Online Electrochemical Impedance Spectroscopy Research Articles

Balancing resistor-based online electrochemical impedance spectroscopy in battery systems: opportunities and limitations

Active dissipative balancing systems are essential in battery systems, particularly for compensating the leakage current differences in battery cells. This study focuses on using balancing resistors to stimulate battery cells for impedance measurement. The value of impedance spectroscopy for in-depth battery cell diagnostics, such as temperature or aging, is currently being demonstrated and recognized by vehicle manufacturers, chip producers, and academia. Our research systematically explores the feasibility of using existing balancing resistors in battery management systems and identifies potential limitations. Here we propose a formula to minimize hardware requirements through signal processing techniques. A quadrupling of the sampling rate, number of averaging values, or the size of the fast Fourier transform is equivalent, concerning the signal-to-noise ratio, to increasing the analog resolution by one bit or reducing the input filter bandwidth by a quarter.

Implementation and optimization of perturbation currents for vehicular proton exchange membrane fuel cells online electrochemical impedance spectroscopy measurements

AbstractThis paper presents an implementation method of perturbation currents for vehicular proton exchange membrane fuel cell (PEMFC) online electrochemical impedance spectroscopy (EIS) measurements. The topology of the parallel dual‐boost DC/DC converter system for the EIS measurement is presented. The DCdc and DCac modules in the converter system implement the DC current and the sinusoidal EIS perturbation current independently. Simulation results show that the proposed perturbation current generation method can be implemented efficiently. In the frequency domain, the current of DCdc couples to the perturbation current of DCac, leading to a reduction in the accuracy of the current amplitude after superposition. The mechanism of current amplitude reduction after superposition is discussed. Feed‐forward compensation and fuzzy compensation optimization are proposed for the DCdc current control. Both compensation algorithms achieve excellent results. A comprehensive framework for evaluating the compensation effect is presented. The evaluation results show that feed‐forward compensation has a better advantage in solving the above problems due to its simplicity and less impact on hardware control. Experimental results show that with the optimization algorithm, the input perturbation current increases from 6% to 83% of the theoretical value.

In operando detection of Lithium plating via electrochemical impedance spectroscopy for automotive batteries

Reducing the charging time is one of the main goals towards increasing the acceptance of electric vehicles. One of the limits of fast charging lithium-ion batteries with graphite-based anodes is lithium plating, a process which occurs mainly at high charging rates, low temperatures and high state of charge. Detecting the onset of lithium plating during a charging procedure is essential in order to optimize fast-charging profiles. This paper introduces a new method that allows the detection of the onset of lithium plating in automotive lithium-ion batteries using on-line electrochemical impedance spectroscopy. Compared to similar approaches, the measurement itself does not result in a significant increase in the charging time. The detection is based on observing the real part of the impedance across the state of charge during the charging procedure. The onset of lithium plating can be detected by a deviation from the nominal behavior in the form of a drop towards lower impedance. The behavior is both explained theoretically using electrochemical equivalent circuits and shown experimentally. The impedance measurements are carried out using an integrated small-scale device to allow on-line impedance analysis in an automotive environment and an integration into future battery management systems.

On-line Electrochemical Impedance Spectroscopy method for PV diagnosis system

PV fault conditions in photovoltaic (PV) systems reduce panel power performance and accelerate cell degradation. In this way, many research have recently turned to the diagnosis of PV generator to minimize the cost of the produced energy and ensure reliable power production. This paper proposes a new PV diagnosis system based on on-line Electrochemical Impedance Spectroscopy. This latter is used to estimate internal parameters of PV panel connected to a resistive load via a DC/DC boost converter. The Nyquist Diagram allows to plot and evaluate dynamic impedance response versus variable low frequency signal injected in conjunction with the high frequency system allowing to operate the PV in MPPT condition. The dynamic single diode model with a series resistance, a shunt resistance and a junction capacitance is used to design the PV model in MATLAB/Simulink. Simulations results are given for normal and for faulty operation whether in the PV panel or in the load. Referring to these results, it is concluded that the proposed diagnosis method allows to detect PV panel faults regardless of load variation.

Binary Sequences for Online Electrochemical Impedance Spectroscopy of Battery Cells

Online diagnostic of lithium-ion battery (LIB) cells may have significant impact on chemical energy storage systems. Electrochemical impedance spectroscopy (EIS) is widely used for the characterization of LIBs and could be the most appropriate technique for online diagnostic, but its response time should be shortened. This work investigates the usage of multisine excitation to shorten the measurement time and simplify the hardware implementation for EIS of battery cells. Two types of multisine binary sequences are considered: sigma–delta modulated multisine sequences (SDMSs) and maximum length binary sequences (MLBSs). Their applicability to online and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> EIS monitoring is evaluated by designing a measurement architecture also suitable to be implemented in a system-on-chip. The calibrated measurement system is compared with a benchtop reference instrument, reporting an RMSE deviation smaller than 5% in the frequency range of interest 1–200 Hz. The realized system is then used for online monitoring of the discharge process of a commercial 18650 LIB cell. The two proposed sequences are compared in terms of accuracy using a digital battery emulator circuit. Both the sequences demonstrated to be suitable for fast measurement and simple hardware integration, enabling online <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> EIS monitoring at cell level.

Power Line Communications for Automotive High Voltage Battery Systems: Channel Modeling and Coexistence Study with Battery Monitoring

As electric vehicles are gaining increasing worldwide interest, advances in driving range and safety become critical. Modern automotive battery management systems (BMS) compete with challenging performance and safety requirements and need to monitor a large amount of battery parameters. In this paper, we propose power line communications (PLC) for high voltage (HV) traction batteries to reduce the BMS wiring effort. By modeling a small-scale battery pack for frequencies up to 300 MHz, we predict the PLC channel transfer characteristics and validate the results using a PLC hardware demonstrator employing a narrowband single-carrier modulation. The results demonstrate that battery PLC is a demanding task due to low access impedances and cell coupling effects, yet transfer characteristics can be improved by optimal impedance matching. PLC for HV BMS not only saves weight and cost, but also improves flexibility in BMS design. PLC enables single-cell monitoring techniques such as online electrochemical impedance spectroscopy (EIS) without additional wiring. Online EIS can be used for in-situ state and temperature estimation saving extra sensors. This work unveils possible coexistence issues between PLC and battery monitoring. In particular, we demonstrate that certain PLC data or packet rates have to be avoided not to interfere with EIS measurements.

Sinusoidal-Ripple Current Control in Battery Charger of Electric Vehicles

This paper proposes a battery charger (BC) for electric vehicles based on sinusoidal-ripple-current (SRC) method. The SRC method is used as an advanced charging-discharging method. On the one hand, the sinusoidal current variations alternately change output active power of the BC, negatively affect AC-side terminal current of the BC, and therefore, cause a power quality problem. On the other hand, the output active and reactive powers must be regulated at constant values without any variations for participation in vehicle-to-grid technology. Thus, a particular topology is suggested and then a control system is precisely designed in order to implement SRC charging-discharging method and adjust the output active and reactive powers for vehicle-to-grid technology without the power quality problem. SRC method can also be used in online electrochemical impedance spectroscopy (EIS) for state of charge and state of health estimation in battery management. The proposed control system can also generate the SRC signals, suitable for online EIS, in a controlled way unlike the recently proposed BCs. The simulation and experimental results demonstrate the effectiveness of the proposed solution.

A novel impedimetric sensor for trace level detection of dimethyl sulfide (DMS)

An easy and effective method for the preparation of a new impedimetric sensor used in the detection of dimethyl sulfide (DMS) at a nanomolar level is presented. The sensor was prepared in two steps from a commercially available screen-printed carbon electrode (SPCE): a simple activation of the SCPE using cyclic voltammetry followed by electroless plating of the working electrode surface with gold clusters. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques confirmed the successful functionalization of the SPCE, revealing the presence of gold particles dispersed on the carbon matrix. Electrochemical impedance spectroscopy (EIS) was used to study the sensitivity of the sensor towards DMS dissolved in aqueous solution and simulated ocean water. Analyses were performed in less than 3 min, and the sensor showed linearity in a concentration range from 1.0 × 10−10 to 1.0 × 10−8 M with a limit of detection of 1.50 × 10−9 M and a limit of quantification of 2.27 × 10−9 M. To simulate the marine environment in which DMS is naturally present in nature, the impedance of the sensor was monitored by online EIS. Moreover, results indicated that, despite not linearly, the sensor is a promising tool to detect the analyte even at 1.0 × 10−11 M, presenting an increase of resistance of 13.5% in relation to its bare condition.

Precise Online Electrochemical Impedance Spectroscopy Strategies for Li-Ion Batteries

This article presents an online electrochemical impe-dance spectroscopy (EIS) technique for a Li-Ion battery. A frequency sweeping method and a precise impedance measurement algorithm are used for the proposed online EIS technique. The proposed algorithm consists of fast Fourier transformations, peak amplitudes, and phase difference estimations. Additional instrumentation with offset clipping and amplifying circuits expand the accuracy of the signal measurement. The offset clipping circuit increases the ripple to measurement voltage ratio without phase delay. The amplifying circuit gives more resolution for the ripple voltage. The proposed instrumentation ensures the precise measurement of ripple voltage and current. The proposed impedance measurement algorithm fulfills the precision level required for industrial Li-Ion battery. To validate the proposed approach, a 40-Ah 13.6 V Li-Ion battery charger was built using a synchronous buck converter and an Opal-RT based controller. The proposed spectroscopy technique will be useful to track and estimate internal electrochemical conditions of a battery.

Online impedance spectroscopy estimation of a dc–dc converter connected battery using a switched capacitor‐based balancing circuit

This study investigates a novel method of undertaking online electrochemical impedance spectroscopy measurements to estimate battery impedance across the frequency range using a battery balancing circuit. A switched capacitor balancing system is used to generate an excitation signal of low-frequency of variable values from which battery voltage and current can be measured to estimate the impedance.

A Comparison of Online Electrochemical Spectroscopy Impedance Estimation of Batteries

This paper compares the methods of undertaking on-line electrochemical impedance spectroscopy that have been published in the literature. This paper describes the different published methodologies and sorts these into categories. This paper looks at the theoretical analysis of the circuits and control techniques and follows up with simulation and/or experimental studies of these methods. This paper focuses on battery systems.

Laboratory and field evaluation of organic corrosion inhibitors in sour media

The expensive and insidious character of corrosion problems encountered in various industries requires appropriate corrosion-monitoring techniques. The specific advantages of using on-line electro-chemical impedance spectroscopy (EIS) to accomplish such a task can be put to profit by analyzing the experimental data points automatically with a mathematical permutation technique. The polarization resistance values calculated from the EIS measurements can then be translated into overall resistance to corrosion. Additionally it is shown that the constant phase element (CPE) necessary to model most EIS results can indicate the progress of localized corrosion. The laboratory evaluation of two proprietary organic inhibitors by EIS measurements showed the two inhibitors to be equally effective in the inhibition of sour gas induced corrosion. Microscopically measured pit depths on exposed carbon steel specimens could additionally be correlated to the integral of the depression angle produced by the CPE. A series of EIS measurements made in a field-pipe loop also showed these two organic inhibitors to be similarly very effective. A post-test analysis of the monitoring electrodes by various surface profile examination techniques revealed the existence of a strong correlation between the extent of pitting corrosion and the CPE analyzed from EIS measurements.