Research Progress of All Organic Polymer Dielectrics for Energy Storage from the Classification of Organic Structures

Roll-to-Roll Manufactured Polyetherimide Nanocomposite With Different Diameters of SiO2 Nanoparticles Exhibiting Improved High-Temperature Dielectric Energy Storage Performance

To enhance the high-temperature energy storage performance of the polymer-based dielectric film, inorganic nanofillers with large band gaps are much more effective and have been widely adopted. However, the impact of nanoparticle diameters on the dielectric properties of polymer nanocomposites has been less studied. Herein, silicon dioxide nanoparticles (SiO2-NPs) with varying diameters (20, 60, 120, 200 nm) prepared by the sol-gel method are incorporated in the PEI matrix to form PEI/SiO2 nanocomposites. The characterization results reveal a distinct correlation between the dielectric properties of polyetherimide (PEI) composites and the diameters of SiO2-NPs. Leakage current density analysis and breakdown strength simulations indicate that SiO2-NPs with smaller diameters generate more deep traps that impede the transport of charge carriers, especially under high temperatures. Notably, PEI/20 nm-SiO2 exhibits a high discharged energy density of 4.4 J cm-3 with an efficiency of 90% at 150 °C. Furthermore, PEI/SiO2 films with 10 µm in thickness are manufactured by a large-scale solution casting process. The continuously prepared PEI/20 nm-SiO2 film exhibits a discharged energy density of 3.2 J cm-3 with an efficiency of 90% at 150 °C. This study not only provides a strategy for the design of high-performance dielectric polymer composites but also offers a large-scale high-temperature dielectric film for practical use.

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.

Mobile energy storage technologies for boosting carbon neutrality

Carbon neutrality calls for renewable energies, and the efficient use of renewable energies requires energy storage mediums that enable the storage of excess energy and reuse after spatiotemporal reallocation. Compared with traditional energy storage technologies, mobile energy storage technologies have the merits of low cost and high energy conversion efficiency, can be flexibly located, and cover a large range from miniature to large systems and from high energy density to high power density, although most of them still face challenges or technical bottlenecks. In this review, we provide an overview of the opportunities and challenges of these emerging energy storage technologies (including rechargeable batteries, fuel cells, and electrochemical and dielectric capacitors). Innovative materials, strategies, and technologies are highlighted. Finally, the future directions are envisioned. We hope this review will advance the development of mobile energy storage technologies and boost carbon neutrality.

Depressing relaxation and conduction loss of polar polymer materials by inserting bulky charge traps for superior energy storage performance in high-pulse energy storage capacitor applications

Polymer-based dielectrics are chiefly used in high-pulse energy storage capacitors for their high breakdown strength, prominent processability, and low cost. Nevertheless, state-of-the-art commercial polymer-based dielectrics such as biaxially oriented polypropylene (BOPP), cannot satisfy the high energy density requirement in many fields because of their low permittivity. Limited success has been achieved in developing polar polymeric dielectrics with high energy density because of the quickly increased energy loss from polarization relaxation and charge conduction under a high electric field and temperature. To achieve high energy density and low loss in polar polymer dielectrics simultaneously, electron-deficient vinyl quinoline (VQQ) units are pre-copolymerized with methyl methacrylate (MMA) followed by blending with a PMMA matrix. The bulky and electron-deficient VQQs have successfully depressed the relaxation of PMMA and significantly decreased charge conduction under an elevated electric field. As a result, a rather high energy discharging efficiency (over 90%) could be finely maintained up to 800 MV m^-1, and an energy density of 16.1 J cm^-3 could be obtained, which are much better than those of reported polymer dielectrics. The strong space charge trapping effect of the low content of VQQ is well addressed by thermally stimulated depolarization currents (TSDC) and density functional theory analysis (DFT) of increasing breakdown strength, energy density and discharging efficiency. This work offers a promising strategy for achieving high energy density and low loss in polar polymer dielectrics for their commercial application in energy storage capacitors.

Integrated exploration of experimentation and molecular simulation in ester-containing polyimide dielectrics

With the growing development of film capacitors in various applications, the requirements for polymer dielectrics have increased accordingly. In this work, a series of ester-cotaining polyimide (EPI) dielectrics were designed and fabricated. Futhermore, integrated exploration of experimentation and molecular simulation is proposed to achieve polymer dielectrics with advanced comprehensive performance, as well as to analyze the dielectric mechanism in-depth. The EPIs show superior thermal resistance and dielectric properties. A Weibull breakdown strength of 440-540 MV m^-1, permittivity of 3.52-3.85, dissipation factor of 0.627-0.880% and theoretical energy density of 3.13-4.90 J cm^-3 were obtained for the EPIs. The relationship between microscopic parameters and dielectric behavior was investigated in detail. According to the experimental and calculated results, there is close correlation between dipolar moment density (μ/V _vdw) and dielectric permittivity (ε _r). It is deduced that the integrated research of experiments and molecular simulation would be an effective strategy to reveal the dielectric mechanism as well as assist in the molecular design of polymer dielectrics.

Progress on Polymer Dielectrics for Electrostatic Capacitors Application

Polymer dielectrics are attracting increasing attention for electrical energy storage owing to their advantages of mechanical flexibility, corrosion resistance, facile processability, light weight, great reliability, and high operating voltages. However, the dielectric constants of most dielectric polymers are less than 10, which results in low energy densities and limits their applications in electrostatic capacitors for advanced electronics and electrical power systems. Therefore, intensive efforts have been placed on the development of high-energy-density polymer dielectrics. In this perspective, the most recent results on the all-organic polymer dielectrics are summarized, including molecular structure design, polymer blends, and layered structured polymers. The challenges in the field and suggestions for future research on high-energy-density polymer dielectrics are also presented.

Energy Storage Application of All-Organic Polymer Dielectrics: A Review

With the wide application of energy storage equipment in modern electronic and electrical systems, developing polymer-based dielectric capacitors with high-power density and rapid charge and discharge capabilities has become important. However, there are significant challenges in synergistic optimization of conventional polymer-based composites, specifically in terms of their breakdown and dielectric properties. As the basis of dielectrics, all-organic polymers have become a research hotspot in recent years, showing broad development prospects in the fields of dielectric and energy storage. This paper reviews the research progress of all-organic polymer dielectrics from the perspective of material preparation methods, with emphasis on strategies that enhance both dielectric and energy storage performance. By dividing all-organic polymer dielectrics into linear polymer dielectrics and nonlinear polymer dielectrics, the paper describes the effects of three structures (blending, filling, and multilayer) on the dielectric and energy storage properties of all-organic polymer dielectrics. Based on the above research progress, the energy storage applications of all-organic dielectrics are summarized and their prospects discussed.