Electrochemical Impedance Spectroscopy
Also known as: EIS, AC impedance, impedance measurement
Electrochemical Impedance Spectroscopy (EIS) is a powerful technique for characterizing electrochemical systems by applying a small AC voltage over a range of frequencies and measuring the resulting current response. Developed in the late 1960s, EIS reveals the frequency-dependent resistance and capacitance of interfaces, allowing researchers to separate charge transfer kinetics, diffusion, and ohmic losses. It is widely used in battery research, corrosion studies, fuel cells, and biosensors.
Key highlights
- Separates kinetic, transport, and ohmic contributions through frequency dependence
- Non-destructive; can monitor system changes in real time
- High sensitivity to interfacial phenomena and electrolyte properties
- Mechanistically interpretable through equivalent circuit models
Intuition
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How it works
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When to use it
Use EIS to diagnose electrochemical systems in situ: batteries under charge/discharge, corrosion at different potentials, or biofouling on electrodes. It is ideal for separating overlapping electrochemical processes and for monitoring gradual changes (aging, degradation). Apply at steady state or quasi-equilibrium. Avoid under transient conditions or when nonlinear effects dominate.
Strengths & limitations
- Separates kinetic, transport, and ohmic contributions through frequency dependence
- Non-destructive; can monitor system changes in real time
- High sensitivity to interfacial phenomena and electrolyte properties
- Mechanistically interpretable through equivalent circuit models
- Complex data interpretation; requires fitting to equivalent circuits (non-unique solutions possible)
- High-frequency measurements are difficult (typically >1 MHz); inductance and parasitic capacitance interfere
- Assumes linear (small-signal) response; large AC amplitudes introduce errors
- Timeconsuming for full frequency sweep; fast measurements require automated systems
Common pitfalls
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Applications
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Frequently asked
What is a Nyquist plot and why is it useful?
A Nyquist plot shows Z'' (imaginary impedance) vs. Z' (real impedance). Semicircles represent time constants; their diameter reveals resistance, and their position on the real axis shows series resistance. This visual representation reveals processes and their timescales intuitively.
Why do I need an equivalent circuit model?
EIS measures overall impedance, not individual process properties. An equivalent circuit (e.g., Rs-Rct-Cdl) maps observed impedance to physical parameters (ohmic resistance, charge transfer resistance, double-layer capacitance). Fitting extracts these parameters.
How small must the AC signal amplitude be?
For linearity, AC amplitude should be 5-10 mV or less (especially near the equilibrium potential). Larger amplitudes introduce harmonic distortion and nonlinear effects, violating the linear impedance model.
Sources
- 1.Barsoukov, E., & Macdonald, J. R. (2005). Impedance Spectroscopy: Theory, Experiment, and Applications (2nd ed.). John Wiley & Sons.ISBN 978-0-471-64749-2
- 2.Orazem, M. E., & Tribollet, B. (2008). Electrochemical Impedance Spectroscopy. John Wiley & Sons.ISBN 978-0-470-04141-9
- 3.Lasia, A. (2014). Electrochemical Impedance Spectroscopy and its Applications. Springer.ISBN 978-1-4614-8932-0
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Cite this page
ScholarGate. (2026, June 3). Electrochemical Impedance Spectroscopy. ScholarGate. https://scholargate.app/applied-physics/electrochemical-impedance-spectroscopy