An alternating multilayer architecture boosts ultrahigh energy density and high discharge efficiency in polymer composites

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.

Toward Design Rules for Multilayer Ferroelectric Energy Storage Capacitors - A Study Based on Lead-Free and Relaxor-Ferroelectric/Paraelectric Multilayer Devices

Future pulsed-power electronic systems based on dielectric capacitors require the use of environment-friendly materials with high energy-storage performance that can operate efficiently and reliably in harsh environments. Here, a study of multilayer structures, combining paraelectric-like Ba0.6Sr0.4TiO3 (BST) with relaxor-ferroelectric BaZr0.4Ti0.6O3 (BZT) layers on SrTiO3-buffered Si substrates, with the goal to optimize the high energy-storage performance is presented. The energy-storage properties of various stackings are investigated and an extremely large maximum recoverable energy storage density of ≈165.6 J cm-3 (energy efficiency ≈ 93%) is achieved for unipolar charging-discharging of a 25-nm-BZT/20-nm-BST/910-nm-BZT/20-nm-BST/25-nm-BZT multilayer structure, due to the extremely large breakdown field of 7.5 MV cm-1 and the lack of polarization saturation at high fields in this device. Strong indications are found that the breakdown field of the devices is determined by the outer layers of the multilayer stack and can be increased by improving the quality of these layers. Authors are also able to deduce design optimization rules for this material combination, which can be to a large extend justify by structural analysis. These rules are expected also to be useful for optimizing other multilayer systems and are therefore very relevant for further increasing the energy storage density of capacitors.

Methyl Methacrylate-co-glycidyl Methacrylate-Based Dielectric Films with High Breakdown Strength and Discharge Energy Density Tailored by PVDF

Linear dielectric polymers are potential candidates for electrostatic capacitors due to their high breakdown strength, high efficiency, and low dielectric loss. In this work, a novel poly (vinylidene fluoride) (PVDF) tailored linear PMMA-co-GMA (MG) copolymer-based all-organic dielectric film with high breakdown strength and discharge energy density was prepared by the solution blending method. Compared with the PMMA homopolymer, the MG copolymer behaved with a higher energy density (5.6 J/cm³) since the GMA component bestowed higher polarity and yielded deep traps for the copolymer. On the other hand, the introduction of PVDF into MG further improved the dielectric constant and overcame the brittleness of MG films. When the concentration of PVDF was 30 wt %, the MG/PVDF film exhibited a high discharged energy density of 10.8 J/cm³ at 600 MV/m with a 78.7% discharge efficiency, which was 2.5 times that of pure PVDF (4.3 J/cm³ at 320 MV/m) and 1.9 times that of pure MG (5.6 J/cm³ at 460 MV/m). The improvement in energy storage performance might be ascribed to the excellent thermodynamic miscibility and hydrogen bond interaction between the linear MG copolymer and the ferroelectric PVDF. This research provides a new and feasible strategy for designing all-organic dielectric films with high energy density for energy storage applications.

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.

Perspective on interface engineering for capacitive energy storage polymer nanodielectrics

Polymer nanodielectrics with high breakdown strength (E_b), high energy density (U_e) and low energy loss have great potential to be used as capacitive energy storage materials of high-voltage film capacitors in modern electrical and electronic equipment, such as smart grids, new energy vehicles and pulse powered weapons. Usually, inorganic nanoparticles with high dielectric constant (ε_r) are added into a high E_b polymer matrix to achieve simultaneously enhanced ε_r and E_b, thus leading to nanodielectrics with high U_e. However, this strategy was seriously hampered by the uneven distribution of electric fields and inhomogeneous microstructures of the multi-phased nanodielectrics until increasing research work was focused on interface engineering. Recent progress in nanocomposites suggests that interface engineering plays a critical role in regulating the polarization and breakdown behaviors of the nanodielectrics, such as balancing ε_r and E_b, enhancing U_e and energy discharge efficiency (η). This article highlights the recent advances in the interface engineering of polymer nanodielectrics, including theoretical models, interface engineering strategies, and the latest characterization and fabrication techniques of high performance nanodielectrics. Finally, the challenges and opportunities in the interface engineering of the nanodielectrics in film capacitors are discussed and predicted from a practical point of view.

Roles of Al2O3@ZrO2 Particles in Modulating Crystalline Morphology and Electrical Properties of P(VDF-HFP) Nanocomposites

Polymer materials with excellent physicochemical and electrical properties are desirable for energy storage applications in advanced electronics and power systems. Here, Al₂O₃@ZrO₂ nanoparticles (A@Z) with a core-shell structure are synthesized and introduced to a P(VDF-HFP) matrix to fabricate P(VDF-HFP)/A@Z nanocomposite films. Experimental and simulation results confirm that A@Z nanoparticles increase the crystallinity and crystallization temperature owing to the effect of the refined crystal size. The incorporation of A@Z nanoparticles leads to conformational changes of molecular chains of P(VDF-HFP), which influences the dielectric relaxation and trap parameters of the nanocomposites. The calculated total trapped charges increase from 13.63 μC of the neat P(VDF-HFP) to 47.55 μC of P(VDF-HFP)/5 vol%-A@Z nanocomposite, indicating a substantial improvement in trap density. The modulated crystalline characteristic and interfaces between nanoparticles and polymer matrix are effective in inhibiting charge motion and impeding the electric conduction channels, which contributes to an improved electrical property and energy density of the nanocomposites. Specifically, a ~200% and ~31% enhancement in discharged energy density and breakdown strength are achieved in the P(VDF-HFP)/5 vol%-A@Z nanocomposite.

Research Advances in Hierarchically Structured PVDF-Based All-Organic Composites for High-Energy Density Capacitors

Polymer film capacitors have been widely applied in many pulsed power fields owing to their fastest energy-released rates. The development of ferroelectric polyvinylidene fluoride (PVDF)-based composites has become one of the hot research directions in the field of high-energy storage capacitors. Recently, hierarchically-structured all-organic composites have been shown to possess excellent comprehensive energy storage performance and great potential for application. In this review, most research advances of hierarchically-structured all-organic composites for the energy storage application are systematically classified and summarized. The regulating strategies of hierarchically structured all-organic composites are highlighted from the perspective of preparation approaches, tailored material choices, layer thicknesses, and interfaces. Systematic comparisons of energy storage abilities are presented, including electric displacement, breakdown strength, energy storage density, and efficiency. Finally, we present the remaining problems of hierarchically structured all-organic composites and provide an outlook for future energy storage applications.

Achieving Concurrent High Energy Density and Efficiency in All-Polymer Layered Paraelectric/Ferroelectric Composites via Introducing a Moderate Layer

Dielectric polymer capacitors are extensively applied in advanced electronics by virtue of their extremely high power density. However, it remains a challenge to concurrently realize high energy density and high discharge efficiency. In order to solve this conundrum, we herein design a novel all-polymer trilayer structure, where the paraelectric poly(methyl methacrylate) (PMMA) is used as the top layer to obtain a high discharge efficiency, and ferroelectric P(VDF-HFP) is employed as the bottom layer to obtain a high energy density. Particularly, the PMMA/poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) blend composite is used as the middle layer to homogenize the electric field inside the trilayer composites, turning out an obviously boosted breakdown strength and elevated energy density. Consequently, an efficiency as high as 85% and an energy density up to 7.5 J/cm³ along with excellent cycling stability are simultaneously realized at an ultrahigh electric field of 490 kV/mm. These attractive characteristics of the all-polymer trilayer structure suggest that the feasible pathway presented herein is significant to realize concurrently a high energy density and discharge efficiency.