High Energy Storage Density Research Articles

Energy consumption reduction in a building by free cooling using phase change material (PCM)

It is significantly important to implement energy storage systems nowadays. Latent heat thermal energy storage (LHTES) systems contain numerous advantages as a result of their small temperature variation and higher energy storage densities during storage. The present paper deals with the cooling load of a room in Zanjan, Iran using Carrier software. Then, a free cooling system using commercial paraffin RT25 was numerically analyzed as phase change material (PCM) while investigating the effects of the flow rate of the storage tank and inlet air temperature overcharging and discharging procedures. Based on cold energy storage simulation, by airflow with the temperature of 20°C at night, the paraffin is solidified in 4 h. Stored cold energy of 1.4 kW in PCM releases energy through a free cooling system within 2.1 h of July afternoon in the room.

Dendrite-Free Li5.5PS4.5Cl1.5-Based All-Solid-State Lithium Battery Enabled by Grain Boundary Electronic Insulation Strategy through In Situ Polymer Encapsulation.

Sulfide-based all-solid-state lithium batteries (ASSLBs) have attracted unprecedented attention in the past decade due to their excellent safety performance and high energy storage density. However, the sulfide solid-state electrolytes (SSEs) as the core component of ASSLBs have a certain stiffness, which inevitably leads to the formation of pores and cracks during the production process. In addition, although sulfide SSEs have high ionic conductivity, the electrolytes are unstable to lithium metal and have non-negligible electronic conductivity, which severely limits their practical applications. Herein, a grain boundary electronic insulation strategy through in situ polymer encapsulation is proposed for this purpose. A polymer layer with insulating properties is applied to the surface of the Li5.5PS4.5Cl1.5 (LPSC) electrolyte particles by simple ball milling. In this way, we can not only achieve a dense electrolyte pellet but also improve the stability of the Li metal anode and reduce the electronic conductivity of LPSC. This strategy of electronic isolation of the grain boundaries enables stable deposition/stripping of the modified electrolyte for more than 2000 h at a current density of 0.5 mA cm-1 in a symmetrical Li/Li cell. With this strategy, a full cell with Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) as the cathode shows high performance including high specific capacity, improved high-rate capability, and long-term stability. Therefore, this study presents a new strategy to achieve high-performance sulfide SSEs.

High energy-storage density and giant negative electrocaloric effect in PLZS antiferroelectric thick film ceramics prepared via the tape-casting process

Antiferroelectric materials are highly desired for high energy-storage density capacitors and electrocaloric refrigerator in the future due to their excellent energy storage properties and giant negative electrocaloric effect, which have attracted great attention in recent years. In the present work, a highly recoverable energy density (Wrec) and a large reversible adiabatic temperature change (ΔT) were obtained simultaneously in PLZS thick film ceramics (TFCs). A maximum Wrec of 9.84 J·cm−3 with an efficiency of 85.2 % at 440 kV·cm−1, and a negative ΔT of −9.50 °C at 280 kV·cm−1 were obtained. Moreover, the maximum value of electrocaloric strength of 0.98 K·m·MV−1 was achieved for Pb0.97La0.02(Zr0.50Sn0.50)O3 TFCs. These results demonstrate that the PLZS TFCs can be applied potentially for high energy-storage density capacitors and refrigerators.

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.

Voltage-assisted 3D printing of polymer composite dielectric films with low energy loss and high energy storage density

PVDF-based polymers have garnered significant attention in the field of high-power density electrostatic capacitors due to their exceptional dielectric strength. However, their practical applications are constrained by low charge-discharge efficiency (η) and energy storage density (Ue), which stem from high ferroelectric relaxation and low breakdown strength (Eb). Here, a hydrogenated glassy polymer poly(styrene-methyl methacrylate-methylallyl alcohol) (PSMA) is designed and synthesized to be homogeneously distributed in PVDF through voltage-assisted 3D printing-hot pressing, resulting in a flexible composite film. The findings demonstrate that PSMA, rich in hydrogen bonds and high modulus strength, effectively mitigates the ferroelectric phase transition of PVDF to enhance η. Additionally, the voltage-assisted 3D printing process induces an entropy gain mechanism, facilitating the uniform distribution of the two phases and enhancing the interfacial properties for enhancing Eb. Remarkably, the study achieves prominent growth in energy storage performance, with Ue and η reaching 18.1 J/cm3 and 80 % at 525 MV/m, respectively. These remarkable results highlight the potential of 3D printing technology in enhancing the energy storage performance of PVDF-based dielectrics.

Achieving high energy storage density and efficiency in (Na0.5Bi0.5)TiO3-based lead-free ceramics

Due to the demands of miniaturization, weight reduction and green development for electronic devices, development of lead-free dielectric ceramic capacitors with high recoverable energy density (Wrec) and energy storage efficiency (η) attracts much attention. To this end, (1-x)[0.75(Na0.5Bi0.5)TiO3-0.25SrTiO3]-xNdNbO4 (abbreviated as: NBST-xNN) ceramics were fabricated through a solid-state reaction method. After adding NN, the non-perovskite phase of Bi2Ti2O7 (BTO) with low dielectric constant (εr) and loss (tan δ) is generated. Finite element software (COMSOL) was used to explore the influence of the BTO phase on breakdown strength (Eb). The simulation result indicates that the BTO phase with a low εr concentrates a larger local electric field (LEF), and thus weakens the LEF loading in the main perovskite phase, which is beneficial for enhancing Eb. Moreover, NN doping significantly decreases the oxygen vacancy concentration in NBST ceramics, which plays a key role in improving Eb. On the other hand, as NN content increases, the hysteresis of the polarization (P)-electric field (E) loops is substantially suppressed, and the polarization saturation is delayed, which can be ascribed to the appearance of the BTO phase having a linear dielectric characteristic and to the enhanced fluctuations of composition and charge by NN doping. Benefitting from the above factors, the optimal energy storage performance (ESP) with a Wrec of 4.14 J/cm3 and an η of 90 % is obtained in NBST-0.08NN ceramics. Meanwhile, the ESP of NBST-0.08NN ceramics shows good charge-discharge properties and thermal stability. In conclusion, these results demonstrate that NBST-0.08NN ceramics are promising candidates as environment-friendly dielectric capacitor materials.

Microencapsulated sodium nitrate with titanium-dioxide shell for high-temperature and high-density latent heat storage

In this study, a molten salt, i.e., sodium nitrate (NaNO3), that melts at 308 °C is microencapsulated with titanium dioxide (TiO2) shells via water-limited surfactant-free sol-gel processes for high-temperature and high-density thermal energy storage. The effects of the catalyst and precursor concentrations are examined to determine the optimal conditions for the two materials to achieve microcapsules with outstanding thermal performance and thermal reliability. The morphological characteristics of the core–shell structures of the microcapsule are investigated using scanning electron microscopy, whereas its chemical composition is analyzed using Fourier transform infrared spectroscopy to corroborate the synthesis of robust TiO2 shells. Calcination heat-treatment is performed at 300 °C to induce a transition from amorphous to anatase such that the shell robustness is enhanced and the thermal reliability of the NaNO3@TiO2 microcapsule is secured. The thermal performance of the NaNO3@TiO2 microcapsule is determined via differential scanning calorimetry between 220 and 360 °C. The encapsulation ratio is calculated to be 72.7–69.0 %. Finally, the thermal reliability of the NaNO3@TiO2 microcapsule is examined using DSC for 50 repeated heating and cooling cycles.

A Review on Energy Storage Technologies: Current Trends and Future Opportunities

Despite the fact that numerous energy storage technologies have already been reviewed in the scientific literature, these innovations are right now at various stages of technological development, with only a few having been demonstrated for use on a large scale. The majority of research articles on energy storage give detailed descriptions of these technologies, but there is little data on how these technologies compared when used for energy storage. This paper provides a comprehensive review on energy storage concepts and also compares the different energy storage technologies in terms of research trends and future opportunities. Among the reviewed energy storage technologies, the thermochemical energy storage (TCES) method stands as an attractive and potential alternative to the conventional heat storage methods like sensible and latent thermal energy storage (STES and LTES) for several reasons that include: high energy storage density, minimal heat losses between the system and surroundings, and long term heat storage.

Water adsorption on microporous chabazites as thermal energy storage materials

Thermochemical energy storage can reduce fossil fuel consumption, which is still dominant in heating of buildings. The efficiency of the sorption technology is determined by the performance of the adsorbent, which should have a high water adsorption capacity and, consequently, a high energy storage density, stability under humid conditions, and fast kinetics of adsorption and desorption. In this study we investigated the effect of different elemental compositions of the commercial and laboratory prepared microporous aluminophosphates, natural and synthetic zeolites with chabazite structure and their modifications in powder and granular form on water adsorption capacity. The highest water uptake among the aluminophosphates was found for APO-34-IL, which was prepared by green synthesis with the low cost ionic liquid, while the highest water uptake of all the samples analysed was found for the composites of the natural zeolite with CaCl2.

(Ag0.80Bi0.04Sr0.04)(Nb1-xTax)O3 ceramics with enhanced energy storage for high-temperature application via synergic optimization

Dielectric capacitors with high power density are essential components in advanced electronic and micro-electronic products. Nevertheless, the limited energy storage density and efficiency, coupled with poor performance at elevated temperatures, severely restrict their usefulness. In this work, Ta was introduced to the (Ag0.80Bi0.04Sr0.04)NbO3 ceramic prepared via the hydrothermal-synthesized powders to improve the room- and high-temperature energy storage performance. A large breakdown strength of 729kV/cm, a high recoverable energy storage density of 8.5J/cm3 and a benign energy efficiency of 75.6% were simultaneously achieved in (Ag0.80Bi0.04Sr0.04)(Nb0.85Ta0.15)O3 ceramics. Moreover, the larger energy storage efficiency (83.5%) at elevated temperatures than room temperature, the benign frequency and cycle stability foreshow great potential in realizing the application of capacitors at high-temperatures.

Research on matching supply of power and cold energy of liquid hydrogen cold chain logistics vehicles

Liquid hydrogen cold-chain logistics vehicle (LHCCLV) is a special vehicle using liquid hydrogen (LH2) as the source of both power and cold energy. A significant weakness of LH2 is its high energy consumption during the hydrogen liquefaction process, thus the utilization of cold energy in LHCCLV can improve the economic performance and competitiveness of LH2. Because of the high energy storage density of LH2 and the relatively high efficiency of fuel cells, we find that cold energy can not meet the demand of LHCCLV. Therefore, we consider enlarging the cold energy by efforts including the para-ortho hydrogen conversion (POC), whose reverse reaction consumes an energy level exceeding 20% during the hydrogen liquefaction process. In this paper, numerical models of discharging hydrogen from the LH2 and subcooling hydrogen tank are established, and the influence of POC and other efforts on the supply of cold energy is analyzed. The changes in instantaneous and total cold energy supply under different working conditions are analyzed, and the important influence of POC and other efforts is confirmed. The beneficial effect of POC is quantified in the paper, especially for the cold energy supply. This paper provides an essential reference for the research and development of LHCCLV. Also, it guides the comprehensive utilization of cold energy in other situations to promote the improvement of the economy of hydrogen energy utilization routes in the form of LH2.

High energy storage performance induced by the introduction of BiScO3 into (Bi0.5Na0.5)TiO3–BaTiO3 lead-free ferroelectric ceramics

In this work, ternary 0.25(Bi0.5Na0.5)TiO3-(0.75-x)BaTiO3-xBiScO3(abbreviated as 0.25BNT-(0.75-x)BT-xBS, x = 0.19, 0.21, 0.23, 0.25, 0.27) lead-free ferroelectric ceramics were synthesized using the solid-state reaction method. The introduction of BiScO3 into (Bi0.5Na0.5)TiO3–BaTiO3 ceramics had a significant impact on changing the phase structures, and microstructures, as well as the dielectric and ferroelectric properties. All ceramics exhibited a coexistence of tetragonal(P4bm) and rhombohedral(R3c) perovskite phases, while the influence of the BiScO3(BS) content on the average grain size was not significant. Slim polarization-electric field hysteresis loops were recorded for the 0.25BNT-(0.75-x)BT-xBS ceramics, with low remnant polarization (Pr) and large maximum polarization(Pmax). 0.25BNT-0.50BT-0.25BS ceramic had the largest Pmax, which induced a high energy storage density of 2.93 J/cm3 and energy storage efficiency of 91 % under a low electric field of 230 kV/cm 0.25BNT-0.50BT-0.25BS ceramic not only yielded excellent fatigue resistance, but also maintained good energy storage performance at high temperature and high frequency, which are considered of great importance since they can be leveraged for the potential development of high temperature and frequency capacitors. In addition, an excellent pulse performance was measured, with a high discharge energy density of 3.42 J/cm3 and a fast discharging rate t0.9 of 130 ns. This good pulse performance was maintained at high temperatures, suggesting that the proposed material is also highly competitive for applications where high-temperature pulse devices are required.

Achieving high energy-storage density and high temperature and frequency stability in 0.88BT-0.12BMT lead-free relaxor ferroelectric ceramics via NaNbO3 doping

In this work, 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3-xmol% NaNbO3 (x = 0, 0.5, 1, 1.5, 2) ceramics have been synthesized by using the traditional solid-state route. The effects of NaNbO3 on the phase structure, microstructure, dielectric, ferroelectric, and energy storage properties of the 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3 ceramics have been studied in detail. The ceramic doped with 1.5 mol% NaNbO3 exhibited a releasable energy storage density of 2.287 J/cm3, significantly higher than the undoped sample (1.194 J/cm3). The breakdown strength increases from 130 kV/cm for the undoped sample to 210 kV/cm for the sample doped with 1.5mol% NaNbO3. The enhanced breakdown strength of the 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3-xmol% NaNbO3 ceramics is primarily due to NaNbO3 doping, which produces a wider bandgap, smaller grain size, and higher specific resistance. The 0.88BaTiO3-0.12Bi(Mg1/2Ti1/2)O3-xmol% NaNbO3 ceramic's energy storage performance exhibits great temperature stability, frequency stability, and cycle stability at 120 kV/cm.

Hectorite aerogel stabilized NaCl solution as composite phase change materials for subzero cold energy storage

Inorganic phase change cold storage materials have garnered significant interest in cold chain transportation due to their high energy storage density. Nevertheless, practical applications have been hindered by inherent limitations such as high supercooling and susceptibility to phase separation. To address these challenges, this study devised 3D-Hectorite/sodium chloride (NaCl) composite phase change cold storage materials by utilizing 3D-Hectorite aerogel to adsorb NaCl solution, effectively mitigating the issue of phase separation common in such materials. Additionally, various concentrations of nucleating agents such as SrCl2·6H2O, borax, and diatomite were introduced for step cooling curve tests, establishing 0.03% diatomite as the optimal concentration for nucleation, reducing the supercooling of the NaCl solution to 1.1 °C. The results showed that the latent heat and thermal conductivity of 3D-Hectorite/NaCl were 215.30 J/g and 0.6315 ± 0.013 W/mK, respectively. The phase transition temperature could be adjusted in the range of -33~0 °C by changing the concentration of NaCl to meet the different temperature requirements. Furthermore, exceptional cyclic stability was observed even after subjecting the material to ten dissolution-solidification cycles. Analyzing the temperature change of the air inside the insulation bag showed that, compared with ice, 3D-Hectorite/NaCl can be applied to meet lower cooling temperature requirements, demonstrating good prospects for its application in cold chain transportation.

Achieving high energy storage performance in PbHfO3-based antiferroelectric ceramics by Sr element doping

Antiferroelectric (AFE) ceramics are the most promising material system for energy storage in dielectric capacitors due to their fast charging-discharging rate, good chemical stability, and high energy storage density. However, it is exceedingly challenging to simultaneously achieve the excellent recoverable energy density (Wre) and high energy storage efficiency (η) at present. In this work, (Pb0.925-xSrxLa0.05)(Hf0.95Ti0.05)O3 AFE ceramics with various Sr contents are fabricated by solid-state sintering processing. It has been found that Sr-doping in the A-site can significantly affect the microstructure, including reducing grain size and modulation period, effectively strengthening the antiferroelectricity, which is responsible for the improved energy storage performance. The high recoverable energy storage density of 10.2 J/cm3 is obtained at 560 kV/cm with an ultra-high efficiency of 93.0% in (Pb0.875Sr0.05La0.05)(Hf0.95Ti0.05)O3 ceramics. These features suggest that Sr-doped PbHfO3-based AFE ceramics can serve as promising candidates for capacitor materials, offering significant potential in the realm of energy storage applications.

High energy storage density in AgNbO3-based lead-free antiferroelectrics using A/B-site co-doping strategy

Lead-free antiferroelectric AgNbO3 ceramics have garnered extensive attention due to their rapid charge/discharge capabilities and environmentally friendly nature, holding immense potential for energy storage applications. However, the practical utilization of AgNbO3 has been hindered by its low energy storage density. This study employed an A/B-site co-doping strategy, which yielded positive effects on the energy performance of AgNbO3 ceramics. By modifying the A/B-sites with equivalent amounts of Bi3+ and Y3+ ions, enhanced maximum polarization, improved breakdown field, and slimmer hysteresis loops were simultaneously achieved, as the combined effects of refined grain size, wider optical bandgap, and randomly distributed antiferroelectric nanodomains, which were verified through the scanning electron microscope, transmission electron microscope, and ultraviolet–visible spectrum. As a consequence, a high energy storage density of 5.40 J/cm3 accompanied by an energy storage efficiency of 56.5% was achieved in the Ag0.97Bi0.01Nb0.994Y0.01O3 ceramic under a relatively low electric field of 190 kV/cm. This study underscores the effectiveness of A/B-site aliovalent co-doping as a viable strategy for developing high-performance ceramic capacitors for energy storage applications.

High energy density in Ag0.5Na0.5(Nb1-xTax)O3 antiferroelectric ceramics

There has been significant interest in AgNbO3-based antiferroelectric ceramics, recently, due to their ability to achieve high energy storage density (Wrec). However, fabricating their commercial products faces challenges due to chemically unstable and expensive Ag2O. To reduce Ag2O contents, we fabricated (Ag0.5Na0.5)(Nb1-xTax)O3 (ANNT100x) ceramics. The results reveal that Ta-substitution plays a dual role: inducing chemical pressure to compress the unit cell along spontaneous polarization direction, enhancing antiferroelectric stability; and increasing the band gap (Eg), boosting intrinsic breakdown strength (Eb). These crucial factors contribute to the enhanced Wrec achieved in ANNT50. Notably, ANNT50 ceramics fabricated by the rolling process exhibit higher Eb (=578 kV/cm) than the conventional process, favoring the complete triggering of “double” polarization with significantly enhanced Wrec (= 6.5 J/cm3). Discharge results indicate that the ceramic displays high power density (Pavg = 78 MW/cm3) and discharge energy (Wdis = 5.86 J/cm3), which can rival currently reported Ag(Nb, Ta)O3 ceramics.

Simultaneously enhanced of energy storage and energy harvesting performances of [(Bi0.5Na0.5)TiO3–BaTiO3] ceramics by addition of SrTiO3

As is well known, relaxor dielectrics are characterized by high energy storage efficiency (η), while high recoverable energy storage density (Wrec) can be achieved by anti-ferroelectric ceramics. Herein, our approach is to find relaxor- anti-ferroelectric coexistence phases of (Bi0.5Na0.5)TiO3- BaTiO3 ceramics for achieving high performance in energy storage and energy harvesting as well. Therefore, [(0.9-x) ( Bi0.5Na0.5)TiO3-xSrTiO3-0.1BaTiO3] (abbreviation (0.9-x) NBT-0.1BT-xST) (0.0 ≤ x ≤ 0.4) were synthesized via the solid-state reaction route in air. The tolerance factor (τ) increased from 0.9901 to 0.9998 when ST-content increased from 0.0 to 0.4, indicating an increase in crystal lattice symmetry. The FT-IR de-convolution vibration modes shown in the TiO6 octahedra exhibit two peaks at ∼550 and 650 cm−1, which indicate present coexistence phases of the crystal structure. Ferroelectric to relaxor phase crossover has been detected by the addition of ST with the present anti-ferroelectric phase in particular dopant ST = 0.2. The increasing into the diffused phase transition (γ) is signified by enhancement of the relaxor degree of NBT-BT at high content of ST. The rapidly suppressed remnant polarization (Pr) at high content of ST is due to substitute iso-valence (Sr2+) by tri-valence (Bi3+) and mono-valence (Na1+). Ultrahigh Wrec = 1.13 J/ cm3 with excellent η = 92.62% were obtained at ST = 0.3 at low electric field (E = 110 kV cm−1). A remarkable response of the strain with a high converse piezoelectric coefficient ( d33* = 390.47 pm V−1) at ST = 0.2 was obtained due to decreasing the non-revisable 180° domain switching. Based on the obtained results, the addition of ST to NBT-BT ceramics can provide a head start in the implementation of ceramic capacitors for potential effective into energy harvesting and energy storage applications.

Ultrahigh breakdown strength of NaNbO3‐based dielectric ceramics for high‐voltage capacitor application

AbstractDielectric ceramics have attracted significant attention in power electronic systems, owing to their exceptional charging and discharging speeds, as well as their high power density. However, simultaneously achieving a high recoverable energy density (Wrec) and high efficiency (η) in high‐voltage dielectric ceramics remains a challenge for applications where a high breakdown electric field (Eb) is required. In this study, high‐quality (1 – x)NaNbO3–xSr0.7Bi0.2(Mg1/3Nb2/3)O3 [(1 – x)NN–xSBMN] ceramics were prepared based on an optimization strategy combining phase structure with microstructural regulation. A quasilinear P–E loop with negligible hysteresis was realized in the ceramic with x = 0.4, excellent Wrec of 5.61 J/cm3, and high η of 85.1% obtained at a largely improved Eb of 710 kV/cm. To the best of our knowledge, the Eb of 710 kV/cm is one of the highest values achieved in dielectric ceramics to date. The noticeable reduction in grain size (∼0.95 µm) and increased bandgap improve the Eb to an ultra‐high level, which is a crucial factor in high energy storage density. The coexistence of a few antiferroelectric phases and the dominant paraelectric phase is the structural origin of the comprehensive energy‐storage performance improvement. Therefore, our research develops a unique approach to unleash the potential in NaNbO3‐based ceramics, holding great promise for application in high‐voltage dielectric capacitors.

Enhanced dielectric constant and concurrently suppressed dielectric loss of PVDF composites incorporating BaTiO3@SSCNT@SiO2 core@double-shell structured fillers

Dielectric capacitor is an important component of power systems, but its low dielectric polarization and undesirable dielectric loss have still held back the development of miniaturized microelectronic devices. Hence, we reported core@shell structured fillers with a conducting material@insulating material double-shell to improve the dielectric performance of the poly (vinylidene fluoride) (PVDF) composites. The hybrid fillers introducing ultra-short carbon nanotube (SSCNT) as an inner layer between BaTiO3 (BT) as a core and silica (SiO2) as an outer shell were synthesized. As the thickness of the insulating shell is enough thin, the BT@SSCNT@SiO2/PVDF composites exhibit an enhanced dielectric constant and a concurrently suppressed dielectric loss with the decreasing thickness. The composite incorporating the filler with the thinnest SiO2 shell has the highest dielectric constant of 12.27 and the lowest dielectric loss of 0.023 at 20 wt% filler loading where the breakdown strength is about 15 less than the maximum value of 192.5 kV/mm. Furthermore, the hybrid fillers endow the composites with impressively stable dependence on frequency in a wide range of 102∼105 Hz. The achievement can be ascribed to the conducting property of the SSCNT inner layer and the suitable thickness of the insulating outer layer. They can synergetically provide the composites with an optimized polarization effect at a broad frequency resulting from the improved electrical field. This work reveals that a proper structure of the core@conducting material@insulating material core@double-shell filler can be an approach to optimize the overall dielectric performance of the polymer-based composites with high energy storage density.