Application of electrochemical impedance spectroscopy to commercial Li-ion cells: a review

With the popularity of electrical vehicles, the lithium-ion battery industry is developing rapidly. To ensure battery safe usage and to reduce its average lifecycle cost, accurate state of charge (SOC) tracking algorithms for real-time implementation are required for different applications. Many SOC estimation methods have been proposed in the literature. However, only a few of them consider the real-time applicability. This paper classifies the recently proposed online SOC estimation methods into five categories. Their principal features are illustrated, and the main pros and cons are provided. The SOC estimation methods are compared and discussed in terms of accuracy, robustness, and computation burden. Afterward, as the most popular type of model-based SOC estimation algorithms, seven nonlinear filters existing in literature are compared in terms of their accuracy and execution time as a reference for online implementation.

An Overview and Comparison of Online Implementable SOC Estimation Methods for Lithium-Ion Battery

https://www.zenodo.org/record/2642457/files/A%20review%20on%20various%20temperature-indication%20methods%20for%20Li-ion%20batteries.pdf

A review on various temperature-indication methods for Li-ion batteries

Impedance is closely related to the internal physical and chemical processes of lithium-ion batteries. And the properties of the processes can be characterized and thus more detailed information be provided based on it. In the past decades, the impedance is frequently reported as a powerful tool used in the field of lithium-ion battery state estimation and diagnosis. This paper reviews more than 170 papers and organizes the related research according to three themes of impedance modeling, acquisition, and application under the premise of electric vehicle implementation. The strength and weaknesses of the research in each theme are discussed. Based on the research, the possibility and the value of impedance in onboard battery management are revealed. However, challenges are still faced due to the cost limitations, the complex vehicular conditions, and the time-varying battery states. The unsolved issues are summarized in the conclusion. To realize a more smart battery management system with the impedance, more significant work is still needed.

A review of modeling, acquisition, and application of lithium-ion battery impedance for onboard battery management

Electrochemical energy storage is critical for a range of applications spanning electrified transportation and grid energy storage, and there is a need to further improve both the active management and diagnostic capability of current battery management systems. Lithium-based battery chemistries have been favored for their high energy and power densities but require precise management to prevent premature degradation and failure. This work presents an efficient power converter (based on a switched-inductor ladder topology), instrumentation, and an embedded control platform that can provide both active balancing and real-time diagnostic capability through electrochemical impedance spectroscopy (EIS). A digital proportional-integral controller enforces sinusoidal reference signals from a direct digital synthesizer, enabling the power converter to perturb the cells and extract their impedance. Cell-level diagnostics allow for noninvasive measurement of physical electrochemical battery properties that can be used to assess the state of charge and state of health of a battery. A ladder converter prototype was implemented on a printed circuit board to perform EIS on two Panasonic 18650 cells in series. Experimental results showed balancing converter efficiency of 95%, and the accuracy of the prototype was validated through comparison to a state-of-the-art commercial benchtop system.

A Scalable Active Battery Management System With Embedded Real-Time Electrochemical Impedance Spectroscopy

Online diagnostics for monitoring of battery cells in a battery pack is necessary in order to determine the state of the battery pack, like its age and safe operation. It could also provide the possibility to adjust the operation strategy of the battery management system and the load to increase the battery lifetime and safety. Impedance spectroscopy is a well-known measurement technique for electrochemical systems, such as a battery half-cell. Once the method is implemented in the battery management system and performed online during operation it could provide a monitoring system for the whole pack. Current solutions are either inaccurate or too big, expensive and energy inefficient. The presented approach proposes a dual use of the battery charger which incorporates a switched mode amplifier to generate the stimuli current necessary to perform an electro impedance spectroscopy. A suitable control is designed to overcome the non-linearities and instabilities introduced by the output filter and the current crossover effects of the electronic switches. This inexpensive, energy efficient technology could allow impedance monitoring of every cell in the battery pack and make a better prediction of the state of the battery possible.

Electrochemical impedance spectroscopy for online battery monitoring - power electronics control

Impedance Spectroscopy is a well-known measurement technique for electrochemical systems, such as a battery half-cell. Once this method would be implemented in the battery management system and performed online during operation it could provide a monitoring system for the whole pack and increase its lifetime and safe operation. Current solutions are either inaccurate or too big, expensive and energy inefficient. The presented approach proposes a dual use of the battery charger which incorporates a switched mode amplifier to generate the stimuli current necessary to perform an Impedance Spectroscopy. The drawback of this method are the distortions associated with the modulation of the measurement frequency onto a carrier frequency. The influence of the DC-link voltage and the switching frequency on the on the total harmonic distortion are analysed. These theoretical results are compared with the ones from experiments. A custom designed switched amplifier was built up, specifically designed for performing Impedance Spectroscopy on a battery pack. This technology could allow impedance monitoring of every cell in the battery pack and make a better estimation of the state of the battery possible.

Impedance spectroscopy for battery monitoring with switched mode amplifiers

https://www.iri.upc.edu/files/scidoc/1421-Ethanol-catalytic-membrane-reformer-for-direct-PEM-FC-feeding.pdf

Ethanol catalytic membrane reformer for direct PEM FC feeding

The batteries in uninterruptable power supplies of telecommunication equipment never run full cycles. Therefore their remaining capacity and state of health is difficult to determine. On-line impedance monitoring could help to monitor the health of the batteries while they are waiting for the next power outage. A cost effective implementation would use already existing components in the system of an uninterruptible power supply. The excitation signal could be generated with the battery charger, the balancing unit, the DC/DC or the DC/AC converter. Depending on the used component, the harmonics of the excitation current changes significantly as well as the components of the converter system which act as a filter for the excitation current Maximum impedance deviations of 1% to a successive measurement were achieved.

Reinhold Koch

Papers

Electrochemical impedance spectroscopy for online battery monitoring - power electronics control

Impedance spectroscopy for battery monitoring with switched mode amplifiers

Ethanol catalytic membrane reformer for direct PEM FC feeding

On-line electrochemical impedance spectroscopy implementation for telecommunication power supplies

Temperature Measurement of Large Format Pouch Cells with Impededance Spectroscopy