Application of Perforated Reference Electrodes in Small Cell Formats for Rate Tests and Electrochemical Impedance Spectroscopy

The use of reference electrodes (REs) in lithium-ion batteries allows enhanced electrochemical analysis of individual electrodes via potential monitoring or electrochemical impedance spectroscopy (EIS). The previous publication presents a concept for a laser-perforated RE (PRE). Herein, this PRE is applied in approximate to 60 mAh graphite/NMC811 pouch cells. Despite more than 17% of the electrode surface being covered by the PRE, only negligible capacity differences are observed for charge rates up to 2C compared to cells without PRE. At higher rates up to 5C, the blocking effect is present but stable. Reproducible and plausible anode voltage curves are obtained and the beginning of Li plating is detected. Cell EIS spectra are in good agreement with comparison cells without RE. The impedance spectra of the individual electrodes recorded by the PRE are confirmative and, with one exception, artifact-free. The results demonstrate that our PRE can be reliably applied for investigating lab-scale electrode coatings in small pouch cell formats.