Constant Current Discharge Research Articles

Experimental study of the effect of different pulse charging patterns on lithium-ion battery charging

This study aims to experimentally investigate the impact of different pulse charging patterns on the charging time and performance of lithium-ion batteries at room temperature. Experimental results indicate that most pulse charging protocols have a positive impact on shortening the total charging time compared to the CC-CV charging method with the same input charge capacity. This effect is observed not only in LFP batteries but also in NMC batteries. Three pulse charging patterns are studied: constant current charge (C–C), charge rest (C–R), and charge discharge (C-D). The C-D mode results in the shortest charging time and the smallest cell internal resistance. Compared to the 1C CC-CV baseline, the pulse C-D mode reduces the charging time by approximately 6.8 %, decreases the average pulse internal resistance by about 17.5 %, and increases the remaining discharge capacity ratio by 3.76 % after 800 cycles. Additionally, a pseudo-2D physics model is used to study the internal effects on the battery using the pulse C-D mode. The results show that using the pulse charging method (C-D) results in a more even distribution of electrolyte salt concentration and electrode particle lithium concentration across the cell, thereby improving battery performance.

Synthesis of Flower-like Crystal Nickel–Cobalt Sulfide and Its Supercapacitor Performance

In order to improve the pseudocapacitance performance of metal sulfide electrode materials and obtain supercapacitor energy storage devices with excellent electrochemical reversibility and long-term cycle stability, the synthesis of flower-shaped crystal nickel–cobalt sulfide and its supercapacitor performance were studied. NiCo2S4 flower-shaped crystal nickel–cobalt sulfide was prepared by the hydrothermal method with nickel foam as the raw material, and electrode materials were added to prepare supercapacitor electrodes for testing of the supercapacitor performance. The physical properties of flower-shaped crystal nickel–cobalt sulfide were tested by a scanning electron microscope and transmission electron microscope, and the voltammetric cycle and constant current charge and discharge of supercapacitor electrodes prepared from this sulfide were analyzed through experiments. The experimental results showed that the flower crystal microstructure had a positive effect on the electrochemical properties. The capacitance value was always high at different current densities, and the capacity was as high as 3867.8 A/g at pH 12. After 2000 voltage–charge–discharge cycle tests, the petal-like sulfide capacity still had a retention rate of 90.57, the flower crystal nickel–cobalt sulfide still showed an excellent supercapacitor performance and the specific capacity was still high, which demonstrates that this sulfide has excellent cyclic stability and durability in electrochemical applications.

Research on the novel spinel structure of Cu0.5Ni0.5MnCoO4 and its application in solid oxide fuel cells

In this study, the Cu0.5Ni0.5MnCoO4 (CNMC) material was developed for use in the cathode of solid oxide fuel cells (SOFC). X-ray diffraction (XRD) confirmed the spinel structure and demonstrated compatibility with Yttria-stabilized zirconia (YSZ) electrolyte at elevated temperatures. The conductivity of CNMC was found to be between 28 and 55 S cm−1 at temperatures ranging from 700 to 900 °C. Oxygen-temperature programmed desorption (O2-TPD) revealed that CNMC powder possesses effective oxygen catalytic characteristics. To enhance performance, CNMC was combined with Gd0.1Ce0.9O2-δ (GDC, H2-bank Co. Ltd.) in a mass ratio of 3:7 (CG37). The thermal expansion coefficient (TEC) of this composite was measured at 12.8 × 10−6 K−1, closely matching that of YSZ and avoiding the issue of strontium segregation, eliminating the need for a barrier layer between the electrolyte and the cathode. The peak power densities of CG37 reached 1175 mW cm−2 and 905 mW cm−2 at 800 °C and 750 °C, respectively. CG37 underwent testing for 1000 h under constant-current discharge at 600 mA cm−2 and 750 °C, showing a voltage degradation rate of 2.5 %/kh. The cell's microstructure remained intact without any signs of elemental diffusion or segregation, indicating excellent chemical compatibility and stable structural integrity. This research is expected to further advance the study and utilization of novel solid oxide fuel cells.

Si/BiPO4 composite anode material for lithium ion batteries prepared by solvothermal method

Lithium ion batteries play an important role in various energy storage technologies due to their good safety performance. As an anode material, silicon has attracted attention for its higher theoretical capacity than commercial graphite. But large volume expansion and unstable solid electrolyte interface (SEI) during the cycling of silicon lead to rapid capacity decay, which limits the commercial application of silicon anode. In this article, Si/BiPO4 anode materials were prepared by solvothermal reaction. After morphology analysis and constant current charge discharge cycle analysis of Si/BiPO4 anode materials with different mass ratios, it was found that Si/BiPO4 anode materials with the mass ratio of 7:3 exhibited more excellent electrochemical performance. The conversion reaction of BiPO4 and Li generates Bi and Li3PO4, and the alloying reaction of Bi generates Li3Bi. Bi and Li3Bi reduce the internal resistance of the Si/BiPO4 composite, and Li3PO4 is distributed on the surface of Si material, participating in the formation of SEI film and improving the stability of the material. At a current density of 500 mA g−1, the first discharge specific capacity of the Si/BiPO4 anode is 2672.1 mA h g−1. After 200 cycles, the discharge specific capacity remains at 1308.9 mA h g−1. The electrochemical impedances of pure Si and Si/BiPO4 anode materials before and after cycling were analyzed. It was found that the resistance of the Si/BiPO4 anode before and after 100 cycles was lower than that of pure Si materials, which further proved that the addition of BiPO4 material helps to improve the charge transfer ability of pure silicon materials.

Improvement effect of Co and Ce oxides on the properties of CeO2-Co2O3-Fe2O3 anode materials

Lithium-ion batteries offer several advantages, including high specific energy, extended lifespan, portability, and environmental friendliness. Transition metal oxides are attractive candidates for negative electrode materials due to their higher theoretical specific capacity. To address issues related to poor stability and volume expansion, cobalt trioxide and cerium oxide were introduced as dopants in iron oxide. This study involved the preparation of Co2O3-Fe2O3 and CeO2-Co2O3-Fe2O3 composites, followed by structural characterization and investigation of their electrochemical properties. The doping of cobalt and cerium oxide proved advantageous in refining particle size. Notably, 1% Co2O3-Fe2O3 particles displayed uniform sizing and tight binding. Additionally, the sample containing 0.05% CeO2 exhibited the smallest particle size and a more homogeneous distribution. Furthermore, cobalt and cerium oxide doping significantly improved electrochemical stability. The discharge capacity of 1% Co2O3-Fe2O3 and 0.05% CeO2-1% Co2O3-Fe2O3 after undergoing 100 constant-current charge and discharge cycle respectively remained at 553.17 mAh/g, 698.57 mAh/g. As a negative electrode material in lithium-ion batteries, the composite oxide 0.05% CeO2-1% Co2O3-Fe2O3 demonstrated superior reversibility and stability during the process of lithium-ion insertion and removal, while also exhibiting low contact resistance and charge transfer resistance.

Comparative analysis of equivalent circuit battery models for electric vehicle battery management systems

Lithium-ion batteries need to be controlled by a Battery Management System (BMS) to operate safely and efficiently. BMS controls parameters, such as current, voltage, temperature, state of charge (SoC),state of health (SoH), state of power (SoP) and etc. The battery models and several prediction algorithms that the BMS uses to carry out these checks are essential to the system's performance. Therefore, the battery model is crucial to the BMS. This model is used to optimize the performance, capacity, lifetime and safety of the battery. Using the accurate battery model for BMS and electric vehicles can improve energy efficiency, extend battery life and reduce safety risks. Therefore, it is important that the model can accurately reflect the battery behavior under different load conditions. In this study, the performance of Rint, Partnership for a New Generation of Vehicles (PNGV), Thevenin, and Dual Polarization (DP) battery models, which are widely known in the literature, to simulate static and dynamic voltage behavior is compared. A 18650 NMC battery was used for this purpose, and Hybrid Pulse Power Characterization (HPPC), Dynamic Stress Test (DST), Worldwide Harmonised Light Vehicle Test Procedure (WLTP), and Constant Current (CC) discharge tests were performed. The performance of the models for the four tests is compared. The maximum error values for WLTP are 2.98 % in Rint, 1.32 % in PNGV, 2.80 % in Thevenin, and 1.09 % in DP. Comparing the performances of models for all tests, it is found that the DP model is the most accurate model under both constant and dynamic current conditions.

Brackish groundwater desalination by constant current membrane capacitive deionization (MCDI): Results of a long-term field trial in Central Australia

A long-term field trial of membrane capacitive deionization (MCDI) was conducted in a remote community in the Northern Territory of Australia, with the aim of producing safe palatable drinking water from groundwater that contains high concentrations of salt and hardness ions and other contaminants. This trial lasted for 1.5 years, which, to our knowledge, is one of the longest reported studies of pilot-scale MCDI field trials. The 8-module MCDI pilot unit reduced salt concentration to below the Australian Drinking Water Guideline value of 600 mg/L total dissolved solids (TDS) concentration with a relatively high water recovery of 71.6 ± 8.7 %. During continuous constant current operation and electrode discharging at near zero volts, a rapid performance deterioration occurred that was primarily attributed to insufficient desorption of multivalent ions from the porous carbon electrodes. Performance could be temporarily recovered using chemical cleaning and modified operating procedures however these approaches could not fundamentally resolve the issue of insufficient electrode performance regeneration. Constant current discharging of the electrodes to a negative cell cut-off voltage was hence employed to enhance the stability and overall performance of the MCDI unit during the continuous operation. An increase in selectivity of monovalent ions over divalent ions was also attained by implementing negative voltage discharging. The energy consumption of an MCDI system with a capacity of 1000 m3/day was projected to be 0.40∼0.53 kWh/m3, which is comparable to the energy consumption of electrodialysis reversal (EDR) and brackish water reverse osmosis (BWRO) systems of the same capacity. The relatively low maintenance requirements of the MCDI system rendered it the most cost-efficient water treatment technology for deployment in remote locations. The LCOW of an MCDI system with a capacity of 1000 m3/day was projected to be AU$1.059/m3 and AU$1.146/m3 under two operational modes, respectively. Further investigation of particular water-energy trade-offs amongst MCDI performance metrics is required to facilitate broader application of this promising water treatment technology.

Study on the Influence of Connection Structure between Batteries on Battery Pack Performance

The primary challenge to the commercialization of any electric vehicle is the performance management of the battery pack. The performance of the battery module is influenced by the resistance of the inter-cell connecting plates (ICCP) and the position of the battery module posts (BMP). This study investigates the impact of different connection structures between battery cells on the performance of lithium-ion batteries. A parallel-connected battery model is constructed by connecting a given number of battery cells in parallel, and this model is used to examine the battery connection structure. We discover the effect of the connection structure on the battery pack’s consistency, the development law of the inconsistency of the conventional connection structure after constant current discharge, the scheme for optimizing the connection structure, and the improvement in the battery pack’s performance by the improved connection structure. The performance of the improved connection structure is verified by experiments. This structure showcases a capacity decay of under 5% after 350 cycles and minimal attenuation after 300 charge/discharge cycles.

Effect of increasing Fe catalytic decomposition layer of ammonia on the performance and stability of ammonia electrode

In a direct ammonia proton ceramic fuel cell (DA-PCFC), attaching a catalyst layer on the surface of the ammonia electrode is known to optimize the cell's electrochemical performance and long-term stability. In this study, the Fe catalyst layer is added to the ammonia electrode of the full cell which is prepared with the structure Ni– BaZr0.1Ce0.7Y0.1Yb0.1O3-δ(BZCYYb) (support layer)|Ni-BZCYYb (active layer)|BZCYYb|La0.6Sr0.4Co0.2Fe0.8O3-δ to investigate its impact on the electrochemical performance and stability of the electrode. Under the conditions of 700 oC and 20 ml min−1 ammonia fuel, the peak power densities of cells with and without the Fe layer reach 585.051 and 463.671 mW cm−2, respectively. It is evident that the addition of the Fe catalytic layer significantly improves the electrochemical performance of the cell. Stability tests are carried out for cells with and without the Fe layer at 650 oC, 0.36 A cm−2, and 0.32 A cm−2 constant current discharge. After discharge for 313 and 372 h, both cells show good stability, and the discharge curves of the two cells are consistent after 100 h. The high M-N binding energy of the Fe catalytic layer improved the initial performance of the cell, but this improvement is not sustained over the stability.

The hydrothermal synthesis of d-Ti3CN/V2O5 hollow spheres for enhanced supercapacitors applications

In this work, d-Ti3CN MXene was obtained by selective etching of Al from Ti3AlCN by hydrofluoric acid, and a hydrothermal method was employed to prepare d-Ti3CN/V2O5 hollow spheres. The prepared d-Ti3CN/V2O5 hollow spheres showed enhanced electrochemical properties. V2O5 hollow spheres expanded the distance between d-Ti3CN MXene sheets, leading to fast electron transport and improved electrochemical performance of d-Ti3CN/V2O5 hollow spheres. A specific capacitance of 340 F g−1 was achieved at 1 A g−1 current density, which is higher than that of d-Ti3CN MXene (321 F g−1) and V2O5 hollow sphere (155 F g−1). The initial capacitance retention is 89 % after 6000 cycles of constant current charge and discharge at the current density of 10 A g−1. In short, d-Ti3CN/V2O5 hollow spheres show excellent supercapacitor performance regarding specific capacitance and stability.

Synthesis of Porous Carbon Nanomaterials from Vietnamese Coal: Fabrication and Energy Storage Investigations

The choice of precursor and simple synthesis techniques have decisive roles in the viable production and commercialization of carbon products. The intense demand for developing high-purity carbon nanomaterials through inexpensive techniques has promoted the usage of fossil derivatives as a feasible source of carbon. In this study, Vietnamese-coal-derived porous carbon (PC) was used to fabricate coal-derived porous carbon nanomaterials (CDPCs) using the modified Hummers method. The resulting porous carbon nanomaterials achieved a nanoscale structure with an average pore size ranging from 3 to 10 nm. The findings indicate that CDPC exhibits well-developed micropores and mesopores. The presence of macropores and mesopores not only facilitates the complete immersion of the material in the electrolyte but also effectively shortens the ion diffusion pathways. CDPC boasts a high carbon content, constituting 80.88% by weight. Electrochemical impedance spectroscopy (EIS) Nyquist plot of electrodes made from CDPC showed good conductivity value with low charge-transfer resistance. This electrode worked well and stably with capacitance retention of 74.7% after 1000 cycles. The CDPC specific capacitance reached 236 F/g under a current density of 0.1 A using the constant current discharge method and then decreased as the current density increased. Based on the results of the electrochemical properties of the materials, the energy storage capacity of the CDPC material was good and stable. This investigation presents an eco-friendly methodology for the judicious utilization of coal in energy storage applications, specifically as electrodes for supercapacitors and anodes for Li-ion batteries.

A quench detection method for parallel co-wound HTS coils based on current redistribution

High-temperature superconducting (HTS) coated conductors (CCs) have become the preferred material for superconducting magnet applications due to their high engineering current density and high mechanical strength. However, due to the low quench zone propagation velocity of CCs, magnets wound with CCs suffer from severe quench risks. Therefore, a rapid, sensitive, and reliable quench detection method is crucial for the safe operation of such HTS magnets. In this paper, we propose a quench detection method based on current redistribution, in which two pieces of HTS CCs are soldered together at each end and insulated in the middle part, which are then parallel co-wound into a double-pancake coil. The two tightly coupled windings and low resistance joints form a very low inductance current loop, resulting in fast current redistribution between the two co-windings even at the inception of quench (with still low quench voltage). We deduced analytical solutions of the current redistribution process under different magnet operational scenarios, including constant current operation, charging and discharging, and proposed quench detection criteria. Corresponding quench tests were performed on a small scale co-wound HTS coil, and the results well verified the analytical solutions and the effectiveness of the quench detection method. Our work may be useful for lowering the risks in HTS magnet quench in various applications.

Effects of flocculant and corrosion inhibitor compounding on the electrochemical corrosion behavior of the anode in Al-air batteries

To solve the problem of precipitates affecting battery performance in aluminum-air batteries. This study employed a variety of techniques—including flocculant-simulated sedimentation experiments, electrochemical assays, constant current discharge tests, and microscopic morphology assessments—to evaluate the synergistic effects of corrosion inhibitors and flocculants in the electrolyte of aluminum-air batteries. The inorganic polymer compound polyalumi rlillm sulfate (PSA) and the inorganic compound aluminum sulfate were investigated in a 4 mol/L NaOH+ 0.06 mol/L Na2SnO3 solution to elucidate the electrochemical corrosion mechanism of the 5052 aluminum alloy anode, as well as the sedimentation time and effect of colloidal precipitation. The results showed that the compounding of the two flocculants with the conventional corrosion inhibitor Na2SnO3 enhanced both the sedimentation rate of aluminum hydroxide in alkaline media and decreased the corrosion rate of the aluminum anode. Specifically, 3 g/L PSA was found to be most efficacious, elevating the sedimentation efficiency by 70.6%. Additionally, 1 g/L PSA demonstrated the most significant inhibitory effect on the self-corrosion of 5052 aluminum alloy, leading to an increase in the anode battery's capacity density by 15.5–35.1%. The synergistic action of flocculants and corrosion inhibitors chiefly accelerated the sedimentation rate of precipitates, maintained electrolyte conductivity, and facilitated the formation of a protective film on the surface of the aluminum anode to reduce the self-corrosion rate of aluminum, thereby promoting the improvement of discharge performance of aluminum-air batteries.

Accelerated 3D Simulation for Analyzing Electrochemical and Thermal Distribution in Lithium-Ion Batteries

Understanding the spatial and temporal internal behavior of lithium-ion batteries (LIBs) is crucial for ensuring safe operation and preventing unexpected faults during manufacturing and diagnosis processes. Traditional approaches, such as the pseudo-two-dimensional (P2D) model, provide a simplified representation of LIBs but limit the analysis of continuum-scale electrochemical distribution inside the cell.This study proposes an accelerated three-dimensional (3D) simulation methodology, expanding the conventional P2D model into a pseudo-four-dimensional (P4D) model, including three dimensions of cell structure and a pseudo-dimension inside electrode particles based on the porous electrode theory. In this study, the electrochemical model in the pseudo-four-dimension is combined with a thermal model, considering energy balance with ohmic heat, reaction heat, entropic heat, and internal short circuit (ISC) heat generation.To analyze the P4D model, we apply the following numerical strategies: 1) Elimination of nonlinearity inside model equations using Taylor series expansion, 2) Separation of electrochemical and thermal model variables using a staggered time-stepping method, and 3) Determination of time step size based on the gradient of model output. The proposed method is validated by comparing simulation results for an LFP cell with experimental results and a commercial software under constant current discharge operations (1C, 2C, 3C, and 5C).The accelerated 3D simulation methodology offers significant advantages for exploring internal inhomogeneous properties under different materials operating conditions, ensuring battery safety and reliability under various scenarios. We demonstrate that the proposed method enables the investigation of internal distributions of concentration, potential, and temperature inside battery cells, paving the way for designing and managing batteries with various materials. Figure 1

Influence from Mechanical Stress on State of Health of Large Prismatic Lithium-Ion-Cells Under Various Temperatures

Volume expansion of lithium-ion cells is a well-known ageing phenomenon, in which the outer and inner geometry of the cell is subject to deformation due to physicochemical reactions during ageing and operation, resulting in corresponding degradation effects such as loss of capacity and higher internal resistance in the cell. In a cell module the external deformation of the cells poses a major challenge to the mechanical design due to the resulting swelling forces.In this work, compression force and thickness measurements were performed on large prismatic lithium-ion cell with various compression magnitudes to quantify the influence of mechanical stress on state of health of the cells. The impact of the bracing is shown for lithium-ion cells cycled with 1C constant current constant voltage charge and 1C constant current discharge up to 500 cycles with 100% depth of discharge and at every 50 cycles, the capacity of the cells was determined, and electrochemical impedance spectroscopy measurements were conducted. The cells were cycled until the threshold of 80 % state of health was reached. In-situ thickness measurements showed cell expansion during charging and contraction during discharging due to lithiation as well as de-lithiation additionally the measurements showed an irreversible thickness change in the cell due to ageing phenomenon. To quantify the increase in internal resistance a distribution of relaxation time (DRT) analysis was performed on the electrochemical impedance spectroscopy (EIS) data.

Isothermal battery calorimetry analysis on a thermal behavior of Li-ion battery for electric vehicle

This paper presents the development of an isothermal battery calorimeter (IBC) for analyzing the thermal characteristics of high-capacity lithium-ion pouch cells used in electric vehicles. The IBC incorporated a Peltier module to maintain an isothermal environment within the test cell, and a PID control was employed for the operation. A Positive-Thermal-Coefficient (PTC) heater was used to calibrate the IBC and determine the heat generation rate of the battery during operation. The heat generation rate of a lithium-ion battery (LIB) was measured under various load conditions, including constant current discharge and driving profiles. The results were compared with those of conventional methods, such as equivalent electric circuit model (EECM)-based simulation and inverse heat analysis. This comparison demonstrated that the IBC accurately captured the thermal behavior of the pouch cell, which exhibited changes in the state of charge (SOC), similar to the inverse heat analysis. Additionally, the IBC effectively identified specific regions with significant heat generation, thus facilitating in the detection of serious heat problems within the battery under driving load conditions. Although a time delay in the heat generation rate was observed in the IBC, owing to the thermal inertia of the Peltier module, this issue could be mitigated by reducing the thermal mass of the module.

Modeling Silicon-Dominant Anodes: Parametrization, Discussion, and Validation of a Newman-Type Model

Silicon is a promising anode material and can already be found in commercially available lithium-ion cells. Reliable modeling and simulations of new active materials for lithium-ion batteries are becoming more and more important, especially regarding cost-efficient cell design. Because literature lacks an electrochemical model for silicon-dominant electrodes, this work aims to close the gap. To this end, a Newman p2D model for a lithium-ion cell with a silicon-dominant anode and a nickel-cobalt-aluminum-oxide cathode is parametrized. The micrometer silicon particles are partially lithiated to 1200 mAh gSi−1. The parametrization is based on values from the electrode manufacturing process, measured values using lab cells, and literature data. Charge and discharge tests at six different C-rates up to 2C serve as validation data, showing a root-mean-squared error of about 21 mV and a deviation in discharge capacity of about 1.3%, both during a 1 C constant current discharge. Overall, a validated parametrization for a silicon-dominant anode is presented, which, to the best of our knowledge, is not yet available in literature. For future work, more in-depth studies should investigate the material parameters for silicon to expand the data available in the literature and facilitate further simulation work.

With the synergistic effect of MnCo2O4/Co3V2O8 composite nanomaterials for high performance supercapacitor electrodes

In this work, MnCo2O4/Co3V2O8 composite nanomaterials were synthesized using a straightforward secondary hydrothermal and calcination process. Importantly, Co3V2O8 as a pseudocapacitive material with unique intercalation/delamination reaction, and the stored charge behavior of MnCo2O4 material is a battery-like behavior. These two different reaction mechanisms, when working in parallel, can produce an interfacial and synergistic effect, thus providing high reversible capacity and better electrochemical activity, and the composite has good electronic conductivity and superior electrochemical properties. The prepared MnCo2O4/Co3V2O8 nanomaterial provides a high specific capacitance of 1460 F g−1 at 1 A g−1 and an excellent capacitance retention of 84.61 % (3500 cycles even at 10 A g−1). Hybrid supercapacitors consisting of MnCo2O4/Co3V2O8 and activated carbon (AC) have a great energy density of 37.5 mAh g−1. After 28,000 turns of uninterrupted constant current charging and discharging, it had an initial capacity ratio of 98.6 %. The electrochemical performance showed that the MnCo2O4/Co3V2O8 nanometer material has broad prospects and can provide a new idea for the electrode materials of supercapacitors.

Assessment of Health Indicators to Detect the Aging State of Commercial Second-Life Lithium-Ion Battery Cells through Basic Electrochemical Cycling

Upon reaching certain limits, electric vehicle batteries are replaced and may find a second life in various applications. However, the state of such batteries in terms of aging and safety remains uncertain when they enter the second-life market. The aging mechanisms within these batteries involve a combination of processes, impacting their safety and performance. Presently, direct health indicators (HIs) like state of health (SOH) and internal resistance increase are utilized to assess battery aging, but they do not always provide accurate indications of the battery’s health state. This study focuses on analyzing various HIs obtained through a basic charging–discharging cycle and assessing their sensitivity to aging. Commercial 50 Ah pouch cells with different aging histories were tested, and the HIs were evaluated. Thirteen HIs out of 31 proved to be highly aging-sensitive, and thus good indicators. Namely, SOH upon charging and discharging, Coulombic efficiency, constant current discharge time, voltage relaxation profile trend, voltage–charge area upon discharging, hysteresis open circuit voltage HIs, and temperature difference between the tabs upon charging. The findings offer valuable insights for developing robust qualification algorithms and reliable battery health monitoring systems for second-life batteries, ensuring safe and efficient battery operation in diverse second-life applications.

Investigation of time domain measurement of electrochemical impedance spectrum in low frequency range for lithium-ion batteries using preset equivalent circuit model

A time domain measurement technique using a preset equivalent circuit model consisting of many series-connected resistor and capacitor parallel elements was examined as a measurement method of the electrochemical impedance spectrum of a lithium-ion battery excluding the apparent impedances from open circuit voltage change in the low frequency range. At first, a comprehensive experimental study was carried out to determine the standard condition of the applied signal suitable for this technique. It was established that an impedance spectrum from several tens of microhertz to several tens of millihertz can be accurately measured by selecting a proper, small rate and long duration constant current charge or discharge as the applied signal. Next, impedance spectra excluding the apparent impedances from open circuit voltage change were measured under various conditions using this technique, and basic characteristics of the impedances of the solid state diffusion processes of lithium that exist in the corresponding low frequency range were investigated. It was revealed that the impedance spectrum excluding the apparent impedances from open circuit voltage change in the low frequency range, from several tens of microhertz to several tens of millihertz, can be reasonably separated into two finite length Warburg impedances that can be clearly characterized by difference in their diffusion time constant values and in the state of charge dependence of their diffusion resistances. An Arrhenius type temperature dependence was confirmed for both of their diffusion resistances.