Electrochemical Impedance Spectroscopy
With the widespread use of high-performance batteries in electric vehicles, the demand for detailed monitoring of the operation and condition of battery stacks is growing rapidly.
Electrochemical Impedance Spectroscopy (EIS) provides insights into the details of the electrochemical reaction down to the level of ions – with the precision and reliability of REGATRON devices!
Key Points
- Modulation Capability and Signal Quality: The G5.Series delivers exceptional modulation capability and high signal quality, making it ideal for precise ElS analysis. This allows for accurate monitoring of charge flow, electrode conditions, and electrolyte states, giving detailed insights into electrochemical processes with minimal noise and interference.
- Bidirectional Operation with Wide Frequency Range: Equipped with bidirectional functionality and a broad frequency range, the G5.Series enables seamless energy flow in both directions, supporting fine-meshed monitoring of processes such as degradation and failure mechanisms. Tnis makes it versatile for applications in batteries, fuel cells, and electrolysers, ensuring comprehensive analysis across a wide spectrum of electrochemical systems.
- Integrated Function Generator and Extensive Data Traffic: With its integrated function generator and extensive data handling capabilities, the G5.Series supports efficient EIS testing with continuous, real-time data collection. This enables highly reproducible resuits, essential for R&D teams looking to conduct detailed evaluations of electrochemical interactions and system performance across various media.
Functional Principle and Description
EIS is based on the determination of the impedance profile of the DUT at different measuring frequencies. An alternating current of low amplitude is modulated onto the working current of the battery stack, the fuel cell or the electrolyser tank, and the corresponding impedance is calculated in real-time from the phase angle between each cell voltage and the exciting current. This procedure is carried out with some predetermined modulation frequencies and then builds up a stack impedance profile.
The picture shows a typical EIS setup consisting of a fuel cell DUT stack, a bidirectional DC power supply unit REGATRON G5.RSS as well as a measurement periphery with data acquisition and analysis tools. The G5 power source simultaneously carries the load current of the fuel cell (red arrow) and modulates them with the alternating current required for the impedance measurement.
It is interesting to note that each electrochemical process has its own characteristic impedance profile. By comparing the impedance curves of the active cells, meaningful conclusions can be drawn about the “health” of the stack. This fact can be used for test purposes, for research and development, but also for close process monitoring.
The Advantages of EIS
The EIS method offers a whole range of advantages over the methods most commonly used today based on the determination of the cell resistance and its limit value monitoring:
- Significantly more precise and versatile insights into the electrochemical system, including statements about the charge flow, condition of the electrodes, condition of the electrolyte, internal resistance and complex impedances
- High sensitivity: Even small process deviations at ion level cause a footprint in the EIS spectrogram and thus enable analyses in the area of electrode/electrolyte interactions
- The EIS method is non-destructive for the analysed process and runs parallel to the actual main electrochemical process
- Good transferability of the method to a variety of electrochemical processes in the fields of batteries, fuel cells, electrolysers, coatings and electrochemical sensors
- EIS works in both liquid and solid-state media
- The high reproducibility of the results enables quantitative data to be obtained for further analysis by chemists and R&D specialists
- EIS is the method of choice when it comes to fine-meshed monitoring of electrochemical processes, the determination of degradation and drift as well as the identification of failure mechanisms
Why REGATRON Devices for EIS
EIS requires a particularly high level of modulation capability from the load current source. In the interests of good signal quality, it must be able to work fully bidirectionally and have an integrated function generator with a very wide frequency range. It must be system-capable in order to handle the extensive data traffic from and to the test environment. The REGATRON G5 device family has established itself as a recommended system source in practical EIS applications thanks to its proverbial accuracy and electrical stability as well as the large number of useful interfaces.
Suitable Products
G5.RSS Series
The G5.RSS series integrates Regatron’s cutting-edge technology in a compact, space-saving design. It features rapid transient response (50…100 µs), ripple modulation up to 10 kHz, and high-precision current and voltage regulation. Its switchable output capacitance ensures stability and maximum dynamic response in both CV and CC modes. Ideally suited for a wide range of demanding laboratory and industrial applications, including testing compliant with automotive and industry standards EIS, P-HIL, and more.
- Power Range: 0…9 to 0…5000+ kW
- Voltage Range: 0…60 to 0…3000 VDC
G5.BT Series
Specialized 1- to multi-channel tester / cycler for battery modules and packs, offering adjustable, high dynamics (50…100 µs), outstanding accuracy, and application-specific safety features. It includes a dual measurement range for maximum accuracy and G5.BatControl software. Mobile racks with IP20 or IP54 ratings are available. Optimized for various battery testing applications and EIS.
- Power Range: 0…9 to 0…5000+ kW
- Voltage Range: 0…60 to 0…3000 VDC
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For added flexibility, selected power supplies may also be available for rent. Please contact REGATRON to discuss your specific requirements and to check availability for your application.
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