Large Energy Storage Density Research Articles

Energy storage performance of Na0.5Bi0.5TiO3-SrTiO3 lead-free relaxors modified by AgNb0.85Ta0.15O3

Exploring eco-friendly energy-storage ceramics simultaneously featuring large recoverable energy storage density (Wrec), high energy storage efficiency (ƞ), and excellent temperature/frequency stabilities is highly desirable for the applications of pulsed power systems. Herein, AgNb0.85Ta0.15O3 was used to modify Na0.5Bi0.5TiO3 based lead-free relaxor ferroelectric ceramics in an effort to enhance the breakdown electric field strength. The ceramics (1-x)(0.75Na0.5Bi0.5TiO3-0.25SrTiO3)-xAg(Nb0.85Ta0.15)O3 (x = 0, 0.05, 0.1, and 0.15) were prepared by the conventional solid-state reaction method. The microstructure, dielectric, and energy storage properties of all the ceramics have been systematically studied. Our results show that the introduction of AgNb0.85Ta0.15O3 leads to a homogeneous microstructure and small grain size, thereby increasing the strength of the dielectric breakdown field (29 kV/mm). In addition, it can also decompose the macroscopic long-range ferroelectric order into randomly-oriented polar nano-regions (PNRS), resulting in a board diffusive phase. A large Wrec (3.6 J/cm3) and high ƞ (80%) as well as excellent temperature and frequency stabilities were simultaneously achieved in the sample with x = 0.1. This work provides a feasible method for designing lead-free ceramics with high energy storage performances.

Novel NaNbO3–Sr0.7Bi0·2TiO3 lead-free dielectric ceramics with excellent energy storage properties

NaNbO3 (NN) is considered to be one of the most prospective lead-free antiferroelectric energy storage materials due to the merits of low cost, nontoxicity, and low density. Nevertheless, the electric field-induced ferroelectric phase remains dominant after the removal of the electric field, resulting in large residual polarization, which prevents NN ceramics from obtaining superior energy storage performance. In this work, the relaxor ferroelectric Sr0·7Bi0·2TiO3 (SBT) was chosen to partially replace the NN ceramics, and the introduction of the nanodomain of the relaxor ferroelectric hinders the generation of field-induced ferroelectric phases, allowing the material to combine the large polarization strength of the relaxor ferroelectric with the near-zero residual polarization of the antiferroelectric. Large recoverable energy storage density (4.5 J cm−3) and ultra-high energy storage efficiency (90.3%) were gained in NN-20SBT under an electric field of 288 kV cm−1. Furthermore, superior temperature (25–120 °C) and frequency (1–500 Hz) stabilities were acquired. These performances demonstrate that NN-20SBT ceramics are potential candidates as dielectric materials for high energy storage density pulsed power capacitors.

Giant energy storage density in lead-free dielectric thin films deposited on Si wafers with an artificial dead-layer

High-performance lead-free thin-film capacitors deposited on the silicon (Si) wafers with large energy storage density ( W ) and high reliability are strongly attractive in the modern electrical and electronic devices. Here, an ultrahigh W was achieved in the Ba 0.3 Sr 0.7 Zr 0.18 Ti 0.82 O 3 (BSZT) relaxor ferroelectric thin films deposited on the Si wafers with the help of an ultrathin Ca 0.2 Zr 0.8 O 1.8 (CSZ) artificial “dead-layer” simultaneously possessing high resistivity, wide band gap and high permittivity among linear dielectrics. As the CSZ was implanted, the W of the Ba 0.3 Sr 0.7 Zr 0.18 Ti 0.82 O 3 (BSZT) thin films was greatly increased from 64.9 J/cm 3 to 89.4 J/cm 3 , which is comparable to the best W of thin film deposited on expensive single crystal substrates, and is the largest one reported so far than those of lead-free thin films deposited on the Si wafers, and even for lead thin films. Due to the formation of ultrahigh electrons injection barrier (3.92 eV) between the interface of the CSZ dead layer and the Au top electrode, the Schottky emission of the BSZT thin films under high electric field and at high temperatures was effective suppressed, which is responsible for the greatly improved dielectric breakdown strength and thermal stability. Moreover, the fatigue endurance was also enhanced. It is concluded that the implantation of the CSZ artificial dead-layer could be used as a universal-simple-effective strategy to improve the electrical performances of ferroelectric materials working in the harsh environment of high electric field. With the help of an ultrathin Ca 0.2 Zr 0.8 O 1.8 artificial “dead-layer”, the energy storage properties of the BSZT thin films was greatly improved. The implantation of the new artificial dead-layer could be used as a universal-simple-effective strategy to improve the electrical performances of ferroelectric materials working in the high electric field. • High quality lead-free thin films deposited on Si wafers were obtained. • An ultrahigh energy storage density ( W ) on Si wafers ~ 89 J/cm 3 was achieved. • Artificial Dead-layer implantation benefits the enhancement of W and DBS. • Artificial Dead-layer implantation benefits the improvement of thermal stability and fatigue endurance. • High electrons injection barrier can suppress Schottky Emission.

High energy storage density and efficiency with excellent temperature and frequency stabilities under low operating field achieved in Ag0.91Sm0.03NbO3-modified Na0.5Bi0.5TiO3-BaTiO3 ceramics

Ag0.91Sm0.03NbO3-modified Na0.5Bi0.5TiO3–BaTiO3 ceramics (0.94−x)Na0.5Bi0.5TiO3–0.06BaTiO3–x(Ag0.91Sm0.03)NbO3 (x = 0, 0.03, 0.06, and 0.09) were prepared by solid-state reaction method. The structural, dielectric, and energy storage properties of the ceramics were systematically studied. Our results indicate that all ceramics exhibit pure perovskite structure with dense microstructure. All the elements in the ceramic are homogeneously distributed. The sample with the doping level x = 0.09, possesses good temperature stability of the dielectric constant (Δe′/e′150 °C ≤ ± 15%) and low dielectric loss (< 0.02) over a wide temperature of 84–318 °C. A large energy storage density value of Wrec = 2.12 J/cm3, high efficiency of ƞ = 83% under a low electric field of 18 kV/mm, as well as excellent temperature/frequency stabilities were simultaneously achieved in the sample. This work provides a viable way to design high energy storage performance lead-free ceramics operating at low fields.

Low-Cost High Energy Density Material for Solar Thermal Heat Storage

A low-cost and enhanced thermal properties composite material for sensible heat storage in solar thermal energy storage applications is introduced. The proposed material is produced primarily for small scale solar thermal applications. However, it can be utilized for large scale solar thermal plants. The material has the advantages of high thermal conductivity and large energy storage density. The introduced material is composed of a mixture of cement and cast-iron particles. To obtain an optimal mixture, different samples of the material are prepared with different ratios of the cement-iron weights. The thermal conductivity of the produced samples is measured by using the linear heat conduction method. The specific heat capacity of the produced mixtures is calculated by using the Rule of the mixture. The obtained results show that the introduced material has a significant enhancement in thermal conductivity. Where, thermal conductivity as high as ~6.0 W/m.K and energy storage density as high as ~788 Joule/cm3 are achieved. The estimated volume energy density is ~89% higher than that of water. The produced material has the advantage of high energy volume density, being unhazardous, chemically stable, eco-friendly, easy to fabricate, and integrate with solar thermal energy systems and is a low-cost material.

Top-seeded solution growth and investigation of electrical and energy storage performance of pure and doped (1−x)Na0.5Bi0.5TiO3–xBaTiO3 ferroelectric single crystals

Urgent requirement exists to develop the lead-free piezoelectric energy storage devices, sensors and actuators for the reduction of toxicity in the environment. This paper deals with the lead-free ferroelectric single crystals with excellent piezoelectric behaviour. A series of pure and doped (Mn and Nb) (1−x)Na0.5Bi0.5TiO3–xBaTiO3 (NBBT) bulk size single crystals was successfully grown by the top-seeded solution growth (TSSG) method. The crystal growth, phase confirmation, compositional analysis, electric properties and energy storage density were investigated. The NBBT crystal belongs to perovskite structure and is confirmed using X-ray Powder diffraction pattern (PXRD). The elemental composition of the NBBT crystals grown by TSSG was investigated by the Inductively coupled plasma-Atomic Emission spectroscopy (ICP-AES). The electrical properties like dielectric constant (er = 674, 700, 837, 694, 2872 and 378) and dielectric loss (tanδ = 0.2, 0.6, 0.5, 0.7, 0.47 and 0.27) were measured and it was found to be relaxor-type behaviour due to diffuseness of NBBT crystals by the dielectric permittivity. The piezoelectric coefficients (d33 = 374, 290, 167, 110, 410 and 103) and piezoelectric voltage coefficients (g33 = 6.26, 4.6, 2.2, 1.79, 1.6 and 3.0) were obtained. Greater value of remnant polarization (Pr = 87, 46, 30, 0.30, 117 and 0.11), maximum polarization (Pm = 104, 55, 49, 1.08, 136 and 0.34) and lower value of coercive electric field (Ec = 16.5, 13.8, 26, 0.64, 20 and 233) were obtained from the P–E hysteresis loop of NBBT crystals studied to identify good performance of the compositions. The NBBT 90/10 crystal was found to be of 94/06 composition as obtained from ICP-AES. Moreover, NBBT 90/10 was doped by Mn and Nb and its electrical properties were measured. The Mn-doped NBBT 90/10 crystal attained a large energy storage density (W) of 0.27 Jcm−3 at ~ 20 kV cm−1 compared to the undoped and Nb-doped NBBT 90/10 crystal.

Tailoring high energy density with superior stability under low electric field in novel (Bi0.5Na0.5)TiO3-based relaxor ferroelectric ceramics

Large energy storage density in relaxor ferroelectrics is commonly accompanied with high breakdown strength, which is adverse to the actual dielectric capacitor applications. We demonstrate that such drawback can be effectively resolved by using Sr0.7Bi0.2TiO3 (SBT) to partially replace relaxor ferroelectric 0.76(Bi0.5Na0.5)TiO3-0.24NaNbO3 (BNT-NN-xSBT). In this study, a high recoverable energy storage density (Wrec∼3.12 J/cm3) and favorable efficiency (η∼75.3 %) are achieved in the BNT-NN-0.1SBT ceramic under a low electric field of 200 kV/cm, which is superior to that of most previously reported dielectric ceramics under the same electric field level. Good temperature stability (25−120 °C), moderate frequency dependence (1−500 Hz), and excellent fatigue resistance (up to 105 cycles) are also realized. More interestingly, the indicated ceramics perform high power density (PD∼36.40 MW/cm3) and fast discharge time (t0.9∼0.149 μs) with remarkable temperature endurance. Moreover, of particular significance is that this study offers a feasible guideline to design comprehensive energy storage performance dielectric ceramics for practical applications.

Numerical simulation of forced bending deformation of temperature-controlled materials based on differential equation model

This paper established the temperature differential model of temperature-controlled materials, performed the numerical simulation of the relationship between mechanical properties and temperature of temperature-controlled materials, and discussed the stress-strain relationship of temperature-controlled materials at different temperatures. The final stimulation experiment showed that temperature-controlled materials have the advantages of large energy storage density, approximately constant temperature and compact structure during phase change. The results of this paper provide a certain reference for the further researches on the numerical simulation of forced bending deformation of temperature-controlled materials based on the differential equation model.

Polymer nanocomposite with enhanced energy storage capacity by introducing hierarchically-designed 1-dimension hybrid nanofiller

Polymer-based nanocomposite with high-dielectric-constant nanofillers has attracted lots of attention in dielectric material for energy storage as film capacitor. However, it is still challenging that the addition of state-of-the-art fillers always leads to electric field distortion and high leakage current resulted from poor insulation and breakdown strength of these fillers. In this study, to address this issue, a novel hybrid nanofiber with hierarchical structure was elaborately designed, which exhibits superior inherent dielectric property than conventional high-dielectric-constant fillers. The hierarchical hybrid nanofiber was fabricated by embedding boron nitride nanosheet (BNNS) into grain boundary interspace of barium titanate nanofiber to strengthen nanofiller straightforward, based on the bold conjecture that BNNS acted as solid barrier for electrical tree propagation and leakage current conduction inside nanofiller. Using hybrid nanofiber as filler, resulting nanocomposite exhibited simultaneously enhanced dielectric constant and breakdown strength and a much larger energy storage density (Ue ≈ 15.25 J cm−3) than conventional nanofiller-incorporated composite, which was 3.07 times of pristine matrix. The hierarchically designed hybrid nanofiber guaranteed good insulation and strong polarization of high-dielectric-constant nanofiller simultaneously and this work provides a novel and effective approach to improve the dielectric performance of composite dielectric.

Manipulating leakage behavior via thickness in epitaxial BaZr0.35Ti0.65O3 thin film capacitors

High quality, epitaxial Ba(Zr0.35Ti0.65)O3 thin films were fabricated via radio frequency magnetron sputtering technique. The leakage current density vs electric field (J–E) tests were conducted using the device structures with Pt top electrodes and Nb-doped SrTiO3 bottom electrodes. The conduction mechanism of the films and the J–E characteristic that changed from the asymmetric structure to the relative symmetric structure were investigated. Analysis of the thin film leakage behavior suggests that, at low electric field, the conduction mechanisms are mainly bulk-limited Ohmic and space-charge-limited current. When the electric field is higher, the interface-limited Schottky emission and the Fowler–Nordheim (FN) tunneling as the dominant conduction mechanism occur for the films with a thickness below 166 nm and only FN tunneling for the films with the thickness of 300 and 400 nm. In addition, the asymmetric structure is strongly dependent on the large relative value of the Schottky barrier height between the positive and negative biases. Moreover, increasing the electric field range used to generate the bulk-limited conduction behavior and decreasing the current density induced by the interface-limited conduction through increasing the film thickness are beneficial for the films to obtain a high breakdown strength and a large energy storage density, as well as excellent efficiency.

Ti3C2Tx@PDA-Integrated Polyurethane Phase Change Composites with Superior Solar-Thermal Conversion Efficiency and Improved Thermal Conductivity

Organic phase change materials (PCMs) have attracted increasing attention in the solar energy utilization field for their large thermal energy storage density, appropriate phase transition temperat...

Enhanced energy storage performance in bismuth layer-structured BaBi2Me2O9 (Me = Nb and Ta) relaxor ferroelectric ceramics

Bismuth layer-structured BaBi2Nb2O9 (BBN) and BaBi2Ta2O9 (BBT) relaxor ferroelectric ceramics were explored as potential energy storage materials. Remarkable energy storage performances were obtained in both BBN and BBT ceramics, featured by large recoverable energy storage density (~0.84 J/cm3 and ~0.68 J/cm3) and high energy storage efficiency (~90% and ~94%), respectively. Furthermore, both the two ceramics exhibit good thermal and frequency stabilities. Delightedly, both the BBN and BBT ceramics can complete the discharge process within 0.15 μs, resulting in ultrahigh current density of 195 A/cm2 and 234 A/cm2 and excellent power density of 10.74 MW/cm3 and 12.89 MW/cm3, respectively. The obtained results suggest that BaBi2Nb2O9 and BaBi2Ta2O9 ceramics could have a promising future in energy storage applications. This study also demonstrates that the bismuth layer-structured relaxor ferroelectric ceramic can be considered as a novel potential lead-free energy storage materials, in addition to the widely studied pervoskite-structured relaxor ferroelectric ceramics.

Electricity-assisted thermochemical sorption system for seasonal solar energy storage

The present paper investigated the seasonal solar thermal energy storage (SSTES) using solid-gas thermochemical sorption technology that has inherently combined function of heat pump and energy storage. The thermochemical reactions that can discharge heat at a higher temperature usually requires a relatively higher desorption temperature during charging process, which could be problematic to efficiently recover solar energy in high-latitude regions like the UK when using the most mature and economic solar thermal collector (flat-plate or evacuated tube type). The present work studied two hybrid concepts where an electric-driven compressor or an electric heater was introduced to supplement the thermochemical desorption process in terms of pressure rise and temperature lift, respectively, when the available solar heat was not sufficiently high. The SrCl2-8/1NH3 chemisorption was selected from 230 ammonia-chemisorption reactions due to its suitable adsorption/desorption temperature and large energy storage density. The performance of two hybrid systems using SrCl2-8/1NH3 chemisorption were evaluated and compared to determine the optimal solution. The results revealed that the hybrid thermochemical sorption with a compressor substantially improved the storage capacity compared to that with electric heater. With a compression ratio of 4, the SSTES system with 20 m2 solar collector under the weather condition of Newcastle upon Tyne can store 3226.8 kWh chemisorption heat in summer by charging 4465.4 kWh solar heat and 848.2 kWh electricity, indicating 60.7% storage efficiency; the corresponding energy density based on the overall system volume is 147.3 kWh/m3. Because of using the renewable solar heat and low carbon intensity electricity in summer, the proposed hybrid SSTES system has noteworthy reduction on carbon emission compared to gas boiler and conventional heat pump.

Large energy storage density in BiFeO3-BaTiO3-AgNbO3 lead-free relaxor ceramics

Lead-free (0.70-x)BiFeO3-0.30BaTiO3-xAgNbO3+5‰mol CuO (abbreviated as BF-BT-xAN) ceramics were fabricated using a modified thermal quenching technique. BF-BT-xAN ceramics are of a perovskite structure with morphotropic phase boundary (MPB) and show strong relaxor properties. Remarkably, the high recoverable energy storage density of 2.11 J/cm3 is obtained for BF-BT-xAN with x = 0.14. For the x = 0.14 ceramics, its energy storage efficiency is as high as 84 % at relative low field of 195 kV/cm, together with an outstanding thermal stability in a broad temperature range from 25 °C to 150 °C. In addition, this ceramic maintains superior energy storage performance even after 8 × 104 electrical cycles due to its high densification after doping Ag2O and Nb2O5. The result suggests that lead-free BF-BT-xAN ceramics may be promising candidate for dielectric energy storage application.

Performance comparison of two eutectic solder based latent heat storage systems during discharging

Latent heat storage systems consisting of phase change materials (PCMs) offer the advantage of a large thermal energy storage density as compared to sensible heat storage systems. Most recent work has focussed on organic and inorganic PCMs which have problems of subcooling and phase segregation. Metallic PCMs are a recent innovation for medium to high temperature applications due to their high thermal conductivities, high volumetric storage capacities and their low degrees of sub-cooling during the release of latent heat. For medium temperature applications like cooking of food, very limited work has been done on metallic PCMs for energy storage. Solder based PCMs have rarely been investigated for medium temperature applications thus it is necessary to carry out an experimental study on the use of a solder as PCM candidate. No work has ever been reported using the eutectic solder (Sn63/Pb37) as a PCM. Its use is justified since it is low cost and locally manufactured solder worldwide. Another recent innovation is cascaded thermal energy storage (TES), whereby two PCMs with different melting temperatures are used in a single storage tank to improve the efficiency of energy storage. No work has also appeared in recent literature involving metallic solders in cascaded systems. In a bid to investigate the suitability of the eutectic solder as a PCM for medium temperature applications, two eutectic solder (Sn63/Pb37) based systems are experimentally evaluated during discharging cycles. The first system is a single PCM system composed of a packed bed of spherically encapsulated eutectic solder capsules. The other system is a two PCM cascaded system comprising of eutectic solder spherical capsules at the top and erythritol spherical capsules at the bottom in a storage ratio of 50 %: 50 %. Discharging experiments are carried with three different discharging flow-rates to investigate the effect of the flow-rate on the thermal performance. The three discharging flow-rates used are 4 ml/s, 6 ml/s and 8 ml/s. For both storage systems, an increase in the discharging flow-rate increases the peak discharging energy and exergy rates. For both storage systems, an increase in the discharging flow-rate increases the peak discharging energy and exergy rates. The single PCM system shows higher energy and exergy rates for most of the discharging duration compared to the cascaded system. An increase in the flow-rate increases the peak energy and exergy discharging rates for the single PCM and the cascaded PCM storage systems. The single PCM system out-performed the cascaded system during the discharging tests possibly due to the lower melting temperature and lower thermal conductivity of the bottom PCM (erythritol) in the cascaded system. However, for the higher flow-rates (6 ml/s, 8 ml/s), the cascaded system shows a slightly better or comparable performance at the start and at end of discharging.

Achieving high-energy storage performance in 0.67Bi1-xSmxFeO3-0.33BaTiO3 lead-free relaxor ferroelectric ceramics

BiFeO3–BaTiO3 (BF-BT)-based lead-free ferroelectric ceramic has attracted immense interest in energy storage applications due to its great spontaneous polarization (Pmax) strength. However, high remanent polarization (Pr) has become a serious obstruction for its practical application. In this work, Sm ions were doped into 0.67BiFeO3-0.33BaTiO3 (0.67Bi1-xSmxFeO3-0.33BaTiO3, BSxF-BT) to tailor the structure and energy storage properties. It was found that the doping of Sm ions effectively reduced Pr by enhancing the relaxor behavior of BF-BT ceramic, which produce an enhancement in the energy storage performance. Large recoverable energy storage density Wrec of 2.8 J/cm3 with moderate energy storage efficiency η of 55.8% (200 kV/cm) were achieved in the ceramics with x = 0.1. Moreover, the energy storage capabilities exhibited good stability at temperature (20–95 °C) and frequency (0.1–50 Hz). Furthermore, the ceramic also possessed a predominant discharge speed with a discharge time less than 0.1 μs in a circuit with a load of 200 Ω. These results showed that the Wrec and η of BF-BT ceramic could be availably promoted by the doping of Sm ions, which may be helpful for the enhancement of energy storage performance of BF-BT-based ceramics.

Composition-driven inverse-to-conventional transformation of electrocaloric effect and large energy storage density in strontium modified Ba(Zr0.1Ti0.9)O3 thin films

Composition-tunable electrocaloric effect and large energy storage density with excellent thermal stability arising from synergistic effects of polar nano-regions and conformed defect dipoles were discovered in (Ba1−xSrx)Zr0.1Ti0.9O3 thin films.

Large energy-storage density in transition-metal oxide modified NaNbO3–Bi(Mg0.5Ti0.5)O3lead-free ceramics through regulating the antiferroelectric phase structure

The combination of AFE phase structural regulation and breakdown strength optimization through chemical modification leads to a large energy-storage density ofWrec∼ 5.57 J cm−3in NN–BMT lead-free bulk ceramics.

Effects of Sintering Method and BiAlO3 Dopant on Dielectric Relaxation and Energy Storage Properties of BaTiO3–BiYbO3 Ceramics

(0.9 – x)BaTiO3–0.1BiYbO3–xBiAlO3 (x = 0, 0.02, 0.04, and 0.08) lead‐free ferroelectric ceramics are synthesized using conventional sintering (CS) and microwave sintering (MWS) methods. The microstructure, dielectric and ferroelectric properties, relaxation behavior, and energy storage properties are investigated systematically. X‐ray diffraction (XRD) patterns show a single perovskite phase for all samples. Scanning electron microscope (SEM) images indicate that MWS method can impede the grain growth, whereas the introduction of BiAlO3 can lead to the increase in the grain size. Dielectric measurements reveal that an obvious dielectric relaxation behavior can be strengthened by MWS, and the improvement of the dielectric constant (εr) of ceramics is realized by MWS. Incorporated with BiAlO3 contributes to enhancement of the frequency and temperature stabilities of the dielectric constant for BaTiO3–BiYbO3 ceramics. The slim hysteresis loops are observed, and the maximum polarization of the sample sintered by MWS is higher than that sintered by CS. The MWS samples possess a higher energy density which is about 2 times larger than that of CS samples, and the largest energy storage density ≈0.86 J cm−3 and energy storage efficiency ≈97.44% are, respectively, obtained at x = 0 and 0.04 for MWS ceramics.

Large energy storage density performance of epitaxial BCT/BZT heterostructures via interface engineering

We grew lead-free BaZr0.2Ti0.8O3 (BZT)/Ba0.7Ca0.3TiO3 (BCT) epitaxial heterostructures and studied their structural, dielectric, ferroelectric and energy density characteristics. The BZT/BCT epitaxial heterostructures were grown on SrRuO3 (SRO) buffered SrTiO3 (STO) single crystal substrate by optimized pulsed laser deposition (PLD) technique. These high-quality nanostructures exhibit high dielectric permittivity (∼1300), slim electric field-dependent polarization (P-E) curve with high saturation polarization (∼100 µC/cm2) and low remnant polarization (∼20 µC/cm2) through interface engineering to develop new lead-free ferroelectric system for energy storage devices. We observe an ultrahigh discharge and charge energy densities of 42.10 and 97.13 J/cm3, respectively, with high efficiency, which might be highly promising for both high power and energy storage electrical devices.