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

An experimental approach to determine the potential deviation of a perforated reference electrode within a NMC811/graphite pouch cell in-operando is presented. By provoking Li plating via the graphite potential and detecting it via cell dilatation, it is possible to evaluate reference potentials more accurately without the need for post-mortem analysis.

Abstract

Reference electrodes (REs) play a crucial role in the accurate assessment and control of battery potentials, but their confidence is overestimated. Researchers have tracked the source of the error to the RE design that blocks the lithium-ion path between anode and cathode. These errors or potential deviations are mostly modeled or less-frequently estimated after observing Li plating post-mortem. This is the first study to showcase an experimental method that allows a more precise error quantification in-operando of a RE. The key idea is to relate the error-affected reference potential to an unaffected quantity, such as the cell dilatation. Although our experimental setups are special, this approach can also be applied to different setups and REs. Using the presented method, we provoked Li plating in NMC811/graphite pouch cells and determined the potential deviation of our perforated RE to be 12 mV under fast charging conditions. In contrast to previous studies, we found the error to be positive, offering a new explanation of the error mechanism of REs.

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