Discharge Tests Research Articles

Amorphous Cobalt Tin Oxide/Reduced Graphene Oxide Decorated on Graphite Felt as Positive Electrode for Vanadium Redox Flow Battery

The Vanadium Redox Flow Battery (VRFB) stands out as one of the most promising large-scale energy storage systems. Nevertheless, the graphite electrode materials commonly used in VRFBs often exhibit drawbacks such as limited electrochemical activity and insufficient conductivity, ultimately resulting in suboptimal performance for the VRFB. In this study, we utilized highly conductive reduced graphene oxide (rGO) as a carrier for cobalt tin oxide (CoSnO3), aiming to enhance their catalytic capability towards vanadium ions. CoSnO3/rGO composite was confirmed using XRD and TEM, revealing nanoboxes morphology and amorphous structure. XPS and EPR analysis showed an increase in oxygen vacancies after composite formation. In order to further prove the effect of CoSnO3/rGO composite catalyst modified graphite felt, the modified graphite felt electrode was applied to the positive electrodes of VRFB, and the charge and discharge tests at different current densities were carried out. At a current density of 160 mA/cm², the composite demonstrated a voltage efficiency of 74.22%, surpassing the heat treated graphite felt by 2.69%. Noteworthy enhancements in capacitance were also evident at this specific current density. Furthermore, stability testing over 50 cycles revealed no significant degradation, underscoring the superior performance and outstanding durability of the CoSnO3-rGO modified graphite felt throughout charge and discharge cycling. The result of this study highlight the promising potential of CoSnO3-rGO composites as efficient catalysts for vanadium redox flow batteries, providing improvements in electrochemical performance and long-term stability.

Dual photoelectrode-drived Fe–Br rechargeable flow battery for solar energy conversion and storage: A cost-effective approach

The integrated design of solar energy conversion and storage systems has attracted increasing attention, and non-spontaneous redox reactions driven by dual photoelectrodes provide a potential solution to this issue. This study presents a solar rechargeable flow battery (SRFB) that combines dual photoelectrodes (BiVO4 or Mo–BiVO4 as photoanode, polyterthiophene (pTTh) as photocathode) with cost-effective redox pairs (Fe3+/Fe2+ and Br3−/Br−). The system charges under simulated solar illumination (100 mW∙cm−2, AM 1.5G) and releases stored energy controllably as electrical energy. Research indicates the Mo–BiVO4 photoanode and pTTh photocathode achieve an open-circuit voltage of 0.34 V and a short-circuit current density of 0.38 mA cm−2. Using a specially designed Fe3+/Fe2+-Br3−/Br− (Fe–Br) SRFB device made via 3D printing, a charging photocurrent of approximately 1.9 mA cm−2 is attained. In constant current discharge tests, an initial discharge voltage of 0.23 V is observed at 0.1 mA∙cm−2 within the 10 discharge cycles, demonstrating system stability and offering a viable solution for low-cost, large-scale solar energy storage and conversion.

MoC@C/RGO with nano-restricted area structure for active electrode in supercapacitor

Metallic carbides are widely used as active electrodes in supercapacitors due to their excellent energy storage activity. In this study, a nano-restricted area strategy was employed to prepare a unique structured MoC@C flower sphere composite RGO active material (MoC@C/RGO). Due to the restricted area effect of RGO, MoC@C is restricted to specific areas, with advantages such as uniform dispersion, prominent active sites, high conductivity, and uniform distribution of current collectors. MoC@C/RGO, as the active electrode material of supercapacitors, was subjected to galvanostatic charge–discharge testing (GCD) tests and showed a specific capacitance value of 420 F/g. In addition, MoC@C/RGO showed a capacitance retention rate of 97.6% in 5000 cycles of GCD, indicating that the material has good electrochemical stability.

Improving rate performance of FeC2O4/rGO composites on lithium storage via single-polymerization‐induced electrostatic self‐assembly

Based on the wide interlayer distance for ions diffusion, iron (II) oxalate exhibits excellent lithium storage ability. However, the local deposition of metallic nanoparticles of Fe0 leads to low electrochemical reactivity, which hinders the actual application of FeC2O4 in large current regions (>5C). To solve this problem, a strong cationic polymeric electrolyte, polyelectrolyte diallyl dimethyl ammonium (PDDA), was introduced to construct a [FeC2O4(PDDA)]+ ligand. By single-polymerization‐induced electrostatic self-assembly, the [FeC2O4(PDDA)]+ ligand was combined with the surface-charged rGO to produce a FeC2O4/rGO material. It is proved that the rGO carrier improves the interparticle conductivity, electrochemical activity and structure stability of the iron (II) oxalate particles, ensuring the stability of Li || FeC2O4/rGO battery at a rapid charging rate of 20C (8 A g−1) for more than 500 cycles (with the special capacity of 713 mAh g−1). Compared with FeC2O4 electrode, owning to high reactivity of rGO and continuously activating on the nanoscale Fe metal generated at ∼0.75 V, FeC2O4/rGO shows higher electrochemical activity of conversion reaction in the first 50 cycles and better reversibility in the rate charge–discharge test (the capacity rapidly increased to 1158.8 mAh g−1 after 20C cycles). This work reveals how the structural design of conducting and supporting the carrier can achieve fast charging for iron (II) oxalate lithium-ion batteries.

MANUFACTURING AND TESTING HIGH VOLTAGE FILTER CAPACITORS

This paper presents the manufacturing and testing methods of 30kV and 33nF high voltage filter capacitors. One of the biggest advantages of small companies is that they are able to produce a high diversity of capacitors in small quantities. One of the prices of this flexibility is a higher level of manual manufacturing process in production. But this higher level of manual manufacturing does not mean lower quality in the final product. For high quality products in the high voltage industry, it is necessary to do routine tests in all of the products. For high voltage capacitors the following three tests must be done to ensure quality: voltage strength test, partial discharge test, capacitance and dissipation factor test. The capacitance and dissipation factor test have to be done at different voltage levels. The voltage strength test has to be done at least 20% higher than the rated voltage. This kind of test gives us information not only about the quality of the product itself, but about distribution of the capacitance for example, or about the strength of the production process, and about the quality management system of the company.

Research on the Optimization of the Heating Effect of Lithium-Ion Batteries at a Low Temperature Based on an Electromagnetic Induction Heating System

Based on an electromagnetic induction heating system that was recently developed in a previous work, an orthogonal test with three elements and nine levels was carried out to improve the heating effect of the system. This was intended to achieve a balance between the heating rate and temperature uniformity, where the electrochemical and thermal behaviors of the heated lithium-ion battery could be characterized by a high-accuracy electrochemical–thermal coupling model. This was validated against constant-current discharge and HPPC test data at room temperature and different low temperatures. Under the optimal parameter combination that was found in the orthogonal test, the battery temperature could rise to 293.15 K from 243.15 K in 494 s, with a maximum temperature rise rate of 0.133 K·s−1. The temperature difference after heating reached 4.21 K, which resulted from the heat conductivity of the battery material due to the skin depth of the battery shell and the material properties inside the battery. Due to the internal resistance, which decreased to no more than a quarter of the low-temperature level, both the usable energy and pulse power were increased more than 2.5 and 3 times, respectively. The enhancement of the energy output ability could provide a greater cruise range and improved dynamics for electric vehicles. The capacity calibration results obtained during the heating cycles indicated that there was only a 3.61% reduction in capacity retention after 120 repetitive heating cycles, which was 0.008 Ah below the normal cycle at 293.15 K, even compared with room-temperature capacity calibration, thus reducing the effect on the battery’s lifetime. Therefore, the electromagnetic induction heating system with a heating strategy could achieve a beneficial compromise between the temperature rise behavior, cycle lifetime, and working ability, indicating considerable potential for the optimization of the heating effect.

Modeling the Discharge Rate of a Screw Conveyor Considering Hopper–Conveyor Coupling Parameters

Developing a flow rate model for the screw feeder and optimizing discharge performance are crucial for achieving automated intelligent precision feeding. This study constructs a mass flow rate model for screw conveyors, considering the coupled structural parameters of the hopper and screw conveyor. The model is developed using single-factor tests and central composite design (CCD) response surface tests and is validated through actual discharge tests. Results indicate that the discharge rate in the hopper–screw conveyor system is primarily influenced by the screw conveyor itself. Among the structural parameters, the hopper inclination angle and the hopper discharge opening length significantly affect the filling coefficient. Validation tests show an average error of 6.8% between the predicted and simulated mass flow rates and 5.0% with the actual mass flow rate, demonstrating the model’s high precision and accuracy.

Effect of hydrochloric acid on the properties of Ni-MOF nanostructures as supercapacitor electrode materials

In this paper, we investigate the effect of hydrochloric acid on the energy storage characteristics of nickel-based metal–organic framework (Ni-MOF) nanostructures. Electrochemical tests reveal that Ni-MOF exhibit high capacitance under hydrochloric acid regulation, achieving a current density of 2567.23 F/g at 2 A/g in 1 ml. Additionally, the synthesized Ni-MOF demonstrate low electrical resistance, with a resistance (Rs) of 1.209 Ω at a hydrochloric acid volume of 1 ml. After 5000 cycles of galvanostatic charge–discharge testing, the cycle retention efficiency of Ni-MOF-0.5 ml remains at 85.71 %.

Clinical course of congenital hypothyroidism with gland in situ and necessity of L-thyroxine therapy after re-evaluation.

Clinical course and need for long-term L-thyroxine (LT4) therapy of congenital hypothyroidism (CH) with gland in situ (GIS) remain unclear. To describe the clinical history of CH with GIS and evaluate the proportion of patients who can suspend therapy during follow-up. Retrospective evaluation of patients followed at referral regional center for CH of Pisa. 77 patients with confirmed primary CH and GIS after positive neonatal screening were included. All children started LT4 at CH confirm. At 3 years of age, 55 children underwent a clinical re-evaluation after withdrawal of therapy with hormonal examinations, imaging of the thyroid gland with ultrasonography and 123-iodine with perchlorate discharge test. Subsequent periodic controls of thyroid function were executed and, when possible, a new attempt to stop LT4 was performed. Adequate follow-up data (at least 6 months after treatment suspension trial) were available for 49 patients. Among the 55 patients who were reassessed, 18 (32.7%) were euthyroid. Considering subsequent follow-up, 49% of patients were no longer treated and 51% were taking therapy. No differences in neonatal parameters were observed between the two groups; LT4 dose before the last trial off medication was higher in permanent CH (p 0.016). Monitoring of thyroid function in children with CH and GIS is necessary to evaluate the need for substitution and avoid overtreatment. Even if therapy can be suspended, patients need to be monitored because apparently normal thyroid function may decline several months after withdrawal of LT4.

A Remote Intelligent Check and Discharge Test System for Substation Battery Pack Based on Raspberry Pi

Abstract Regular check and discharge test of the battery pack is an effective means to ensure the normal state of the battery and timely detect outdated batteries. However, conventional manual check and discharge test methods are costly, cumbersome, and inefficient in maintenance. This article introduces a remote intelligent check and discharge test system for a substation battery pack based on Raspberry Pi. The system monitors the battery status in real-time, allowing operators to detect battery faults on time through the front-end management interface. At the same time, remote check and discharge tests can be carried out, greatly ensuring battery safety and solving the shortcomings of conventional manual methods.

Research on discharge characteristics of synthetic ester-paper insulation under power frequency and low frequency

Abstract Synthetic ester insulating oil transformer has broad application prospects in offshore wind power low-frequency power transmission. This paper carried out discharge tests on synthetic ester-paper insulated used sharp plate electrodes at a power frequency of 50 Hz and a low frequency of 17 Hz based on the pulse current method. The research results show that some basic characteristics do not change under 50 Hz and 17 Hz, that is, the discharge is distributed near the voltage peak in a peak shape. The main differences are that the positive peak characteristics at 17 Hz tend to be blurred; the positive maximum discharge amount, and discharge times show an overall downward trend; the phase-resolved partial discharge pattern (PRPD) and the statistical map (n-φ, n-q) have the same overall shape, but different distribution ranges. The test results can be used as a reference for partial discharge pattern identification and insulation design in synthetic ester low-frequency transformers.

Synthesis and electrochemical properties of high entropy titanate powders (La0.2X0.2Ba0.2Sr0.2Y0.2)TiO3 (X = Na or K, Y = Ca or Pb) with perovskite structure

In this paper, four new high entropy titanate powders (La0.2X0.2Ba0.2Sr0.2Y0.2)TiO3 (X = Na or K, Y = Ca or Pb) were successfully synthesized by a sol‒gel strategy. When the pH value of the sol ranged from 3 to 4, it was easier to obtain pure high entropy powders with a perovskite structure. When the calcination temperature was in the range of 700 °C–900 °C, the high entropy powders were more beneficial to form a single solid solution with high XRD diffraction intensity and crystal quality. The as-synthesized powders with uniform distribution of A-position elements had a particle size between 50–120 nm and good dispersibility. The cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) tests showed that these powders had better electrochemical properties and energy storage potential. When the discharge current was 1 A/g, the specific capacitance was higher than 136 F/g, even if the current density was 10 A/g, the specific capacity remained about 60 % of the initial.

Analysis of gap distance of ultra high voltage AC transmission lines in areas with altitude above 2000m

Abstract Research on long-wave front discharge characteristics of lines and long gaps of substation equipment in high-altitude areas needs to be conducted in a systematic manner immediately in order to guarantee the safety and economy of high-altitude UHV lines with respect to external insulation. However, at present, the gap discharge test of transmission lines is mainly carried out in areas below 2000m above sea level. The actual test is challenging to conduct in the high altitude region, and the test data is incomplete. To further confirm the validity of extrapolation of existing altitude test data to high altitude areas, this paper conducts theoretical analysis based on the real test data under standard meteorological conditions provided by GB/T 24842 standard. The altitude correction methods in IEC 60071-2: 2018 and IEC 60060-1: 2010, the m-coefficient method and g-parameter method, are used to correct the lightning impulse, power frequency, and standard switching impulse of AC transmission line gaps. The discharge voltage in areas below 5000m above 2000m is obtained, and several significant discharge characteristic parameters are obtained. Based on the 50% discharge voltage requirements of various voltage types of 1000kV transmission lines, combined with the discharge voltage curves at multiple altitudes, the minimum air gap distance of transmission lines at the altitude of 2000m-5000m is obtained. The comparative analysis of the correction results of the two methods provides a way of thinking for the next step to carry out the true test of UHV AC transmission line gap discharge in higher elevation regions.

Breakdown calculation of zoning tests by positive lightnings

To simulate a natural lightning strike, the breakdown should occur within 1–3 μs in an aircraft lightning zoning test. However, the breakdown voltage–time characteristic of the combined gap is hard to derive because of the complex breakdown process. In this paper, a series of positive lightning impulse discharge tests in a rod electrode–floating aircraft model–plate combined gap were conducted. The leader propagation processes in both sub-gaps were observed using a high-speed camera. The potential of the floating aircraft model was analyzed. We propose a potential calculation model for the floating aircraft during the leader propagation phase. After fitting test data, an empirical formula for the connected streamer plasma was given. Taking that model into account, the calculation result of the average breakdown time of the combined gap has an error of <5.7%.

Influences of the vibration frequency and phase of the core of ultra-high voltage shunt reactors on suspended discharge in oil-paper insulation

Severe vibration of the core of ultra-high voltage (UHV) shunt reactors under operating conditions often leads to the occurrence of suspension electrode, and such a suspended discharge defect will destroy the oil-paper insulation. It is necessary to investigate the influence of vibration on suspended discharge when determining the best operating condition of UHV shunt reactors. The vibration frequency of the suspension electrode and the phase difference between the applied voltage and the vibration are studied by simulation and experiment. The simulation results show that the phase difference between the voltage and the vibration parameters will lead to an increase in the surface maximum field strength. The distortion of the field intensity caused by several typical vibration frequencies of reactor vibration is ranked (in ascending order) thus: 100, 300, 50, and 200 Hz. There is a coupling relationship between the phase difference and the vibration frequency on the suspended discharge, which will lead to an inconsistency between the field intensity and each single factor. The partial discharge test results of the collision between the suspension electrode and the high-voltage electrode show that the discharge generated by vibration at 100 Hz is much higher than that at other frequencies, followed by those at 300 and 50 Hz, and the discharge generated by vibration at 200 Hz is very small. When the phase difference of voltage advance vibration is between 0° and 90°, the quantity of local discharge is large. When the phase difference is between 90° and 180°, the local discharge is small.

Research on the method of air gap clearance selection for bushing at high-altitude areas

Abstract As an important component of the core equipment of the UHV substation, the operation reliability of the bushing is directly related to the safe operation of the main equipment. There are some technical problems in the development of casing in the Sichuan-Chongqing project, such as technical problems at high altitudes and a lack of relevant experience in the correction of air gap and equipment external insulation altitude. Therefore, there is an urgent need to research the selection of gap distance for UHV AC substation bushing electrical characteristics test in high altitude areas. In this paper, based on the standard meteorological conditions and the rod-plate gap switching impulse discharge test data at an altitude of 4300 m, the minimum gap distance of UHV AC substation bushing withstanding 1800 kV and 1950 kV under different methods is obtained. The results show that by comparing the two calculation methods, the minimum distance calculation method of the true test combined with the gap coefficient method avoids the error of altitude correction, and the minimum gap distance is reduced by 7.84%-14.17% compared with the former. The research content can provide a reference for selecting the dry arc distance of the casing. The next step should be to carry out the discharge characteristic test of the true-size electrode at a high altitude, so as to simulate the field situation more realistically and provide more powerful technical support for the project.

Analysis and Treatment of a Partial Discharge Fault in a 220kV Transformer

Abstract Partial discharge test of transformer is one of the most important detection items in the factory test of transformer, which is related to whether the transformer can operate safely and stably. This article will analyze a case of partial discharge exceeding the standard in a 220kV transformer. Based on the joint detection technology of ultrasonic partial discharge and ultra high frequency partial discharge, the defect location will be found. And the structure of the transformer will be researched to identify the cause of the defect. The diagnosis and treatment will be successfully completed. Finally, the conclusion will be verified through finite element analysis. This provides reliable guidance for partial discharge detection and rectification measures in transformers’ production and operation.

Relating state-of-charge to impedance and equivalent circuit parameters in lithium-ion cells: An experimental study

The wide-band impedance of Lithium-ion (Li-ion) batteries has become a focal point for researchers interested in State-of-Charge (SOC) estimation and battery modeling. However, the interplay between SOC, wide-band impedance, and model parameters has not been extensively explored. This paper addresses this gap by investigating how SOC impacts the impedance and Equivalent Circuit Model (ECM) parameters of a Li-ion battery cell through empirical measurements. The study utilizes discharge tests to vary the SOC and employs the Coulomb Counting Method (CCM) to estimate the approximate SOC from the response signals. A novel measurement technique is introduced and applied to determine a cell’s wide-band impedance at different SOC levels. This innovative approach uses a Pseudo-random Impulse Sequence (PRIS) perturbation signal to measure wide-band cell impedance. The collected impedance data is then used to estimate the ECM parameters. Experimental findings reveal an inverse relationship between impedance and SOC. Additionally, the ECM parameters exhibit significant correlation with SOC, particularly in mid- to low-frequency regions. This research highlights that SOC profoundly influences ECM parameters, offering valuable insights into the performance of Li-ion batteries under various conditions.

Li1.4Al0.4Ge0.1Ti1.5(PO4)3: A stable solid electrolyte for Li-CO2 batteries

In this study, a solid electrolyte, Li1.4Al0.4Ge0.1Ti1.5(PO4)3 (LAGTP), with a sodium superionic conductor-type crystal structure, was prepared using a facile solution-based method. LAGTP exhibited exceptional ionic conductivity (1.05 × 10−3 S cm−1) and a low activation energy (0.237 eV). The LAGTP pellet was employed as a solid-state electrolyte in a Li-CO2 battery, showcasing charge-discharge characteristics via a reversible electrochemical reaction (4Li+ + 3CO2 ↔ 2Li2CO3 + C). As-synthesized multi-walled carbon nanotubes, drop-cast on carbon cloth, were used as the cathode. The battery underwent 60 cycles with a cut-off capacity of 1000 mAh g−1 at various current densities, and a full-depth charge and discharge test was conducted at 100 mA g−1. During the charge/discharge process, the particle size of the dead lithium increased on the cathode surface, leading to the blockage of active sites for conversion. Post-cycling analyses were performed to elucidate the cathode degradation mechanism. The incorporation of LAGTP significantly enhanced battery cycle life and safety, making it a suitable candidate for use in next-generation, high-performance Li-CO2 batteries.

Accurate Internal Monitoring of Batteries by Embedded Piezoelectric Sensors

AbstractAdvancements in operando techniques have unraveled the complexities of the Electrode Electrolyte Interface (EEI) in electrochemical energy storage devices. However, each technique has inherent limitations, often necessitating adjustments to experimental conditions, which may compromise accuracy. To address this challenge, a novel battery cell design is introduced, integrating piezoelectric sensors with electrochemical analysis for surface‐sensitive operando measurements. This innovative approach aims to overcome conventional limitations by accommodating commercial‐grade battery electrodes within a single body, alongside a piezoelectric sensor. This enables operando electrogravimetric measurements to be realized, and the electrochemistry of a battery to be more faithfully reproduced at the sensor level. A proof of concept is carried out on both Li‐ion (LiFePO4//Graphite) and Na‐ion (Na3V2(PO4)2F3//Hard carbon) systems, utilizing commercially available powder electrodes. In both cases, the results reveal rational mass variations at the sensor level during the cycling of commercial electrodes with mass loadings several orders of magnitude higher, while performing Galvanostatic Charge Discharge (GCD) tests across various C‐rates. This innovative design opens up possibilities for a broader application of operando electrogravimetry within the battery community, to enhance the understanding of EEI behavior and facilitate the development of more efficient energy storage solutions.