Electrostatic Energy Storage Research Articles

Enhanced voltage endurance capability of Ba(Zr0.2Ti0.8)O3 thin films induced by atomic-layer-deposited Al2O3 intercalations and the application in electrostatic energy storage

Ultrathin Al2O3 insulating intercalations with different thicknesses and numbers, prepared by atomic layer deposition technology, were introduced into Ba(Zr0.2Ti0.8)O3 (BZT) relaxor ferroelectric films as the dielectric for electrostatic energy storage capacitors. The phase structure, microstructure and electrical properties were investigated in detail. Due to the insertion of insulating layers, the films show less leakage current and enhanced voltage endurance capability when the thickness of single Al2O3 intercalation exceeds a threshold (0.45–0.9 nm). The voltage endurance capability can be more enhanced by increasing the number of Al2O3 intercalations. For energy storage applications, the energy storage density and efficiency obtained from the polarization-electric field loops are significantly improved owing to the suppressed leakage and enhanced voltage endurance ability. The results promote the application of BZT-based films in electrostatic energy storage. It is demonstrated that the introduction of atomic-layer-deposited insulating intercalations with controllable thickness, such as those fabricated by ALD method, is an effective way to improve the electrical performance of devices based on composite materials.

Effect of shape of inorganic particles on dielectric properties of polymer composites with high energy density

The formation of two-phase composite materials by adding inorganic ceramic particles in the organic matrix is a hot and difficult point in the current study of high energy storage density. The electrostatic energy storage characteristics of the material are determined by its internal electric field distribution. For pure polymer materials, the internal electric field is uniformly distributed in a uniform external electric field environment, but when the inorganic particles are filled to form a composite material, the local electric field of the material will be distorted, which will affect the dielectric properties of the composite material. In this paper, the electric response properties of particles with different shape, including sphere, fiber and disk and its special arrangement has been systematically studied. The results show that both the shape and the spatial arrangement of the particles in the polymer matrix affect the local distribution of electric field. For spherical particles, there will exist be field concentration up and below the particle. For fibers, the field caused by the terminal surface bound charge should not be neglected when the aspect ratio is not large enough. At last, three three-dimensional simulation models of composites with spherical, fiber and disk particles have been established. It is indicated that composites with fiber particle possess the highest effective permittivity, while the disk particle is the lowest under the same concentration. The investigation of this paper is of great significance to understand the microscopic mechanism of energy storage.

Fully Additive Fabrication of Electrically Anisotropic Multilayer Materials Based on Sequential Electrodeposition

MEMS-enabled multilayer composites, in which microfabrication is used to create micron-scale thickness layers within the volume of meso-scale thickness structures, can be exploited to create materials with highly anisotropic electromagnetic properties. Such materials have utility in both sensing and energy applications, including electrostatic and magnetic energy storage and conversion. A fabrication challenge in realizing these classes of materials lies in the size-scale disparity between the thickness of an individual layer and the desired thickness of the final anisotropic material. We demonstrate a fully additive sequential electrochemical deposition approach for such structures, which enables scalable composite volume while maintaining micron-scale individual layer thicknesses. Alternating metal and polymer layers, which exhibit very different electrical conductivities, are continuously electrodeposited in batch-scale. Individual layer thicknesses are controlled by deposition currents and times, while lateral extents are defined by lithographically defined molds. The fabrication process is illustrated using electrodeposited NiFe alloys and polypyrrole, and the anisotropy of electrical conductivity is assessed for potential use of these structures as magnetic cores for high frequency switching converters. Due to the relatively resistive polypyrrole layers, electrical anisotropy of lateral to vertical conductivity exceeding 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> was achieved. This approach offers a solution-based, microfabrication compatible, and manufacturable route to functional composite materials that exhibit high electrical anisotropies.

Energy storage and dielectric properties of a novel Bi1.5MgNb1.5O7-Bi2Mg2/3Nb4/3O7 thin film

Lead-free Bi1.5MgNb1.5O7-Bi2Mg2/3Nb4/3O7 (BMN1.5-BMN2) thin films have been deposited on Pt/Ti/SiO2/Si substrates by RF magnetron sputtering. A very low loss tangent of ~0.005 with a high dielectric constant of 158 is achieved in a BMN1.5-BMN2 thin film annealed in an oxygen pressure of 0.03 MPa. The BMN1.5-BMN2 thin film possesses superior energy storage properties due to its slim P-E loops, large maximum polarization (Pmax~36.97 μC/cm2) and high charge storage density (Pmax-Pr~32.25 μC/cm2), with an energy storage density of 40.59 J/cm3 and an energy conversion efficiency of 61.67% at 2.91 MV/cm. The energy storage density is superior to other the reference ferroelectric thin films. In addition, the BMN1.5-BMN2 thin film exhibits a large power density of 16.34 MW/cm3 due to the low dielectric loss. More importantly, BMN1.5-BMN2 as a new system provides new ideas for the design of lead-free linear dielectrics with ultrahigh energy storage density, indicating it is a very promising candidate for electrostatic energy storage capacitors.

Polymer/molecular semiconductor all-organic composites for high-temperature dielectric energy storage

Dielectric polymers for electrostatic energy storage suffer from low energy density and poor efficiency at elevated temperatures, which constrains their use in the harsh-environment electronic devices, circuits, and systems. Although incorporating insulating, inorganic nanostructures into dielectric polymers promotes the temperature capability, scalable fabrication of high-quality nanocomposite films remains a formidable challenge. Here, we report an all-organic composite comprising dielectric polymers blended with high-electron-affinity molecular semiconductors that exhibits concurrent high energy density (3.0 J cm−3) and high discharge efficiency (90%) up to 200 °C, far outperforming the existing dielectric polymers and polymer nanocomposites. We demonstrate that molecular semiconductors immobilize free electrons via strong electrostatic attraction and impede electric charge injection and transport in dielectric polymers, which leads to the substantial performance improvements. The all-organic composites can be fabricated into large-area and high-quality films with uniform dielectric and capacitive performance, which is crucially important for their successful commercialization and practical application in high-temperature electronics and energy storage devices.

Significantly enhanced electrostatic energy storage performance of P(VDF-HFP)/BaTiO3-Bi(Li0.5Nb0.5)O3 nanocomposites

Abstract Microelectronics and electrical power systems require dielectric polymer-based dielectrics with high energy density that are simple to process. However, the currently available polymer-based dielectric materials require demanding process conditions and relatively low energy density. Herein, we propose P(VDF-HFP)-based nanocomposite by a simple and practical mechanical method based on a combination of solid phase reaction and sieving to prepare 0.88BaTiO3-0.12Bi(Li0.5Nb0.5)O3 nanoparticles (BT-BLN nps). The experimental and simulation result verify that the BT-BLN nps significantly improve the breakdown strength and energy storage performance of dielectric materials. Remarkably, the highest discharge energy density of the BT-BLN/P(VDF-HFP) nanocomposite film reached 14.2 J/cm3 with the addition of 3 vol% BT-BLN nanofiller at 497 MV/m, which is much higher than that of pure P(VDF- HFP) (Ud ≈ 6.6 J/cm3 and Eb ≈ 391.3 MV/m). Encouragingly, the Young's modulus of BLN-3vol%/P(VDF-HFP) reached 2.6 GPa, which is approximately 2.65 times higher than that of pure P(VDF-HFP) (0.98 GPa). This work established a simple and effective strategy, for solution casting processable dielectrics with performance comparable to that of fillers prepared by the liquid phase method.

Ultrahigh dielectric constant induced by the interfacial polarization between liquid crystal droplets and polymer matrix

Polymer composites mixed with high dielectric constant nanofillers are thought of as excellent candidates of high-performance dielectrics for electrostatic energy storage. In this contribution, we report a new kind of all-organic composites composed of liquid crystal (LC) 5CB and polymer PMMA. They present an ultrahigh dielectric constant of above 103 at high-temperature/low-frequency conditions, attributed to the effect of Maxwell–Wagner–Sillars polarizations proportional to the LC/polymer interface area. Moreover, adding a negligible amount (0.2 vol%) of BaTiO3 nanoparticles into composites for better 5CB-domain dispersion, we realize a further enhancement of dielectric constant at the same measurement conditions as the expectation.

Bioinspired Hierarchically Structured All‐Inorganic Nanocomposites with Significantly Improved Capacitive Performance

AbstractLead‐free dielectric ceramics have been the spotlight in the search for environmentally benign materials for electrostatic energy storage because of the ever‐increasing environmental concerns. However, the inverse correlation between the polarization and dielectric breakdown strength is the major barrier hindering the provision of sufficient energy densities in lead‐free dielectric ceramics and practical applications thereof. Herein, a rational structure design inspired by nature is demonstrated as an effective strategy to overcome these challenges. Bioinspired raspberry‐like hierarchically structured all‐inorganic nanocomposites have been prepared by enclosing microsized BaTiO3‐Bi(Mg0.5Zr0.5)O3 (BT‐BMZ) relaxor ferroelectrics using core‐shell BT‐BMZ@SiO2 nanoparticles. The synergistic effects of the bioinspired hierarchical structure and insulating SiO2 nano‐coating result in significantly improved dielectric breakdown strength and sustained large polarization in the nanocomposites, as corroborated by experimental characterizations and theoretical simulations. As a result, an ultrahigh energy density of 3.41 J cm−3 and a high efficiency of 85.1%, together with outstanding thermal stability within a broad temperature range, have been simultaneously achieved in the hierarchically structured nanocomposites. This contribution provides a feasible and paradigmatic approach to develop high‐performance dielectrics for electrostatic energy storage applications using bioinspired structure design.

Kinetic energy release (KER) of vibrationally cold HeH+: experiments at the reaction microscope in the Frankfurt low-energy storage ring (FLSR)

SynopsisThe installation of a reaction microscope (COLTRIMS [1]) in the electrostatic Frankfurt Low Energy Storage Ring (FLSR) [2] has been completed. A first experiment, exploring the KER for dissociative electron transfer to HeH+ ions at 20 keV from a cold supersonic He gas target have been carried. Even at the moderate vacuum of 10−8 mbar a change of the KER and the Q value distribution due to cooling of the molecular ions during the storage time can be observed. In this contribution the final experiment, performed after heating the ring will be discussed.

Multiscale structural engineering of dielectric ceramics for energy storage applications: from bulk to thin films.

Dielectric capacitors with the prominent features of ultrafast charging-discharging rates and ultrahigh power densities are ubiquitous components in modern electronics. To meet the growing demand for electronics miniaturization, dielectric capacitors with high energy storage properties are extensively researched. Here we present an overview of the recent progress in the engineering of multiscale structures of dielectric ceramics ranging from bulk to thin films. This article commences with a brief introduction of the fundamentals of dielectric ceramics, including primary parameters, a library of dielectric ceramics, and multiscale structures. Emphases are placed on the relationship between multiscale structures and energy storage properties and the rational structure design principles in dielectric ceramics. Also included are currently available multilayer ceramic capacitors based on multiscale engineered ceramic structures. Finally, challenges along with opportunities for further research and development of high-performance dielectric ceramics for electrostatic energy storage are highlighted.

High energy-storage density under low electric field in lead-free relaxor ferroelectric film based on synergistic effect of multiple polar structures

Although dielectric energy-storage devices are frequently used in high voltage level, high voltage risk and large cost of insulation technology have increased the demand on the energy-storage devices at finite electric field strength. Here, we propose an approach on enhancing energy-storage density (Wrec) of dielectric materials under low electric field by utilizing the synergistic effect of multiple polar structures. An excellent Wrec of 40.8 J/cm3 under only 1500 kV/cm is obtained in 0.5(Bi0.5Na0.5)TiO3-0.5Bi(Zn0.5Zr0.5)O3 (BNT-0.5BZZ) relaxor ferroelectric film, resulting in a large energy-storage coefficient that exceeds most of the dielectric materials. It is revealed that the addition of BZZ to BNT matrix induces the distortion of the octahedral [TiO6] in the lattice and establishes a coexistence structure of ferroelectric domains and polar nanoregions (PNRs), which enlarges the discrepancy between the maximum polarization and the remnant polarization. Besides, the BNT-0.5BZZ film shows strong fatigue endurance after 5 × 107 cycles and good thermal stability in a wide temperature range (25–145 °C). This work not only develops a promising lead-free candidate for low electric field electrostatic energy storage, but also, more importantly, opens up a new door to systematically design lead-free dielectrics for high-energy-storage applications at low electric field via microstructural engineering.

Microelectrostatic simulation of insulated graphene–polymer nanocomposites using COMSOL Multiphysics

Graphene–polymer nanocomposites have shown promising potential as high dielectric constant and electrostatic energy storage materials. However, such nanocomposites often faced challenges of high energy dissipation and low voltage endurance due to direct contact of graphene nanosheets and localized electric field concentration. Various efforts have been made to address these shortcomings such as the insulative coating of graphene nanosheets in a polymer matrix. In this study, we simulated (using COMSOL Multiphysics) the effects of such insulative coatings on localized voltage concentration around graphene nanosheet in a polymer matrix. The simulation was done by consideration of various insulative materials with different dielectric constant and coating thickness on graphene nanosheets. It was noted that insulative coating can reduce localized voltage concentration around a graphene nanosheet in a polymer matrix, thereby improve the breakdown strength. Further increase in the coating thickness with low dielectric constant coating materials can further enhance breakdown strength. However, high coating thickness resulted in lowering the microcapacitance of the microcapacitor in the polymer matrix. Therefore, for the optimal energy density of such nanocomposites, a compromise dielectric constant of a coating material and coating thickness on graphene nanosheet must be reached. This study showcased the influence of insulative coatings on graphene nanosheets. It will be a guide for further studies on the selection of coating materials for graphene nanosheets for high breakdown strength nanocomposites.

Enhancement of dielectric properties and energy storage performance in 3Y‐TZP ceramics with BaTiO3 additives

AbstractWith the fast charge‐discharge speed and ultrahigh power density, electrostatic energy storage materials offer great potential in the applications for pulsed power systems. As a very important member of structural ceramics, 3Y‐TZP (3 mol% Y2O3 doped tetragonal zirconia polycrystals) has shown extraordinary mechanical properties. However, the research on their energy storage performance is still lacking. Herein, a ferroelectric phase, BaTiO3 (BT), was introduced and demonstrated to improve the dielectric properties and energy storage performance of 3Y‐TZP ceramic matrix via the conventional solid‐state reaction method. With increasing the BT content from 0 to 15 mol%, the permittivity of the composite ceramics could be effectively increased from 40.2 to 64.1 measured at 1 kHz. Simultaneously, the dielectric loss could be effectively decreased by depressing the response of charged defects, which was further interpreted by the thermally stimulated depolarization current technique. Meanwhile, the breakdown strength showed a typical increase‐then‐decrease trend with increasing BT content, and reached their maximum values when doped with 7 mol% BT. Together with the enhancement of dielectric properties, the 7 mol% BT‐doped 3Y‐TZP ceramics exhibited a maximum energy storage density of 0.42 J/cm3, which was approximately 150% larger than that of the pure 3Y‐TZP ceramics.

Negative Capacitance for Electrostatic Supercapacitors

AbstractThe increasing demand for efficient storage of electrical energy is one of the main challenges in the transformation toward a carbon neutral society. While electrostatic capacitors can achieve much higher power densities compared to other storage technologies like batteries, their energy densities are comparatively low. Here, it is proposed and demonstrated that negative capacitance, which is present in ferroelectric materials, can be used to improve the energy storage of capacitors beyond fundamental limits. While negative capacitance was previously mainly considered for low power electronics, it is shown that ferroelectric/dielectric capacitors using negative capacitance are promising for energy storage applications. Compared to earlier results using (anti)ferroelectric materials for electrostatic energy storage, much higher efficiencies of more than 95% even for ultrahigh energy densities beyond 100 J cm−3 are demonstrated using nonepitaxial thin films suitable for integration on 3D substrates. Stable operation up to 150 °C and 108 charging/discharging cycles is further demonstrated.

Multifunctional All-Inorganic Flexible Capacitor for Energy Storage and Electrocaloric Refrigeration over a Broad Temperature Range Based on PLZT 9/65/35 Thick Films.

Multifunctional capacitors can efficiently integrate multiple functionalities into a single material to further down-scale state-of-the-art integrated circuits, which are urgently needed in new electronic devices. Here, an all-inorganic flexible capacitor based on Pb0.91La0.09 (Zr0.65Ti0.35)0.9775O3 (PLZT 9/65/35) relaxor ferroelectric thick film (1 μm) was successfully fabricated on LaNiO3/F-Mica substrate for application in electrostatic energy storage and electrocaloric refrigeration simultaneously. The flexible PLZT 9/65/35 thick film presents a desirable breakdown field of 1998 kV/cm, accompanied by a superior recoverable energy density (Wrec) of 40.2 J/cm3. Meanwhile, the thick film exhibits excellent stability of energy-storage performance, including a broad operating temperature (30-180 °C), reduplicative charge-discharge cycles (1 × 107 cycles), and mechanical bending cycles (2000 times). Moreover, a large reversible adiabatic temperature change (ΔT) of 18.0 °C, accompanied by an excellent electrocaloric strength (ΔT/ΔE) of 22.4 K cm/V and refrigerant capacity (RC) of 11.2 J/cm3, is obtained at 80 °C in the flexible PLZT 9/65/35 thick film under the moderate applied electric field of 850 kV/cm. All of these results shed light on a flexible PLZT 9/65/35 thick film capacitor that opens up a route to practical applications in microenergy-storage systems and on-chip thermal refrigeration of advanced electronics.

Stress-Induced Crystallization of Thin Hf1- XZr XO2 Films: The Origin of Enhanced Energy Density with Minimized Energy Loss for Lead-Free Electrostatic Energy Storage Applications.

Increasing interest in the development of alternative energy storage technologies has led to efforts being taken to improve the energy density of dielectric capacitors with high power density. However, dielectric polymer materials still have low energy densities because of their low dielectric constant, whereas Pb-based materials are limited by environmental issues and regulations. Here, the energy storage behaviors of atomic layer-deposited Hf1- XZr XO2 ( X = 0-1) thin films (10 nm) and the phase transformation mechanism associated with an enhancement of their energy density are reported using unipolar pulse measurements. Based on electrical and material characterization, the energy density and energy efficiency are dependent on the Zr content, and stress-induced crystallization by the encapsulating Hf1- XZr XO2 films with TiN top electrodes prior to annealing can enhance the energy density (up to 47 J/cm3 at a small voltage value of 3.5 MV/cm) while minimizing energy loss even at low process temperatures (400 °C). This work will facilitate the realization of Hf1- XZr XO2-based capacitors for lead-free electrostatic energy storage applications.

Non-intuitive concomitant enhancement of dielectric permittivity, breakdown strength and energy density in percolative polymer nanocomposites by trace Ag nanodots

In situ synthesized Ag nanodots enhances electrostatic energy storage by tuning dipoles.

Atomic-scale structure characteristics of antiferroelectric silver niobate

Antiferroelectric materials are a kind of functional material, which are widely used in electrostatic energy storage, energy conversion devices, and magnetoelectric coupling devices. As a typical lead-free antiferroelectric material, silver niobate has attracted much attention in recent years due to its excellent performance in energy storage. In this work, using the spherical aberration corrected electron microscopy technique, atomic-resolution images of pure silver niobate were obtained, which revealed typical microscopic physical characteristics of such complex antiferroelectric oxides: in such materials, all cations deviate from the average positions of the main lattice, and the displacement of each kind of cation varies periodically in two opposite directions, resulting in periodic wavy (1–10)c atomic planes, and the period of cation displacement is 15.6 Å. At the same time, the 90° antiferroelectric domain boundary and the antiphase domain wall defects are further revealed and analyzed.

Significantly Enhanced Electrostatic Energy Storage Performance of Flexible Polymer Composites by Introducing Highly Insulating‐Ferroelectric Microhybrids as Fillers

AbstractA hybrid nanoparticle, consisting of BaTiO3 nanoparticles tightly embedded in bronnitride (BN) nanosheets, has been fabricated based on a daring supposition that BN may act as a host to incorporate ferroelectric nanoparticles to improve insulation and polarization under a high electric field. Using the hybrids as fillers in poly(vinylidene fluoride) (PVDF) composites, a high electric breakdown strength (Eb ≈580 kV/mm), which is 1.76 times of the PVDF film, is obtained when the filler content is 5 wt%. A large displacement (9.3 µC/cm2 under 580 kV/mm) is observed so as to obtain a high discharged energy density (Ud ≈17.6 J/cm3) of the BT@BN/PVDF composites, which is 2.8 times of the PVDF film. The enhancement ratio of Eb achieved in this study demonstrates the highest among the reported results. This hybrid structure of fillers provides an effective way to adjust and improve the energy storage properties of the polymer‐based dielectrics.

Enhanced ferroelectric properties and energy storage density in PLZT/BNKT heterolayered thin films prepared by sol-gel method

The PLZT/BNKT heterolayered thin films on Pt/Ti/SiO2 /Si substrates were fabricated by chemical solution deposition. The influence of different heterolayered structures on the microstructures, ferroelectric and energy storage properties of the films was investigated and clarified in detail. Based on the heterolayered structures, ferroelectric properties and energy storage density (J reco ) of the films were significantly enhanced. The maximum polarization (P max ) and P max -P r get the maximum values of 71.4 μC/cm2 and 56.7 μC/cm2 , respectively. The extreme value of recoverable energy storage density was 8.1 J/cm3 for the heterolayered film S(7-1). These results demonstrate that the PLZT/BNKT heterolayered films are real potential candidates for electrostatic energy storage devices that are environment-friendly.