Discharge Speed Research Articles

Giant comprehensive energy storage performance in Pb-doped Bi0.25Na0.25Sr0.5TiO3 ceramics via multiscale regulation of grain size and relaxation behavior

Developed ceramic capacitors with excellent recoverable energy storage density (Wrec) and efficiency (η) are greatly desired for next-generation pulsed power devices but challenge as well. Herein, outstanding Wrec of 5.2 J/cm3 and η of 82% are achieved in the PbO-doped fine grain Bi0.25Na0.25Sr0.5TiO3 (BNST-P) based relaxor ferroelectric ceramics. The corresponding mechanism is that A-site Pb-doping increases maximum polarization and breakdown strength, and suppresses remnant polarization simultaneously. Meanwhile, the energy storage property possesses excellent temperature and frequency stability, and the variation of Wrec and η is less than 5% within the range of 25–100 °C and 2–100 Hz. Encouragingly, superior charge-discharge performance with fast discharge speed t0.9 of 24 ns and high power density PD of 296 MW/cm3 is obtained. These striking comprehensive results suggest BNST-P ceramics possess potential prospects for applications.

Enhanced energy storage performance of Na0.5Bi0.5TiO3 lead–free ceramics under low electric field

The rapid progress of science and technology miniaturizes and integrates pulse power capacitors. High electric fields constrain miniaturized size applications and electric device integration; hence, ceramics with substantial recovered energy density (Wrec) at comparatively low electric fields are sought for high energy storage capacitors. Herein, (1-x)Na0.5Bi0.5TiO3-x(Sr0.7Bi0.2)(Ti0.8Zr0.2)O3 ((1-x)NBT-xSBTZ) lead–free ceramics with good energy storage properties were fabricated by solid-state reaction. The phase structures, dielectric properties, relaxation behavior, breakdown behavior, and energy storage properties were systematically investigated by the experiments and simulation method. Phase structure of NBT-based shifts from rhombohedral to pseudo-cubic phase and the relaxor behavior increases with SBTZ content. In addition, the 0.70NBT-0.30SBTZ ceramic demonstrates commendable temperature (25–150 °C) and frequency (1–200 Hz) stability at 120 kV·cm–1. A substantial power density of 40.48 MW·cm–3 and a fast discharge speed of 90.4 ns were attained. This research broadens the potential uses for ceramic capacitors operating in low electric field.

Core–shell structured PVDF-based copolymer fiber design for high energy storage performance

Polymer-based capacitors are very promising for high-power systems due to their high power density and ultrafast charge–discharge speed, yet reaching high dielectric constant and high breakdown strength simultaneously in dielectric polymers required by high-performance capacitors still remains a huge challenge. Herein, poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) were coaxial electrospun in core–shell structured fibers to create locally inhomogeneous microstructures deliberately. Through adjusting the functional group HFP/TrFE monomer ratio, P(VDF-HFP)/P(VDF-TrFE) hybrid polymer films with topological composition distribution have been elaborately designed, enabling gradient polarization distribution from core to shell. Compared with homogeneous hybrid films of the same composition, the core–shell structure significantly boosts breakdown strength, thus resulting in a significantly improved energy storage capacity. At an HFP/TrFE monomer ratio of 10:1, an optimal comprehensive energy storage performance has been achieved with Ue ∼ 20.7 J/cm3 and efficiency 67.8%; moreover, the film could maintain its energy storage performance after 106 charge/discharge cycles without reduction. Molecular dynamic simulation and finite element analysis have been employed in combination to reveal the dipole moments distribution at the molecular level and polarization distribution at the microscale, which further demonstrates that elaborate polarization distribution adjustment is an effective strategy toward high-performance electrostatic energy storage capacitors.

Amorphous Cobalt Phosphate Porous Braced-Frame Nanocubes as Highly Efficient Supercapacitor Electrodes

It is extremely urgent to develop novel electrode materials with large capacity, high charge–discharge speed, and cycle stability for the particular application of supercapacitors in electric vehicles. Cobalt-based phosphate materials have attracted increasing attention due to their outstanding properties. Herein, cobalt phosphate with a braced-frame nanocube morphology consisting of amorphous nanoparticles is synthesized through a one-step ion-exchange method using Prussian Blue Analog Co3[Co(CN)6]2 nanocubes as precursors. Benefiting from the special nanostructure, this material shows a specific capacitance of up to 539.2 F g–1 at 1 A g–1, a capacitance retention of 92% even at 8 A g–1, and remarkable cycle stability characteristics, with a capacity preservation of 89.1% after 3000 charge–discharge cycles at 2 A g–1. The kinetic mechanism demonstrates that the diffusion-controlled procedure has made a great contribution to the large capacitance. This study will be helpful for the development of new electrode materials for supercapacitors.

Avoiding thermal runaway during spent lithium-ion battery recycling: A comprehensive assessment and a new approach for battery discharge

Discharge is a critical step to decrease the risk of explosion and fire in the recovery of spent lithium-ion battery (LIB). This study is the first to provide a comprehensive and detailed assessment of the discharge process of spent LIB. The thermal runaway was analyzed through the voltage, state of charge (SOC), battery status and dismantling of spent LIBs under different discharge degrees. The results show that the spent LIB could be safely disassembled when the voltage was lower than 1.5 V (SOC<5%). Under the guidance of comprehensive assessment, this paper developed a new method for fast and efficient discharge of spent LIBs. By using graphite electrode to replace battery tabs for discharge, the corrosion of battery could be avoided, and the discharge speed was faster and more thorough in reductant-ultrasonic system. Compared with traditional electrolyte solution (NaCl), the voltage of battery was easier to drop to 1.5 V, and the overall discharge time had been shortened by 3/4. Finally, abuse experiments show that the new discharge method and assessment results were reliable. Therefore, this study provides an important reference for the discharge of spent LIB and is more conducive to the safe recycling of spent LIB.

Experimental investigation of energy storage and reuse of recovered waste heat based on thermoelectric generation

Heat energy may be converted into electric energy via a thermoelectric generator (TEG). It is an effective method of recovering and utilizing low-grade energy. However, the output voltage of a TEG is typically too low for direct applications. A waste heat recovery system based on thermoelectric generation was developed to convert waste heat energy into electric energy for energy storage and to operate an LED car light. The variability of thermal-electrical conversion and energy distribution in different stages of the system, as well as the response characteristics of the LED car light under heating temperature fluctuations, are investigated experimentally. The performance of different energy storage components on the time-dependent output characteristics of the light is also analyzed. The results indicate that the energy storage elements can store the energy derived from waste heat, power an LED car light independently, and buffer the power fluctuations caused by the heat source's temperature variation. The energy distribution ratio differs for different energy storage components. Lithium batteries have a high energy density and can store more electricity. The cold start of the LED car light is quick, and the illumination time is longer, but it requires more time to obtain a full charge. The supercapacitor has a sluggish cold start but a high charge and discharge speed, reducing voltage fluctuations when the waste heat recovery system is turned on for a short period. In addition, the system may be utilized to power additional low-power devices.

Realizing ultrahigh breakdown strength and ultrafast discharge speed in novel barium titanate-based ceramics through multicomponent compounding strategy

Lead-free dielectric ceramics have been an important segment in the energy storage field. In this work, a synergistic optimization strategy of multicomponent compounding involving 0.9[0.88Ba1-xCaxTiO3-0.12Bi(Mg2/3(Nb0.85Ta0.15)1/3)O3]− 0.1Bi0.5Na0.5TiO3 (B1-xCxT-BMNT-BNT) ceramics were proposed. With the increase of Ca2+ content (x), the content of the CaTiO3 phase increases, which obviously enhances the breakdown strength (BDS) and energy storage properties. The optimal energy storage performances were obtained in the B0.6C0.4T-BMNT-BNT ceramic, showing a large recoverable energy density (Wrec) of 3.59 J/cm3 and ultrahigh efficiency (η) of 90.86% at 430 kV/cm. Meanwhile, the B0.6C0.4T-BMNT-BNT material also exhibits good temperature stability (20–180°C), frequency stability (1–500 Hz) and fatigue resistant (1–105 cycles). In addition, the B0.6C0.4T-BMNT-BNT ceramic also possesses ultrafast discharge time (t0.9 = 38.6 ns) in the charge and discharge test. The above merits make the B0.6C0.4T-BMNT-BNT ceramic a promising candidate for wide-temperature dielectric capacitors in pulse power applications.

A Suggested Equivalent Method for a Drainage Structure to Analyze Seepage in Tailings Dam.

To better understand the seepage field in tailings dam with a drainage structure that combines drainage mat, drainage tube, and geotextile, an equivalent seepage analysis method for the drainage structure is presented. In the method, an equivalent drainage structure is suggested to replace the original drainage. It has enough size to be easily presented in the three-dimensional (3d) model of a tailings dam. According to a back analysis procedure using the quasi-3d models of a tailings dam with original and equivalent drainage structures, the material properties of the equivalent drainage structure can be obtained under the principle of drainage capacity equivalence. It is demonstrated that the suggested method is accurate enough to capture the seepage field in a tailings dam based on comparing the calculated and measured phreatic lines in a tailings dam for verification. Then, the method is employed to investigate the seepage field in a tailings dam in China for a case study. The rise of water level, damage of drainage structure, or increase of tailings discharge speed and time will lift up phreatic line. After terminating tailings discharge, phreatic line will first rise and then fall. The effect of tailings discharge on phreatic line will almost disappear after terminating tailings discharge for 24 h.

Energy storage properties of PLZST-based antiferroelectric ceramics with glass additives for low-temperature sintering

PLZST-based antiferroelectric (AFE) ceramics with high recoverable energy density (Wre) and efficiency (η) can be applied to pulsed power electronic devices. However, this application is constrained by the high sintering temperature (ST, 1250–1320 °C) of the ceramics per se. In this context, this study introduced a new glass phase of Ba2CO3–Al2O3–SiO2–K2CO3 (BASK) into Pb0.95La0.02Sr0.02(Zr0.50Sn0.40Ti0.10)O3 (PLSZST) AFE ceramics by using a traditional solid-state method. By doping 0.5 wt% BASK, the ST of PLSZST ceramics was significantly reduced from 1300 °C to 1020 °C and a high Wre of 3.54 J/cm3 and a high η of 86% were yield, when the electric breakdown strength increased to 230 kV/cm. In addition, a pulse discharge energy density of 2.47 J/cm3, and an extremely fast discharge speed (<0.5 μs), as well as acceptable thermal stabilities of both Wre and η within 30–110 °C temperature range, were achieved. Conclusively, this AFE ceramic composition with glass additives has a great potential to be used in base metal inner-electrode multilayer ceramic capacitors for pulse power applications.

Ceramic‐Polymer Nanocomposites Design for Energy Storage Capacitor Applications

AbstractGiven the remarkable advantages of high power density, fast charge–discharge speed, good stability, and low cost, the dielectric capacitors have sparked tremendous research interest in recent years for their unique applications in electrical systems and modern electronics. As for satisfying the future demands of the miniaturization and integration of the electrical devices, novel dielectric material with high energy storage density should be developed urgently. Importantly, ceramic‐polymer nanocomposites, which combine the high permittivity of the ceramic fillers and the excellent breakdown strength of the polymer matrix, are regarded as promising candidates. In this review, the various designs of the emerging nanocomposites are introduced from three aspects. First, the diverse design of the nanofillers, including tailoring the size, engineering the dimension, and selecting the species is focused. In addition, the design of the interfaces between the two phases by organic surface coating and inorganic surface coating is demonstrated. Furthermore, the spatial structure design of the nanocomposites, such as sandwich structure, gradient structure, and array structure, is presented as well. Finally, the bottlenecks along with opportunities of this booming field at present are concluded and outlined.

Numerical flow simulation of fresh concrete in mixing truck

The structure of concrete truck not only affects the homogeneity of fresh concrete but also influences the construction efficiency. The repeatability of fresh concrete's test is worse and its cost is high. With this in mind, the simulation of fresh concrete flowing in concrete truck was conducted. The effects of screw pitch and height of blade on discharging speed were analyzed. The numerical results shown that increasing the screw pitch of blade at posterior cone can significantly promote the discharging speed. The discharging uniformity was also investigated. It is shown that increasing the height of blade or decreasing the screw pitch of blade can improve the homogeneity. Fig. 1. Discharge speed and increase percentage of series 1–6. Fig. 2. Discharge uniformity and increase percentage of series 1–6. • A numerical method was developed to simulate flow of fresh concrete in mixing drum. • The screw pitch and height of blade have an effect on discharge uniformity. • Increasing the screw pitch of blade at the posterior cone can increase discharge speed.

Experimental study of the flow of the Tr-Francis turbine along the no-load curve

Emergence of new renewable energies, such as solar or wind power, has introduced intermittency on the grid. Hydraulic turbines, initially designed to perform close to their best efficiency point, are more and more at off-design operating conditions, such as no-load regimes, when the runner rotates without energy extraction. These no-load regimes are characterized by complex flow phenomena inducing fluctuations of the blade loading and resulting in a reduced lifetime of the runner. Understanding the origins of pressure fluctuations in no-load conditions is consequently essential to prevent fatigue damage to the turbine. This paper presents the study, with experimental flow visualization, pressure measurements and numerical simulations, of the flow behavior at speed no-load in a medium head Francis turbine model. Evolution of the different flow structures along the no-load curve is then assessed. At speed-no-load, flow visualizations show the presence of a cavitating zone at the blade trailing edge. According to the results of the numerical simulations, this zone seems to correspond to the region where a backflow in the draft tube enters the runner. This interaction results in a backflow inside the runner and in a blockage of the upper part of the inter-blade channel. Sensitivity of this cavitating region to test parameters (discharge and rotation speed) is investigated for different no-load operating points with high-speed visualization at a constant cavitation number. Decrease of the energy coefficient tends to intensify the phenomena and increase the volume of cavitation.

Satellite assessment of coastal plume variability and its relation to environmental variables in the Sofala Bank

Monthly composites of remote sensing reflectance at 555 nm wavelength (Rrs555) from ocean color imagery of the MODIS sensor onboard the Aqua platform were used to characterize the spatial and temporal variability of coastal plume in the Sofala Bank and its relation to river discharge, local rainfall, and wind speed. To achieve the objective, maps of monthly composites of Rrs555 over the Sofala Bank were inspected and statistical analysis was performed, including correlation, analysis of variance, and wavelet coherence between environmental variables and both plume area and Rrs555. Climatology of Rrs555 revealed that both plume dispersion and Rrs555 values are higher during June to December and lower during January to May. A positive correlation (r = 0.77) between wind speed and monthly time series of Rrs555, and a negative correlation between the Zambezi river discharge (r = −0.21) and rainfall (r = −0.67) with Rrs555 were found. These results suggest that variation of suspended matter in the Sofala Bank is mainly controlled by erosion and re-suspension by winds rather than the input of terrigenous matter by the Zambezi River discharge and rainfall, assuming that Rrs555 can be a valid proxy for the inorganic suspended matter. The southern portion of the Sofala Bank (i.e., near the mouths of the Pungue and Buzi Rivers) presented higher values of Rrs555 if compared to the center region near Zambezi river mouth and the northern region near Licungo river mouth. The higher Rrs555 values in the southern region might be associated with higher re-suspension rates due to increased tide mixing, dredging activities, and the shallower nature of bathymetry in the southern region. The dominance of wind in controlling the variability of suspended sediments and the eventual relatively greater contribution of Pungue and Buzi River than the Zambezi in supplying sediments could represent an evidence of weakening of Zambezi River supply of sediments, a process that might have started after damming the Zambezi Catchment.

Achieving ultrafast discharge speed and excellent energy storage efficiency in environmentally friendly niobate-based glass ceramics

Environmentally friendly Na2O–BaO–Nb2O5–SiO2 glass ceramics (GCs) with different vanadium pentoxide (V2O5) contents were successfully synthesized using the conventional melt-quenching method and heat treatment. The microstructure and dielectric energy storage properties of the GCs could be related to the addition of V2O5. When 1 mol% of V2O5 was added, the activation energy of crystallization decreased from 282 to 221 kJ/mol, and the GCs had the highest energy efficiency of 95.96% and breakdown strength of 1326 kV/cm. Moreover, the GCs could also achieve an ultrafast discharge time of 14 ns and an actual discharge energy density of 0.724 J/cm3. These results indicate that these environmentally friendly GCs can be used in energy storage devices.

Enhanced energy storage properties under low electric fields in (Bi0.5Na0.5)TiO3-based relaxor ferroelectrics via a synergistic optimization strategy

Lead-free dielectric ceramics with high energy storage performance (ESP) are strongly desired for pulse power capacitor applications. However, low recoverable energy storage density (Wrec) under low electric fields seriously hinders their applications in miniatured and integrated electronic devices. In this work, we adopted a synergism strategy to develop (Bi0.5Na0.5)0.7Sr0.3Ti(1-x)(Al0.5Nb0.5)xO3 (BNST-xAN) ceramics with substantially enhanced low-field ESP through combining composition design and tape-casting approaches. Complex-ion substitution of (Al0.5Nb0.5)4+ for Ti4+ shifted the temperature of maximum dielectric constant towards room temperature direction, made relaxor behavior stronger and promoted formation of highly dynamic nanodomains, thus reducing the remanent polarization. Besides, refined submicron grains and improved densification behavior were achieved in those ceramics fabricated by tape casting, further increasing the breakdown strength. Consequently, a large Wrec of 4.30 J/cm3 was achieved at a low electric field of 230 kV/cm at x = 0.10, which is superior to previously reported lead-free energy storage ceramics under low electric fields. Moreover, our ceramics exhibited brilliant thermal endurance (20–140 °C) and frequency stability (0.2–200 Hz) together with fast discharge speed. These characteristics suggest the great potential of the BNST-0.10AN ceramic for low-field and high-performance energy storage capacitor applications.

Experimental Study of Inductive Pulsed Power Supply Circuit With Residual Energy Recovery Branch

Inverse current commutation with semiconductor devices (ICCOS) has been proved to be able to shut off the high current of inductors. Inductive pulsed power supply (IPPS) is considered to have great potential in the field of Electromagnetic Launch (EML) due to its high energy density and fast discharge speed. A repetitive IPPS circuit with ICCOS technique has been proposed based on a high-temperature superconducting pulsed power transformer (HTSPPT) in our previous studies. This circuit can recover the remaining energy and generate continuous current pulses. However, due to the low voltage of the primary power supply, the circuit uses the primary power supply to recover the remaining energy, resulting in a slower process of recovering the remaining energy. For this issue, this article proposes a method to improve the original circuit by adding a residual energy recovery branch on the secondary side. The new circuit can recover most of the remaining energy on the secondary side through a designated capacitor. The working process of this circuit is illustrated detailed in this article, and the preliminary simulation verification is carried out. To further study the feasibility of this circuit, an experimental platform was built with a small HTSPPT. Experimental results and comparative analysis show that the new circuit has better characteristics in terms of remaining energy recovery and increasing pulse amplitude.

Influences of crystallization temperature on the structure, dielectric, and energy storage characteristics of KBaSrNb5O15‐based glass–ceramics

AbstractGlass–ceramics capacitors have great application potential in pulsed power systems, due to ultrafast discharge speed and high dielectric breakdown strength (BDS). Here, lead‐free niobate glass–ceramic dielectric materials were synthesized, and the effects of heat treatment temperature on the dielectric, ferroelectric, and energy storage properties of glass–ceramics were investigated comprehensively. The results exhibit that the dielectric permittivity first increases and then decreases as the crystallinity increases; however, the dielectric BDS diminishes. At the optimum crystallization temperature of 740°C, the maximum value of discharge energy density is 2.2 J/cm3 at 600 kV/cm, which is about 7.6 times that of mother glass. Furthermore, an ultrahigh power density of about 380.9 MW/cm3 and ultrafast discharge speed of about 11.2 ns were achieved simultaneously. Meanwhile, great thermal stability of charge–discharge property was verified in this glass–ceramics. According to P–E loops and dielectric test result, a high dielectric constant (∼207) and low dielectric loss (&lt;0.005) as well as high energy storage efficiency of about 94.9% were achieved for G740 sample. The previous results make the obtained glass–ceramic as potential candidates in dielectric capacitors.

The architecture and operating mechanism of a cnidarian stinging organelle

The stinging organelles of jellyfish, sea anemones, and other cnidarians, known as nematocysts, are remarkable cellular weapons used for both predation and defense. Nematocysts consist of a pressurized capsule containing a coiled harpoon-like thread. These structures are in turn built within specialized cells known as nematocytes. When triggered, the capsule explosively discharges, ejecting the coiled thread which punctures the target and rapidly elongates by turning inside out in a process called eversion. Due to the structural complexity of the thread and the extreme speed of discharge, the precise mechanics of nematocyst firing have remained elusive7. Here, using a combination of live and super-resolution imaging, 3D electron microscopy, and genetic perturbations, we define the step-by-step sequence of nematocyst operation in the model sea anemone Nematostella vectensis. This analysis reveals the complex biomechanical transformations underpinning the operating mechanism of nematocysts, one of nature’s most exquisite biological micro-machines. Further, this study will provide insight into the form and function of related cnidarian organelles and serve as a template for the design of bioinspired microdevices.

Energy storage performance of BiFeO3–SrTiO3–BaTiO3 relaxor ferroelectric ceramics

AbstractDielectric capacitors reveal great potential in the application of high power and/or pulsed power electronic devices owing to their ultrafast charge–discharge rate and ultrahigh power density. Among various dielectric capacitors, the environment‐friendly lead‐free dielectric ceramics have drawn extensive investigations in recent years. Nevertheless, the relatively small recoverable energy storage density (Wrec) is still an obstacle for their application. Herein, the (0.55−x)BiFeO3–0.45SrTiO3–xBaTiO3 ternary ceramics with 0.1 wt% MnO2 were prepared by the solid‐state reaction, and achieved enhanced relaxor behavior as well as breakdown strength Eb. As a result, the x = 0.12 ceramic exhibited superior comprehensive energy storage performance of large Eb (50.4 kV/mm), ultrahigh Wrec (7.3 J/cm3), high efficiency η (86.3%), relatively fast charge–discharge speed (t0.9 = 6.1 μs) and outstanding reliability under different frequency, fatigue, and temperature, indicating that the BiFeO3‐based relaxor ferroelectric ceramics are prospective alternatives for electrostatic energy storage.

Ultrahigh Energy Storage Density and High Efficiency in Lead-Free (Bi0.9Na0.1)(Fe0.8Ti0.2)O3-Modified NaNbO3 Ceramics via Stabilizing the Antiferroelectric Phase and Enhancing Relaxor Behavior.

Dielectric capacitors have attracted growing attention because of their important applications in advanced high power and/or pulsed power electronic devices. Nevertheless, the synergistic enhancement of recoverable energy storage density (Wrec > 10 J/cm3) and efficiency (η > 80%) is still a great challenge for lead-free dielectric bulk ceramics. Herein, by introducing complex perovskite compound (Bi0.9Na0.1)(Fe0.8Ti0.2)O3 with a smaller tolerance factor into an NaNbO3 matrix (NN-BNFT), we have achieved and explored stable relaxor antiferroelectric ceramics with enhanced relaxor behavior. Of particular importance is the composition of 0.88NN-0.12BNFT, which exhibits a large electric breakdown strength Eb of 87.3 kV/mm, an ultrahigh Wrec of 12.7 J/cm3, and a high efficiency η of 82.5%, as well as excellent thermal reliability and an ultrafast discharge speed, resulting from the dense microstructure, the moderate dielectric constant, the reduced grain size, the dielectric loss, and the sample thickness. The outstanding energy storage properties of NN-BNFT display great promise in advanced dielectric capacitors for energy storage applications.