Discharge Current Pulse Research Articles

Pulse Current-Induced Homogeneous Phase Nucleation for High-Performance Conversion-Type Cathodes.

Conversion-type transition metal-based materials (MZx) are considered promising cathodes for lithium metal batteries due to their low cost, abundant availability, and high theoretical energy density. However, they suffer from rapid capacity decay caused by the transformation into two inhomogeneous phases during discharge. Herein, we use a pulse current discharge activation method (under 3C) to induce homogeneous phase nucleations. As a result, the microsized FeS2 cathode transforms into a homogeneous mixture of nanosized Fe and Li2S, effectively mitigating volume expansion. It exhibits exceptional cycling performance, delivering a specific capacity of 572.8 mAh g-1 after 800 cycles at 0.33C. Even at a high areal capacity of 5.4 mAh cm-2, it undergoes 180 cycles with a capacity retention of 89.3% at 0.33C. This work highlights the crucial role of homogeneous nucleation in achieving long cycling life for conversion-type cathodes.

Numerical simulation of surface charge accumulation under negative discharge of different humidities and pressures

The surface discharge phenomenon of polymers severely limits their applications in electrical and electronic devices, especially in complex environments. In this study, a drift-diffusion model based on a hydrodynamic approach was developed to investigate the influence of humidity and gas pressure on the negative surface discharge. The results indicate that the discharge pattern did not change under different humidity conditions. The increased humidity accelerated the formation of discharges and increased the discharge pulse current. In particular, as the humidity increased, tiny pulses occurred at the tail of the first pulse, and the number of tiny pulses increased. The appearance of these tiny pulses changed the surface charge distribution from a “ring-like” distribution to a “spot-like” distribution. Meanwhile, the accumulation of surface charges significantly distorted the spatial electric field distribution and suppressed the electron multiplication stage of the subsequent discharges, thus reducing the current in the Trichel pulse discharge stage. It is precisely because the discharge is stronger under high humidity, resulting in more surface charges accumulating on the surface, which is in keeping with the experimental results. The measured charges at different humidities show a similar distinct spot-like distribution, illustrating a constant pattern of discharge. All these results demonstrated the correctness and applicability of the simulation. The surface discharge under different pressures exhibited some similarities with the case of different humidity levels. As the pressure increased, the number of discharge current pulses and the pulse amplitude decreased, resulting in a decrease in the surface charge density.

Modeling High Current Pulsed Discharge in AA Battery Cathodes: The Effect of Localized Charging during Rest

Modeling High Current Pulsed Discharge in AA Battery Cathodes: The Effect of Localized Charging during Rest

Distribution of volumes of plasma channels components between metal granules in working liquids

Introduction. Expanding the capabilities of a number of modern technologies and improving quality of their products require detailed spark and plasma erosion processes control in metal granules layers (MGL). Problem. Traditional measurement of exclusively electrical parameters of these processes, even in the case of multi-electrode systems, provides only a general vision, not allowing monitoring processes in individual plasma channels. Optical control methods make it possible to simultaneously have information about almost every plasma channel in the MGL. The aim of the article is to study the characteristic components of plasma channels arising as a result of the flow of discharge currents in the MGL and to establish the laws of distribution of their volumes and their ratios. Methodology. During the experiments, photographs of plasma channels resulting from the flow of discharge current pulses between Al granules immersed in distilled water were obtained. Using the specialized ToupView program, the volumes of equivalent ellipsoids of rotation, approximating the colored halos and white cores of the plasma channels were determined. Discrete distributions of the volumes of the halo and cores of plasma channels, as well as their ratios were constructed both with and without procedures for screening out «anomalous» results. The efficiency of approximation of discrete distributions obtained in practice by continuous theoretical distributions Weibull, Rosin-Rammler and log-normal was estimated. Results. It is shown that of all the considered theoretical distributions of halo and cores of plasma channels volumes, as well as their ratios, the most adequate is the log-normal one. Originality. For the first time distributions of volumes of halo and cores of plasma channels were studied and their comparative analysis with the size distributions of erosion particles and dimples on the surface of Al granules was given. Practical significance. Taking into account the new obtained results, a technique for constructing distributions of volumes of halo and cores of plasma channels and determining their parameters has been developed. References 53, figures 7, tables 5.

Pulse diffusion welding of female joints

Special feature of operation of electrovacuum tubes, in particular the cathode assembly, is constant heating due to bombardment of its surface with electrons. Stable characteristics and durability of the cathode assembly depend on high-quality connection (welding) of the core surfaces with the emitter over the entire area of ​​the overlapped conjugation. The use of diffusion welding for joining a cathode assembly made of dissimilar materials is not possible due to the occurrence of poor welding fusion due to the presence of gaps in the ring sectors of the equipment, and, consequently, a decrease in the service life of the cathode assembly. The authors proposed to implement the process by combining magnetic pulse welding with diffusion welding. The originality of the work is the possibility of remote action on the joint through a dielectric quartz cup, which is a part of the technological vacuum chamber. The inductor system is outside the quartz cup, which allows heating the assembled unit without heating the tool – an inductor made of dissimilar materials – to a temperature of 700 ° C and higher. The authors determined the main parameters of the process of pulse diffusion welding in vacuum: pressure in the working chamber is В=0.66·10−2Pa (5·10−5mmHg); preheating temperature is T=700–1250°C; magnetic field pulse energy is W=5÷17kJ; operating frequency of current pulse discharge is fd=5–15kHz; magnetic pressure is Pm∙107N/m2. In this way, cathode assemblies of a wide range of metal pair combinations with a base diameter of d=20mm and a sample length of L=40mm were produced. The proposed technology has been successfully implemented and introduced at Tantal (Open Joint Stock company). The economic effect consists in reducing labor intensity and obtaining joints of stable quality.

The dynamics of the electron temperature and density in short-pulse HiPIMS discharge

This work studies the change in electron density and temperature in short-pulse high power impulse magnetron sputtering (HiPIMS) discharge. A planar magnetron with a copper target of 100 mm in diameter was used in the experiments. Plasma measurements were made using a Langmuir probe placed 85 mm from the target. The discharge current pulse durations were 8, 15, and 100 μs, with a fixed amplitude of 100 A and an average discharge power of 1 kW. To maintain the average discharge power at a constant level, a decrease in the pulse duration was accompanied by an increase in the frequency. When the discharge current pulses started, the electron temperature exceeded 10 eV and then decreased to a few eV. The main time of plasma existence in short-pulse HiPIMS is the afterglow phase, during which the electron density reaches a maximum of 1.9–3.2 × 1012 cm−3 and the electron temperature is less than 1 eV. Because the duration of the afterglow phase in short-pulse HiPIMS is longer than the duration of the discharge current pulse, the average integral electron temperature is lower than that in DC and middle-frequency magnetron sputtering. The average integral electron temperature in HiPIMS decreases with decreasing pulse duration.

Revisiting Pulse-Based OCV Incremental Capacity Analysis for Diagnostics of Li-Ion Batteries

This paper presents the concept of applying incremental capacity analysis (ICA) on the OCV curve in the SoC space. The OCV curve can be obtained from any sequence of discharge or charge current or power pulse with a necessary rest period to allow the cell to reach a pseudo-OCV after each pulse. With a high resolution (>100 pulses) in the full SoC window, an OCV-vs.-SoC curve can be obtained with sufficient accuracy to perform an ICA on the obtained OCV curve. ICA as a diagnostic technique has commonly been applied on Li-ion cells with constant charge and discharge at slow currents. However, a slow controlled constant current charge or discharge is normally not feasible and cannot be easily applied to a battery in an application. Here, we revisit pulse-based ICA to supplement the conventional constant-current-based technique. Based on actual ageing data, we show that ICA performed on a selection of high-resolution OCV curves is comparable or better than conventional ICA with constant current. The main advantage of OCV-ICA is that it can be applied to most cells and systems without a significant interruption of normal cell operation. OCV-ICA can provide valuable insights into ageing mechanisms as well as, e.g., detailed information on changes in internal resistance.

Improving the wear and heat resistance of niobium substrate via reactive electrospark treatment using fusible AlCaSiY electrode

Protective coatings with a heterophase layered structure were obtained by reactive electrospark treatment (EST) of niobium substrate with a fusible AlCaSiY electrode. The effect of the frequency–energy modes of EST on the phase composition, structure and properties of the coatings was studied. A combination of high discharge current values (400A) and long pulses (100 μs) yields a double-layer coating with the total thickness of 80 μm, which consists of the (Al) matrix strengthened with Nb2CaAl20 particles and a hard (10 GPa) NbAl3 layer. The results of pin-on-plate tribological testing revealed that this structure made it possible to reduce the coefficient of friction from 0.42 to 0.24 and increase wear resistance 3.5-fold compared to those of niobium. Oxidative annealing of Nb plates in air at 700 °C causes their fracture due to the formation of Nb2O5. Indeed, oxidative annealing of the samples subjected to EST leads to in situ formation of a dense Ca12Al10Si4O35-oxide based near surface layer that inhibits oxygen diffusion into the bulk, thus suppressing Nb2O5 formation. Mass gain of the sample having a protective coating after 300-min isothermal exposure was 2.54 mg/cm2, which is 3.6-fold lower than that for the Nb substrate (9.04 mg/cm2).

Formation of Wave Fields in a Metal Melt under the Influence of Magnetic-Pulse Loading and Discharge Current Pulses

Based on mathematical modeling, a study of the wave fields in molten aluminum formed by the action of a pulse, electric discharge and combined sources was carried out. A comparative analysis of their influence on the wave fields in the melt was performed. An increase in the intensity of the wave fields under the influence of a combined method of loading the melt was registerd. The occurrence of cavitation in the melt under the influence of the considered sources of pressure pulses has been determined. The energy features of the action of pressure fields on the melt are noted. The influence of the mass of the melt on the pressure fields arising in it is shown.

Internal temperature estimation for lithium-ion batteries through distributed equivalent circuit network model

Lithium-ion cells experience significant internal thermal gradients during operation, with a direct impact on their safety, performance, cost and lifetime. The estimation of the internal temperature of cells is therefore particularly important. In this work, a 3D distributed electro-thermal model for internal temperature estimation is developed for a cylindrical cell (LG M50T, NMC811). The model is parameterized and comprehensively validated against experimental data for 21700 cells, including direct core temperature measurements. Multiple types of electrical load are considered, including constant current discharge, pulse discharge, drive cycle and instant discharge/charge switching. The developed model is used to estimate core temperature based on surface temperature measurement. The predictions are shown to have good accuracy at relatively low computational cost. We show that the widely adopted two-node lumped thermal estimation model is increasingly inaccurate for more aggressive discharges, when thermal gradients become higher. Compared to the standard two-node model, the distributed equivalent circuit network model predicts the effects of detailed internal cell structure (electrode, current collector, metal can and tab) and distributed internal heat generation. The results are of immediate interest to cell manufacturers and battery pack designers, while the modelling and parameterization framework is a useful tool for energy storage systems design.

Effect of peak discharge current on the ion current density on the substrate in the short-pulse HiPIMS

The bombardment of the substrate with accelerated ions from the plasma during the magnetron sputtering process is an effective way of controlling the energy transfer to the coating. One of the ways to increase the ion flux on the substrate is to change the parameters of the discharge power supply pulses. This work investigates the effect of the discharge current pulse amplitude on the average ion current density on the substrate in short-pulse high power impulse magnetron sputtering (s-HiPIMS). During sputtering, the peak discharge current varied from 25 to 250 A with a fixed pulse duration of 6 μs and an average discharge power of 1 kW. Experimental results and theoretical calculations show that the average ion current density on the substrate increases twofold when the amplitude of the discharge current pulses is increased from 25 to 60 A. As the amplitude of the discharge current pulses is further increased, the average ion current density on the substrate stops growing and begins to decrease at currents above 150 A. The paper discusses the reasons for the nonlinear dependence of the average ion current density on the substrate on the amplitude of the discharge current pulses.

Fast Estimation of Entropy Profiles for Lithium-Ion Batteries

The operating temperature of a lithium-ion battery (LIB) has strong effects on its electrochemical performance, safety, and lifetime. Reliable predictions of cell temperature and heat generation are required for the design and thermal management of battery systems. During the normal operation of LIBs, heat sources can be classified into irreversible heat from resistive losses such as ohmic resistance, charge-transfer overpotentials, and mass-transfer limitations; and reversible heat from entropy change . The irreversible heat generation is related to the cell's internal resistance and the applied current. The reversible heat depends on the entropy variation of electrode materials, the state of charge (SoC), and the temperature. An accurate measurement of entropy-variation will not only help to improve the battery operation under optimal thermal conditions but can also be used to diagnose the battery aging since it can reveal crystal structure changes in the electrodes [1, 2].Techniques for measuring the entropy of a battery can mainly be classified into potentiometric [3] and calorimetric methods. The potentiometric method measures the open circuit voltage (OCV) changes while the cell temperature is varied at different SoCs. This method requires a long relaxation time to obtain the OCV equilibrium state following each SoC point and temperature step. The calorimetric method [4-6] is based on measuring the heat generation during charge and discharge, and various models are applied to differentiate between and quantify the reversible and irreversible heat sources. The entropy variation with SOC is obtained via the reversible heat rate.Recent improved methods include e.g., Schmidt et al. [4] who proposed a reversible heat extraction method based on electrothermal impedance spectroscopy (ETIS) and Damay et al. [5] proposing a fast calorimetric method to obtain a continuous entropy profile. The cell surface temperature is monitored while the battery is charged and discharged continuously. A thermal balance is used to estimate the heat generation from the monitored cell temperature changes during charge and discharge. The benefit of this method can be low cost, fast and high resolution. Bedürftig et al. [6] proposed a calorimetric method named ‘Double Pulse Method’ to measure reversible heat in lithium-ion battery cells by exciting the cell with charge and discharge current pulses.Here we present a new entropy characterization method via charge and discharge cycles of a LIB at low constant C-rates using simple insulating condition. Through monitoring the variations of cell surface temperature and voltage with the state of charge, the continuous variation of entropy with the state of charge can be extracted. These results were compared to classical entropy measurements obtained through the potentiometric method as shown in Figure 1. In addition, the extracted entropy variation data is input into a LIB modelling approach, combining a P2D-electrochemical sub-model for battery operation and a 3D-finite-element sub-model for thermal behavior while battery charge and discharge. The model predictions on the cell outer surface temperature variation while charge and discharge under different C-rates are compared with the data obtained in the battery characterization tests as shown in Figure 2. Good agreements between the model predictions and tests are achieved.

Current Pulse-Based Measurement Technique for Zinc–Air Battery Parameters

Zinc–air batteries possess advantages such as high energy density, low operational costs, and abundant reserves of raw materials, demonstrating broad prospects for applications in areas like stationary power supplies and emergency power sources. However, despite significant advancements in zinc–air battery technology, a comprehensive measurement model for zinc–air battery parameters is still lacking. This paper utilizes a gas diffusion model to separately calculate the concentration polarization of zinc–air batteries, decoupling it from electrochemical polarization and ohmic polarization, simplifying the equivalent circuit model of zinc–air batteries into a first-order RC circuit. Subsequently, based on the simplified equivalent circuit model and gas diffusion model, a zinc–air battery parameter measurement technique utilizing current pulse methods is proposed, with predictions made for the dynamic voltage response during current pulse discharges. Validation of this method was conducted through single current pulses and step current pulses. Experimental results demonstrate the method’s capability to accurately measure zinc–air battery parameters and predict the dynamic voltage response.

Residual energy extraction from near end-of-life lithium-ion batteries using a self-adaptive pulse discharge method

A modified self-adaptive pulse discharge (SAPD) method is adopted by this study to examine the feasibility of extracting residual energy from near end-of-life non-reusable lithium-ion batteries before disassembled. The SAPD model is used to determine the optimal frequency and duty cycle in the process of energy recovery, so the highest pulse discharge current can be obtained. A prototype including an improved active cell-balancing circuit, a modified SAPD control circuit, and a supercapacitor module switching circuit is developed to extract a battery bank that consists of at least one and at most 12 cells in parallel to reduce the discharge current as well as prevent damaged circuit components. The results of testing Sanyo UR14500P batteries show that the energy recovered from six to 12 cells ranges from 2630 to 2955 joules, and the corresponding recovery efficiency is from 64.97 to 66.19 %. Besides, with a randomly selected eight-cell pack, the SAPD method yields higher recovery efficiency than the short circuit discharge and pulse discharge methods, and the recovery efficiency increases by 11.74 % and 9.39 %, respectively. Although the results presented are far from being satisfactory from the perspective of efficiency, this study serves as a starting point for reusing and recycling resources.

The influence of pulse duration and duty cycle on the energy flux to the substrate in high power impulse magnetron sputtering

The paper focuses on measurements of the total energy flux and normalized energy flux onto the substrate during high power impulse magnetron sputtering (HiPIMS) in a wide range of the pulse duration and discharge current. Al, Cr and Ti targets with a diameter 76 mm are used for sputtering. HiPIMS parameters include 1 kW discharge power, 15 to 150 А discharge current, 0.4–10 kHz pulse frequency, and 5–100 μs pulse duration. It is shown that the use of short pulses leads to ∼40 and 70% growth in the total energy flux onto floating and biased (−100 V) substrates, respectively. The energy per unit volume of the deposited coating increases by several times, if the pulse duration and the duty cycle are reduced. The paper examines reasons for the increased total and normalized energy fluxes onto the substrate observed after the pulse parameter modulation in the sputtering process.

Experimental investigation to optimize machining parameters for super duplex stainless steel in spark EDM using die-sinking and MQL system

The current experimental work discusses the electric discharge machining (EDM) of super duplex stainless steel with conventional die-sinking and minimum quantity lubrication (MQL) approach. The dielectric used in the conventional die-sinking EDM process is kerosene, and sunflower oil with air mixture is used in MQL-type machining conditions. The solid-type alpha brass electrodes of diameter 10 mm were used for machining. The most prominent input variables like pulse time (OFF and ON) and discharge current (varied at 3 levels) were selected, and Taguchi's L9 orthogonal array design was selected for experimentation. The responses like electrode wear rate (EWR), hole circularity (HC), material removal rate (MRR), and surface roughness (SR) were analyzed. The output results obtained from the experimental trials were analyzed using S/N ratios and analysis of variance (ANOVA). The most contributing input parameter affecting the responses like SR, HC, MRR, and EWR outputs were analyzed. The results showed that the optimum machining conditions were obtained at L3 and L9 levels for conventional die-sinking and MQL-type machining conditions, respectively. Out of three varying input parameters, pulse time (OFF) is the most contributing factor in deciding various responses. The same has been confirmed by ANOVA analysis. The theoretical prediction of experimental data was made using the Fuzzy logic approach, and the best optimal level is found out individually for all four responses.

Identification of corona discharges based on wavelet scalogram images with deep convolutional neural networks

This paper presents a new wavelet-based approach to automate the identification of positive and negative DC corona discharge current pulses. Two electrode systems with variable gap spacings formed corona discharges, and two commercial sensors (a high-frequency current transformer (HFCT) and a shunt resistor) captured transient corona discharge currents. The proposed method employs a continuous wavelet transform to generate time-frequency representations of corona discharge pulse currents, called scalogram images. The effects of sampling interval, data acquisition time, data shifting, and external noise components in the signals on the scalogram images were examined. The well-known pre-trained convolutional neural network models, AlexNet, MobileNet, and ShuffleNet, were tailored, and their ensemble structure was generated to discriminate scalogram images of discharge pulses. A framework was constructed to increase the generalization ability of the study. The results demonstrate that the scalogram images are robust candidates for corona discharge identification.

Powerful Elliptically Polarized Terahertz Radiation from Oscillating-Laser-Driven Discharge Surface Currents

This work presents a general concept of an intense laser-driven source of strong electromagnetic waves, which can be used for obtaining powerful terahertz radiation with controlled polarization. It is shown that the irradiation of a solid target surface by short relativistic laser pulses at small angles provides the excitation of strong compact relativistic discharge current pulses, propagating in a certain direction. For elliptical targets, this current emits elliptically polarized electromagnetic radiation at a given frequency with the ellipticity and the spectra defined by the target geometry. The proposed setup allows reaching extreme THz intensities and provides easy control of the radiation parameters, making it attractive for various scientific and technological applications.

Influence of the Wire Spatial Structure on the Distribution of Product and the Peak Overpressure of Shockwave Generated by the Electric Explosion

The deposition energy and the peak overpressure of shockwaves are the leading engineering parameters of wire electric explosion technology applied to enhance oil recovery. The thicker Cu wire deposits more energy, which transforms into the shockwave efficiently. Therefore, the effects of three diameters (0.3, 0.4, and 0.5 mm) and hollow ratios (0, 0.5, and 0.7) on the electric explosion efficiency were studied by collecting pulse current, explosion products, and shockwaves during the test. All spatial structure designs of the wire depend on the skin effect parameters of the pulse discharge current. The results found that the peak overpressure of the shockwave soars with the increase of the hollow ratios when the diameter is constant. The range of the peak overpressure is 25.2~47.7 MPa. However, the correlation between shockwave and wire diameter changes from negative to positive with the increase of the hollow ratio from 0 to 0.7. The phase distribution deduced by the particle morphology and quantity distribution indicates that it is going to be uniform gradually with the hollow ratio rising from 0 to 0.7. When the extreme simplification is carried out without considering the magnetic diffusion process, it is indicated that the distribution of temperature and phase states along the wire radial is a Bessel function depending on the skin effect of the current density when three times the theoretical enthalpy drives the Cu wire. It means that the desired shockwave could be obtained efficiently by increasing the diameter and the hollow ratio of wire during a wire electric explosion.

Key Modes of Ignition and Maintenance of Corona Discharge in Air

Theoretical and experimental studies of various modes of corona discharge operation in atmospheric pressure air are presented in this short review. The original results of modeling negative corona discharges are presented, taking into account the non-stationary plasma-chemical kinetics of charged particles in air plasma. The space–time evolution of the discharge in needle-to-plane geometry is investigated and analyzed. Several stages of discharge development are revealed from the moment of initiation of a low-negative current corona to the quasi-stationary mode of a glow discharge. Experimental data of the authors are presented. Modern technology and diagnostic equipment with a wide variation of the main parameters (the shape and polarity of the applied voltage, the type of gap, etc.) was used. The measurement of the optical characteristics of the plasma glow was carried out with high spatial resolution. Corona discharge current pulse profiles in the air at atmospheric pressure have been recorded with subnanosecond time resolution. With a positive polarity of the pin electrode and high voltage, a transition from a spherical streamer initiating a corona discharge to a cylindrical streamer is shown. The author’s results are rigorously evaluated through a critical comparison with findings from other research groups.