I am working on solid polymer electrolytes and experiencing issues while measuring their conductivity. I use a coin cell setup, placing the polymer film between two stainless steel electrodes and performing impedance measurements. However, I observe a gap in the Nyquist plot around 1.2 × 10⁵ Hz, along with a drop in the phase angle at the same frequency. What could be the reason for this behavior?
Additionally, is it acceptable to use the data from 1 MHz down to 100 kHz to fit an equivalent circuit and calculate the bulk resistance (R)?
o calculate the bulk resistance (RbR_bRb) of a polymer electrolyte using stainless steel electrodes, Electrochemical Impedance Spectroscopy (EIS) is typically used. The choice of frequency range is crucial for accurately identifying the bulk resistance.
Recommended Frequency Range:
- High-frequency region: Typically 100 kHz to 1 MHz
- Mid-frequency region: Around 1 kHz – 100 kHz (to observe transitions)
- Low-frequency region: Around 1 Hz – 1 kHz (to study electrode polarization effects)
Why Use High Frequencies for Bulk Resistance?
- Bulk resistance (RbR_bRb) is mainly determined from the high-frequency intercept of the Nyquist plot (real axis, Z’).
- At high frequencies, electrode polarization and interface effects are minimized, allowing measurement of the intrinsic resistance of the polymer electrolyte.
- The characteristic frequency where RbR_bRb is found depends on the material composition and ion conductivity of the polymer.
Experimental Procedure:
If you are dealing with highly conductive polymer electrolytes, you may need to extend the frequency range beyond 1 MHz to capture an accurate resistance value.
The choice of frequency range is crucial for accurately identifying the bulk resistance. Recommended Frequency Range: High-frequency region: Typically 100 kHz to 1 MHz. Mid-frequency region: Around 1 kHz – 100 kHz
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