Electrochemical impedance spectroscopy (EIS) is a core tool for analyzing large-format lithium-ion cells. However, the very low cell impedance of these cells amplifies inductive artifacts at high frequencies and can mask a cathode-side contact resistance. This study presents a practical approach to identify this contribution: by linking electrode-resolved T-cell EIS with a micro-reference electrode to spectra from a multilayer pouch cell, a cathode-side contact resistance dependent on state of charge (SoC) and state of health (SoH) is determined directly from the large-format cell. This enables correct attribution of high-frequency features in the ~1–100 kHz range, improving aging analysis and model fidelity.
🔗 Open Access: DOI:10.1149/1945-7111/ae2402
📌 Highlights:
- Artifact clarification: The low impedance of large pouch cells amplifies inductive artifacts and can obscure a cathode-side contact resistance.
- Method: Coupling electrode-resolved T-cell EIS (with a micro-reference electrode) with multilayer pouch-cell EIS to deconvolve the contact resistance.
- Key finding: The cathode-side contact resistance varies with SoC and SoH and shapes the cell’s high-frequency signature.
- Why it matters: Misinterpretation above ~1–100 kHz can lead to incorrect conclusions about ohmic rise and aging.