Maximum Energy Storage Density Research Articles

Influence of lanthanides (Ln = La, Nd, and Y) in [Ba0.95Ln0.05] [Zr0.25Ti0.75]O3 lead-free piezoelectric solid solutions

Influence of lanthanides (Ln = La, Nd, and Y) in [Ba0.95Ln0.05] [Zr0.25 Ti0.75]O3 ceramics, synthesized by high-temperature solid-state reaction technique. Investigation on the phase structure, ferroelectric, piezoelectric and energy storage performance of BZT-Ln ceramics was done. X-ray diffraction studies revealed that the specimen belongs to cubic phases with the space group of Pm3m. Maximum ferroelectric properties at room temperature were observed an electric field of 65 kV/cm. A maximum energy storage density of 1.03 J/cm3 was achieved at 65 kV/cm for BZT-Nd. The piezoelectric (d33) and piezoelectric voltage (g33) coefficients exhibited a maximum of 21 pC/N and 9.11 (mV.m/N) respectively when Nd3+ substituted with BZT. The dielectric properties of BZT-Nd showed maximum dielectric constant (εr) ∼2148 at 573 K. Thus, the obtained good electrical properties of the ceramics enhance its potential use in sensor and energy storage applications.

Enhanced energy storage properties of fine-crystalline Ba0.4Sr0.6TiO3 ceramics by coating powders with B2O3–Al2O3–SiO2

A core–shell mixing technique was utilized to modify the Ba0.4Sr0.6TiO3 (BST)particles in order to obtain the fine-crystalline Ba0.4Sr0.6TiO3 ceramics and improve ceramics energy storage capability. Coating layers of (9B2O3–13Al2O3–78SiO2, mol%) (BAS)were deposited onto Ba0.4Sr0.6TiO3 nanoparticles by a sol-precipitation method. The microstructures, phase composition and dielectric properties were investigated. And fine-crystalline BST ceramics with an average grain size below 150 nm by coating BAS has been prepared. The dielectric breakdown strength and energy storage density significantly improved due to the addition of BAS. The maximum energy storage density obtained from coating 3 wt% BAS was 1.8 J/cm3 at 410 kV/cm, which was higher than pure BST ceramics. Thus, the core-shell architecture is an effective strategy to improve the energy storage performance.

Reduced conductivity in sandwich-structured BFT@DA/PVDF flexible nanocomposites for high energy storage density in lower electric field

The Ba(Fe0.5Ta0.5)O3@DA/PVDF flexible composite films with sandwich-structured are prepared by solution-casting method. According to SEM image, the thickness of the composite film is about 15 μm and the each layer is about 5 μm. The sandwich-structured nanocomposite films not only have higher permittivity but also lower AC conductivity. The high permittivity is due to the large permittivity of BFT and the enhanced interface polarization between ceramic particles and polymer matrix. The low AC conductivity is due to the absence of conductive pathways in the PVDF layer. At low electric field strength of 150 MV/m, the energy density of sandwich-structure composite films filled with 1 vol% is 1.93 J/cm3. When the breakdown strength is 250 MV/m, the maximum energy storage density is increased to 4.87 J/cm3. The sandwich-structure Ba(Fe0.5Ta0.5)O3@DA/PVDF flexible composite films with outstanding energy storage properties in lower electric field can be used for wearable devices in the future.

Effect of SnO2 doping on electric field-induced antiferroelectric-to-ferroelectric phase transition of Pb(Yb1/2Nb1/2)0.98Sn0.02O3 ceramics

Pb(Yb1/2Nb1/2)0.98Sn0.02O3-xSnO2 (PYNS-xSn) antiferroelectric ceramics with high Curie temperatures (Tc), were prepared by the solid state reaction method. The double P-E hysteresis loops of PYNS-xSn ceramics (0.02 ≤ x ≤ 0.08) were observed at the temperatures higher than 180 °C, confirming its antiferroelectric nature. The electric fields (EAFE-FE) inducing the transition from antiferroelectric (AFE) phase to ferroelectric (FE) phase were decreased to be lower than the average dielectric breakdown strength (Eb) by SnO2 doping. The decrease of EAFE-FE can be attributed to the larger lattice constant ratio a/b and the lower B-site cation ordering. The energy storage performance is enhanced effectively with the decrease of EAFE-FE. The maximum energy storage efficiency (67.9%) and recoverable energy storage density (2.38 J/cm3) were obtained in PYNS-0.06Sn ceramics at the temperature of 180 °C. The results indicated that SnO2-doped PYNS antiferroelectric ceramics could be potential candidates for energy storage applications at elevated temperatures.

Effect of bismuth excess on the energy storage performance of 0.5Na0.5Bi0.5TiO3–0.5SrTiO3 ceramics

Lead free 0.5Na0.5Bi0.5TiO3–0.5SrTiO3 ceramics with Bi excess (NB0.5+xT-ST) were prepared by a conventional solid-state reaction method. The effects of bismuth excess on microstructure, dielectric properties and energy storage performances of NB0.5+xT-ST ceramics were investigated systematically. The results show that all ceramics exhibit a perovskite structure with excess Bi doping, the grain size decreased and density enhanced. Typical relaxor ferroelectric P-E hysteresis loops were observed with introduction of Bi2O3. The sample with Bi2O3 excess concentration of 1 mol% exhibits the maximum energy storage density 1.05 J cm−3, which is 2 times higher than that of pure NBT-ST. Meanwhile, the sample displays a high current density of 245.6 A cm−2 and a power density of 6.5 MW cm−3. These results indicate that the Bi2O3 excess improved NB0.5+xT-ST ceramics are useful for potential applications in energy storage ceramic capacitors.

Performance optimization of Mg-rich bismuth-magnesium-titanium thin films for energy storage applications

Due to advances in electronic device integration, miniaturization, and performance requirements, dielectric materials with a high energy storage density are required. Here, new BiMg0.5Ti0.5O3 lead-free energy storage thin films with excess Mg (i.e., nominal BiMgyTi0.5O3, with y = 0.50-0.62) were deposited on Pt/Ti/SiO2/Si substrates by sol-gel and spin-coating methods. The introduction of excess Mg can obviously increase the dielectric breakdown strength of thin films due to the appearance of an amorphous phase. The maximum recoverable energy storage density increased from 26 J/cm3 at y = 0.50 to 44.1 J/cm3 at y = 0.56. Furthermore, the dielectric films exhibited excellent thermal stability of the energy storage density from 30 °C to 100 °C, indicating that bismuth-magnesium-titanium films are promising candidates for next-generation lead-free energy storage capacitor applications.

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.

Temperature Dependence of Energy Storage Density and Differential Permittivity and Bandgap Study of Relaxor (Pb,La)Zr0.65Ti0.35O3

Pb(1-3x/2)LaxZr0.65Ti0.35O3 (x = 6, 7, 8 and 9%) show diffusivity values as 1.55, 1.72, 1.94 and 2.18, respectively. The differential permittivity strongly depends on temperature and electric field and get maximum value at certain temperature and fields. These temperatures and fields vary with La-content. The maximum energy storage density observed is 131.90 mJ/cm3 with an efficiency of 82.26% for 6% doped sample. With increasing La-doping it is found to decrease. For 9% doped sample, it is 92 mJ/cm3 with an efficiency of 65%. The bandgap changes from 3.37 eV (6% La) to 3.26 eV (9% La).

Enhanced dielectric and energy storage properties of BaTiO3 nanofiber/polyimide composites by controlling surface defects of BaTiO3 nanofibers

BaTiO3 (BT) nanofibers with different surface defects were prepared by electrospinning process through controlling the sintering atmospheres (Air, N2 and H2), and introduced into polyimide (PI) matrix to form composite films. The effects of different surface defects on dielectric and energy storage properties of PI composites were systematically investigated. The results showed that the fabricated composite films under a reducing (H2) atmosphere exhibited excellent dielectric properties, compared with that under Air and O2. The dielectric constant (εr) of PI composite films with 20 wt% BT-fibers reached up to 17.6, while maintaining lower loss (tgδ = 0.006@100 kHz), which was about four times greater than that of pure PI (εr = 4.1). When the content of BT-fiber was up to 15 wt%, the composite film exhibited a maximum energy storage density of Ue = 6.12 J/cm3. These results provide an effective method to tune the dielectric and energy storage properties of ferroelectric/polymer composites.

Enhanced magneto-electric coupling and energy storage analysis in Mn-modified lead free BiFeO3-BaTiO3 solid solutions

The present study pertains to magnetoelectric coupling and energy storage analysis of (1 − x)BiFe0.95Mn0.05O3-xBaTiO3 (BFMO-BT) with x = 0.1, 0.2, 0.3 lead free solid solutions. BFMO-BT solid solutions possessed a cubic structure as confirmed from powder XRD and the Rietveld refinement. A maximum ferroelectric polarization of 0.82 μC/cm2 was observed in BFMO-0.3BT. BFMO-0.3BT exhibited a maximum energy storage density (WU) of 1.97 J/cm3 and an energy conversion efficiency of 81.7%. Enhanced bulk magnetization was associated with the lattice defects; however, it decreased with increased BT content. For BFMO-0.3BT, temperature dependent susceptibility, dielectric measurement, and differential scanning calorimetry measurement revealed the magnetic transition temperature to be 275 °C, 293 °C, and 223 °C, respectively. The linear magnetoelectric coupling coefficient was measured by quantifying change in maximum polarization with respect to the applied magnetic field and was found to be 28.55 mV cm−1 Oe for BFMO-0.3BT. Conductivity measurements of BFMO-0.3BT revealed a maximum value of activation energy, i.e., 0.21 eV at 1 kHz.

A novel lead-free NaNbO3–Bi(Zn0.5Ti0.5)O3 ceramics system for energy storage application with excellent stability

Many researches have been referred to the AFE structure of NaNbO3 in order to develop high power energy storage for NaNbO3-based ceramic. However, the square P-E loops with large Pr was observed in NaNbO3 ceramics due to the coexistence of AFE and the field-induced metastable FE, which suppress the energy storage property of NaNbO3-based ceramics. In the present work, lead-free (1-x)NaNbO3-xBi(Zn0.5Ti0.5)O3 (abbreviated as (1-x)NN-xBZT) dielectric ceramics were prepared via the traditional solid-state route. The structures, relaxor behavior and energy storage property of (1-x)NN-xBZT ceramics were investigated with the introduction of BZT. The slim P-E loops were obtained while x = 0.09–0.12 and the maximum discharge energy storage density (Wrec = 2.1 J/cm3) was obtained while x = 0.09, meanwhile a high energy storage efficiency (η = 76%) was achieved. Moreover, the charge-discharge tests show that 0.91NN-0.09BZT ceramics can achieve fast discharge rate (50 ns) and exhibit excellent stabilities of temperature and electric field, which guarantee the application prospect of 0.91NN-0.09BZT ceramics for lead-free plus power system in a wide temperature range.

Synthesis and properties of modified polyimide/polyvinylidene fluoride composite films with excellent dielectric properties by adding coupling agent

Modified polyimide (PI)/polyvinylidene fluoride (PVDF) composite films were synthesized by introducing the coupling agent (KH570). Results indicated that the modified composites exhibited high tensile strength, high tensile modulus and excellent thermal properties when the KH570 content increased. The dielectric constant slightly decreased to 4.82 with an increasing amount of KH570, but it was still not low. Noticeably, the dielectric loss of the composite films was small (<0.01, 1 kHz). The breakdown strength significantly increased to 169.65 kV mm−1 when 3 wt% KH570 was added, which was about 173% greater than that of unmodified composites. In addition, the largest value of the maximum energy storage density for the modified composites was 0.651 J cm−3, which was about 6.7 times higher than that of unmodified composites.

Dielectric and energy storage density studies in electrospun fiber mats of polyvinylidene fluoride (PVDF)/zinc ferrite (ZnFe2O4) multiferroic composite

Flexible free standing electrospun poly (vinylidene fluoride)/ZnFe2O4 composite fiber mats were synthesized through electrospinning technique. Structural and morphological studies of PVDF/ZnFe2O4 composite fibers were examined by X-ray diffraction and scanning electron microscopy. The functional groups and the percentage of β phase were analysed using FTIR studies. 92% beta phase was achieved with the incorporation of ZnFe2O4 filler. The enhancement in dielectric and ferroelectric properties of the composite fiber mats were observed with a maximum dielectric constant and polarization values of 15 and 0.72 μC/cm2 respectively for 20 wt% filler loading. The domain switching behaviour of the mats were analysed using DC-EFM. Vibration sample magnetometry results revealed the antiferromagnetic nature of the composite fiber mats with a maximum magnetization of 0.18 emu/cm3. Further, the energy storage density of the mats was studied and a maximum energy storage density of 239 mJ/cm3 was obtained which was 1.4 times than that of pure PVDF mat.

Significantly enhanced dielectric and energy storage properties of plate-like BN@BaTiO3 composite nanofibers filled polyimide films

In this study, a new type of plate-like boron nitride (BN) and barium titanate (BT) composite nanofiber (BN@BT) was fabricated by an electrospinning technology, and introduced into polyimide (PI) matrix to form nano-composite films by in-situ polymerization method. The composite film with 20 wt% BN@BT-fiber shows a high dielectric constant of εr = 47.57 and a low dielectric loss of tgδ = 0.0334 at room temperature. When the content of BN@BT-fiber is up to 1 wt%, the composite film exhibits a maximum energy storage density of Ue = 7.1 J/cm3 at 3438 kV/cm, which is about three times greater than that of PI (≈2.4 J/cm3 at 3628 kV/cm). Meanwhile, the plate-like boron nitride (BN) also enables the composite film to have an improved heat dissipation and thermal stability, and then improves the breakdown field strength.

Influence of SnO2 additive on the energy storage properties of Ba0.65(Bi0.5Na0.5)0.35TiO3-SrY0.5Nb0.5O3 relaxor ferroelectrics

In this paper, SnO2 was introduced to prepare 0.92Ba0.65(Bi0.5Na0.5)0.35TiO3-0.08SrY0.5Nb0.5O3: SnO2 ceramics by the traditional solid-state sintering method. And the effects of SnO2 on phase composition, microstructure, dielectric behavior, ferroelectric behavior and energy storage performance for samples have been systematically investigated. All the as-prepared ceramics possess an obvious relaxor behavior. The introduction of SnO2 significantly enhances the breakdown strength for ceramics from 152 to 320 kV/cm, which is beneficial to the energy storage properties. Meanwhile, the maximum recoverable energy storage density of 2.94 J/cm3 is obtained under 302 kV/cm with a high energy storage efficiency of 88.9%. Besides, the energy storage properties show a good frequency stability (1-400 Hz). All the above results suggest that the ceramics have a good application foreground in the energy storage field.

Ultrahigh Energy Storage Density and Excellent Charge–Discharge Properties of Bi2O3-Nb2O5-SiO2-Al2O3 Glass Ceramic with CeO2 Doping

Bi2O3-Nb2O5-SiO2-Al2O3 glass–ceramic composites with different levels of CeO2 doping have been fabricated by controlled crystallization from a homogeneous glass matrix. The influence of the CeO2 doping level on the crystal phase, breakdown strength, microstructure, and energy storage performance was investigated. The results showed that the microstructure was clearly improved by CeO2 doping. A maximum theoretical energy storage density (J) of 20.9 J/cm3 was achieved in samples with 0.2 mol.% CeO2 doping, being clearly improved compared with samples without such addition (14.2 J/cm3). Also, the discharge time was found to be as short as 20 ns and the maximum power density exceeded 80 MW/cm3 under an electric field of 300 kV/cm. These results suggest that CeO2-doped Bi2O3-Nb2O5-SiO2-Al2O3 glass–ceramic composites are promising energy storage materials for use in pulsed-power systems.

Summary of gas turbine power generation technology based on solar power

With the increasing pressure of energy shortage and the environment pollution, it’s important to take the advantage of the renewable clean energy for newpower generation technology. Solar energy, as a kind of energy with a wide range of sources, has become a new type of clean energy with the most potential for development. This study introduces the project test and progress of solar gas turbine combined generation technology at home and abroad as well as the research status of key technologies. The key technologies of heat collection, heat storage and heat recovery are analyzed and summarized, it has been pointed out that the concentrator ratio achieved by the dish and tower is more than an order of magnitude higher than that of the linear Fresnel and slot; Thermochemical heat storage technology has the theoretical maximum energy storage density, the heat storage of chemical bonds is about 5 times of latent heat, 10 times of sensible heat, and has the advantages of stable chemical bonds, small energy loss and other advantages, energy storage in the future has more development advantages. At the same time, the future research direction of solar thermal power generation technology is prospected.

Enhanced dielectric performance and energy storage of PVDF‐HFP‐based composites induced by surface charged Al2O3

ABSTRACTIn order to enhance dielectric properties and energy storage density of poly(vinylidene fluoride‐hexafluoro propylene) (PVDF‐HFP), surface charged gas‐phase Al2O3 nanoparticles (GP‐Al2O3, with positive surface charges, ε’ ≈ 10) are selected as fillers to fabricate PVDF‐HFP‐based composites via simple physical blending and hot‐molding techniques. The results show that GP‐Al2O3 are dispersed homogeneously in the PVDF‐HFP matrix and the existence of nanoscale interface layer (matrix‐filler) is investigated by SAXS. The dielectric constant of the composites filled with 10 wt % GP‐Al2O3 is 100.5 at 1 Hz, which is 5.6 times higher than that of pure PVDF‐HFP. The maximum energy storage density of the composite is 4.06 J cm−3 at an electrical field of 900 kV mm−1 with GP‐Al2O3 content of 1 wt %. Experimental results show that GP‐Al2O3 could induce uniform fillers’ distribution and increase the concentration of electroactive β‐phase as well as enhance interfacial polarization in the matrix, which resulted in enhancements of dielectric constant and energy storage density of the PVDF‐HFP composites. This work demonstrates that surface charged inorganic‐oxide nanoparticles exhibit promising potential in fabricating ferroelectric polymer composites with relatively high dielectric constant and energy storage. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 574–583

Polymer-derived SiCN ceramics as fillers for polymer composites with high dielectric constants

High-dielectric-constant (high-e) ceramic/polymer composites are an important class of advanced functional materials due to their applications in energy storage fields, such as embedded capacitors. Here, we synthesized novel polymer-derived silicon carbonitride (SiCN)-filled polyvinylidene fluoride (PVDF) composites by the tape-casting method. For comparison, commercial BaTiO3-filled PVDF composites were synthesized following the same process. The SiCN/PVDF composites showed much higher e than the BaTiO3/PVDF composites over a broad frequency range (10−1–106 Hz). Furthermore, the SiCN/PVDF composites showed ultrahigh e at low frequencies. The e of the 40 vol% SiCN/PVDF composite was as high as 2600 at 10−1 Hz. Although the dielectric breakdown strengths of the SiCN/PVDF composites were slightly lower than those of the BT/PVDF composites, the calculated maximum energy storage density of the 40 vol% SiCN/PVDF composites (17.5 J cm−3) was much higher than that of 40 vol% BT/PVDF (0.773 J cm−3) at 10−1 Hz. This is the first report on the use of polymer-derived ceramics as a component of ceramic/polymer composites. The results indicate that the polymer-derived SiCN ceramics can serve as promising ceramic fillers for high-e composites and that the obtained SiCN-filled composites have promising applications in energy storage fields.

Improved energy storage performance of Ba0.4Sr0.6TiO3 nanocrystalline ceramics prepared by using oxalate co-precipitation and spark plasma sintering

The oxalate co-precipitation method was employed to synthesize nanocrystalline Ba0.4Sr0.6TiO3 having an average particle size of 100 nm. The conventional sintering (CS) and spark plasma sintering (SPS) methods were used to fabricate Ba0.4Sr0.6TiO3 ceramics with different microstructures. The SPS sample presented uniformly dense microstructure and ultrafine grains, while abnormal grain growth and some pores were discerned in the CS sample. The differences in microstructure significantly affected the dielectric properties and energy storage performance of the ceramics. The dielectric constant of the SPS sample was high (εʹ ˜1200), its dielectric loss was low (tanδ ˜0.003), and the sample presented diffuse phase transition and high breakdown strength (Eb = 260 kV/cm) at room temperature. Compared with the CS sample, the maximum energy storage density and energy storage efficiency of the SPS sample were increased from 0.61 to 1.20 J/cm3 and 72.6% to 91.6%, respectively. All results revealed that SPS is a powerful technique to produce dense ceramics with high energy storage performance.