Cyclic Voltammetry and Electrochemical Impedance Spectroscopy measurements carried out with the Microcell HC setup, the TSC SW Closed and the TSC Battery cells

Significance of the Topic

Electrochemical methods such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are essential tools in analytical chemistry for characterizing resistive and reactive properties of materials. In particular, accurate measurement of internal resistance and impedance is critical when working with air- or moisture-sensitive samples in battery research, solid-state electrolytes and related fields.

Objectives and Study Overview

This application note demonstrates two straightforward testing procedures using the Autolab Microcell HC with TSC SW Closed and TSC Battery cells. By employing four 100 Ω test resistors, the study aims to:

• Validate CV and EIS protocols in a controlled environment.
• Assess the accuracy of resistance measurements.
• Determine the internal resistance contribution of the measurement cells.

Methodology and Instrumentation

The experiments were conducted at 25 °C using an Autolab Microcell HC connected to a PGSTAT204 potentiostat/galvanostat. Two electrochemical cells designed for sensitive materials—the TSC SW closed cell and the TSC Battery cell—were tested in a two-electrode configuration. Four cylindrical metal film resistors (1 cm diameter, 4 mm thickness) with nominal values of ~100 Ω served as model samples.

Cyclic Voltammetry:

• Potential range: –1 V to +1 V, starting at 0 V.
• Scan rate: 0.1 V/s with 2.44 mV step increments.
• Resistance calculated from the inverse slope of the linear current–potential regression.

Electrochemical Impedance Spectroscopy:

• AC amplitude: 100 mV RMS, 0 V DC offset.
• Frequency range: 1 kHz to 1 Hz, 10 points per decade.
• Resistance determined from the real part of the Nyquist response.

Main Results and Discussion

Both CV and EIS yielded resistance values slightly above the nominal 100 Ω, reflecting an additional 1–5 Ω internal cell resistance. Key observations include:

• Consistent overestimation of resistor values across both cells and methods.
• Good reproducibility between the TSC SW and TSC Battery cells.
• The internal resistance component can be quantified by comparison with manufacturer-supplied resistor data.

Benefits and Practical Applications

The described procedures offer a reliable approach to:

• Calibrate and verify electrochemical cell performance before testing precious or sensitive materials.
• Quantify and correct for internal resistance in battery test cells.
• Ensure high-precision measurements in QA/QC and research laboratories.

Future Trends and Opportunities

Advancements may include:

• Integration of in situ environmental control (humidity, gas atmosphere) with impedance analysis.
• Extension to complex electrode materials and solid electrolytes in next-generation batteries.
• Automated data analysis workflows powered by AI for rapid assessment of cell performance.

Conclusion

The application of CV and EIS with simple 100 Ω test resistors in the TSC SW and TSC Battery cells provides accurate evaluation of cell and sample resistance. The slight overestimation relative to datasheet values highlights the internal resistance of the measurement cells, which can be readily determined and compensated for in subsequent analyses.

References

1. Metrohm Autolab Application Note AN-EC-017, March 2019.