discharge energy density of 6.43 J cm-3 at 230 °C, which is greater than that of lots of reported PI dielectrics. This work offers an important strategy to break the adverse correlation between electrical insulation and heating resistance of PI dielectrics, promoting their application in capacitive energy storage at elevated temperatures.

Achieving ultrahigh charge-discharge efficiency and energy storage in high-temperature polar polymeric dielectrics via restrained dipole interactions

Advancements in microelectronics and electrical power systems require dielectric polymeric materials capable of maintaining high discharged energy density and charge-discharge efficiency over a wide temperature range. Intrinsic polar polymers with enhanced dielectric constants are crucial for achieving high energy density and are extensively utilized at room temperature. However, the compatibility of high energy density and efficiency remains a significant challenge. Most polar polymer dielectric films suffer a considerable drop in capacitive performance as the temperature rises, with efficiency falling below 50%, and the waste Joule heat generated from conduction loss may lead to a vicious cycle. Herein, a new strategy of restraining dipole interactions in polar polymers is proposed to achieve optimal molecular chain stacking configurations, significantly decreased conductivity, and deeper charge trap sites, thus exhibiting enhanced energy density with outstanding efficiency at elevated temperatures. Remarkably, an energy density of 4.61 J cm-3 at an ultra-high efficiency above 95% was achieved, as well as cycling stability exceeding 150 000 cycles with an energy density of 2.4 J cm-3 at 150 °C, surpassing current high polar polymers and most advanced polymer composites. This discovery presents a promising solution for preserving high capacitive performance in polar polymeric materials at elevated temperatures.

Multiscale Structural Regulation of Energy Storage Properties and Their Mechanism of the (1 - x) (Bi0.5Na0.5)0.7Sr0.3TiO3-xCa(Mg1/3Ta2/3)O3 Ceramics

Ceramic dielectric capacitors have gained significant attention due to their ultrahigh power density, current density, and ultrafast charge-discharge speed. However, their potential applications have been limited by their relatively low energy storage density. Researchers have employed various approaches to enhance their energy storage density. In this study, (1 - x)(Bi0.5Na0.5)0.7Sr0.3TiO3-xCa(Mg1/3Ta2/3)O3 ceramics were prepared via a solid-phase reaction, and the effect of their structure on the energy storage properties was investigated. The results indicate that the introduction of Ca(Mg1/3Ta2/3)O3 significantly alters the multiscale structures of the (Bi0.5Na0.5)0.7Sr0.3TiO3 ceramic, including the transformation from the T-phase to the C-phase, refinement of ceramic grains, and the formation of polar nanoregions (PNRs), accompanied by an increase in the bandgap and relaxation degree. These structural changes collectively contributed to the improved overall energy storage properties of the modified ceramics. Notably, the 0.92(Bi0.5Na0.5)0.7Sr0.3TiO3-0.08Ca(Mg1/3Ta2/3)O3 ceramic demonstrated a recoverable energy storage density (Wrec) of 8.37 J/cm3 with an energy storage efficiency (η) of 87.7% at an electric field of 530 kV/cm. It also exhibited good temperature stability (25-120 °C), frequency stability (1-100 Hz), and fatigue stability (1-105). Furthermore, it displayed exceptional charge and discharge properties, with the discharge energy density (WD), discharge time (t0.9), current density (CD), and power density (PD) attaining 4.06 J/cm3, 35.2 ns, 2143.28 A/cm2, and 460.71 MW/cm3, respectively. These findings suggest that modified (1 - x)(Bi0.5Na0.5)0.7Sr0.3TiO3-xCa(Mg1/3Ta2/3)O3 ceramics are promising candidates for high-power pulsed electronic systems.

A Double-Gradient All-Organic Dielectric Polymer Film Achieving Superior Breakdown Strength and Energy Density

Ferroelectric polymers have drawn tremendous attention in film capacitors owing to their high permittivity and ease of processing. Nevertheless, the energy density of such materials is severely constrained due to inferior breakdown strength. To address this dilemma, a double-gradient multilayered all-organic dielectric composite film is proposed, fabricated via a simple layer-by-layer solution-casting process. The experimental results demonstrate that the composite film significantly suppresses the leakage current compared to the pristine films, resulting in remarkable enhancement of the insulation properties. The finite element simulation results further reveal that the optimized electric field distribution induced by the gradient structure and the carrier traps at the interfaces between the adjacent layers play a crucial role in impeding the propagation of the breakdown path. As a result, the developed dielectric film reaches an unexpected breakdown strength of 712 MV m-1 along with a high energy density of 19.68 J cm-3, surpassing the bench-mark biaxially oriented polypropylene as well as the existing ferroelectric-based composites reported in the recent works. The synergy of gradient and multilayered structure presented in this work offers a novel perspective and approach for the scalable fabrication of dielectric films with eminent capacitive performance.

Self-healing, deformable and safe integrated supercapacitor enabled by synergistic effect of multiple physical interactions in gel polymer electrolyte with dual-role Co2

With the rapid development of wearable electronic devices, flexible supercapacitors have gained strong interest. However, traditional sandwich supercapacitors have weak interfacial binding, resulting in high interface resistance and poor deformability. Herein, a self-healing integrated supercapacitor based on a polyacrylic acid-polyisodecyl methacrylate-CoSO4 gel polymer electrolyte (GPE) was developed. By incorporating ion coordination into a hydrophobic association network, a double network structure was formed, endowing the GPE with remarkable mechanical properties and self-healing abilities. Specifically, Co2+ ions functioned both as charge carrier and crosslinker, simultaneously enhancing the electrochemical (2.87 S/m) and mechanical (0.262 MPa) properties of the GPE. In situ growth of polyaniline electrode material on the GPE surface resulted in an integrated supercapacitor with a continuous morphology at the electrode/electrolyte interface, minimizing interface resistance and improving electrochemical performance. The supercapacitor exhibits high specific capacitance, exceptional cyclic stability, superior deformability and security due to the unique integrated structure. Furthermore, it demonstrates remarkable electrochemical and self-healing properties even at quite low temperature. Overall, this work offers a promising approach for reliable self-healing energy storage devices with high performance and adaptability to complex usage conditions.

All-Organic Polystyrene-Based Copolymer Dielectrics for Superior High-Temperature Charge Energy Storage with Robust Stability

Enhancing dielectric constant and breakdown field strength simultaneously, and exploring the design strategy of high charge energy storage properties at high-temperature environments are the core problems in thin film dielectrics. In this paper, γ-methyl-α-methylene-γ-butyrolactone (MeMBL) and styrene (St) are randomly copolymerized by free radical emulsion polymerization to obtain dielectric films with high energy density. The introduction of MeMBL units containing highly polar groups (ester groups as well as lactone rings) not only improves the dielectric constant and Tg of the copolymer but also creates trap sites for the capture of free charge carriers. The homogeneously distributed trap sites can effectively trap free space charges and thus significantly suppress the conduction under high electric fields and improve the breakdown strength under high temperatures. When utilized for dielectric energy storage, Poly(St-co-MeMBL) can achieve a discharge energy density of 8.08 J cm-3 at room temperature. Even at 150 °C, Poly(St-co-MeMBL) can still provide a discharge energy density of 4.69 J cm-3 with a charge/discharge efficiency of 88%. Moreover, Poly(St-co-MeMBL) dielectric films present excellent robustness and long-term working stability over 103 charge-discharge cycles. The proposed design concept presents a novel way of manufacturing linear dielectric materials for high-temperature energy storage and electronics.

In-plane aligned doping pattern in electrospun PEI/MBene nanocomposites for high-temperature capacitive energy storage

To achieve superior energy storage performance in dielectric polymer films, it is crucial to balance three key properties: high dielectric constant, high breakdown strength, and low dielectric loss. Here, we present the realization of ultrahigh efficiency and energy density in electrospun MBene/PEI composite films, achieved through an in-plane aligned doping pattern. The 1.0 wt% film exhibits a dielectric constant of 10.7 at 1 kHz while maintaining a low dielectric loss below 0.0074. Compared to the random doping pattern, the dielectric constant increases by 25.9%, and dielectric loss is suppressed by 40.3%. The uniform and non-connected dispersion of MBene fillers promotes a homogeneous electric field distribution and minimizes the risk of developing continuous leakage current paths. Therefore, the breakdown strength remains high at 494 kV mm-1. Possessing ultrahigh dielectric constant, minimal dielectric loss, and well-preserved breakdown strength, the MBene/PEI film yields an energy density of 8.03 J cm-3 at room temperature, and achieves 5.32 J cm-3 at 150 °C, with an efficiency exceeding 90%. Additionally, this in-plane aligned doping pattern also enhances mechanical properties. This work provides a unique solution to mitigate side effects by utilizing conductive fillers, presenting a valuable strategy to fabricate dielectric films for high-performance energy storage.

Scalable assembly of micron boron nitride into high-temperature-resistant insulating papers with superior thermal conductivity

With the rapid development of modern electrical equipment towards miniaturization, integration, and high power, high-temperature-resistant insulating papers with superior thermal conductivity are highly desirable for ensuring the reliability of high-end electrical equipment. However, it remains a challenge for current insulating papers to achieve this goal. Herein, we demonstrate the design of high-temperature-resistant micron boron nitride (m-BN) based insulating papers with superior thermal conductivity by a universal and scalable one-step assembly strategy. Inspired by the floating shape of jellyfish in the ocean, aramid nanofibers (ANF) resembling the tentacles of jellyfish were employed to support the bell-shaped m-BN, which effectively addresses the kinetically stable dispersion and film-forming ability of m-BN. The resultant m-BN@ANF papers exhibit excellent high-temperature-resistant insulating performance with an ultra-high breakdown strength of 359.0 kV mm-1 even at a high temperature of 200 °C, far exceeding those of these previously reported systems. In addition, the optimal m-BN@ANF paper demonstrates a superior thermal conductivity of 26.4 W m-1 K-1 and an excellent thermostability with an initial decomposition temperature of 486 °C. This outstanding comprehensive performance demonstrates the promise of applying these m-BN@ANF papers in advanced electrical systems operating under high-temperature circumstances.

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.

High energy storage density in high-temperature capacitor films at low electric fields

High-power applications, particularly in electromagnetic catapults, electric vehicles, and aerospace, necessitate the use of polymer dielectrics that demonstrate reliable performance in high-temperature environments. This study focuses on synthesizing three distinct morphologies of innovative wide-bandgap high-dielectric materials-hydroxyapatite (HAP). By conducting a combination of experiments and Multiphysics finite element simulations, a comprehensive comparison was made regarding the properties exhibited by three polyimide (PI) composites: PI/sea urchin-like HAP, PI/spherical HAP, and PI/rodlike HAP. The incorporation of high-surface-area spherical HAP or high aspect ratio rodlike HAP introduces intricate and convoluted growth paths for electric tree formation within the PI matrix, thereby augmenting the energy storage density (Ue) at elevated temperatures (Uη > 90% = 4.82 J/cm3, Uη > 80% = 6.11 J/cm3, Uη > 70% = 8.73 J/cm3, at 150 ℃). The incorporation of HAP increases the dielectric constant εr to a maximum value of 4.96 in pure PI matrices, enabling the resulting PI/HAP composites to achieve remarkable values for both Ue (4.82 J/cm3) and η (92.4 %) even under low electric field (E) conditions (350 MV/m). The PI/HAP composite film demonstrates high energy storage density under low E, offering an innovative solution for energy storage applications in film capacitors operating in high-temperature environments.

Overcoming Energy Storage-Loss Trade-Offs in Polymer Dielectrics Through the Synergistic Tuning of Electronic Effects in π-Conjugated Polystyrenes

Achieving high-performance dielectric materials remains a significant challenge due to the inherent trade-offs between high energy storage density and low energy loss. A central difficulty lies in identifying a suitable dipolar unit that can enhance the polarity and dielectric constant of the material while effectively suppressing the high energy losses associated with polarization relaxation, charge injection, and conduction. To address this, a novel strategy is proposed that introduces electron-donating and electron-withdrawing substituents on the benzene ring of polystyrene-based polymers, creating bulky dipole groups that are resistant to reorientation under an electric field. This approach mitigates relaxation losses associated with dipole reorientation and manipulates the band structure via substituent modification to suppress conduction losses. Additionally, the deformation of the π-electron cloud under an electric field enhances the dielectric constant and energy storage density. Ultimately, the optimized chlorostyrene-methyl methacrylate (MMA) copolymer exhibits an 85% discharge efficiency and an energy storage density of 18.3 J cm- 3, nearly three times that of styrene-based copolymers under the same conditions. This study introduces a new approach for designing high-energy density, low-loss polymer dielectric materials by precisely controlling electron-donating and electron-withdrawing effects to modulate the distribution of π-conjugated electron clouds.

High-Temperature Polymer Composite Dielectrics: Energy Storage Performance, Large-Scale Preparation, and Device Design

Film capacitors are widely used in advanced electrical and electronic systems. The temperature stability of polymer dielectrics plays a critical role in supporting their performance operation at elevated temperatures. For the last decade, the investigations for new polymer dielectrics with high energy storage performance at higher temperatures (>200 °C) have attracted much attention and numerous strategies have been employed. However, there is currently still a large gap between lab research and large-scale production. In this review, the main effects of high temperature on the dielectric properties are analyzed and core modification strategies are summarized. The scientific and technological reasons for the performance difference between lab research and practical application are also discussed. Further, several processes for large-scale film preparation and typical device structure design are reviewed. The current research and product launches pertaining of high-temperature film capacitors are also summarized. Conclusive insights and future perspectives are delineated to offer strategic direction for the ongoing and prospective innovation in polymer dielectric materials.

Ordering-Structured Antiferroelectric Composite Ceramics for Energy Storage Applications

Dielectric capacitors possessing high power density and ultrashort discharge time are valuable for high-power energy storage applications. However, achieving high energy storage density remains challenging due to the limited breakdown strength of dielectric ceramics. In this study, inspired by the layered architecture of natural nacre and with the guidance of phase-field simulations, a strategy of constructing a nacre-like layered structure is proposed to improve the breakdown strength and energy storage density of the ceramics. This unique structure is formed by controlling the morphology and ordering of high-voltage-resistant fillers in a ceramic matrix. The (Pb0.98La0.02)(Zr0.7Sn0.3)0.995O3-Al2O3 antiferroelectric composite ceramics, containing 5vol% parallel-aligned Al2O3 plates, demonstrate a remarkable enhancement in breakdown strength from 390 to 570 kV cm-1. Of particular importance is that an ultrahigh recoverable energy storage density of up to 13.2 J cm-3 is achieved, representing a 50% enhancement compared to the pure ceramic (8.7 J cm-3). The parallel-aligned Al2O3 plates are strongly bound together with the ceramic matrix, effectively blocking charge migration and controlling the breakdown path, thus greatly enhancing the voltage endurance of the composite ceramics. This work provides an innovative approach to designing high-performance composite ceramics for next-generation energy storage applications.

Enhanced energy storage performance of nano-submicron structural dielectric films by suppressed ferroelectric phase aggregation

Maintaining high charge/discharge efficiency while enhancing discharged energy density is crucial for energy storage dielectric films applied in electrostatic capacitors. Here, a nano-submicron structural film comprising ferroelectric material P(VDF-HFP) and linear dielectric material PMMA has been flexibly designed via the electrospinning process. Nano-submicron structure enables the film to maximize the ferroelectric material component and obtain improved dielectric performance without sacrificing breakdown strength and charge/discharge efficiency. As a result, the 40%-420 nm PMMA-P(VDF-HFP)@PMMA sample achieved an discharged energy density of 13.72 J/cm³ at a field of 740 kV/mm, with an impressive charge/discharge efficiency of 80%. This work presents a composite dielectric film that excels in breakdown strength, discharged energy density, and charge/discharge efficiency, offering a strategy for designing reliable, industrial-grade energy storage dielectrics.

Decorating Biaxially Oriented PVDF Nanocomposites with Ultralow Contents of Functionalized BNNSs for Excellent Energy Storage

Poly(vinylidene fluoride) (PVDF) polymers are considered as promising high energy density capacitor dielectrics because of their high dielectric constants and melt processability. However, their industrialization and practicalization suffer from low breakdown strengths and high leakage conduction losses. Hence, it is of great necessity to develop dielectrics with a high energy storage capability. Herein, we fabricated biaxially oriented nanocomposite PVDF films decorated with ultralow contents of surface-functionalized boron nitride nanosheets (BNNSs) by combining melt blending and biaxial orientation technology. The functionalized BNNSs exhibited an ideal horizontal distribution. Both experimental characterization and phase-field simulation validate that the horizontally distributed BNNSs effectively inhibit the propagation of the dielectric breakdown phase and reduce the leakage conduction loss of the composite films. The breakdown field strength of the nanocomposite film doped with only 0.1 wt % functionalized BNNSs reached up to 755.94 MV/m, which is 16.8% higher than that of the pristine biaxially oriented PVDF film. Meanwhile, a maximum discharge energy density of 15.66 J/cm3 was attained, which was 1.57 times that of the pristine counterpart (9.98 J/cm3). This study sheds light on the fundamental understanding of dielectric breakdown behavior of polymer nanocomposites and provides a promising strategy for the scaled-up fabrication of dielectric capacitors with high insulating and low loss properties.

Emerging Potential of Conjugated Polyelectrolytes beyond Boundaries

Conjugated polyelectrolytes (CPEs) constitute a distinct class of materials defined by a π-conjugated backbone and ionic side chains. The delocalized π electrons offer distinct electronic and optical properties, while the presence of ionic moieties enables precise adjustments of hydrophilicity, pH neutrality, self-doping, and ionic conductivity. A recent proliferation of applications for CPEs underscores their dual nature, marking a notable expansion in their potential in technological innovation. The ability to fine-tune both electronic and ionic traits broadens horizons for their utility, spanning organic/inorganic optoelectronics, electrochemical transistors, photocatalytic water splitting, thermoelectric devices, and energy storage systems. This review highlights recent advancements in CPE research, emphasizing synthetic strategies for integrating a wide range of structural units that can tailor optoelectronic and ion transport functions. It also explores innovative applications across diverse domains and discusses a range of operational mechanisms. Additionally, the review addresses persistent challenges and prospects in the field, contributing to ongoing progress toward the implementation of CPEs in emerging technological opportunities.

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.

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.

All-Organic Quantum Dots-Boosted Energy Storage Density in PVDF-Based Nanocomposites via Dielectric Enhancement and Loss Reduction

Dielectric capacitors offer immense application potential in advanced electrical and electronic systems with their unique ultrahigh power density. Polymer-based dielectric composites with high energy density are urgently needed to meet the ever-growing demand for the integration and miniaturization of electronic devices. However, the universal contradictory relationship between permittivity and breakdown strength in traditional ceramic/polymer nanocomposite still poses a huge challenge for a breakthrough in energy density. In this work, all-organic carbon quantum dot CDs were synthesized and introduced into a poly(vinylidene fluoride) PVDF polymer matrix to achieve significantly boosted energy storage performance. The ultrasmall and surface functionalized CDs facilitate the polar β-phase transition and crystallinity of PVDF polymer and modulate the energy level and traps of the nanocomposite. Surprisingly, a synergistic dielectric enhancement and loss reduction were achieved in CD/PVDF nanocomposite. For one thing, the improvement in εr and high-field Dm originates from the CD-induced polar transition and interface polarization. For another thing, the suppressed dielectric loss and high-field Dr are attributed to the conductive loss depression via the introduction of deep trap levels to capture charges. More importantly, Eb was largely strengthened from 521.9 kV mm-1 to 627.2 kV mm-1 by utilizing the coulomb-blockade effect of CDs to construct energy barriers and impede carrier migration. As a result, compared to the 9.9 J cm-3 for pristine PVDF, the highest discharge energy density of 18.3 J cm-3 was obtained in a 0.5 wt% CD/PVDF nanocomposite, which is competitive with most analogous PVDF-based nanocomposites. This study demonstrates a new paradigm of organic quantum dot-enhanced ferroelectric polymer-based dielectric energy storage performance and will promote its application for electrostatic film capacitors.

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.

Metal-organic cage crosslinked nanocomposites with enhanced high-temperature capacitive energy storage performance

Polymer dielectric materials are widely used in electrical and electronic systems, and there have been increasing demands on their dielectric properties at high temperatures. Incorporating inorganic nanoparticles into polymers is an effective approach to improving their dielectric properties. However, the agglomeration of inorganic nanoparticles and the destabilization of the organic-inorganic interface at high temperatures have limited the development of nanocomposites toward large-scale industrial production. In this work, we synthesize metal-organic cage crosslinked nanocomposites by incorporating self-assembled metal-organic cages with amino reaction sites into the polyetherimide matrix. The in-situ crosslinking by self-assembled metal-organic cages not only achieves a homogeneous distribution of inorganic components, but also constructs robust organic-inorganic interfaces, which avoids the interfacial losses of conventional nanocomposites and improves the breakdown strength at elevated temperatures. Ultimately, the developed nanocomposites exhibit exceptionally high energy densities of 7.53 J cm-3 (150 °C) and 4.55 J cm-3 (200 °C) with charge-discharge efficiency of 90%.

The Effects of Chain Conformation and Nanostructure on the Dielectric Properties of Polymers

The dielectric properties of polymers play a pivotal role in the development of advanced materials for energy storage, electronics, and insulation. This review comprehensively explores the critical relationship between polymer chain conformation, nanostructure, and dielectric properties, focusing on parameters such as dielectric constant, dielectric loss, and dielectric breakdown strength. It highlights how factors like chain rigidity, free volume, molecular alignment, and interfacial effects significantly influence dielectric performance. Special emphasis is placed on the impact of nanofillers, molecular weight, crystallinity, and multilayer structures in optimizing these properties. By synthesizing findings from recent experimental and theoretical studies, this review identifies strategies to enhance energy efficiency, reliability, and mechanical stability of polymer-based dielectrics. We also delve into techniques such as electrostatic force microscopy (EFM) and focused ion beam (FIB) milling for characterizing breakdown mechanisms, offering insights into molecular design for next-generation high-performance polymers. Despite considerable progress, critical challenges such as achieving an optimal balance between dielectric permittivity and breakdown strength, understanding nanoscale interfacial phenomena, and scaling these materials for industrial applications persist. These gaps can be addressed by systematic structure-property relations, advanced processing techniques, and environmental studies.

Remarkably boosted high-temperature energy storage of a polymer dielectric induced by polymethylsesquioxane microspheres

Polymer dielectrics are the key materials in next-generation electrical power systems. However, they usually suffer from dramatic deterioration of capacitive performance at high temperatures. In this work, we demonstrate that polymethylsesquioxane (PMSQ) microspheres with a unique organic-inorganic hybrid structure can remarkably enhance the energy storage performance of a typical high-temperature dielectric polymer polyetherimide (PEI). Compared with traditional ceramic fillers, there exists -CH3 on the surface of PMSQ microspheres, which results in good compatibility between PMSQ and PEI. In addition, the PMSQ microspheres with excellent insulating properties can effectively block the charge transport, yielding significantly enhanced breakdown and energy storage performance. Consequently, the PEI based composite film with 5 wt% PMSQ microspheres exhibits ultrahigh energy storage densities of 12.83 J cm-3 and 9.40 J cm-3 with an efficiency (η) above 90% at 150 °C and 200 °C, respectively, which are 10.5 and 50.5 times those of the pure PEI film. This work demonstrates that microspheres with an organic-inorganic hybrid structure are excellent candidates for enhancing the high-temperature performance of polymer dielectrics, and these PMSQ/PEI composite films have huge potential for application in high-temperature film capacitors.

One-step fabrication of high energy storage polymer films with a wide bandgap and high melting temperature induced by the fluorine effect for high temperature capacitor applications with ultra-high efficiency

The development of polymer dielectrics with both high energy density and low energy loss is a formidable challenge in the area of high-temperature dielectric energy storage. To address this challenge, a class of polymers (Parylene F) are designed by alternating fluorinated aromatic rings and vinyl groups in the polymer chain to confine the conjugating sequence and broaden the bandgap with the fluorine effect. The target films with desired thickness, ultra-high purity, and a wide bandgap are facilely fabricated by a one-step chemical vapor deposition (CVD) technique from monomers. The symmetric and bulky aromatic structures exhibit high crystalline performance and excellent stability at high temperature. The presence of strongly electronegative fluorine atoms effectively enhances bandgap and electron trapping capability, which effectively reduces the conduction loss as well as the possibility of breakdown at high temperatures. CVD technology avoids the post-processing film-forming process, ensuring the fabrication of thin films with high quality. These benefits allow Parylene F films to effectively store electrical energy at temperature up to 150 °C, exhibiting a record discharged energy density of 2.92 J cm-3 at charge-discharge efficiency exceeding 90%. This work provides a new idea for the design and synthesis of all-organic polymer dielectric films for high temperature applications.

A Broad-High Temperature Ceramic Capacitor with Local Polymorphic Heterogeneous Structures

Crafting high-performance dielectrics tailored for pulsed power capacitors, in response to the escalating demands of practical applications, presents a formidable challenge. Herein, this work introduces a novel lineup of lead-free ceramics with local polymorphic heterogeneous structures, defined by the formula (1-x)[0.92BaTiO3-0.08Sr(Mg1/2Ti3/4)O3]-x(Na0.5Bi0.5)TiO3 (BT-SMT-xNBT). This innovative multi-scale synergistic strategy, spanning from the atomic to grain scale, yields materials with a giant recoverable energy density (Wrec) of 10.1 J·cm-3 and an impressive energy efficiency (η) of 95.0%. The integration of linear end elements SMT can significantly mitigate the polarization hysteresis while concurrently boosting the breakdown strength, thus enhancing overall energy efficiency. Furthermore, the inclusion of NBT with high polarization serves to amplify domain size, thereby reinforcing the electric field-induced polarization. This addition also stimulates the creation of polymorphic heterostructures, where tetragonal and rhombohedral nanodomains coexist, as validated by aberration-corrected transmission electron microscopy. Notably, the BT-SMT-0.2NBT ceramics have demonstrated outstanding high-temperature energy storage capabilities, with a Wrec of 7.2 J·cm-3 and an η of 92.2% at 150 °C, along with remarkable broad-temperature stability (ΔWrec, Δη ≤ 4.0%, ≈20-150 °C). These achievements in this work propel the field toward more practical and durable solutions of energy storage dielectrics.

Superior Capacitive Energy Storage Enabled by Molecularly Interpenetrating Interfaces in Layered Polymers

Polymer dielectrics are essential for advanced electronics and electrical power systems, yet they suffer from low energy density (Ue) due to their low dielectric constant (K) and the inverse relationship between K and breakdown stength (Eb). Here a scalable approach utilizing the designed molecularly interpenetrating interfaces is presented to achieve all-organic dielectric polymers with high Ue and charge-dischage efficiency (η). Distinctive intermolecular interactions and microstructural changes, as demonstrated experimentally and theoretically, are introduced by the molecularly interpenetrating interfaces, resulting in simultaneous improvements in dielectric responses and mechanical strength while inhibiting electrical conduction - outcomes unattainable in conventional layered polymers. Consequently, exceptional improvments in both K and Eb are achieved, yielding a very high Ue of 22.89 J cm-3 with η ≥ 90%, outperforming current layered polymer dielectrics. The bilayers can be easily fabricated into large-area films with high uniformity and outstanding capacitive stability (>500 000 cycles), offering a practical route to scalable high-Ue polymer dielectrics for electrical energy storage.

Ultralow k covalent organic frameworks enabling high fidelity signal transmission and high temperature electromechanical sensing

As integrated circuits have developed towards the direction of complexity and miniaturization, there is an urgent need for low dielectric constant materials to effectively realize high-fidelity signal transmission. However, there remains a challenge to achieve ultralow dielectric constant and ultralow dielectric loss over a wide temperature range, not to mention having excellent thermal conductivity and processability concurrently. We herein prepare dual-linker freestanding covalent organic framework films with tailorable fluorine content via interfacial polymerization. The covalent organic framework possesses an ultralow dielectric constant (1.25 at 1 kHz, ≈1.2 at 6 G band), ultralow dielectric loss (0.0015 at 1 kHz) with a thermal conductivity of 0.48 Wm-1K-1. We show high-fidelity signal transmission based on the large-sized (>15 cm2) COF films, far exceeding the most commercially available polyimide-based printed circuit board. In addition, the covalent organic framework also features excellent electret properties, which allows for active high-temperature electromechanical sensing. The electrode nanogenerator maintains 90% of the output voltage at 120 °C, outperforming the traditional fluorinated ethylene propylene electret. Collectively, this work paves the way for scalable application of ultralow dielectric constant covalent organic framework thin films in signal transmission and electromechanical sensing.

Insights into multi-scale structural evolution and dielectric response of poly(methyl acrylate) under pre-strain: A simulation study

The structural evolution of dielectric elastomer induced by pre-strain is a complex, multi-scale process that poses a significant challenge to a deep understanding of the effect of pre-strain. Through simulation results, we identify the variation in the dielectric constant and multi-scale (electronic structure, molecular chain conformation, and aggregation structure) response of poly(methyl acrylate). As the pre-strain increases, the dielectric constant initially rises (below 200% pre-strain) and then declines (above 200% pre-strain). Analysis of the charge distribution, surface electrostatic potential, HOMO-LUMO bandgap, and electron density differences reveal that adjusting chain conformation appropriately could enhance polarity domain and electron polarization. The correlation between permittivity and segment dynamics of deformed molecules is explored, encompassing segment orientation, mean shift displacement, and diffusion coefficient. Following molecular chain orientation, the kinematic capability of the chain segment improves, which leads to an increase in the number and activity of effective dipoles and the enhancement of orientation polarization. Excessive stretching restricts the polymer molecular chain mechanically, reducing the number and activity of effective dipoles and negatively impacting electron polarization. The permittivity transitions from isotropic to anisotropic behavior when the system is subjected to strain. This study provides an interesting solution for research on multiscale responses and intrinsic mechanisms of pre-strain.

Dilute nanocomposites for capacitive energy storage: progress, challenges and prospects

Electrostatic capacitors (ECs) are critical components in advanced electronics and electric power systems due to their rapid charge-discharge rate and high power density. While polymers are ideal for ECs due to their high voltage tolerance and mechanical flexibility, their low dielectric constants (K) and limited energy density remain significant limitations. Traditional polymer nanocomposites, which incorporate high-K ceramic fillers, have shown promise in enhancing dielectric properties but often at the cost of electric breakdown strength and scalability. In this perspective, we explore a pioneering approach that utilizes ultralow loadings of small-sized inorganic nanofillers to significantly improve dielectric constants without compromising other key properties. We delve into the unconventional effects observed in these polymer nanocomposites, including dielectric enhancements, charge trapping, mechanical reinforcements, and microstructural changes, and highlight the impressive energy storage performance achieved with minimal filler contents. We discuss innovative design strategies from viewpoints of polymer and filler structures and showcase recent advancements in nanoscale characterization and theoretical modelling for understanding the crucial role of polymer-filler interfaces. Finally, we stress fundamental challenges and prospects, providing insights into the transformative potential of these nanocomposites for next-generation energy storage applications.

Unifying and Suppressing Conduction Losses of Polymer Dielectrics for Superior High-Temperature Capacitive Energy Storage

Superior high-temperature capacitive performance of polymer dielectrics is critical for the modern film capacitor demanded in the harsh-environment electronic and electrical systems. Unfortunately, the capacitive performance degrades rapidly at elevated temperatures owing to the exponential growth of conduction loss. The conduction loss is mainly composed of electrode and bulk-limited conduction. Herein, the contribution of surface and bulk factors is unified to conduction loss, and the loss is thoroughly suppressed. The experimental results demonstrate that the polar oxygen-containing groups on the surface of polymer dielectrics can act as the charge trap sites to immobilize the injected charges from electrode, which can in turn establish a built-in field to weaken the external electric field and augment the injection barrier height. Wide bandgap aluminum oxide (Al2O3) nanoparticle fillers can serve as deep traps to constrain the transport of injected or thermally activated charges in the bulk phase. From this, at 200 °C, the discharged energy density with a discharge-charge efficiency of 90% increases by 1058.06% from 0.31 J cm-3 for pristine polyetherimide to 3.59 J cm-3 for irradiated composite film. The principle of simultaneously inhibiting the electrode and bulk-limited conduction losses could be easily extended to other polymer dielectrics for high-temperature capacitive performance.

Ultra-Low Loading Fillers Induced Excellent Capacitive Performance in Polymer-Based Multilayer Nanocomposites under Harsh Environments

Multilayer-structured nanocomposites are recognized as a prominent strategy for overcoming the paradox between the breakdown strength (Eb) and polarization (P) to achieve superior energy storage performance. However, current multilayer-structured nanocomposites involving substantial quantities of nanofillers (>10 vol.%) for high dielectric constant as polarization layer will inevitably deteriorate mechanical properties and breakdown strength. Herein, an innovative approach is reported to breaking conventional rules by designing a multilayered polymer composite with ultralow loading of Al2O3 nanoparticles, i.e., 0.3 vol.% for polarization layers and 2 vol.% for insulation layers. By modulating the spatial distribution of Al2O3 nanoparticles in polymer, a significantly increased interfacial dipole response is induced, and deep interfacial traps are constructed to capture the mobile charges, thereby suppressing high-temperature conduction loss. The resulting multilayered polymer composite exhibits an unparalleled discharged energy density of 7.8 J cm-3 with a charging/discharging efficiency exceeding 90% at 150 °C. This work provides valuable insights into achieving superior capacitive performance in multilayer composite films operating under extreme conditions.

Alicyclic Polyimide With Multiple Breakdown Self-Healing Based on Gas-Condensation Phase Validation for High Temperature Capacitive Energy Storage

Polymer dielectrics with combined thermal stability and self-healing properties are specifically desired for high-temperature film capacitors. The high thermal stability of conventional polymers benefits from the abundance of aromatic rings in the molecule backbone, but the high carbon content sacrifices their self-healing properties. Here, analicyclic polyimide with a high glass transition temperature (256 °C) and wide energy bandgap (4.58 eV) is designed, which exhibits electric conductivity more than an order of magnitude lower than that of classical polyimide at high electric fields and high temperatures. As a result, alicyclic polyimide achieves a discharged energy density of 4.54 J cm-3 and a charge-discharge efficiency of above 90% at 200 °C, which is superior to existing dielectric polymers and composites. The alicyclic polyimide benefits from a low pyrolytic residual carbon rate, retaining 93% of the dielectric breakdown strength after four electrical breakdown cycles. Distinguishing from the current condensed-phase self-healing concept, for the first time, exploring the self-healing capability of high-temperature polyimide dielectric is presented based on dual self-healing mechanisms of gas-phase and condensed-phase. The high energy density at high temperatures and the superior self-healing capability of alicyclic polyimide further indicate the promise of polyimide dielectric film capacitors for extreme conditions.

Dilute Nanocomposites: Tuning Polymer Chain Local Nanostructures to Enhance Dielectric Responses

Dielectric polymers possessing high energy and low losses are of great interest for electronic and electric devices and systems. Nanocomposites in which high dielectric constant (high-K) nanofillers at high loading (>10 vol%) are admixed with polymer matrix have been investigated for decades, aiming at enhancing the dielectric performance, but with limited success. In 2017, it is discovered that reducing nanofiller loading to less than 0.5 vol% in polymer matrix can lead to marked enhancement in dielectric performance. Here, we reviewed the discoveries and advances of this unconventional approach to enhance dielectric performance of polymers. Experimental studies uncover that nanofillers lead to interfaces changes over distances larger than 100 nm. Experimental and modeling results show that introducing free volume in polymers reduces the constraints of glass matrix on dipoles in polymers, leading to enhanced K without affecting breakdown. Moreover, low-K nanofillers at low-volume loading serve as deep traps for charges, lowering conduction losses and increasing breakdown strength. The dilute nanocomposites provide new avenues for designing dielectric polymers with high K, minimal losses, and robust breakdown fields, thus achieving high energy and power density and low loss for operation over a broad temperature regime.

Dynamic Covalent Adaptable Polyimide Hybrid Dielectric Films with Superior Recyclability

Polyimides (PIs) used in advanced electrical and electronic devices can be electrically/mechanically damaged, resulting in a significant waste of resources. Closed-loop chemical recycling may prolong the service life of synthetic polymers. However, the design of dynamic covalent bonds for preparing chemically recyclable crosslinked PIs remains a challenging task. Herein, new crosslinked PI films containing a PI oligomer, chain extender, and crosslinker are reported. They exhibit superior recyclability and excellent self-healable ability owing to the synergistic effect of the chain extender and crosslinker. The produced films can be completely depolymerized in an acidic solution at ambient temperature, leading to efficient monomer recovery. The recovered monomers may be used to remanufacture crosslinked PIs without deteriorating their original performance. In particular, the designed films can serve as corona-resistant films with a recovery rate of approximately 100%. Furthermore, carbon fiber reinforced composites (CFRCs) with PI matrices are suitable for harsh environments and can be recycled multiple times at a non-destructive recycling rate up to 100%. The preparation of high-strength dynamic covalent adaptable PI hybrid films from simple PI oligomers, chain extenders, and crosslinkers may provide a solid basis for sustainable development in the electrical and electronic fields.

Engineering hierarchical interfaces in high-temperature polymer dielectrics for electrostatic supercapacitors

Dielectric capacitors are pivotal elements in advanced pulsed power devices and high-voltage, high-capacity power electronic converters, crucial for efficient energy storage. However, a major challenge remains the significant reduction in energy density and charge-discharged efficiency of dielectric polymers under high temperatures, primarily due to heightened electrical conduction losses. This study introduces a universal approach of heterojunction interface engineering in polyethersulfone (PESU) composites, aimed at improving capacitive performance across a broad temperature range. The introduction of one-dimensional heterojunction BaTiO3@Al2O3 nanofibers with large aspect ratios could enhance both the dielectric constant (εr) and breakdown strength (Eb). Specifically, the creation of hierarchical interfaces increases the trap density and energy levels for mobile charges, effectively reducing conduction losses and improving Eb under high-temperature conditions. Consequently, the PESU-3 vol% BaTiO3@Al2O3 nanocomposite achieves an excellent energy density of 7.3 J cm-3 with over 90% retention at 150 °C and 550 MV m-1. Finite element simulations further confirm that the heterojunction structure of BaTiO3@Al2O3 nanofibers effectively inhibits the growth of breakdown paths. This work demonstrates that hierarchical interface engineering offers a powerful strategy to enhance capacitive performance in dielectric polymer composites under harsh conditions.

Flexible Graphene Field-Effect Transistors and Their Application in Flexible Biomedical Sensing

Flexible electronics are transforming our lives by making daily activities more convenient. Central to this innovation are field-effect transistors (FETs), valued for their efficient signal processing, nanoscale fabrication, low-power consumption, fast response times, and versatility. Graphene, known for its exceptional mechanical properties, high electron mobility, and biocompatibility, is an ideal material for FET channels and sensors. The combination of graphene and FETs has given rise to flexible graphene field-effect transistors (FGFETs), driving significant advances in flexible electronics and sparked a strong interest in flexible biomedical sensors. Here, we first provide a brief overview of the basic structure, operating mechanism, and evaluation parameters of FGFETs, and delve into their material selection and patterning techniques. The ability of FGFETs to sense strains and biomolecular charges opens up diverse application possibilities. We specifically analyze the latest strategies for integrating FGFETs into wearable and implantable flexible biomedical sensors, focusing on the key aspects of constructing high-quality flexible biomedical sensors. Finally, we discuss the current challenges and prospects of FGFETs and their applications in biomedical sensors. This review will provide valuable insights and inspiration for ongoing research to improve the quality of FGFETs and broaden their application prospects in flexible biomedical sensing.

Enhanced high-temperature energy storage performances in polymer dielectrics by synergistically optimizing band-gap and polarization of dipolar glass

Polymer dielectrics play an irreplaceable role in electrostatic capacitors in modern electrical systems, and have been intensively studied with their polarization and breakdown strength (Eb) optimized for high discharged energy density (Ud) at elevated temperatures. Small molecules have been explored as fillers, yet they deteriorate thermal stability of matrix which limits their optimal loading to ~1 wt%. Herein, we develop a polymer blend dielectric consisting of common polyimide and a bifunctional dipolar glass polymer which are synthesized from two small molecule components with wide band-gap and large dipole moment. The bifunctional dipolar glass with large molecular weight not only maintains thermal stability of polymer blends even at a high loading of 10 wt%, but also induces substantial enhancement in polarization and Eb than any of individual components does, achieving an ultrahigh Ud of 8.34 J cm-3 (150 °C) and 6.21 J cm-3 (200 °C) with a charge-discharge efficiency of 90%.

Data science-centric design, discovery, and evaluation of novel synthetically accessible polyimides with desired dielectric constants

Rapidly advancing computer technology has demonstrated great potential in recent years to assist in the generation and discovery of promising molecular structures. Herein, we present a data science-centric "Design-Discovery-Evaluation" scheme for exploring novel polyimides (PIs) with desired dielectric constants (ε). A virtual library of over 100 000 synthetically accessible PIs is created by extending existing PIs. Within the framework of quantitative structure-property relationship (QSPR), a model sufficient to predict ε at multiple frequencies is developed with an R 2 of 0.9768, allowing further high-throughput screening of the prior structures with desired ε. Furthermore, the structural feature representation method of atomic adjacent group (AAG) is introduced, using which the reliability of high-throughput screening results is evaluated. This workflow identifies 9 novel PIs (ε >5 at 103 Hz and glass transition temperatures between 250 °C and 350 °C) with potential applications in high-temperature capacitive energy storage, and confirms these promising findings by high-fidelity molecular dynamics (MD) simulations.

Increased Deep Trap Density in Interfacial Engineered Nanocomposite Revealed by Sequential Kelvin Probe Force Microscopy for High Dielectric Energy Storage

Nanocomposites combining inorganic nanoparticles with high dielectric constant and polymers with high breakdown strength are promising for the high energy density storage of electricity, and carrier traps can significantly affect the dielectric breakdown process. Nevertheless, there still lacks direct experimental evidence on how nanoparticles affect the trap characteristics of nanocomposites, especially in a spatially resolved manner. Here, a technique is developed to image the trap distribution based on sequential Kelvin probe force microscopy (KPFM) in combination with the isothermal surface potential decay (ISPD) technique, wherein both shallow and deep trap densities and the corresponding energy levels can be mapped with nanoscale resolution. The technique is first validated using the widely-used commercial biaxially oriented polypropylene, yielding consistent results with macroscopic ISPD. The technique is then applied to investigate polyvinylidene fluoride-based nanocomposites filled with barium titanate nanoparticles, revealing higher deep trap density around surface-modified nanoparticles, which correlates well with its increased breakdown strength. This technique thus provides a powerful spatially resolved tool for understanding the microscopic mechanism of dielectric breakdown of nanocomposites.

Dipole Orientation Engineering in Crosslinking Polymer Blends for High-Temperature Energy Storage Applications

Polymer dielectrics that perform efficiently under harsh electrification conditions are critical elements of advanced electronic and power systems. However, developing polymer dielectrics capable of reliably withstanding harsh temperatures and electric fields remains a fundamental challenge, requiring a delicate balance in dielectric constant (K), breakdown strength (Eb), and thermal parameters. Here, amide crosslinking networks into cyano polymers is introduced, forming asymmetric dipole pairs with differing dipole moments. This strategy weakens the original electrostatic interactions between dipoles, thereby reducing the dipole orientation barriers of cyano groups, achieving dipole activation while suppressing polarization losses. The resulting styrene-acrylonitrile/crosslinking styrene-maleic anhydride (SAN/CSMA) blends exhibit a K of 4.35 and an Eb of 670 MV m-1 simultaneously at 120 °C, and ultrahigh discharged energy densities (Ue) with 90% efficiency of 8.6 and 7.4 J cm-3 at 120 and 150 °C are achieved, respectively, more than ten times that of the original dielectric at the same conditions. The SAN/CSMA blends show excellent cyclic stability in harsh conditions. Combining the results with SAN/CSMA and ABS (acrylonitrile-butadiene-styrene copolymer)/CSMA blends, it is demonstrated that this novel strategy can meet the demands of high-performing dielectric polymers at elevated temperatures.

High-Density Capacitive Energy Storage in Low-Dielectric-Constant Polymer PMMA/2D Mica Nanofillers Heterostructure Composite

The ubiquitous, rising demand for energy storage devices with ultra-high storage capacity and efficiency has drawn tremendous research interest in developing energy storage devices. Dielectric polymers are one of the most suitable materials used to fabricate electrostatic capacitive energy storage devices with thin-film geometry with high power density. In this work, we studied the dielectric properties, electric polarization, and energy density of PMMA/2D Mica nanocomposite capacitors where stratified 2D nanofillers are interfaced between the multiple layers of PMMA thin films using two heterostructure designs of the capacitors, PMMA/2D Mica/PMMA (PMP) and PMMA/2D Mica/PMMA/2D Mica/PMMA (PMPMP). The incorporation of a 2D Mica nanofiller in the low-dielectric-constant PMMA leads to an enhancement in the dielectric constant, with ∆ε ~ 15% and 53% for PMP and PMPMP heterostructures at room temperature. Additionally, a significant improvement in discharged energy density was measured for the PMPMP capacitor (Ud ~ 38 J/cm3 at 825 MV/m) compared to the pristine PMMA (Ud ~ 9.5 J/cm3 at 522 MV/m) and PMP capacitors (Ud ~ 19 J/cm3 at 740 MV/m). This excellent capacitive and energy storage performance of the PMMA/2D Mica heterostructure nanocomposite may inform the fabrication of thin-film, high-density energy storage capacitor devices for potential applications in various platforms.

Poly(ether imide) Film Doped with Protonated Tetra(aniline) Molecules for Efficiently Enhancing the Capacitive Energy Storage Performance

The polymer dielectric spacer plays a key role in the performance of film capacitors. However, currently, commercial polymer dielectric films generally have low relative dielectric constants (<4) and low capacitive energy storage densities (<3 J cm-3). Here, we report the use of protonated tetra(aniline) (TANI) molecules with a length of 1.3 nm to improve the energy storage performance of poly(ether imide) (PEI) films. With only a small content of TANI doping, i.e., 0.7 wt %, both the dielectric constant and energy storage density of PEI film can be significantly improved, while the dielectric loss remains as low as that of pure PEI. A maximum energy density of 9.4 J cm-3 is achieved. To manifest the efficacy of protonated TANI, polyaniline and deprotonated TANI are also prepared and used as dopants in PEI. The PANI filler can also increase the dielectric constant, while the dielectric loss is increased as well. The deprotonated TANI doped in PEI has no influence on both the dielectric constant and energy density, implying that the protonated amino groups of TANI molecules are responsible for the enhanced dielectric constant of the PEI/TANI composite. The correlation between protonation of TANI dopants and dielectric properties is discussed in detail.

Scalable Dual In Situ Synthesis of Polyester Nanocomposites for High-Energy Storage

Incorporating ultralow loading of nanoparticles into polymers has realized increases in dielectric constant and breakdown strength for excellent energy storage. However, there are still a series of tough issues to be dealt with, such as organic solvent uses, which face enormous challenges in scalable preparation. Here, a new strategy of dual in situ synthesis is proposed, namely polymerization of polyethylene terephthalate (PET) synchronizes with growth of calcium borate nanoparticles, making polyester nanocomposites from monomers directly. Importantly, this route is free of organic solvents and surface modification of nanoparticles, which is readily accessible to scalable synthesis of polyester nanocomposites. Meanwhile, uniform dispersion of as ultralow as 0.1 wt% nanoparticles and intense bonding at interfaces have been observed. Furthermore, the PET-based nanocomposite displays obvious increases in both dielectric constant and breakdown strength as compared to the neat PET. Its maximum discharged energy density reaches 15 J cm-3 at 690 MV m-1 and power density attains 218 MW cm-3 under 150 Ω resistance at 300 MV m-1, which is far superior to the current dielectric polymers that can be produced at large scales. This work presents a scalable, safe, low-cost, and environment-friendly route toward polymer nanocomposites with superior capacitive performance.

Enhanced dielectric constant and breakdown strength of sandwiched polymer nanocomposite film for excellent energy storage

Enhanced dielectric constant and high breakdown strength offers immense promise for excellent energy storage performance, which is of critical significance in modern electronics and power systems. However, polymer nanocomposites with traditional routes have to balance between dielectric constant and breakdown strength, hence hindering substantive increases in energy density. Herein, a sandwiched polymer nanocomposite film has been constructed to take full advantage of the individual component layers. BaTiO3 nanoparticles are coated with a fluoropolymer to form core-shell structures and then introduced into a polymer as the top and the bottom layers of a sandwich film for enhancing polarization. Moreover, boron nitride nanosheets (BNNSs) in the middle layer of the sandwich film exert positive effects on the inhibition of current leakage for high breakdown resistance. The breakdown strength increases from 480 MV m-1 of the neat polymer to 580 MV m-1 of the sandwiched film. Additionally, the film exhibits a higher dielectric constant in comparison with the neat polymer. The sandwiched film displays a superior energy density (15.75 J cm-3), which is about 1.9 times that of the neat polymer. This work proposes a feasible route to achieve excellent energy storage of polymer dielectrics by synergistically introducing insulating fillers and additional dipoles in a sandwiched polymer nanocomposite film.

Ferroelectric Bi2O2Te-Based Plasmonic Biosensor for Ultrasensitive Biomolecular Detection

Ultrasensitive detection of biomarkers, particularly proteins, and microRNA, is critical for disease early diagnosis. Although surface plasmon resonance biosensors offer label-free, real-time detection, it is challenging to detect biomolecules at low concentrations that only induce a minor mass or refractive index change on the analyte molecules. Here an ultrasensitive plasmonic biosensor strategy is reported by utilizing the ferroelectric properties of Bi2O2Te as a sensitive-layer material. The polarization alteration of ferroelectric Bi2O2Te produces a significant plasmonic biosensing response, enabling the detection of charged biomolecules even at ultralow concentrations. An extraordinary ultralow detection limit of 1 fm is achieved for protein molecules and an unprecedented 0.1 fm for miRNA molecules, demonstrating exceptional specificity. The finding opens a promising avenue for the integration of 2D ferroelectric materials into plasmonic biosensors, with potential applications spanning a wide range.

Explainable Prediction of Hydrophilic/Hydrophobic Property of Polymer Brush Surfaces by Chemical Modeling and Machine Learning

Polymer informatics has attracted increasing attention as a specialized branch of material informatics. Hydrophilicity/hydrophobicity is one of the most important properties of interfaces involved in antifouling, self-cleaning, antifogging, oil/water separation, protein adsorption, and bioseparation. Establishing a quantitative structure-property relationship for the hydrophilicity/hydrophobicity of polymeric interfaces could significantly benefit from machine learning modeling. In this study, we aimed to construct machine learning models that could predict the static water contact angle (CA) as an indicator of hydrophilicity/hydrophobicity based on a data set of polymer brushes. The features of the polymer brush surfaces were numerically described using their grafted structures (thickness) and molecular descriptors derived from their chemical structures. We achieved accurate prediction and understanding of important parameters by employing appropriate molecular descriptors considering the Pearson correlation and machine learning models trained with nested cross-validation. The model interpretation by Shapley additive extension analysis indicated that the amount of partial polar/nonpolar structure in the molecule as well as the averaged hydrophobicity represented by MolLogP plays an important role in determining the CA. Moreover, the model can predict the CAs of polymer brushes composed of chemical structures that are not present in existing databases. The CA values of the hypothetical polymer brushes are predicted.

Atomic-Level Matching Metal-Ion Organic Hybrid Interface to Enhance Energy Storage of Polymer-Based Composite Dielectrics

In this work, a distinctive "metal-ion organic hybrid interface" (MOHI) between polyimide (PI) and calcium niobate (CNO) nanosheets is designed. The metal ions in the MOHI can achieve atomic-level matching not only with the inorganic CNO, but also with the PI chains, forming uniform and strong chemical bonds. These results are demonstrated by experiment and theory calculations. Significantly, the MOHI reduces the free volume and introduces deep traps across the filler-matrix interfacial area, thus suppressing the electric field distortion in PI-based composite dielectrics. Consequently, PI-based dielectric containing the MOHI exhibits excellent energy storage performance. The energy storage densities (Ue) of the composite dielectric reach 9.42 J cm-3 and 4.75 J cm-3 with energy storage efficiency (η) of 90% at 25 °C and 150 °C respectively, which are 2.6 and 11.6 times higher than those of pure PI. This study provides new ideas for polymer-based composite dielectrics in high energy storage.

Advances in electroactive biomaterials: Through the lens of electrical stimulation promoting bone regeneration strategy

The regenerative capacity of bone is indispensable for growth, given that accidental injury is almost inevitable. Bone regenerative capacity is relevant for the aging population globally and for the repair of large bone defects after osteotomy (e.g., following removal of malignant bone tumours). Among the many therapeutic modalities proposed to bone regeneration, electrical stimulation has attracted significant attention owing to its economic convenience and exceptional curative effects, and various electroactive biomaterials have emerged. This review summarizes the current knowledge and progress regarding electrical stimulation strategies for improving bone repair. Such strategies range from traditional methods of delivering electrical stimulation via electroconductive materials using external power sources to self-powered biomaterials, such as piezoelectric materials and nanogenerators. Electrical stimulation and osteogenesis are related via bone piezoelectricity. This review examines cell behaviour and the potential mechanisms of electrostimulation via electroactive biomaterials in bone healing, aiming to provide new insights regarding the mechanisms of bone regeneration using electroactive biomaterials.

The translational potential of this article

This review examines the roles of electroactive biomaterials in rehabilitating the electrical microenvironment to facilitate bone regeneration, addressing current progress in electrical biomaterials and the mechanisms whereby electrical cues mediate bone regeneration. Interactions between osteogenesis-related cells and electroactive biomaterials are summarized, leading to proposals regarding the use of electrical stimulation-based therapies to accelerate bone healing.

Versatile Landscape of Low-k Polyimide: Theories, Synthesis, Synergistic Properties, and Industrial Integration

The development of microelectronics and large-scale intelligence nowadays promotes the integration, miniaturization, and multifunctionality of electronic and devices but also leads to the increment of signal transmission delays, crosstalk, and energy consumption. The exploitation of materials with low permittivity (low-k) is crucial for realizing innovations in microelectronics. However, due to the high permittivity of conventional interlayer dielectric material (k ∼ 4.0), it is difficult to meet the demands of current microelectronic technology development (k < 3.0). Organic dielectric materials have attracted much attention because of their relatively low permittivity owing to their low material density and low single bond polarization. Polyimide (PI) exhibits better application potential based on its well permittivity tunability (k = 1.1-3.2), high thermal stability (>500 °C), and mechanical property (modulus of elasticity up to 3.0-4.0 GPa). In this review, based on the synergistic relationship of dielectric parameters of materials, the development of nearly 20 years on low-k PI is thoroughly summarized. Moreover, process strategies for modifying low-k PI at the molecular level, multiphase recombination, and interface engineering are discussed exhaustively. The industrial application, technological challenges, and future development of low-k PI are also analyzed, which will provide meaningful guidance for the design and practical application of multifunctional low-k materials.