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

Abstract

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 ≈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.

An Experimental Method to Determine the Measurement Error of Reference Electrodes within Lithium‐Ion Batteries

“…Since reliable REs and reference potentials are paramount for the entire field, we developed a method to experimentally determine the error and applied it to our setup as an example. This work is therefore based partly on our previous studies, where we fabricated and tested a perforated reference electrode (PRE), basically a mesh‐like design that we encourage to try [10,18] . It must be emphasized that the core idea of this work is not confined by its experimental characteristics, but should be understood as a general approach; a method to inspire researchers to empirically validate their REs.…”