Simultaneous EIS measurements of a Li-ion battery cathode and anode

Importance of the Topic

Electrochemical impedance spectroscopy is a critical technique for probing interfacial and transport processes in battery electrodes. Traditional two-electrode EIS requires separate tests to isolate cathode and anode responses, which may introduce variability and complicate interpretation, especially when time constants overlap.

Objectives and Study Overview

This work demonstrates a method for simultaneous EIS measurement on both cathode and anode of a Li-ion pouch cell. By employing a three-electrode configuration with an internal reference, the study aims to capture impedance data at both electrodes under identical cell conditions in a single experiment.

Methodology

A pouch cell with an internal reference electrode was held at open circuit potential of 3.71 V. Potentiostatic EIS scans were performed from 100 kHz to 100 mHz at 10 frequencies per decade with 30 mV amplitude. The signal between cathode and reference and between anode and reference was recorded concurrently to generate parallel impedance spectra.

Instrumentation Used

• VIONIC potentiostat/galvanostat powered by INTELLO software
• Compliance voltage up to ±50 V and current range ±6 A
• EIS capability to 10 MHz and sampling interval down to 1 μs
• Second Sense functionality for dual-lead potential measurement
• NOVA 2 software for fitting and data analysis

Main Results and Discussion

Nyquist plots show that the cathode exhibits a higher overall impedance than the anode. Bode modulus and phase plots confirm these differences across the frequency spectrum. A generic equivalent circuit was applied to both data sets, yielding chi2 values of 0.0010 for the cathode and 0.0295 for the anode. These fits serve as an example; accurate modeling requires detailed electrode and electrolyte composition data.

Benefits and Practical Applications

Simultaneous EIS eliminates the need for separate measurements, reducing experimental time and ensuring consistent conditions. This approach supports rapid screening of new electrode materials, optimization of battery designs, and quality control in manufacturing.

Future Trends and Opportunities

Future developments may include advanced reference electrode materials that minimize disturbance, refined equivalent circuit models tailored to specific chemistries, and integration of EIS with optical or spectroscopic diagnostics. High-frequency extensions and machine learning-driven analysis could enable real-time monitoring and state-of-health assessment in commercial battery management systems.

Conclusion

Second Sense technology in a VIONIC system enables concurrent impedance spectroscopy at both electrodes of a Li-ion cell in a single measurement. This method enhances comparative analysis of electrode processes and offers a practical tool for battery research and development.

References

• West AR Middlemiss LA Rennie AJR Sayers R Characterisation of Batteries by Electrochemical Impedance Spectroscopy Energy Reports 2020 6 232 241
• Liu W Wang Y Li Y Guo R Pei H Luo Y Xie J Lithium Sodium Storage Behavior of an Amorphous Carbon Derived from the Used Acticarbon for Rechargeable Batteries Journal of the Electrochemical Society 2019 166 A1585